Cichlidae (I) A very speciose family in fresh and brackish waters of Africa and South America, derived from marine ancestors, and related to the 'wrasses and 'parrotfishes.
The cichlids share with the 'damselfishes the feature of having only one nostril on each side oftheir snout, and this is the reason why, in earlier classifications, they were considered members of a broadly defined 'Chromidae' family (Berg 1958, pp. 254-5).
Some cichlid species, notably among the lepi-dophages ('scale-eaters) display a strong 'asymmetry in the orientation oftheir mouth, which may be bent left or right, thus facilitating lateral attacks (Barlow 2000, p. 36).
The only member of the Family Cichlidae sampled by CD is Cichlasoma facetum (Jenyns, 1842), formerly Chromis facetus, from 'Maldonado, Uruguay (Fish, pp. 104-5; Above, greenish black; the sides paler; slightly iridescent).
Cichlidae (II) CD discussed cichlids at length, as they provided neat examples for 'sexual selection. Thus: In many of the Chromidae, for instance in Geophagus, and especially in Cichla, the males, as I hear from Professor Agassiz,21 have a conspicuous protuberance on the forehead, which is wholly wanting in the females and in the young males. Professor Agassiz adds, 'I have often observed these fishes at the time of spawning when the protuberance is largest, and at other seasons when it is totally wanting, and the two sexes show no difference whatever in the outline of the profile of the head. I never could ascertain that it subserves any special function, and the Indians on the Amazon know nothing about its use.' These protuberance resemble, in their periodical appearance, the fleshy caruncles on the heads of certain birds; but whether they serve as ornaments must remain at present doubtful. (Descent II, p. 340; n. 21 reads: See also A Journey in Brazil, by Professor and Mrs. Agassiz, 1868, p. 220); the protuberance on the forehead is now called a 'nuchal hump' and appears to be caused by a 'local edema', i.e. the hump is filled with fluid, and probably serves to signal maleness; Barlow 2000, p. 142].
With the various species of Chromids, as Professor Agassiz likewise informs me, sexual differences in colour may be observed, 'whether they lay their *eggs in the water among aquatic plants, or deposit them in holes, leaving them to come out without further care, or build shallow nests in the river mud, over which they sit, as our *Pomotis does. It ought also to be observed that these sitters are among the brightest species in their respective families; for instance, Hygrogonus is bright green, with large black ocelli, encircled with the most brilliant red.' Whether with all the species of Chro-mids it is the male alone which sits on the eggs is not know. It is, however, manifest that the fact of the eggs being protected or unprotected by the parents, had had little or no influence on the differences in colour between the sexes. It is further manifest, in all the cases in which the male take exclusive charge of the nests and young, that the destruction of the brighter-coloured males would be far more influential on the character of the *race, than the destruction of the brighter-coloured females; for the death of the males during the period of incubation or nursing would entail the death of the young, so that they could not inherit his peculiarities; yet, in many of these very cases the males are more conspicuously coloured than the females. (Descent II, pp. 345-6; based on a letter from *Agassiz dated July 22, 1868; Calendar no. 6286; see also Sexual selection).
An important group of cichlids are those of the Great Lakes of Africa, felt by many ichthyologists to be the aquatic counterparts of *Darwin's Finches, owing to their rapid *spe-ciation. Hence the title of a recent, if mis-leadingly titled, book on fish collecting on the shore of Lake Victoria, Darwin's Dreampond (Goldschmidt 1996), which does not seriously explore any issue raised by CD's work. These issues, on the other hand, are masterfully handled in Fryer and Iles (1972), Greenwood (1974), Kingdon (1989), and Barlow (2000), and regularly updated taxonomic and biological accounts of the many cichlid and other fish species involved here may be found in *Fish-Base.
Ciguatera A form of ichthyotoxicity due to the consumption of coral reef fishes containing toxins secreted by a dinoflagellate Gambierdiscus toxicus (Lewis and Holmes, 1993). Herbivorous fishes ingest this toxin and remain unaffected by it, but concentrate it in their gut and muscle tissues. Further concentration occurs when predatory fish consume ciguatoxic herbivores.
CD appears to have consumed at least two kinds of fish now known to be often ciguatoxic. In the case of the *barrow cooter (barracuda), he clearly did not know of the potential danger their consumption represents (De Sylva 1963, pp. 128-53). However, in the *Cocos Islands he appears to have deliberately consumed a *parrotfish to test whether it contained poison. This test was dangerous, as parrotfishes are frequently ciguatoxic (Auerbach 1991; Bagnis et al. 1974; Chungue et al. 1977). Indeed, they contributed 12% of more than 500 cases attributed to fish in the ciguatera database assembled by the Secretariate of the Pacific Communities, Noumea, New Caledonia (Dalzell 1993), and incorporated in *FishBase.
Was this article helpful?