| AN UNUSUAL TERRITORIAL ADAPTATION |
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Many fishes possess well defined territories in which they perform most or all of their feeding activities. To protect these foraging sites, such fishes routinely drive away all others of their own species. Since a fish of the same species feeds on the same thing you do, it is obviously to your advantage to keep your conspecifics at bay in order to have more food for yourself. Thus researchers were puzzled when they discovered broad overlap in feeding territories in Lobochilates labiatus , a big lipped cichlid from lake Tanganyika. The cichlids probe into crevices for small crustaceans, worms and other small invertebrates. Further investigation showed that the territories of the same sized fish did not overlap, but that the territories of fish of very different sizes often did. Apparently the smaller fish probe into correspondingly small crevices that the adults cannot reach, so do not compete with the adults even though they are eating the same food. This phenomenon of "sharing" is called resource partitioning.
Source M. Kohida and K. Tanida in the Journal Environmental Biology of Fishes.
| MAYAN CICHLID INVADES THE EVERGLADES |
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There is yet another piscine invader loose in Florida: a Central American cichlid, Nandopsis urophthalmus, the Mayan cichlid. There are a lot of exotic species, fishes and otherwise loose in Florida, but the Mayan cichlid is causing biologists special concern because it seems to be quickly takin over some of the remote wetlands in the interior of Everglades National Park. While no portion of the park can still be called pristine, the cichlid has appeared in some areas that had been considered the least disturbed. First identified at Anthinga Trail and two remote areas in Taylor Slough in 1983, the Mayan cichlid is hitting the system like a freight train. The fish has now spread through the park and has swarmed into canals and mangrove wetlands all the way to Palm Beach County. The rate at which this fish is spreading is surprising. For the sake of comparison, consider the oscar (Astronotus ocellatus) another cichlid loose in Florida. Since it appeared there in the 1950s, it took more than thirty years to expand to the region's canals, whereas the Mayan has done it in half that time! One thing the scientists do agree on is that whatever its impact on the Everglades, the Mayan cichlid is there to stay.
| UNUSUAL TANGANYKAN CICHLID MOUTHBROODERS |
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Compared with those of the other African Great Lakes, the cichlids of Lake Tanganyika encompass a remarkable diversity of breeding behaviour. This breeding diversity is enriched by members that are categorized as monogamous mouthbrooders. We have all seen "normal" mouthbrooding cichlids, but this unknown species is among the first of its kind. Their breeding patterns are more diverse than those of the substrate brooders and the typical (maternal) mouthbrooders, which account for one third and a little more than half of the Tanganykan cichlids, espectively.
Among the monogamous mouthbrooders, Microdontochromis sp. May well be unusual; young are fed in the parent's buccal cavity and then become mixed with broods of other mouthbrooding species, at least of those that have been well studied. Other species simply starve themselves while they are carrying their young in the buccal cavity. Microdontochromis sp, is an example of independence from the substrate , where competitive interactions prevail for breeding.
It is interesting to question why this cichlid behaves this way. Intrabuccal feeding is not a common occurrence-or is it? Perhaps if hobbyists examined their cichlids a bit more closely, they would find other occurrences of this unusual brooding behaviour in one of their species. Only time will tell.
Source Environmental Biology
of Fishes 47(2);191-201
| SHARING THE SPACE |
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In the swampy jungles of Surinam, three closely related catfishes live and spawn in the same area. These are all species popular in the aquarium hobby: Hoplosternum thoracatum, H littorale, and Callichthys callichthys.
All are bubblenest spawners that breed at the same time of the year, and are very similar in form and behaviour, so ichthyologists wondered how they could live in the same area without competition or hybridization. A paper by Jan H. Mol in Environmental Biology of Fishes [45(4):363-381] provides the answer-resource partitioning. Nests of H littorale were found in relatively deep water, never in holes, and at a considerable distance from trees, swamp margins, and nests of conspecifics. C. callichthys nests were found in very shallow water very close to shore, often with sandy bottom, with relatively little vegetative cover over the nest, and often situated in earthen or tree-root holes. H thoractaum nest positions were intermediate in water depth, distance from swamp edges, and only one nest was found in a hole; the vegetation cover over the nest was greatest in this species. Once again it has been shown that similar several similar species can divide a habitat according to their individual preferences in such a way that negative interactions are kept to a minimum. Catfish enthusiasts may glean much from this important ecological study that will aid them in the captive spawning of these fishes.