Ashley Rademacher Animal Care and Education Coordinator Zoo Med Labs For many people, summertime means vacation, traveling, and sunny days at the beach or the lake. For reptile keepers like me, summertime means extra feeding, collecting eggs, caring for newly hatched babies, tending the greenhouse and turtle yards, and maybe even a reptile or fish show! While this tends to be the busiest time of year for us and our ectothermic pets, it is also the
most exciting. By the middle of May this year, the incubators at Zoo Med held over 300 eggs and babies had already begun to hatch. This year has been especially exciting with the hatching of our very first Yellow Blotch Sawback Turtle! We have also hatched eight other turtle species including Box Turtles, Sawbacks, Diamondback Terrapins, and other aquatic turtles. Our lizards have been busy as well with nine different species hatching such as Jeweled Lacertas, Green Basilisks, Electric Blue Dwarf Geckos, and Veiled Chameleons. One of the most rewarding events that can happen in our animal room is to watch a new baby hatch. It is then that I realize that our efforts have paid off. We have provided care for the parent animals -frequently since they were babies themselves, in a way that has allowed them to grow to adulthood, remain healthy, perform natural breeding behaviors, select nesting sites and lay eggs. We have provided an environment that has made these animals feel comfortable and secure. We have done our research to learn the requirements of the animals and of their eggs. Finally, we have tended the eggs and waited patiently for the offspring to emerge. The cycle is complete and it is time to begin again. So, whether you are on vacation, planning your trip to the lake, or at home cleaning tanks and yards, I hope you enjoy your summer and this issue of The Vivarium and Aquarium News!
NEW ON THE 22-26 MARKET!
Focus on the Lesser Siren
The Redbellied 27-33 Shortneck Turtle
The Malagasy Giant Chameleon
Wild killies from Peru
Terrestrial hermit crabs
The Vivarium - Issue 3
Terrestrial hermit crabs Hermit crabs can easily be recognized by the fact that they usually protect the posterior part of their body by concealing it in an empty gastropod shell. Some species also use the empty homes of other creatures, for example tubeworms, and there are also specialized species that live in symbiosis with stinging coelenterates or sponges that grow around the posterior body of these hermit crabs. But all these specialists are exclusively marine species that won’t be discussed further here. by Wolfgang Löll
here are, however, two genera of terrestrial hermit crabs – Birgus and Coenobita – which are regularly offered for sale in the pet trade.
Of the five pairs of peraeopods or walking legs - the hermit crabs are decapods (Decapoda) – only three are readily visible. The powerful pair of claws constitutes the first pair of peraeopods. A typical feature of all Anomura (the next zoological-systematic category down from the
Coenobita brevimanus from South East Asia
Decapoda, and that to which the hermit crabs are assigned) is that one of the two claws is larger than the other. The claws are used to block the opening of the shell the hermit crab has chosen as its residence and make it impregnable. Next there are two large, well-developed pairs of peraeopods. The fourth pair of peraeopods are much abbreviated and located inside the shell; they are used to move the crab backwards and forwards within the shell. The fifth pair of peraeopods are even more specialized; the tips are modified and brush-like and are used to clean the complex structure of the respiratory apparatus and expel excrement. The posterior body (pleon) is soft and curved.
Coenobita clypeatus from the USA are very attractively colored.
The Vivarium - Issue 3 Sexual dimorphism
The females have pleopods (legs on the posterior body, absent in males), which they use to hold the eggs securely in place. At the end of the pleon we find the uropods, which are used to anchor the crab securely in the shell. In females the sexual openings (gonopores, again lacking in males) are located at the base of the third pair of peraeopods. There are no sexual differences visible in hermit crabs that are ensconced in their shells. The only way of differentiating the sexes reliably is to examine the underside of the pleon and the base of the third pair of peraeopods. But this is not possible in the pet store as a hermit crab cannot be persuaded to leave its shell without resorting to measures that constitute cruelty to animals. Under no circumstances whatsoever should such an attempt be made! The only possible exception – and this requires both patience and skill – involves exploiting the fact that many hermit crabs are rather “impatient” members of their kind. If the shell is picked up and held so that the opening is directed upwards then they will relatively quickly endeavor to turn the shell back into the correct position, i.e. with the opening downwards. In the process they come a long way out of their “house” and in relatively large specimens the practiced observer can then see whether or not there are gonopores present at the base of the third pair of peraeopods. And it is also often possible in such situations to see the pleopods in females. Sometimes, however, the attempt will be thwarted by the hermit crab remaining obdurately in its shell for hours…... Terrestrial hermit crabs don’t nip very often, but Coenobita compressus from Ecuador.
when they do it hurts, even with small specimens. So if you allow one to clamber over your hand, make sure that the latter is fully outspread, as if the crab decides to grab hold of a fold of skin with its claws then it may well deliver a powerful nip! In the final analysis males grow larger than females, but, as all hermit crabs available in the trade are wild-caught specimens of indeterminate age, this fact is only rarely of practical help. So there is often nothing for it but to buy a large number of hermit crabs and hope thereby to obtain both sexes. But this is a good idea anyway, as terrestrial hermit crabs are sociable creatures that should not be kept singly (see below).
This Coenibita clypeatus turned up in a consignment from Ecuador!
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The stripe on the second joint of the leg is species-typical for Coenobita compressus.
All hermit crabs belong to the primitive reproductive type and thus must return to the sea in order to breed. The larvae pass through several zoëa stages, then a megalopa stage, before adopting the lifestyle of their parents. To date there have been no reports of the breeding of terrestrial hermit crabs by private individuals, but it is nevertheless essentially possible, as Coenobita compressus, for example, has already been reared successfully under laboratory conditions (BRODIE & HARVEY, 2001) and marine aquarists have already reported success in rearing some small marine species. The rearing of the zoëae takes place in full-strength sea water using Artemia nauplii as food. The zoëae are positively phototactic, in other words they will swim towards a light source. This means they can be attracted using “light-traps”. And because Artemia nauplii are also positively phototactic it is in addition readily possible to concentrate the zoëae and the food organisms with the aid of a localized light source. The number of zoëa stages varies, even within a single species. In Coenobita compressus, for
example, 88% of the larvae undergo five zoëa stages and 12 % four such stages, before metamorphosing into megalopae after 21 to 33 days at 78 °F (26 °C). The megalopae leave the water after seven days and bury themselves in damp sand for 29 days. A further one to five days later their metamorphosis into fully-formed little terrestrial hermit crabs is complete. The rearing of hermit crabs is undoubtedly time-consuming and of no economic interest, but it is extremely interesting to work with the offspring of these crabs. On the one hand details of the reproductive behavior of many species are still completely unknown, while on the other hand some, for example the Palm Thief (Birgus latro), are seriously endangered in parts of their natural distribution. Thus it may one day prove to be exceptionally popular and are expedient to stabilize some populations by planned breeding programs - and that will be possible only if the appropriate knowledge is available. Hermit crabs mate in a belly-to-belly position and come a long way out of their shells to do so. The male transfers spermatophores (sperm packets) into the gonopores of the female.
The Vivarium - Issue 3 Terrestrial hermit crabs – Coenobitidae: overview of the species
The family Coenobitidae Dana, 1851 contains two genera and 17 species, 16 of which belong to the genus Coenobita LATREILLE, 1829. The name is derived from the Latin coenobium, which actually means “monastery”, but what is meant is life in a religious community. The genus name perhaps relates to the fact that the lifestyle of human hermits is usually religiously motivated, but perhaps the original describer was aware that Coenobita species live in colonies. There is also the monotypic genus Birgus LEACH, 1816 (the name Birgus is supposedly a personal name, but whose is unknown). These are highly specialized animals which, when adult, live entirely on land. You can read about the Palm Thief in AQUALOG News no. 80, which can be downloaded free of charge at www.aqualog.de. A number of the 16 known species of the genus Coenobita are regularly seen in the trade, with further species available occasionally. But it isn’t always clear which species are involved as they are very similar to one another. The easiest way of identifying the species is by their origin, as only two come from the New World: C. compressus H. MILNE EDWARDS, 1837 (the specific name means compressed) comes exclusively from the west (Pacific) coast, while from the east coast (Florida, Caribbean, and parts of the AtCoenobita pseudorugosus, red morp.
lantic coast) we have C. clypeatus (FABRICIUS, 1787) (the name signifies “shield-bearing”, from the round shield known as a clypeus carried by Roman legionaries). These two species are frequently seen in the pet trade. Additional Coenobita species are exported from south-east Asia, mainly via Singapore and Thailand. The following names have been applied to them: C. brevimanus, C. cavipes, C. perlatus, C. purpureus, C. rugosus, C. variabilis, and C. violascens. All these species are valid, and all are widespread in the western Indo-Pacific area, but in general it is doubtful whether the imported species are correctly identified.
Until recently C. clypeatus was the species most frequently sold in the USA, while this species turns up only comparatively rarely in the European pet trade. C. clypeatus maintained correctly in a terrarium can attain an age of more than 30 years. These crabs grow astonishingly large and can supposedly achieve basketball size, though I personally have never yet seen such a giant. In fact specimens the size of a good-sized fist are generally considered large. These hermit crabs appear to follow a seasonal cycle, as mating and egg-laying have so far been achieved only under outdoor maintenance in Florida. A winter rest period at lower temperatures, and above all a reduced photoperiod, may
The Vivarium - Issue 3 be a prerequisite for successful breeding. It has been established that in three of the larger (Asian) Coenobita species (C. brevimanus, C. cavipes, and C. perlata) females by preference cast their young adrift at new moon. The lunar cycle thus appears to be important in the breeding of Coenobita species. The eggs are very numerous and visible when the gravid female emerges from her shell. In C. clypeatus the eggs attached to the pleopods change color from brick red to dark gray during the development period. The initial coloration derives from the color of the yolk and changes as the embryos develop. When the eggs are ready to hatch they develop a mechanism that allows them to rupture very quickly when they come into contact with sea water. This adaptation clearly makes sense as the female could easily drown if she had to remain in the water for too long. In captivity, as soon as the eggs are ready to hatch the female will automatically make for the water if a suitably large dish filled with sea water is available. Full-strength sea water is necessary for rearing. The zoëae can be fed with Artemia nauplii. Under laboratory conditions – to date there have been no published reports of successful rearing by private individuals – the zoëae are reared either individually in 20 ml containers or in groups of five in 75 ml containers.
C. compressus, the Pacific coast counterpart of Coenobita clypeatus, is very similar, although it appears to remain considerably smaller. As far as aquarists are concerned the best way to distinguish them is by differences in coloration. It is a fact that all decapods are very variable in their coloration, and this applies equally to Coenobita species, but essentially C. clypeatus has a reddish or red-brown base coloration verging on violet, while C. compressus tends more towards gray and brown shades, and is often also striped. Because strikingly red-colored specimens are sometimes to be found among Coenobita compressus imported from Ecuador, it cannot be ruled out that Coenobita clypeatus has made use of the Panama Canal and now also occurs on the Pacific side of the Americas. A relatively reliable distinguishing characteristic between the two species is the coloration of the merus (i.e. the third element of the leg, counting from the tip of the foot) of the second pair of peraeopods. In C. compressus the upper surface of this leg element
Coenobita perlatus is very attractively colored.
The huge smooth claw is typical for Coenobita brevimanus.
always exhibits a dark stripe, absent in C. clypeatus. If these two Coenobita species are compared in anatomical terms, then it is noticeable that C. clypeatus is “hairier” and has more “pimples” on the upper surfaces of the peraeopods. Egg-bearing females of C. compressus have been observed in Panama from March to May.
Australian and Indo-Pacific species
There are two species of hermit crab in Australia: Coenobita variabilis and C. perlatus. Of these two species, however, only C. variabilis (the specific name means “variable”) is endemic to Australia. But this species is not available in the international pet trade, as since the 1980s no commercial exports of living wild animals or plants have been permitted from Australia. That is a pity, as to date C. variabilis is the only Coenobita species that has been shown to have an abbreviated larval development, making the breeding of the species under vivarium conditions at least a possi-
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Coenobita cavipes is only rarely imported.
bility. According to Harvey (1992), following two non-feeding zoeal stages, the feeding megalopa larvae develop in only six days at 86 °F (30 °C); they metamorphose only on land, similar to what was described for C. compressus. The second species mentioned above, C. perlatus, occurs in Australia only on coral islands and is regarded as rare there. It is unclear what the species name signifies. It probably represents a Latinized form of the word “pearl” and hence means “pearly”, referring to the striking white granulae (i.e. the little “pimples”) on the surface of the armor in this species. The Latin for pearl is margarita, but the Italian is perla. The rare occurrence of the species in Australia has been blamed on excessive collecting for the Coenobita compressus.
pet trade, but it is difficult to determine whether that is in fact the case or merely propaganda from those who oppose the keeping of pet animals, who have a powerful lobby in Australia. There are confirmed locations for C. perlatus in Polynesia (the Gambier Archipelago, the Marquesas, the Society Islands and Tuamotu) and other South-Sea islands. The species supposedly also occurs from the Seychelles to Madagascar, on isolated islands, and on the East African coast opposite. Its easternmost occurrence is given as Japan. The species has purportedly been introduced elsewhere by Man, who uses it for culinary purposes, and hence there are nowadays even self-sustaining colonies reported from the USA (e.g. Cape Cod, Massachusetts). In many cases, however, it appears that the species may have been incorrectly identified. C. perlatus is a very attractive species, known in English-speaking countries as the Strawberry Hermit, which describes its coloration very aptly. Full-grown specimens are bright red and the numerous granulae on the claws and legs are whitish. Juveniles are white initially and later become beige with brown stripes. At all stages the antennae are red, and this is regarded as a diagnostic characteristic for distinguishing this crab from other, similar species. The other species are likewise distributed in the western Indo-Pacific. Coenobita brevimanus (the species name means ”with a short hand”) and C. rugosus (the species name means ”wrinkly”) are imported quite frequently, and occasionally C. cavipes (the species name means ”hollow foot”),
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C. pseudorugosus (the species name means “false rugosus”), C. purpureus (the species name means ”purple”), and C. violascens (the species name means ”with a violet sheen”) are seen for sale. The last two species listed originate from Japan. In view of the considerable variability in coloration in all these species, however, it is highly debatable whether they are always actually correctly identified in the pet trade.
We have already looked at the most important species of terrestrial hermit crabs and discussed their biology. Now it’s time to summarize the framework of conditions required for the successful maintenance of all terrestrial hermit crabs. All terrestrial hermit crabs are fundamentally nocturnal and become active during the day only if the humidity is appropriately high. This means – in terms of terrarium maintenance – that their quarters should be sprayed once or more per day and that a relative humidity of 70% to 80% needs to be achieved for a period of several hours during the day (and if necessary also during the night). If this isn’t the case then the terrestrial hermit crabs will initially respond with inactivity and ultimately die. Because terrestrial hermit crabs have evolved to breathe via “lungs” instead of gills, they will drown in water after just a few hours! Hence their maintenance is possible only in a terrarium. They do, however, require water to be permanently available in shallow dishes, into which they can easily climb - and also get out again – in order to drink and moisten their respiratory cavities. There are species or populations that originate from entirely
The Vivarium - Issue 3 fresh water, while others require full-strength sea water. But because you can’t tell which from their appearance, the terrestrial hermit crab terrarium should always contain a dish of clean fresh water and one of clean sea water. Only top quality salt mixes, such as are manufactured for coral-reef aquaria, are suitable for preparing the sea water. Cooking salt intended for human consumption is unsuitable and can even prove lethal to the crabs if it contains an admixture of iodine or fluorine. This also applies to so-called “sea salt” from the health-food shop. Ideally the sea water should be mixed according to the instructions given (4.4oz of salt per gallon (33 grams of salt per liter)) and stored in a container made of food-quality plastic, so that the daily changing of the water requires little effort. A third essential prerequisite for the successful maintenance of terrestrial hermit crabs is an adequate depth of substrate, which should be kept moist (but never wet!). “Adequate depth” means at least three times as deep as the crab is long, and in any case at least 6 in (15 cm). The substrate should consist of a mixture of three to five parts sand and one part garden soil. The garden soil will serve as a binder to help stabilize the caves and passages excavated by the hermits. It will also simultaneously introduce a bacterial and fungal flora that will prevent the substrate from going bad. Hermits need to “dig themselves in” when molting. Molting is generally the most dangerous phase for a terrestrial hermit crab in the terrarium. Many owners do not realize that the hormone required for molting is secreted in adequate quantity only in darkness, and this, fundamentally, is the reason why terrestrial hermit crabs dig in to molt. From this it can be deduced that an inadequate depth of substrate is the commonest cause of death in terrestrial hermit crabs in captivity. Of course Mother Nature is flexible and, in extremis, terrestrial hermit crabs can also molt on the surface of the soil, but that causes these creatures enormous stress, especially when they are maintained in groups, and does them no good in the long term (i.e. over the course of several years). In addition, terrestrial hermit crabs need to remain underground for some time after molting, while they regenerate and the new armor hardens. The younger the hermit crab the more times it molts every year and the shorter Terrestrial hermit crabs are sociable creatures.
The Vivarium - Issue 3 the periods required for molting and regeneration. It may thus be that they survive for a few years even if an adequate depth of substrate isnâ€™t available, especially in the case of specimens kept alone. This is, however, the absolute exception and should not normally be the case. In principle it can be stated that a young Coenobita will molt several times per year and disappear into the substrate for around two weeks per molt, while fully grown individuals molt only once every 12-18 months and then bury themselves in the substrate for up to three months (!). There are various indications that a hermit is about to molt. Firstly, it will dig relatively more than otherwise. But because terrestrial hermit crabs are nocturnal this may go unnoticed. Secondly, the terrestrial hermit crab that is about to molt will spend more time than usual at the saltwater dish, as it requires salts to generate sufficient pressure for splitting the old armor. Thirdly the crab will eat more than usual, as it needs to be in good condition in order to survive the period after molting when it has nothing to eat except its old skin. Supplies of food and water are stored in a bubble-like structure on the posterior body. If this is full to bursting this often means that the crab is about to molt. And finally, it is often noticeable that a hermit that is about to molt changes to a smaller snail shell. That may sound paradoxical, as in the final analysis the crab grows larger by molting, but this behavior may be linked to digging in. Specifically, while as large a snail shell as possible is advantageous on the surfaCoenobita pseudorugosus, blue variant.
ce of the soil, as the crab can withdraw well into it on encountering a potential predator, a large snail shell with a correspondingly large opening is more of a hindrance when digging in. When it comes to feeding, terrestrial hermit crabs are simple to keep. They are carrion feeders that will take any sort of organic material of animal or plant origin. There are also special foods that have been developed for terrestrial hermit crabs and are available from any well-equipped pet store. Surprisingly these crabs often eat only small amounts of food. A cuttlefish bone can be placed in the terrarium as a nutritional supplement. These can be obtained in the pet trade, where they are sold as a calcium supply for cage birds. There are in fact hermits that simply ignore such a source of additional minerals, but there are many other Coenobita that will utilize it with enthusiasm. Food can be simply scattered on the substrate. It makes no sense to offer food in dishes. Leftover food should be removed when it starts to go moldy or dry out, even though, being carrion eaters, terrestrial hermit crabs are not particularly fussy. A frequently seen phenomenon is that these crabs spontaneously change their snail shell. But if they leave their home and run around â€œnakedâ€? that is a sign of enormous stress! Although they live in large colonies in the wild, these crabs are often very quarrelsome among themselves and may squabble vehemently over a particular snail shell, while another, apparently equally suitable by human standards, is ignored and left
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lying nearby. These quarrels can even result in fatalities. It often happens that a hermit crab is evicted from its snail shell by a conspecific and then wanders around homeless. For this reason a certain number of snail shells of various sizes should always be available to permit freedom of choice. Obtaining suitable snail shells can be a problem, but a specialist pet shop will usually be able to acquire some. The various Coenobita species also have different preferences when it comes to snail shells. Thus, for example, C. perlatus prefers the shells of Tonna spp. and Turbo spp., which have relatively round entrances. But because the identification of tropical marine snails is not exactly easy, and in view of the usually uncertain identification of the hermits themselves, it makes little sense to list their preferred snail genera here. Instead it is advisable to obtain suitable extra snail shells when buying the hermits themselves. Because of the curvature of their pleons, terrestrial hermit crabs are able to occupy only right-handed snail shells. The direction of a snail shell can be
determined by holding it with the opening facing you and the tip of the shell pointing upwards. If the coils wind clockwise then it is a right-handed shell, if they wind counterclockwise then it is left-handed. There are companies, at least in the USA (where terrestrial hermit crabs are particularly popular), that manufacture artificial snail shells especially for terrestrial hermit crabs. I do not know if these products are available in Europe as well or whether they are any good. It may seem difficult to believe, but terrestrial hermit crabs are skilled and enthusiastic climbers, so it is strongly recommended that a number of branches for climbing should be included in the terrarium. The best-suited are those of fruit trees (apple, pear, cherry), as they not only look attractive, but are also guaranteed non-toxic and they rot comparatively slowly. However it is important to make sure they arenâ€™t taken from trees that have been sprayed with insecticide, as only tiny traces of such sprays are lethal to Coenobita. It is best to take such branches from old gardens that have been allowed to go wild.
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Coenobita pseudorugosus, red-orange variant. The species can also be colored deep red or blue.
As far as the rest of the décor is concerned, it is important that rockwork, if included, is founded on the bottom glass of the terrarium. Otherwise it will inevitably be undermined, collapse, and become a death trap for the hermits. Piles of dry leaves are far better. Here too the leaves of fruit trees are again very suitable, but those of oak or beech can also be used. In addition “tunnels” of bark lying on the bottom are very suitable as daytime hiding-places for the crabs. The terrarium itself should – as can be gathered from the suggestions for setting up (deep substrate, branches for climbing) – be tall rather than long. The size of terrarium required is a matter of some debate, as restricted space is often a subordinate problem when it comes to the captive maintenance of wild creatures, including Coenobita. But at the same time they must, of course, be provided with adequate freedom to move around. A bottom area of 20-32 x 16-20 in (50-80 x 40-50 cm) with a height of 16-32 in (40-80 cm) will be adequate for a group (6 to 15 specimens) of small hermits 1 to 2 in (3 to 5 cm) in length. If the container is too large then it will not be easy
to keep tabs on the secretive nocturnal hermits. But if it is too small then group maintenance is likely to result in deaths, as the hermits will cause reciprocal stress. By the same token, correspondingly more space is required for larger hermits. However, as can be seen from everything said above, terrestrial hermit crabs are suitable for maintenance only by enthusiasts with a special interest, as they are nocturnal and secretive in their habits and require relatively time-consuming daily care. Hence there is no need for a lengthy discussion of terrarium size here. Another controversial question is whether they are best kept singly or in groups. The species of the genus Coenobita live in colonies in the wild. We know that these creatures have developed highly evolved communication among themselves, even including the production of sounds. (These noises sound like a gentle chirping and are produced using special stridulation organs. Stridulation means that the sounds are produced by friction and not, as in us humans, by vocal chords being set in motion by air pressure.) Coenobita are thus essentially social ani-
The Vivarium - Issue 3 mals. Even so, the assertion that Coenobita that are kept singly will live shorter lives than those maintained in groups belongs to the realm of legend. On the contrary, it can be argued that terrestrial hermit crabs that are kept singly will have a higher individual life expectancy because of the absence of social stress. As already mentioned, Coenobita have lived to more than 30 years old in the terrarium! It is a fact that terrestrial hermit crabs that are kept singly are less active, but the interpretation of this as a reduction in enjoyment of life is in any case anthropomorphic. Nobody knows how and what an animal feels, let alone when in the case of a creature as remote from us in terms of evolutionary history as a terrestrial hermit crab. The reduction in activity in a Coenobita kept singly versus one kept in a group can equally well be interpreted as a sign of inner peace and relaxation. Nevertheless, group maintenance should definitely be regarded as preferable, as the main object of maintaining wild creatures should be to study their behavioral repertoire in full. This inclu-
des aspects of social interaction such as mating, battles for order of rank, and so forth. Only species that are strictly solitary or have only a very small degree of social tolerance towards conspecifics should be kept singly as the method of choice. But obviously several individuals can be maintained even then â€“ albeit in separate containers â€“ in order to observe the complete life cycle of the species in question under vivarium conditions. Hence for purely pragmatic reasons it is suggested that particularly expensive species that will be difficult to obtain again should initially be maintained separately. Once they have settled in you can try keeping them together. In any case this procedure increases the likelihood of successful acclimatization of imported specimens. And finally, it is important always to buy an adequate number of individuals of the same population of a species right at the start. It is often impossible to acquire suitable additional specimens at a later date. Essentially you should buy 6 to 15 specimens right at the beginning.
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Focus on the Lesser Siren Siren intermedia Salamanders have four legs and possess external gills during their larval stages, losing the latter as they change into adults and adopt a more terrestrial lifestyle. There are exceptions, though, the best-known of which is the Axolotl (Ambystoma mexicanum), which permanently retains its external gills and aquatic lifestyle. And then there are salamanders that not only retain their gills throughout their lives, but have just two, rather than four, legs! by John Dawes
hese interesting creatures are known as sirens (family Sirenidae). At the moment only two genera are recognized: Pseudobranchus (two species) and Siren (two species). The two Pseudobranchus are commonly referred to as dwarf sirens, while Siren lacertina, the largest of all the four species, is known as the Greater Siren. Quite logically, therefore, the subject of this article, the Lesser Siren, lying – as it does – halfway between the dwarves and its larger sibling, is known as Siren intermedia.
The size attained by adult Lesser Sirens varies quite widely, with the range given as 7-27 in (1868 cm). The Greater Siren, by comparison, can grow to nearly a meter in length, while the dwarves attain only some 10 in (25 cm) in total length. The species Siren intermedia is widely distributed in the USA and Mexico, occurring in Florida, Virginia, Texas, north-eastern Mexico, Illinois, Indiana, along the Mississippi valley, and in Michigan. It isn’t found in every part of these states, but it is, nevertheless, relatively abundant, except in Michigan. As often (almost always!) happens in species which have a wide geographical distribution, distinct differences can be detected between Lesser Sirens from different locations, and these forms are generally recognized as subspecies: the Eastern Lesser Siren (S. i. intermedia), the Western Lesser Siren (S. i. nettingi), and the Rio Grande Lesser Siren (S. i. texana). The reference to being “generally recognized as subspecies” is made above because there are authors who dispute the identity of the third-mentioned subspecies. Some believe that the Rio Grande Lesser Siren may be a
The Vivarium - Issue 3 subspecies not of S. intermedia but of the greater Siren, S. lacertina. There are also those who believe that it constitutes a separate species altogether. Irrespective of the debate, all types of Lesser Siren exhibit the typical characteristics of their family. These include a flattened head, a small dorsal fin located well back on the body, fourtoed front legs (but no back legs), well-formed feathery external gills, and a long eel-like body. This last characteristic is responsible for one of the common names of these salamanders: Two-Legged Eels! Although Lesser Sirens are predominantly nocturnal, they can also be active during the day in the aquarium, especially once they settle down. Once this happens they will feed quite happily, even in brightly illuminated aquaria. Indeed, some individuals can become quite aggressive at feeding time, with less-dominant specimens being bullied by their more active tankmates. Steps should therefore be taken to ensure that The mouth of the Lesser Siren is subterminal.
every siren gets a square meal. With regard to the actual range of organisms that can be offered as food, the choice is quite wide. All types of worms will be consumed, the actual kind and size chosen depending on the size of the sirens themselves. Snails, silkworm pupae, meat chunks, fish, and other meat-based items will all be accepted. However, the diet must be varied to ensure that no essential nutrients and vitamins are missed out. Juveniles can be fed daily, while adults are fine being fed two or three times per week (but see below). While juvenile Lesser Sirens can be accommodated in a relatively small aquarium, say, 9-10 gallons (35-40 liters), adults should be provided with more room (15 gallons (60 liters) upwards, depending on the size and number of individuals). A well-fitting cover is important, as are efficient filtration and regular water testing to ensure that ammonia and/or nitrite levels donâ€™t rise too much. As a preventive measure, regular partial water changes will help maintain water quality (not as
The Vivarium - Issue 3
Lesser Sirens swimming in open water look like eels with little arms.
a replacement for an efficient filter, but as an additional measure), especially if water testing isn’t possible. Water quality is particularly important because of the wastes produced by these ‘substantial’ animals. In addition, any uneaten food must be removed to prevent water-quality problems from arising. Lesser Sirens are quite powerful creatures. Hence the shelters that should be provided, whether of rock, or bogwood, or whatever, should be sturdy enough to resist their attentions. If rocks or other objects are to be piled on top of one another, they must either be too heavy for the sirens to shift, or should be stuck together, e.g. with aquarium sealant. The rooting around that these creatures perform not only poses risks for their safety (from collapsing shelters), but also spells disaster for rooted plants, unless these are really well anchored, e.g. by being secured with the rocks used to construct the shelters. If the decorative element provided by submerged plants is desired, it may be sensible to use synthetic types, as these can stand up to rough treatment better than their natural counterparts; they can also be washed, if necessary.
Owing to its wide geographical distribution, S. intermedia can tolerate temperatures ranging from those associated with coldwater aquaria to those suitable even for warmth-loving fish species, such as discus. Consequently water kept anywhere between 59 and 82 °F (15 and 28 °C) will be OK. The sirens will, of course, be much more active at the higher end of this spectrum, requiring more feeding, tighter water quality control, etc. In the wild Lesser Sirens breed from December to April, depending on location. Breeding in captivity is, however, rare, though the few reports that are available indicate that it occurs more or less at these same times of the year. Females can deposit anywhere between 200-700 eggs (although some reports refer to 12-300 eggs). These are usually laid in bunches and, while it is not known with absolute certainty if they are guarded in the wild, at least one report of captive breeding states that the eggs, which had been laid in a depression, were defended by an adult. Courtship appears to be a rough affair, if the bite marks observed in adults during the breeding season are anything to go by. Fertilization is presumed to be external, since females lack a cloacal sperm-storing chamber. Incubation may take 1-2 months and the larvae measure around 0.4 in (1.1cm) at birth.
The Vivarium - Issue 3
The Malagasy Giant Chameleon The huge island of Madagascar off the East African coast is an Eldorado for zoologists. The island, which is the fourth largest in the world, separated off from the ancient continent of Gondwana some 135 million years ago. Since then evolution there has followed a unique course and more than 90% of the Malagasy species are endemic – in other words they occur nowhere else on Earth. There are numerous chameleon species on Madagascar, including the largest chameleon species of them all, the Malagasy Giant Chameleon, Furcifer oustaleti. by Thorsten Holtmann How large can it grow?
In fact nobody knows precisely. There are rumors of individuals up to a meter long, but the largest specimen measured to date was “only” 27 in (68.5 cm) in length. But that is total length, i.e. including the tail.
The Malagasy Giant Chameleon is found in the coastal lowlands of Madagascar. It is found all over the island, but its occurrence in the eastern part of Madagascar is linked to the relatively high temperatures there. The species is well adapted to the hot savannah climate and hence has benefited from alterations to the landscape resulting from human activity (deforestation). There is supposedly an introduced population in Kenya (Ngong Forest near Nairobi) and a breeding population also exists in southern Florida.
Malagasy Giant Chameleons and humans Chameleons are generally regarded as easily upset. They are noted/notorious for some particularly territorial species suffering stress-induced kidney problems as the result of a conspecific simply being constantly in view (for example if two individuals can see one another in adjacent terrariums), and this can lead to death! The Malagasy Giant Chameleon is, however, a comparatively calm and peaceful member of the chameleon tribe. Males don’t tolerate one another, and gravid females are likewise strictly solitary.
Males of the Malagasy Giant Chameleon have a brown or gray base color.
The Vivarium - Issue 3 But they can generally be kept in pairs in an adequately large terrarium (a winter garden is a lot better in view of the size of these animals). Malagasy Giant Chameleons also exhibit this laidback attitude towards humans. They donâ€™t get excessively upset even when they are picked up carefully; and the threatening mouth-opening known from many other chameleons is seen in Malagasy Giant Chameleons only if they are seriously provoked. Researchers in the field say that you can usually simply perch a Malagasy Giant Chameleon on your shoulder and it will stay there quietly for hours on end. Because the Malagasy Giant Chameleon is comparatively common and is also associated with human settlements, the native people like to make use of the greedy appetites of these animals, and place these chameleons in their gardens, where they devour unwanted pests up to the size of a mouse and thereby keep them in check. However, these positive (from a maintenance viewpoint) characteristics of the Malagasy Giant Chameleon donâ€™t alter the fact that these animals can develop a quite remarkable turn of speed when necessary. Malagasy Giant Chameleons in the terrarium All the usual basic rules of chameleon maintenance apply to the Malagasy Giant Chameleon. These include a relatively high food require-
The Malagasy Giant Chameleon is a relatively peaceful and sociable species.
ment, which is, however, easy to satisfy in the case of the Malagasy Giant Chameleon, as they will take not only all the usual food insects (crickets, grasshoppers, and Zophabas beetles, but also baby mice - in the wild they also eat small birds and reptiles. All food insects should always be dusted with one of the usual calcium-vitamin powders available in the trade. The high requirement for drinking water always makes chameleon maintenance rather time-consuming, as the majority of individuals donâ€™t automatically learn to drink from a dish. For this reason they need to be given water via a pipette at least every other day.
The females of Furcifer oustaleti, the Malagasy Giant Chameleon, are very attractively colored.
The Vivarium - Issue 3
The Vivarium - Issue 3 There are, however, a number of tricks to get round this. Many chameleon-keepers use drop dispensers, which drip water at intervals of 1-2 seconds into a collecting container placed below. This simulates rain water, which the chameleons recognize as such and drink. The most natural way of providing chameleons with water to drink is by spraying, with the reptiles taking the water from plant leaves, etc. But that too is labor-intensive and can also result in the terrarium becoming too wet. A more elegant method is the installation of an artificial waterfall using a small aquarium pump. However, such systems are somewhat prone to disturbance and the pump may fail – and, following Murphy’s Law, invariably at the least convenient time, for example when you are on holiday. A very neat way of setting the water in the drinking dish in motion, and thus making it recognizable as water to the chameleons, is to aerate the dish with one of the standard aquarium air pumps available in the trade. You simply suspend the airline in the dish and set the air supply to produce around two bubbles per second from the airline. A nice side-effect of this method is that it simultaneously raises the humidity in the terrarium; in the case of the Malagasy Giant Chameleon this should be a relative humi-
dity of around 70% during the day, rising to up to 100% at night. Because of its natural habits, the Malagasy Giant Chameleon can be classified as one of the easier chameleon species to maintain, as it doesn’t immediately react adversely, followed by the onset of illness, if things get a bit too warm in the terrarium. The daytime temperature should be between 71 °F and 82 °F (22 and 28 °C), rising to up to 113 °F (45 °C) under the spot-lamp. It is, however, essential always to provide these reptiles with a relatively cool, well-ventilated area in the terrarium, to visit when they so choose.
Furcifer oustaleti is an egg-laying species. After a gravid period of around six weeks the females lay up to 61 eggs. At an incubation temperature of around 82 °F (28 °C) it takes between 210 and 280 days until the young hatch. Many breeders use vermiculite as a brood substrate. The young grow very rapidly and attain sexual maturity in as little as a year. All in all, maintenance and breeding are similar to those of the well-known Panther Chameleon, Furcifer pardalis.
When resting, the Malagasy Giant Chameleon usually curls up its “fifth leg”, the prehensile tail.
The Vivarium - Issue 3
NEW ON THE MARKET! Geophagus harreri
his attractive “eartheater” has recently been available commercially in Germany for the first time ever. The parent stocks originated from Surinam - the Tapanahoni River, to be precise, although the species also occurs in other rivers in Surinam (the Maroni, for example). These fish prefer a moderate to strong current, but move to habitats with less current for breeding. Maintenance conditions: this species needs comparatively high water temperatures - at least 82 °F (28°C), and it will experience no problems at all up to 90 °F (32 °C)! Soft, acid water with a low bacteria count will improve coloration and condition in general. Maximum size: probably around 10 in (25 cm). Males grow larger and are more elongate. Females remain smaller and look plumper. Old fish may develop a slight hump, but this seems not to be sex-linked.
© Text & Photos: Thomas Weidner
The Vivarium - Issue 3
The Vivarium - Issue 3
G. harreri is an open brooder and uses wood or stones for spawning. The species can be very aggressive compared to other eartheaters, and hence should be kept only in very spacious tanks (80 in (200 cm) minimum length). It is possible to keep the species with other large cichlids (other eartheaters, Mesonauta, Heros, Uaru, etc), and keeping them in the company of numerous other fish reduces the aggression. I personally have so
far had up to 150 fry, but I guess that a good pair can produce around 400 young. Lexicon: Geophagus means „eartheater“. harreri: named in honor of one of the collectors of the type material. Suggested common name: Marowijne Eartheater © Text & Photos: Thomas Weidner
The Vivarium - Issue 3
Corydoras sp. “San Juan”
© Frank Schäfer / Aquarium Glaser
his pretty and very variably colored cory originates from Peru. It remains an open question whether the „San Juan“ belongs to Corydoras napoensis, C. bilineatus, or an undescribed species. The Corydoras elegans group, to which the „San Juan“ without doubt belongs, is in need of revision. Be that as it may, the „San Juan“ is a very pretty, peaceful, and active (note the large caudal fin!) species of Corydoras.
The Vivarium - Issue 3
his cichlid originates from a comparatively small collecting site in Peru and hence is imported only very occasionally. The species lives in soft, acid water in the wild, but is very hardy and adapts well to variable water conditions in the aquarium. Another plus point is that it is quite Male and female.
peaceful. Hence, despite its maximum size of 5-6 in (12-15 cm), this fish can be bred even in rather small tanks with a volume of 50 gallons (200 liters) upwards. But always bear in mind that small surface-dwelling fishes, e.g. hatchetfishes, may be taken as food by the cichlids! ÂŠ Frank SchĂ¤fer / Aquarium Glaser
The Vivarium - Issue 3
The Redbellied Shortneck Turtle (Emydura subglobosa) - a dream of an aquatic turtle There is always a demand for easy-tokeep, attractive, lively turtles that don’t grow too large. And the Redbellied Shortneck Turtle is just the animal to provide all these attributes. The tongue-twister of a popular name is undoubtedly the most complicated thing about this turtle! by Christoph Fritz, www.reptilia24.com
hese attractive turtles, in which males attain a carapace length of some 8 in (20 cm) and females a good 10 in (25 cm), have been in the hobby since the late 1970s. The past master of the terrarium hobby, Wilhelm Klingelhöffer, didn’t mention them at all in his standard work Terrarienkunde in 1959, but in 1984 Obst, Richter & Jacob wrote in their classic Lexikon der Terraristik und Herpetologie that the species had been bred for generations and was suitable even for beginners. What a change in the space of just 20 years or so! Until the 1990s captive-bred EmyYoung Emydura subglobosa are delightful.
In Emydura the neck is withdrawn into the shell in an S shape (sideneck turtles). Photo: F. Schäfer
dura subglobosa were available everywhere, but then things all went quiet as far as the species was concerned. Not until around 10 years ago did the species resurface, and since then it has enjoyed constantly increasing popularity.
Initially the Redbellied Shortneck Turtle was known in the hobby under the name Emydura albertisii. This species was described in 1888 Photo: Chris Lukhaup
The Vivarium - Issue 3 Mainly aquatic
The Redbellied Shortneck Turtle is a fluviatile turtle that only occasionally comes ashore. There are reports on maintenance that state that they can be kept in an aquarium that is completely without a land area, but I donâ€™t recommend that. Although the species suns itself appreciably less frequently than many other turtles, on the one hand individual specimens differ considerably in their preferences in this respect, and on the other the presence of a dry (!) land area helps prevent disease as, being an inhabitant of running water, E. subglobosa has high requirements as regards water quality. If the latter is poor then these turtles tend towards infectious diseases of the skin and shell. But even when the water is in good order these turtles, like all creatures, can sometimes fall ill, and they then like to seek out the land area and sun themselves, and in this way slight infections often clear up by themselves, without any intervention at all by the owner.
The aquarium for Redbellied Shortneck Turtles
Because of its splendid pink, black, and white coloration Emydura subglobosa is an excellent ornamental animal that can be readily maintained in large aquaria with a variety of dĂŠcor. It is partiAdult male viewed from above....
... and from beneath.
The Vivarium - Issue 3
The Vivarium - Issue 3
Portrait of a male.
by Boulenger, who regarded it as distinct from E. subglobosa. But it was subsequently realized that the two species were one and the same and so E. albertisii became a junior synonym of E. subglobosa, which had been described back in 1876 by Krefft. The species is quite obviously rather variable and other names have also been assigned to it; the most recent scientific review of the turtles of Australia (Georges & Thomson, 2010) distinguishes the typical red-bellied form from southern New Guinea (where it occurs from the Vogelkop and Bomberi peninsulas in the west to the Kemp Welsh drainage in the east) and the Jardine River on the Cape York Peninsula in Australia as Emydura subglobosa subglobosa, and another, yellow-bellied subspecies, E. s. worrelli, which in addition develops a broader head with age, from the upland drainages of the Arnhem Land plateau in the Northern Territory and the rivers that empty into the Gulf of Carpentaria. The scientific description of the latter was severely criticized by the authors, but that doesn’t alter its validity. On the other hand it cannot be ruled out that the two subspecies actually represent separate species.
Photo: F. Schäfer
Be that as it may, wild-caught Redbellied Shortneck Turtles are so rare in the trade that one can safely say that they don’t occur at all, and that all the strains found in the hobby correspond to the nominate form, while E. s. worelli, is maintained only by a small number of specialists, if at all. Portrait of an adult Redbellied Shortneck Turtle. Photo: C. Fritz, www.reptilia24.com
The Vivarium - Issue 3
Underside of an adult female.
cularly advisable to keep fish in the same aquarium, as the latter will very quickly indicate (by falling ill) that the water quality isnâ€™t as good as it might be, and they also help produce a varied, constantly interesting scene. Adequately fed turtles rarely go hunting fish. Occasionally a sick or weak small fish may fall prey to the turtles, but the same would also happen in the wild. A tank of length 60 in (150 cm) or more should be chosen for a paludarium of this type. This will make it easier to set up and will suit the turtles very well, as they are excellent swimmers with a strong urge to keep moving. The water chemistry is of lesser importance, while the water temperature should be 72-79 Â°F (22-26 Â°C). A powerful filter will ensure clear, good quality water. For safety reasons it will ideally contain an integrated heater - a separate heater-stat such as is used in fish-only aquaria is less suitable because of
The Vivarium - Issue 3
Adult albino specimen.
the risk of breakage by larger turtles. It is extremely important that the air temperature above the aquarium is not significantly lower than the water temperature, as otherwise respiratory diseases can easily occur. The temperature on the land area beneath the heat lamp should reach 86-95 °F (30-35 °C). It is wisest to choose a spotlamp with a UV component. Heavily gravid females in particular will make extensive use of this “sun bed”. Redbellied Shortneck Turtles are usually very peaceful among themselves so group maintenance is possible. If space permits, one male should be kept with several females, in order to allow the females a little rest from the constant attentions of the male. But even males tolerate one another astonishingly well. After the onset of sexual maturity the males can be recognized very easily by the length of their tails – almost double that of the females.
Feeding the Redbellied Shortneck Turtle is easy. These turtles are mainly flesh-eaters (carnivoro-
Photo: Christoph Fritz, www.reptilia24.com
us). Adults can be fed with proprietary food sticks, dried Gammarus, and deep-frozen foods such as shrimps, whitebait, mussel meat, squid, etc. As far as possible warm-blood meat shouldn’t be offered, as it is only poorly digested and heavily pollutes the water. But balls of raw meat are useful treats if the turtles need to be given medication via their food. The rearing of specimens available in the trade presents no problems. Essentially, they should be treated in the same way as adults, though naturally the food should be correspondingly smaller. In addition to the items listed above, deep-frozen bloodworms (for aquarium fish) are an important food for rearing. You can try offering vegetable food as well now and then, for example sweet fruit, Dandelion, or similar. Some individuals enjoy this a lot, while others won’t touch it – this is something their owner must find out for himself. It should be borne in mind, however, that green food is highly laxative and hence should be used with care.
The Vivarium - Issue 3
The attractive red color of the shell is retained life-long.
Easy and productive to breed
The world demand for Redbellied Shortneck Turtles in the terrarium trade has long been met by captive-bred stocks. Even though no species of animal has ever yet gone extinct through being traded alive, this is a positive sign, as it shows that we are getting everything about the maintenance of these attractive turtles right. Albino specimens (in this case white with red eyes) sometimes occur as a very rare mutation among captive broods. The Redbellied Shortneck Turtle is very productive and a female can easily produce several clutches per year, each comprising 6-12 (maximum 15) eggs. These turtles aren’t very demanding when it comes to somewhere to lay their eggs. If necessary they will even lay them under water, but such eggs are not normally viable. The eggs should be incubated in damp Vermiculite or similar at 81-86 °F (27-30 °C) and 90-95% relative humidity, with hatching taking place after 45-60 days. The courtship behavior of the male, which is characterized by a very rapid nodding of the head, is interesting to watch. If a male is bothering the female(s) excessively then it is advisable to remove him from the group, at least for a while.
Photo: Frank Schäfer
Being inhabitants of the tropics, these turtles don’t actually require special over-wintering. It has, however, proved beneficial to keep them for 3-4 months at a lower water temperature (68-72 °F (20-22 °C)) - no cooler, and if in doubt somewhat warmer is better!) so that the female(s) can recover properly from egg-laying. All in all, the Redbellied Shortneck Turtle is one of the most suitable aquatic turtle species for terrarium maintenance. So if you are now filled with the desire to keep these turtles, then your pet dealer can undoubtedly order them for you from a wholesaler of his acquaintance.
Lexicon: Redbellied Shortneck Turtle
Emydura means „Emys with tail“; Emys is another turtle genus. albertisii: named in honor of the collector, the controversial Italian explorer Luigi Maria d’Albertis (1841-1901). subglobosa: refers to the shape of the shell and means „almost spherical“. worrelli: named in honor of Eric Worrell of the Australian Reptile Park, Gosford, New South Wales.
The Vivarium - Issue 3
Wild killies from Peru The name “killifish” for the egg-laying toothcarps has become current all over the world. To the uninitiated it may sound somewhat brutal, but it has nothing to do with the English word “kill”. The name killifish originated in the New York area, where it was used for the species Fundulus heteroclitus macrolepidotus. by Wolfgang Löll
he first mention of the name in the literature dates from the year 1788, when D. J. Schoepf published a paper entitled “Beschreibungen einiger Nord- Amerikanischer Fische, vorzüglich aus den Neu-Yorkischen Gewässern” (= Descriptions of some North American fish, mainly from the waters of New York) in the journal Schriften der Berlinischen Gesellschaft naturforschender Freunde. In this paper he gives the local common name for the above-mentioned Fundulus as “Killfish”, but doesn’t explain it. There are two possible derivations for the name: the comAphyolebias schleseri, male
Aphyolebias peruensis, female
monest is that the word killifish comes from the Dutch word kill (meaning river) plus fish, in other words, “river fish”. However, this Fundulus hardly ever lives in rivers; hence the second derivation may well be the correct one, according to which the phrase “killing bait” is used for a particularly effective angling bait. To the present day Fundulus heteroclitus is used as a bait fish in the area around New York. Be that as it may, the name killifish in no way reflects the behavior of these wonderful creatures in the aquarium!
The Vivarium - Issue 3 Wild-caught or captive-bred?
Only a few groups of fish have so many aquarium populations as the killifish, or are bred to such a high level of (scientifically demanding) expertise. In theory there is no need to rely on imports for the hobby. Nevertheless the importation of wild-caught killifish species is very welcome, as although inbreeding isnâ€™t usually a significant problem in aquarium fish (the high reproductive rate of fish invariably permits any inheritable defects in captive-bred strains to be eliminated by careful selection), the majority of aquarium strains trace their ancestry to only a very small number of founder specimens. This means that often only very little is known about the range of natural intraspecific variation. The importation of comparatively large numbers of specimens can fill these gaps in our knowledge and thus help us understand the biology of such species. The capture of these fish for live maintenance poses no problems from a conservation viewpoint, so there is really no need to have a guilty conscience about buying wild-caught specimens.
Moema cf. ortegai, male
Seasonal fish and survival specialists
All the species discussed here live under extreme conditions in the wild. For starters, there are the classic seasonal fish, including Austrolebias schleseri, A. peruensis, and Moema cf. pirana. Seasonal fish is the term used for killifish that in the wild sometimes inhabit waters that dry up the periodically. A feature they have in common is the ability to grow incredibly rapidly; from hatching to sexual maturity takes only a few weeks. And Moema cf. pirana, for example, can easily reach 6 in (15 cm) long! But others, such as Austrolebias schleseri, attain barely 2 in (5 cm) in length. From the moment that they attain sexual maturity these fish mate every day. The species discusRivulus ornatus, female
Rivulus retrocaudatus, male
sed here are bottom-divers, i.e. the spawning pair dive right into the substrate of the body of water and lay their eggs â€œundergroundâ€?. In the wild the lifespan of such fish is usually only a few months. Then their home waters dry up and they die. Only the eggs survive in the substrate and hatch many months later when it next rains. They live considerably longer in the aquarium.
Rivulus retrocaudatus, female
The Vivarium - Issue 3
Moema cf. ortegai, female
Rivulus, the â€œgrasshoppersâ€?
The strategy of the Rivulus species is quite different. These slender fish have learned to travel on land. In wet weather they jump out of the water and cling to damp terrestrial plants. In this way they significantly reduce predation pressure from piscivorous fish and can simultaneously colonize small waters that in fact hardly deserve the name, such as damp meadows containing a few small puddles. These fish live considerably longer than their fellow killies, the seasonal fish. Rivulus are adhesive spawners that lay their eggs on plants, among fine roots, etc. The eggs usually develop within 2-3 weeks. Because Rivulus are particularly fond of mosquito larvae they are of great interest for the biological combating of mosquitoes. Rivulus ornatus, male
Aphyolebias peruensis, male
Aphyolebias schleseri, female
We hope you enjoyed our third issue of
© Text & Images: Frank Schäfer / Aqualog