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A sparkling jewel: Xenotilapia melanogenys (Boulenger, 1898)
|Von Thomas Andersen, 2005.|
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Xenotilapia melanogenys was until recently known under the name of Enantiopus melanogenys, but was moved to the genus Xenotilapia by Takahashi in 2003 - for more information on this topic please see Synopsis of Xenotilapia Boulenger, 1899.
Xenotilapia melanogenys was originally described as Ectodus melanogenys by Boulenger in 1898 using specimens from Moliro Bay in DR Congo. It was transferred to the new genus Enantiopus by Boulenger in 1906, to the genus Xenotilapia in 1951 by Max Poll and back to the genus Enantiopus by Greenwood in 1978 and by Poll in 1986 (Maréchal & Poll, 1991).
Xenotilapia melanogenys has an almost lake-wide distribution, but it has never been seen in the distributional range of the potentially undescribed species X. sp. "kilesa", which extends along the western shore between Kalamie and the Kavala Islands in DR Congo (Konings 1998). There are only minor color differences in the distributional range of X. melanogenys, being mainly slightly differences in the overall coloration of sexually active males that could have a more or less bluish, greenish or purple hue on the body. The number and size of the black spots in the dorsal fin can also vary a lot. Outside the breeding period both sexes are colored in the same silvery coloration that reflects the sand, making it difficult for predators to make them out.
Xenotilapia melanogenys is a very slender, elongate cichlid with a body being 5-6 times as long as high and with a rather long snout. It reaches a total length of app. 15 cm (app. 6 inches) in the wild, but it can grow slightly bigger in captivity. Females generally stay a little smaller.
X. melanogenys differ from X. sp. “kilesa" by having a longer lower jaw and a longer snout and the bright yellow throat, chin and lips seen in the in males of the latter are missing in X. melanogenys (Konings 1998).
Xenotilapia melanogenys forage in large schools over the vast sandfloors, sifting through the sand for anything eatable like small crustaceans and invertebrates. Stomach investigations have also revealed copepods and ostracodes (Poll 1956). Outside the breeding period it is found in rather deep water, but when the breeding period sets in it moves to much shallower water. The maximum depth recorded for X. melanogenys is 40 meters (Konings 1998).
Quite interesting is that most individuals of a single school seem to remain together in that selfsame school their entire life. The school is properly formed at the moment the females releases the fry simultaneously and since most members of the school are the same age they all later in life attain their reproductive phase at about the same time (Konings 1998).
When the breeding season sets in the males start staking out territories in the sandy bottom of the shallow water in form of a saucer-shaped nest with a diameter of app. 50 cm. The nests are situated right next to each other and forms great breeding arenas. Interestingly it seems that Xenotilapia ochrogenys has attached itself to the breeding colonies of X. melanogenys since there are usually found breeding together (Brichard 1978 cited in Konings 1998).
Xenotilapia melanogenys could be kept in an aquarium with just a layer of fine sand and nothing more, maybe with a large group of Vallisneria in one corner to provide mouthbrooding females a place to seek shelter. The tank should not be too small and in order to have room for several displaying males and their nests as well as females, it should have a minimum length of around 150 cm (app. 5 feet). One of the reasons that the schools migrate to shallower water in the breeding season, is that the displaying males are seen much easier by the females in the bright shallow water and in the aquarium X. melanogenys likes bright light as well. You can actually see the males competing for the brightest spot in the aquarium. X. melanogenys should be kept in group of no less than eight individuals and order to maximize the coloration of the males such a group should consist of at least two males.
It is possible to keep Xenotilapia melanogenys together with other Xenotilapia species and even Ophthalmotilapia and Cyathopharynx if the aquarium is big enough, but to get the maximum out of Xenotilapia melanogenys - their nest-building and beautiful displaying - it’s recommended that they are be kept by themselves or with a free-swimming species like Cyprichromis leptosoma. As X. melanogenys is a carnivore their diet should consist of frozen mosquito larvae (not the red ones!), cyclops, mysis and artemia. They also eagerly take flakes, but as feeding with flakes seldom can get the females in proper breeding condition, this should not be their main diet.
Beware that Xenotilapia melanogenys could react quite violently to sudden moves in front of the aquarium and when the light has to be turned off at night. Their natural response to a danger on the bare sandfloor is to flee with the speed of light to deeper water - this is not possible in captivity and they often panic hitting the class or a stone.
Xenotilapia melanogenys is a maternal mouth-brooder, so only the female incubates the eggs and larvae. In contrast to the normal silvery coloration of X. melanogenys out of the breeding period, the males breeding dress is quite another story: It sparks like a jewel. Breeding begins as soon as the males become sexually mature and starts by the digging of nests by the males. The breeding territory of X. melanogenys consists of a saucer-shaped nest with a diameter of about 50 cm. In the centre of the territory the males dig a small pit with a diameter of app. 15 cm, where the spawning will take place (Konings, 1998).
Interestingly Eysel have noticed differences in the shape of the nest, depending on which locality the fish were collected. Males from Zambia construct saucer-shaped nests without a pit, while males from Burundi dig nests with the above mentioned spawning pit in the center (Eysel 1990).
When the nests are built the courting begins - rivals are chased with all fins erect, but females are seduced to the nest with all fins clamped. The only thing extended is the buccal cavity. Furthermore the male lies almost completely on his side when attracting the females.
When a female passes over the different territories, which lie next to each other, the males one by one, still remaining in their territories, lie on their sides and try to seduce her with their sparkling colors. As soon as a female enters the nest, the male start circling around her with all fins erect and gently pushes the female to encourage her to start circling too. After some rounds the female slows down and lays some eggs. The male waits till she finished and fertilizes the eggs before the female takes them in. Fry are released after three weeks and the clutch size varies between 30 and 80 (Konings, 1998). The small fry should be feed with newly hatched artemia.
Xenotilapia melanogenys is a stunning cichlid and highly recommendable, just remember that the aquarium should be decorated and tank-mates chosen for their needs to get 100 % out of these remarkable cichlids. If this is done, Xenotilapia melanogenys for sure is a sparkling jewel on the sand-floor!
© Copyright 2005 Thomas Andersen, all rights reserved
Andersen, Thomas. (Dezember 01, 2005). "A sparkling jewel: Xenotilapia melanogenys (Boulenger, 1898)". Der Cichlid Room Companion. Abgerufen am Mai 18, 2013, von: http://www.cichlidae.com/article.php?id=360&lang=de.