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文章 The Genus Tropheus |
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作者 Ad Konings, 1992.
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(This article was originally published in "Cichlids Yearbook Volume 2, Cichid press; 1995; pp. 13-15. It is here reproduced with the permission of Ad Konings, Cichlid Press).
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Tropheus moorii Murango. Photo by Ad Konings. |
The species of the genus Tropheus have for many years been some of the most popular cichlids among aquarists. There are many hobbyists who keep exclusively Tropheus species. Although there are only six known species, at least four of these show great geographical variability. Fortunately most aquarists are aware of this fact and rarely house different variants of the same species in one tank. This would lead inevitably to bastardization.
The members of the genus Tropheus are usually well represented on most rocky coasts. Except for T. duboisi, they all inhabit the upper 10 metres of the biotope. Not only for their protection but also for their food, Tropheus species are restricted to areas with rocks. The feeding habits of T. duboisi have not been extensively investigated, but those of the other species have. T. moorii, T. brichardi, T. polli and T. sp. "Black" are all grazers which shear the filamentous algae from the rocky substrate (Yamaoka, 1983). T. annectens, which is restricted to the western, Congonese, shores of the lake, is closely related to and maybe even conspecific with T. polli, and behaves similarly to that species. It seems that Tropheus has a feeding relationship with several species of the genus Petrochomis. Members of the latter group, which are browsers combing unicellular diatoms from the algae strands, partially clear the biocover from sediment and make it thus more suitable for Tropheus to feed on (Takamura, 1984).
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| A male Tropheus brichardi from the Kavalla islands, Congo. Photo by Ad Konings. |
In the artificial environment of the aquarium T. moorii, from the southern part of the lake, and T. sp. "Black", form the northern, behave as strongly territorial cichlids. Typically the largest males will divide the available space in the tank among themselves and leave the border areas of their territories as living space for females and weaker males. Territories in the aquarium measure more than 60 cm in diameter. In nature, the territoriality of these two species is not always as evident as it is in a tank. Although males have a territory where spawning takes place and in which they forage, conspecifics are not always chased from the premises. Sometimes we may observe a group of about 20 (T. sp. "Black") to 100 (T. moorii) individuals grazing on the same rock. In the wild, T. brichardi and T. polli are permanently territorial and, especially T. brichardi, are difficult to keep in small numbers in an aquarium.
Many aquarists have great interest in maintaining a breeding group of a particular variant of one of the species. Not only for the continuous interactions between the members of the group but also to spread the aggression of the most dominant males, it is advisable to have as large a group as possible. If each individual is given 25 to 40 litres of water a balanced breeding group can be established in a suitably decorated aquarium. Caves are not necessary as they will not provide shelter for harassed individuals; only the dominant males will occupy caves. Stones should be placed in such a way that clearly separate groups are created. Each group or heap of stones, if approximately 50 cm in diameter, will be regarded as a territory by a male and respected by the others.
Often more females are kept than males. This may work for most species of Tropheus but not always for T. brichardi. The latter species is best kept with as many males as females.
Before a group of Tropheus is introduced into the aquarium all of the fish must be in good condition or at least be in the same condition, and all of the fish must be introduced at the same time. The introduction of additional specimens to the group at a later stage must be avoided at all times! Newly introduced fish more often than not upset the established hierarchy in the group and frequently end up being chased by all other individuals. If the additional specimens are wild caught fishes which have not been quarantined long enough, an early death is generally the result. Currently this is the most important problem aquarists have maintaining Tropheus.
Wild caught fishes and fishes from aquaria in which wild caught specimens are housed have many different kinds of parasites. In the wild, these parasites live in balance with the host's immune system and are rarely present in harmful quantities. By virtue of the presence of a low number of parasites the host continuously maintains its resistance against an explosive increase in numbers of that parasite, although it never becomes totally immune. Fish in a healthy aquarium have very few parasites and thus mostly lack this semi-immunization. When a wild caught fish is introduced to an established group, it is immediately weakened by the repeated physical assaults it endures from all members of the group. This has a weakening effect on its immunity to parasites and a serious infestation is liable to result. Not only may the newly introduced fish die but the disease usually infects the non-resistant inhabitants as well. A single fish may thus completely wipe out a long established breeding colony. Therefore, never introduce untreated wild caught fish into a group of Tropheus. Several parasites are specific to a group of cichlids; they affect only those species while other species in the same aquarium do not show any sign of disease. Species that carry some of the Tropheus -affecting parasites are Goby Cichlids (Eretmodus , Spathodus and Tanganicodus) , Petrochromis , Simochromis , and Pseudosimochromis , There are several ways of "cleaning" wild caught fish, but all of them involve a quarantine period. A wild caught fish, living in balance with its parasite burden, can be cleansed of them by killing the existing parasite or by preventing re- infection where the parasites have left the fish in the course of their life cycle. To do this, however, one needs to know what organisms are involved. In Tropheus broad spectrum antibiotics and anti-parasitic solutions have had little effect in damming the spread of disease. What kills most Tropheus seems to be highly infectious agents, either virus or parasites. Many aquarists have -tried numerous medicines to cure their fish, some with success. Reasoning tells us, however, that there may be several diseases involved and that thus one medicine will not automatically cure all fish.
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Tropheus sp. "black", a geographical variant from Kiriza, Ubwari Peninsula, Congo. Photo by Ad Konings. |
As mentioned before, a fish may also be cured by preventing the parasite from re-infecting the host. If a parasite cannot find a host it will die. The infectious phase may live a long time but the agent infecting Tropheus seems to have a relatively short livespan. My personal experience and that of Hans Herrmann (pers. comm.) is that a biological trickle filter strongly inhibits the spreading of the disease. This can be explained by the fact that infectious parasites are carried away from the fish into the filtration system. It is our experience that water coming from the filter is free of pathogens. The faster the water is recycled through the trickle filter the more effectively it frees it from parasites. When the volume of water passed through the filter in one hour equals that of the tank's volume, an optimum treatment has been achieved. It is not known if faster cycles have a better or even the same effect. Slower cycles don't work that well.
So, wild caught fish could be cured by placing them in a quarantine tank which is filtered by a trickle filter; even when the tank is a part of a central filter system! It is important to leave the fish for at least two months on their own in that quarantine tank and have a separate hand-net for that tank only. When direct water-to-water contact with other tanks is avoided the result is healthy fish.
引用文獻:
- Takamura, Kenzi. 1984. "Interspecific relationships of aufwuchs-eating fishes in Lake Tanganyika". Environmental Biology of Fishes. v. 10; pp. 225-241 (crc01309) (摘要).
- Yamaoka, Kosaku. 1983. "Feeding behaviour and dental morphology of algae scraping cichlids (Pisces: Teleostei) in Lake Tanganyika". African Study Monographs. v.4; pp 77-89 (crc02403) (摘要).
© Copyright 1992 Ad Konings, all rights reserved
引語:
Konings, Ad. (八月 14, 1996). "The Genus Tropheus". 慈鯛魚室同好網. 檢索 五月 22, 2013, 來自: http://www.cichlidae.com/article.php?id=22&lang=zh.
