Cichlid

Cichlid (Cichlidae), a family of Acanthopterygian fishes, related to the perches and wrasses, and confined to the fresh and brackish waters of Central and South America, Africa, Syria, and India and Ceylon. It has recently assumed special importance through the large number of genera and species, many of them showing extraordinary modifications of the dentition, which have been discovered in tropical Africa, especially in the great lakes Victoria, Tanganyika and Nyasa. About 180 species are known from Africa (with Syria and Madagascar), 150 from America, and 3 from India and Ceylon. They were formerly known under the inappropriate name of Chromides.

These fish are further remarkable for their nursing habits. It was formerly believed that the male takes charge of the eggs, and later the young, by sheltering them in the mouth and pharynx. This may still be true of some of the American species, but a long series of recent observations have shown that this most efficacious parental care devolves invariably on the female in the African and Syrian species. We are now acquainted with a large number of species in which this extraordinary habit has been observed, the number having lately been greatly increased by the collections made in Lakes Tanganyika and Victoria.

L. Lortet had described a fish from Lake Tiberias in which he believed he had observed the male take up the eggs after their deposition and retain them in his mouth and pharynx long after eclosion, in fact until the young are able to shift for themselves, and this fish he named Chromis paterfamilias. A. Günther had also ascribed the same sex to a fish from Natal, Chromis philander, observed by N. Abraham to have similar habits. G.A. Boulenger has since had an opportunity to examine the latter specimen and found it to be a female, as in all other nursing individuals from various parts of Africa, previously observed by himself; whilst J. Pellegrin has acertained the female sex of a specimen with eggs in the mouth presented to the Paris museum by Lortet as his Chromis paterfamilias (= Tilapia simonis). Further observations by Pellegrin on Tilapia galilaea and Pelmatochromis lateralis, by E. Schoeller on Paralilapia multicolor, have led to the same result.

It therefore remains unproven whether in any of the African Cichlidae the buccal “incubation,” as it has been called by Pellegrin, devolves on the male; the instances previously adduced being unsupported by the only trustworthy evidence—an examination of the genital glands.

The relative size and number of the eggs thus taken charge of vary very much according to the species. Thus they may be moderately large and numerous (100 to 200) in Tilapia nilotica and galilaea, larger and only about 30 in number in Paratilapia multicolor, while in Tropheus moorii, a fish measuring only 110 mm., the eggs filling the mouth and pharynx measure 4 mm. in diameter and are only four in number, they being proportionally the largest Teleostome eggs known. In Paratilapia pfefferi, a fish measuring 75 mm., the eggs found in the pharynx were only about a dozen in number, and they measure 2½ mm. in diameter. In Tilapia dardennii, which grows to a length of 240 mm., a score of eggs fills the mouth and pharynx, and each measures 5 to 6 mm. in diameter, an enormous size for so small a fish.

Pellegrin has made the interesting observation on Tilapia galilaea that while the eggs are developing in the bucco-pharyngeal cavity the ovarian eggs are rapidly growing towards maturity, so that a fresh deposition of ova may almost immediately follow the release of the young fishes from maternal care.

(G. A. B.)

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