Spirulina – superfood for aquarium fish – Aleksandra Kwaśniak-Płacheta, PhD

SPIRULINA

SUPERFOOD FOR AQUARIUM FISH

Aleksandra KWAŚNIAK-PŁACHETA, PhD

Hydrobiologist, expert on feeding and breeding of ornamental fish, aquarium enthusiast. A highly recognized speaker of many aquarium training courses and symposiums. Author of articles published in domestic and foreign magazines including ”Nasze Akwarium”, ”Magazyn Akwarium”, ”Planeta Zwierząt”, ”Tanganika”, ”Fauna & Flora”, ”Pet Market”, ”Aquafeed Magazine”, ”Pet Worldwide” and various publications of Wrocław Aquarium Association.

Humans have long been searching for sources of protein to meet the growing needs of Earth’s population. Protein that will be cheap and efficient to produce and will have high nutritional value. These qualities can certainly be found in spirulina, a microalgae that has been widely cultivated and used in many industries for years. Its composition makes spirulina an excellent source of plant protein that can replace animal-derived protein used in aquaculture. In addition, it is a source of many valuable components with health-promoting effects.

HOW SPIRULINA BECAME POPULAR In 1940, French phycologist Pierre Dangeard pub- lished information about a sample of interesting algae in the journal of the Linnaean Society of Bordeaux. He found out about the algae from a pharmacist stationed at Lama Fort, in what is now the Republic of Chad. The sample came from a local market in a small village, Massakora, located about 50 km from Lake Chad. Dangeard claimed that these strange algae, called dihé in the local language, were part of the local people’s diet. They are harvested from small lakes and ponds located around Lake Chad. The green and blue algae floating on the surface of the water are fished out and dried. The resulting dry ”dough” is divided into small pieces and sold at the local market. Microscopic analysis carried out by the researcher revealed them to be filamentous, spirally twisted algae – Spirulina platensis. They are a major component of the phytoplankton of many lakes located within the African Great Rift.

It is likely that World War II caused this information to receive only little attention in the scientific world. Europe had to wait 25 years for further reports on spirulina, when the rediscovery of dihé was made by botanist Jean Léonard. The scientist confirmed that the green, dry ”cookies” available in the local market consist mainly of spirulina extracted from numerous lakes around lake Chad with alkaline and highly saline water. At the same time, another species of spirulina, Spirulina maxima, was found across the Atlantic in Lake Texcoco near Mexico City. Although it was not used as a human food in Mexico at that time, historical records from the Spanish Conquest period indicated that it was a component of the Aztec diet. Spanish people mentioned in their notes tecuitlatl cookies which the local people baked from a substance resembling blue-green sludge pulled from the lake with dense nets. These discoveries indicating the use of spirulina as a food by humans initiated a number of studies on the properties of these algae. However, it should be mentioned that spirulina was known to science even before Dangeard’s reports.

SYSTEMATICS Spirulina was first isolated by Pierre Jean Turpin in 1827 from a sample taken from a stream. Originally, these photosynthetic-capable organisms were classified as algae, a very large and diverse group of thallophytes (not having tissues or organs). It is worth mentioning that algae are a morphological-ecological (rather than systematic) grouping of organisms that are not related to each other. Spirulina belongs to the prokaryotes, which are organisms that lack a nucleus. For this reason, it is often excluded from algae, which are considered to be eukaryotic organisms (having a cell nucleus). Since 1974, spirulina began to be classified in the cyanobacteria division (Cyanobacteria) and now cyanobacteria in type rank are included in the bacteria domain. Domain is a systematic category higher than kingdom, introduced in 1990 as the category with the highest taxonomic rank. This systematic approach is now increasingly popular. Three domains were created: domain: Eukaryota (all nuclei) domain: Archaea (single-celled organisms known from extreme habitats, such as geysers) domain: Bacteria type: Cyanobacteria

SPIRULINA OR ARTHROSPIRA? The genus Spirulina was created by Pierre Jean Turpin in 1827. The algae he discovered had no visible transverse walls (septa) dividing the trichomes, this is what we call the thread-like colonies of cells that form cyanobacteria. Following the isolation of species that possessed such septa, Stizenberger created the genus Arthrospira in 1852. Over the ensuing years, there has been an ongoing debate about the validity of this division. In the 1960s, scientists concluded that septa are also found in species of the genus Spirulina, they just didn’t have the right equipment to see them before. Of course, the new possibilities that scientists gained from year to year meant that more differences began to be discovered, such as the structure of the cell wall, which triggered further discussions about systematic classification. Now we know that we are dealing with two distinct types: Spirulina and Arthrospira. And it is the latter type that includes species that have health-promoting properties and are used as food. Therefore, it is worth remembering that the correct species names of organisms used in the composition of products with ”spirulina” in the name are Arthrospira platensis and Arthrospira maxima. However, ”spirulina” will probably stay with us for good, because in the cosmetics industry, as well as in the dietary supplement or pet industry, this is the name used by manufacturers and recognized by clients.

OCCURRENCE OF SPIRULINA Spirulina can be found in a wide variety of environments. It has been discovered in fresh water, sea water, brackish water, soil and sand, and even in hot springs. Arthrospira platensis occurs naturally in Africa, Asia and South America, while Arthrospira maxima can be observed in Central America. The fact that spirulina was included in the diet of people living in the area of lakes Chad and Texcoco is related to the specific conditions of the reser- voirs from which it was harvested. Collected and

Pools for spirulina cultivation

dried green mats contained almost exclusively Arthrospira platensis or Arthrospira maxima cells. The formation of these monocultures was closely related to the chemical parameters of the water, which was characterized by significant salinity (>30 g/l, caused mainly by carbonates and bicarbonates) and high pH (8.5-11 pH). These conditions are ideal for the development of spirulina and at the same time effectively limit the development of other algae, cyanobacteria and bacteria, the consumption of which could be dangerous for the health and even life of humans and animals.

SPIRULINA IN FISH NUTRITION Due to its composition, spirulina is an excellent source of protein for fish to replace animal proteins. Numerous studies are available on the utilization of this component in the diet of both fish intended for consumption such as beluga (Huso huso), rainbow trout (Oncorhynchus mykiss), olive flounder (Paralichthys olivaceus), Nile tilapia (Oreochromis niloticus), Cirrhinus mrigala, the walking catfish (Clarias batrachus), Oplegnathus fasciatus, and ornamental fish such as guppy (Poecilia reticulata), goldfish (Carassius auratus).

SPIRULINA PROTEIN Initially, the main reason for the interest in spirulina was the extremely high protein content in its cells, which ranges from 55% to 70%. This is impressive compared to the protein content of meat (15-25%) or soy (35%). In addition, spirulina protein was found to be more valuable than legume protein and only slightly inferior to milk or egg protein (it contains fewer amino acids such as cysteine, methionine and lysine). This high protein content was so promising that numerous studies were initiated on many species of fish

intended for consumption. Fish were fed with feeds containing 1 to 100% spirulina. The effects were varied. In some fish, such as Nile tilapia (Oerochromis niloticus) and carp (Cyprinus carpio), a significant effect of this algae on growth has been observed. However, there were also fish, such as African sharptooth catfish (Clarias gariepinus), in which high doses of spirulina inhibited growth. On this basis, the thesis was put forward that carp or tilapia, which in their natural diet have a significant share of plant components, are better adapted to utilize spirulina due to having appropriate digestive enzymes.

NATURAL PIGMENTS CONTAINED IN SPIRULINA Spirulina subjected to careful study gradually revealed more of its secrets. It turned out that these spirally twisted cells are extremely rich in pigments, including chlorophyll, beta-carotene, zeaxanthin, canthaxanthin, xanthophyll and phycobilins. In terms of chlorophyll content (0.8-1.5% of dry weight), spirulina ranks among the top in nature. The bacteriostatic effect of this green pigment and its beneficial effects on the body is used in the cosmetic and pharmaceutical industries. Carotenoid content in spirulina dry matter is estimated at 0.5%. Beta-carotene is predominant (0.2-0.4%). It is responsible for the pink color of the feathers of spirulina-eating flamingos. Carotenoids are an indispensable component of fish’s diet, and it is not only about intensifying their coloration; these compounds also have many important physiological functions, including stimulation of the immune system and playing an important role in the process of maturation and reproduction of fish.

The role of carotenoids in the fish body:

a As antioxidants, carotenoids protect valuable cell components, including nucleic and fatty acids, from the destructive effects of free radicals. a Some carotenoids are converted by fish into vitamin A, which affects growth and skin function. a They increase resistance to viral, bacterial and fungal infections. a They are beneficial for fish reproduction. a They protect skin and eggs from UV rays. a They also intensify fish’s coloration.

Due to its high carotenoid content, spirulina is often used in the feeding of both ornamental fish and fish intended for consumption. However, we should keep in mind that the effect of coloration will depend on the species of fish and the frequency of food intake and spirulina dosage. Species with the ability to convert ß-carotene or zeaxanthin to astaxanthin will in-

Pools for spirulina cultivation

tensify their coloration better and faster compared to fish that do not have this ability. Rainbow trouts needed only 2.5% spirulina to significantly increase the concentration of pigments in their skin (24.98 µg/g dry weight, compared to a control group of 9.05 µg/g), while in koi carp, color enhancement occurred at a spirulina content of 7.5% in the food. The blue coloration of Metriaclima lombardoi gained intensity at 20% spirulina in the feed, similar observations were made for Pseudotropheus acei, where both blue and yellow colors were enhanced. An example of a fish in which spirulina did not improve coloration would be the red porgy (Pagrus pagrus), a fish intended for consumption that lacks the ability to convert ß-carotene to astaxanthin. Phycobilins are also a significant group of spirulina pigments, which include blue phycocyanin and allophycocyanin and red phycoerythrin. Their function is to absorb the greenish-yellow radiation from the sun that chlorophyll does not absorb. Like carotenoids, they have antioxidant properties, effectively protecting fatty acids and other valuable compounds from free radicals

UNSATURATED FATTY ACIDS The active ingredients of spirulina also include unsaturated fatty acids. Spirulina contains high amounts of linoleic acid and gamma-linolenic acid, which are precursors to arachidonic acid. It is arachidonic acid that plays an important role in the formation of prostaglandin, which helps in oocyte maturation and ovulation. How important these acids are was shown in an experiment in which two-spotted gurami (Trichopodus trichopterus) was given food containing 2.5%, 5.0%, and 10% spirulina, respectively. The higher dose of spirulina in the feed reduced the time to first spawning by about 12 days compared to the control group. Pseudotropheus acei cichlids that received as little as 2.5% spirulina in their feed produced significantly more eggs compared to the control group.

The positive effect of spirulina on reproduction of some fi sh species is attributed to its specifi c components. These include essential fatty acids, vitamins C and E, and carotenoids.

EFFECT OF SPIRULINA ON THE IMMUNE SYSTEM Numerous studies with fi sh intended for consumption have shown positive effects of spirulina on the immune system of fi sh. Immunoactive components contained in it stimulated the activity of cells conducting phagocytosis, increased the production of lysozyme (a protein that breaks down the cell wall of bacteria, it is one of the mechanisms of non-specific immunity), increased the antimicrobial activity of fi sh mucus and increased the number of white blood cells, whose task is to protect the body from bacteria and viruses.

IS SPIRULINA SAFE? Many species of cyanobacteria have been attributed with toxic effects on living organisms. Spirulina as a representative of this group of organisms was also questionable, especially as it began to be used extensively in human nutrition as a source of protein and medicinal substances. Many studies have been carried out to resolve doubts about its toxicity to living organisms. These studies involved a variety of animal species, including fi sh, and were often conducted on several generations. Scientists evaluated the overall condition of the animals and their reproduction. Indepth histopathological studies were also performed. They did not show any toxic effects of spirulina on living organisms, regardless of the dose used. Positive research results allow to use spirulina on a large scale both in animal and human nutrition.

HOW TO CHOOSE FISH FOOD WITH SPIRULINA? Tropical offers several foods for ornamental fi sh, where spirulina is an important ingredient. We offer to our customers foods in the form of fl akes, granules, sticks, pellets and tablets with the content of spirulina ranging from 6% to 36%.

FLAKE FOODS WITH SPIRULINA Flake foods can be used to feed both surface-feeding and bottom-feeding fi sh. It all depends on how the food is given. Flakes placed on the surface of the water will stay there for quite a while. On the other hand, given under the surface of the water, they will sink quite quickly. Flake foods are especially recommended for delicate fi sh, particularly those prone to gastrointestinal problems, as they are digested faster and easier than granulated foods. Flakes also work well in aquariums where fi sh compete strongly for food. When dispersed all over the tank, the fl akes allow the food to be taken up also by fi sh that are lower in the hierarchy or simply more timid.

GRANULATED FOODS WITH SPIRULINA Granulated foods are the perfect solution for medium and larger fi sh species that prefer to feed from the

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bottom of the aquarium. Mini granules with spirulina are ideal for young fish and small species. Special production technology of Tropical granules ensures safety of fish feeding. Granules under the influence of water increase their volume only to a very small extent, so even a larger portion of granules does not lead to swelling of the food in the digestive tract and consequently to digestive problems.

SPIRULINA FOODS FOR FRY Aquarists who have ever tried to breed their fish know how difficult it is to find a fine food that will be accepted by the fry. To meet hobbyists’ needs Tropical offers foods with spirulina, which intensify growth and development of young fish. For smaller fry we recommend Mikro-vit Spirulina, for slightly older ones Super Spirulina Forte Mini Granulat.

FOODS IN THE FORM OF TABLETS WITH SPIRULINA Tablets are ideal for bottom-feeding fish, as a large group of popular bottom-feeding fish require plant foods in their diet. It is worth noting that adhesive tablets also allow feeding of young fish and those with small mouths. Adhered to the glass, they also give aquarists the opportunity to closely observe fish.

Mikro-vit Spirulina

Super Spirulina Forte Mini Granulat

SUPER SPIRULINA FORTE TABLETS HI-ALGE DISCS XXL POLECO’S TABLETS

SUMMARY Benefi cial effect of spirulina on living organisms is a result of combined action of all its components. Spirulina is not just another interesting ingredient of ready-made food that is eagerly eaten by the fi sh but it also signifi cantly affect their condition. Regular use of foods with spirulina makes colors of fi sh more intense and limit digestive problems in sensitive, herbivorous species. Thanks to spirulina the overall condition of the fi sh and their vitality can be maintained at the highest level.

LITERATURE Chronakis I., Galatanu A., Nylander T., Lindman B. (2000), The behaviour of protein preparations from blue-green algae (Spirulina platensis strain Pacifi ca) at the air/water interfac, Colloids and Surfaces A: Physicochemical and Engineering Aspects, 173(1-3), 181-192. Ciferri O. (1983), Spirulina the edible microorganism, Microbiologica Reviews, Dec, 551-578. Gouveia L., Rema P., Pereira O., Empis J. (2003), Colouring ornamental fi sh (Cyprinus carpio and Carassius auratus) with microalgal biomass, Aquaculture Nutrition, 9(2), 123-129. Gupta S.K., Jha A.K., Pal A.P., Venkateshwarlu G. (2007), Use of natural carotenoids for pigmentation in fi shes, Natural Product Radiance, 6(1), 46-49. Tang G., Suter P.M. (2011), Vitamin A, Nutrition, and Health Values of Algae: Spirulina, Chlorella, and Dunaliella, Journal of Pharmacy and Nutrition Sciences 1, 111-118. Zahira Y., Ehsan A., Afi fi Z., Masita M., Mohd S.T. (2014), An overviev: biomolecules from microalgae for animal feed and aquaculture, Journal of Biological Research, 21:6. Zhang F., Bon Man Y., Yin Mo W., Hung Wong M. (2019), Application of Spirulina in aquaculture: a review on wastewater treatment and fi sh growth, Reviews in Aquaculture, 1-18.