King of the Hill by ALEXANDER A. PRIEST he "Hillstream Loach" is but one of the common names associated with several different species. Many of these species are very similar in appearance, and the identification of which species you might have can be quite difficult. I have seen the following scientific names, all supposedly referring to the same fish with the "common" name of "Hillstream Loach": Beaufortia kweichowensis, Hemimyzon sinensis, Pseudogastromyzon cheni, Hemimyzon myersi, Homaloptera yuwonoi, and Pseudogastromyzon myersi. I have also seen the following other "common" names for what appears to be the same species of "Hillstream Loach": "Borneo Loach," "Borneo Sucker," "Butterfly Loach," "Hong Kong Pleco," "Meyers Hillstream Loach," and "Stingray Pleco." To further complicate things, there are fish that are somewhat similar in appearance (I'll get to that soon), that also have "Hillstream Loach" as part of their common names, including: Borneo Hillstream Loach (Gastromyzon borneensis), Chinese Hillstream Loach (Balitora kwangsiensis), Broken Band Hillstream Loach (Linipaxhomatoptera disparts), Funkien Hillstream Loach (Formosiana tinkhami), Saddled Hillstream Loach (Homaloptera orthogoniata), Spotted Hillstream Loach (Gastromyzon punctulatus), and Striped Hillstream Loach (Gastromyzon ctenocephalus). I'm not trying to confuse you (at least not any more than I became confused while trying to research this fish), but it's necessary to keep in mind that if, after reading this article, you want to acquire this fish, you may have a difficult time communicating to your local fish store exactly what it is you want. (I wouldn't even attempt to ask for this fish in any of the large pet chain stores — no telling what you'd wind up getting!) Generally speaking, if you find this fish in your local store, it will most likely: (1) be incorrectly identified as a "pleco," and (2) actually be either Beaufortia kweichowensis, Pseudogastromyzon myersi, or Gastromyzon punctulatus. Your best bet, if you decide to get the same fish this article is being written about, is to take this issue of Modern Aquarium (or, more specifically, its cover photo) with you when you go shopping. This article is about my experience with Pseudogastromyzon
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myersi (at least that's what I believe the fish on our cover this month to be, based on its identification in the Axelrod Atlas1). As I mentioned, one of the common names for this fish (and the name it was selling under when I bought it for the first time) is "Stingray Pleco." While this is very misleading scientifically, it just happens to be a very good practical description. For one thing, the shape of the fish bears a strong resemblance to a miniature Stingray (Paratrygon sp.). This is because this fish has adapted itself in several ways to adhering tightly to the rocks and tree branches in the swiftly moving streams where it normally lives. The body of this fish is fairly flat. This results in a body that provides very little resistance to fast moving water. It also has what looks like a true "tail" where its caudal fin should be. This long pointed "tail" is also very similar to that of a Stingray. Unlike a pleco, which has a sucking mouth, the Hillstream Loach's paired fins flatten out and overlap to form a sort of "suction cup" under its body, with its mouth located on the underside. (Visualize the overlapping wings of a butterfly, and you can see why another common name for this fish is "Butterfly Loach.") The evolution of the adhesive paired fins has at least one obvious advantage over that of a sucking mouth — because the fins do an excellent job of attaching the fish to rocks (or, in the aquarium, the glass walls or the substrate), the fish's mouth is left free to eat, while the body still clings to the rock, branch or tank wall. So strong is the adhesion formed by this fish's "sucker body," that it is nearly impossible to pry it from a smooth hard surface, such as a tank wall. The highly compressed (nearly flat, in fact) shape of this fish gives the aquarist trying to net it (or a predator looking for a meal) very little to grab. In fact, I had one Hillstream Loach die while sticking to the tank wall, and it was still quite a struggle for me to remove it. This strange arrangement of fins (remember that the paired fins face down and overlap) does not prevent the fish from moving surprisingly fast when it wants to do so, in an almost "jet propelled" fashion. In fact, one book2 gives, as a common name for the Saddled Hillstream Loach (Homaloptera orthogoniatd) "Rocket Fish," so called for probably just this reason.
June 2001
Modern Aquarium - Greater City A.S. (NY)