Crenilabrus spp See Wrasses

Cretaceous

Cretaceous

Fig. 6. Creole perch Percichthys trucha, Family Percichthyidae, described as Perca laevis in Fish (Plate I). Hawkin's lithograph is based on a specimen found dead on a bank of the Santa Cruz, River, Patagonia, Argentina.

Creole perch Common name of Percichthys trucha (Valenciennes, 1833), a species of temperate bass (Percichthyidae), found in Andean streams in Chile and Argentina.

A specimen pale yellowish brown, with dark mottlings was "found dead by Mr Darwin, high up the river of Santa Cruz, in South Patagonia," and described as Perca laevis (Fish, pp. 1-4; Fish in Spirits, no. 947; Fig. 6). The low productivity of the Santa Cruz River (which flows from the Andes nearly straight eastward and discharges into the Atlantic at 50° S) and its banks was noted by both CD and Captain FitzRoy, following an ascent deep into the Patagonian interior, on board three of the Beagle's whale-boats.

Thus, CD wrote that [t]he curse of sterility is on the land. The very water running over the bed of pebbles are stocked with no fish. Hence there are no water-fowl, with the exception of some few geese and ducks (Diary, April 22, 1834). This is confirmed by his Captain (FitzRoy 1837, pp. 123, 126), who "could not have believed that the banks of any large freshwater river could have been so devoid of wood, or so unfrequented by man, beast, bird or fish". Indeed, "only one fish was taken, - [...] which was similar to a trout. Not more than half a dozen live fish were seen, and none that could be caught, either with hook or nets."

Cretaceous A period of the Mesozoic era, lasting from 146 to 65 million years ago, named after its mighty layers of sedimented 'chalk' (Latin: creta) that occur in the United Kingdom, France, and elsewhere in Europe.

In a paper presented before the Geological Society of London on Nov. 1, 1837, CD had suggested that In recent coral formations, the quantity of stone converted into the most impalpable mud, by the excavations ofboring shells and of nereidous animals, is very great. Numerous large fishes (of the genus Sparus) likewise subsist by browsing on the living branches of coral. Thus, "a large portion of the chalk of Europe was produced from coral, by the digestive action ofmarine animals, in the same manner as mould has been prepared by the earth-'worm on disintegrated rock" (see Barrett (1977), Vol. I, p. 53, Note 4). This was neatly rephrased by CD's first cousin Elizabeth Wedgwood, as "your hypothesis of chalk being made by fishes- if fish made Chalk Hill I dont see why 'worms may not make a meadow" (Correspondence, Nov. 10,1837).

However, William Buckland, in his referee's report to the Geological Society of London, to which CD's paper had been submitted for publication, recommended "that the Author be advised to withdraw the passage relating to the origin of Chalk - as introducing very disputable matter into a paper that is otherwise unexceptionable" (Correspondence, March 9, 1838). Though he saw Buckland as a vulgar and almost coarse man (Autobiography, p. 102), CD had no option but to drop this hypothesis from the published version of his talk (Darwin 1840). It was a good idea, as chalk consists almost exclusively of foraminiferan shells. However, he left this bit in the first (though not the second) edition of the Journal (April 6,1836; see Parrotfishes).

The other error to be noted here is that the fish in question should be 'parrotfishes (Scarus),

Cuckoo-fish not porgies (Sparus), an error also popping up elsewhere (see Porgies; Geology).

Croaker(s) My trusty Random House Dictionary defines a 'croaker' as a person who grumbles, or forebodes evil. Thus CD, when complimenting *Huxley on his editorship of a new series of the Natural History Review, noted I am rather a croaker & I do rather fear that the merit of the articles will be above the run of common readers & subscribers. (Correspondence, Jan. 3, 1861).

However, this is not the reason why we have croakers here. Rather, our main croakers are fishes of the Family Sciaenidae. CD sampled several species of this widespread group, though all in South America, and we shall take stock of these by moving clockwise around that continent.

First we have Otolithus guatucupa, now Cynoscion striatus (Cuvier, 1829) and Corvina adusta, now Ophioscion adustus (Agassiz, 1831), both based on specimens from *Maldonado, Uruguay (Fish pp. 41-2; Fish in Spirits, nos. 458, 694, 695). This is followed by the Southern king croaker Umbrina arenata, from both Maldonado and *Bahia Blanca, Argentina (Fish in Spirits, nos. 392, 714). This species ranges from New York to Buenos Aires, and is now identified as Menticirrhus americanus (Linnaeus, 1758). CD described its colouring as follows: Body mottled with silver and green: dorsal and *caudal fins lead-colour. (Fish, p. 44).

Next is the Snakehead king croaker Umb-rina ophicephala - now Menticirrhus ophicephalus (Jenyns, 1840) - from Coquimbo, Chile (Fish in Spirits, nos. 1218,1220). We conclude with the Peruvian weakfish Otolithus analis Jenyns, 1842, based on a specimen from 'Lima' (i.e. Callao), *Peru (Fish, p. 164).

Our grand tour ends here, since *Prionodesfas-ciatus, sampled in Chatham Island, *Galapagos (Fish in Spirits, no. 1284), and originally, if hesitantly, assigned by *Jenyns to the croaker family (Fish, pp. 46-7,164), turned out to be a *grouper.

Crustacea(-ans) A class of articulated animals, having the skin of the body generally more or less hardened by the deposition of calcareous matter, breathing by means of gills. (Examples, crab, lobsters, shrimp, etc.) (Origin VI, p. 432).

CD sampled numerous crustaceans during the voyage of the *Beagle, and devoted several years of his life to the study of a group of crustaceans, the *barnacles.

In this book, crustaceans occur only in the context provided by CD's writing on fishes. (See Entomostraca, Zooplankton.)

Ctenoid A type of fish *scale, typical of *Acan-thopterygians, characterized by spikes, arranged in comb-like fashion (hence the name) along the trailing edge. Previously used to identify a group of fish roughly overlapping with the Acanthopterygians. (See Trout-perch, and CD's annotations to Agassiz 1850, Pictet 1853-4 and Sedgwick 1850).

Cuckoo-fish Term used by CD to characterize the (then) hypothetical behaviour of a fish that would somehow force another fish to care for its *eggs, as the cuckoo does to other birds.

CD regretted such fish did not seem to exist, especially as J. Wyman (1859) had described buccal gestation in frogs and *catfish: It is quite a pity that there are not fish of the same group with cuckoo-like habits; your fact would so well have explained how the habit might have arisen. (Correspondence., Dec. 3,1860).

As it turns out, fish of the same group with cuckoo-like habits have evolved. The upside-down catfishes Synodontis multipunctatus and S. petricola (Family Mochokidae), *endemic to Lake Tanganyika, lay their small eggs at the same time as their target hosts, *mouth-brooding members of the Family *Cichlidae. The hosts pick up the foreign eggs along with theirs, but the eggs of the *parasites hatch faster, owing to their smaller size (Pauly and

Cyprinidae

Pullin 1988), enabling the newly hatched catfish to consume the host's eggs (Wisenden 1999; Barlow 2000, pp. 205-8).

Moreover, there are many species of fish that parasitize the nests built by other species, though without the eggs of the parasitized species being consumed or ejected. Here, the parasites, often *minnows and other members of the *Cyprinidae, benefit from not having to construct their own nests, nor guard and oxygenate the eggs, activities that lead to exposure to predation (Wisenden 1999).

However, as the review of Wisenden (1999) emphasizes, the evolution of'alloparental care' in fishes is known only in its broadest outline, and much of the job of explaining how the habit might have arisen is still to be done.

Cusk eels Members of the Family Ophidiidae, whose elongated bodies make them look similar to true *eels.

CD notes, concerning the emission of *sound by fish, the cases of two *species of *Ophid-ium, in which the males alone are provided with a sound-producing apparatus, consisting of small movable bones, with proper muscles, in connection with the swim-bladder41. (Descentll, p. 347; n. 41 cites Dufosse (1858a,b, 1862)).

Summarizing earlier writing on this, Gunther (1880, p. 145) confirmed that "[a] peculiar mechanism has been observed in the air-bladder of the Ophidiidae, the anterior portion ofwhich can be prolonged by the contraction of two muscles attached to its anterior extremity, with or without the addition of a small bone".

Cycloid A type of roundish, thin *scale occurring in various teleost groups, notably the *Cyprinidae and the *catfishes, and earlier

*lumped into a single group, the 'Cycloids', defined by their having such scales. The term is used by CD in his annotations to contributions by Agassiz (1850), Pictet (1853-1854), and Sedgwick (1850). (See also Trout-perch.)

Cyprinidae The family of fish comprising the *Carp and their relatives, the *Goldfish, *Min-now, *Roach, *Tench, etc., and of which many species are used for aquaculture, notably in Central Europe, India and China.

Thus, we have CD's observation that many of the carnivorous Cyprinidae in India are ornamented with 'bright longitudinal lines of various tints'.31 Mr. M'Clelland, indescribing these fishes, goes so far as to suppose that 'the peculiar brilliancy of their colours' serves as 'abetter mark for *king-fishers, terns, and other birds which are destined to keep the number of these fishes in check'; but at the present day few naturalists will admit that any animal has been made conspicuous as an aid to its own destruction.

It is possible that certain fishes may have been rendered conspicuous in order to warn birds and beasts of prey that they were unpalatable, as explained when treating of caterpillars; but it is not, I believe, known that any fish, at least any fresh-water fish, is rejected from being distasteful to fish-devouring animals. On the whole, the most probable view in regard to the fishes, of which both sexes are brilliantly coloured, is that their colours were acquired by the males as a sexual ornament, and were transferred equally, or nearly so, to the other sex. (Descent, p. 343, with CD's view on this now being widely accepted; n. 31 reads: Indian Cyprinidae, by Mr. J. M'Clelland, Asiatic Researches, vol. xix, part ii, 1839, p. 230). (See also Altruism; Carp, Indian; Perilampus perseus; Sexual selection.)

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