Carcharias megalodon See Megatooth shark

Carp The common carp Cyprinus carpio (Linnaeus, 1758), one of the few fishes that are truly domesticated for aquaculture (Balon 1995a), a reason for their morphological variability.

CD commented on this: A *species may be highly variable, but distinct *races will not be formed, if from any cause selection be not applied. It would be difficult to select slight *variations in fishes from their place of habitation; and though the carp is extremely variable and is much attended to in Germany, only one well-marked race has been formed, as I hear from Lord A. Russell, namely the spiegel-carpe; and this is carefully secluded from the common scaly kind. On the other hand, a closely allied species, the *goldfish, from being reared in small vessels, and from having been carefully attended to by the Chinese, has yielded many races. (Variations II, p. 222; 'Spiegelkarpfen' [mirror carp], or, as CD put itlooking-glass carp, is so named because it has only a few, large, shiny scales on its chest and back; Russell's letter to CD, correcting a statement in the first edition of Variations, was sent on May 19,1873; *Calendar, no. 8915).

Lord Arthur Russell's studies in Germany (Tort 1996, p. 3754) may not have been that deep, as he misled CD. There were, at the beginning of the nineteenth century in Germany, at least two well-established 'races' of carp besides that mentioned above (Balon 1995b), namely the 'line' carp, with a single row of pectoral scales along the body, and the 'leather' or 'naked'carp, entirely wanting scales.

Carp, Crucian Common name of Carassius caras-sius (Linnaeus, 1758), Family *Cyprinidae. CD mentions the ability of Crucian carp to hybridize with a close relative, C. gibelio (see Carp, Prussian).

Carp, Indian Members of the Family Cyprinidae, important in South Asian aquaculture.

CD noted that: in India several species of freshwater fish are only so far treated artificially, that they are reared in great tanks; but this small change is sufficient to induce much variability13. (Variations II, p. 246: n. 13: McClelland on Indian Cyprinidae, Asiatic Researches, vol. xix, part ii, 1839, pp. 266, 268, 313).

The relevant quotes, from McClelland (1839), are as follows: "Cirrhinus rohita var. attains a large size in Assam, and is probably the true Ruee of the natives. That which is figured by Buchanan is as far as I have seen a small fish, though the larger kind which I have figured would seem to be the one he has described. This as well as the preceding species present so many *varieties, probably the result of artificial means resorted to for their propagation; from their value as an article of food, that it is difficult to define their true characters." (p. 266, footnote; for 'Buchanan,' see Hamilton 1822).

"They correspond with the species named by Buchanan, Cyp. curchius, C. cursa and C. cursis, but I cannot altogether reconcile them with his descriptions; they appear to me to be varieties resulting from domestication" (p. 268, referring to what is now Labeo rohita (Hamilton, 1822)).

"Cyp. rohita, Buch. Ruee of the natives; no less celebrated in India than the *Carp in Europe. It is the fish described by Buchanan, though not the one he has figured as the Ruee, the principal difference being in the form of the mouth. The various slight modifications ofform under which the Ruee appears, prove the extent to which this species must have, at one period, been propagated in India. It is one of the largest and most abundant fishes in all parts of the country." (p. 313, in figure legend).

Returning to the CD quote, we note, with Eknath and Doyle (1990), that in India, as in most other parts of the world, traditional aquaculture practices usually lead to inbreeding, i.e. to less variability than occurs in wild stocks...

Carp, Prussian Common name of Carassius gibelio (Bloch, 1782), a member of the Family *Cyprinidae, originally from East Asia, and now established in Eastern Europe.

CD comments on specimens of this Prussian carp hybridizing with, and also somehow changing into Goldfish (Carassius auratus):

I will now give a single case in Fish taken from Bronn;3 the Cyprinus gibelio & carassius have generally been considered distinct species, for they differ in almost every part in proportion, as shown by the table given by Bronn; but Eckstrom narrates that the offspring of the C. carassius removed from a large lake into a small pond, assumed an intermediate form; & on the other hand the offspring from C. gibelio from a small pond turned into alarge lake 40-50years before, had become changed into C. carassius. (Big Species Book, p. 124; Eckstrom 1840; n. 3, referring to Bronn 1843, reads: Ges[ch]ichte der Natur. B. 2. s. 106; note CD's use of'B.' for Band or volume, and's' for Seite or page, as he usually did for German references. Remember: CD was not xenoglossophobic!)

Given the complex taxonomy of European members of the cyprinids (see FishBase), and the fact that Prussian carp is one of the few existing species offish practising parthenogenesis, their having changed into Crucian carp (C. carassius) is probably due to misidentifications. However, their forming *hybrids, with intermediate characteristics, maybe possible. Moreover, Prussian carp can be seen as 'changing into' another species, if one accepts, with several authors (see FishBase), that Prussian carp is a *subspecies of Goldfish, with the name Carassius auratus gibelio (Bloch, 1782).

Cartilaginous fishes A group of fishes also known as 'Chondrichthyes' (meaning the same thing) and including the *sharks, *rays, and *chi-maeras, all appearing in CD's writings.

Their lack of bone tissue, previously thought to be a primitive condition, is now seen as secondary, since their ancestors (Devonian placo-derms) had bodies covered by a bony armour. Indeed, the fine 'teeth' covering the skin of sharks are remainders of this armour.

In the 1820s, when young CD was a student of medicine in *Edinburgh, the *Lumpfish Cyclopterus lumpus, though a *bony fish, was still *lumped with the Chondrichthyes, owing to its cartilaginous body cover (see Cuvier (1828) for a review of early 'classifications of fishes). This explains the conundrum faced by the young CD when he dissected this fish (see also Seeing).

Caspian Sea A large body of brackish water, surrounded by Russia, Turkmenistan, Iran, and Uzbekistan.

A remnant of the ancient Tethys Sea (see Distribution), the Caspian Sea was repeatedly connected to the Sea of Aral and to the Black Sea, forming a large Pontocaspian Sea, and is now in deep ecological trouble (Stone 2002). The Caspian Sea was subjected to large changes of salinity in the course of its long history, and as a consequence, its 'fauna consists ofseveral components: (1)a relict brackish-water fauna (Pontocaspian 'endemics, e.g. the Caspian 'lamprey Caspiomyzon wagneri Kessler 1870); (2) a Mediterranean element (e.g. 'mullets); (3) an Arctic-Baltic element (mainly crustaceans); and (4) numerous freshwater species of the Pontacaspian region (Remane 1971, pp. 143-57).

The origin of the Caspian fauna were in CD's time already a matter of considerable debate, and he noted on this: Annals of. Natural. History. p. 135. Natural History of the Caspian. Fresh Water Fish!!?Adapted to salt water? -peculiar species, crabs & molluscs few. - ? are not some same - what is the alliance with the Black sea. - it would be ocean, what is land to continent - Original Paper, worth studying. (Notebook D, p. 379; Eichwald 1839, p. 135); Decemb. 21th. - L'Institut 1838. p. 412.1 M. Eichwald has published Fauna of Caspian. -2 fishes fresh water kinds. (yet living in the salt?.) - very few animals of any kind - Fauna, mustbe very curious. - (NotebookE, pp. 418-19; n. 1 refers to Eichwald 1838; n. 2 to Eichwald 1834-8).

Some jottings on modifications of the shell of Cardium from tertiary strata in the Crimea may be viewed as related to this: Bulletin Geologique April 1837, p. 216 Deshaye on changes in shells from salt & F. Water - on what is species. very good Has not Macculloch written on same changes in Fish? (NotebookB,p. 184; Deshaye 1836; Macculloch 1824).

Catadromy(-ous) Referring to fish that migrate from freshwater to the sea to spawn, as do 'eels. (See also Diadromy.)

Catalogue Short name for CD's master list of the plants and animals he collected during the voyage of the 'Beagle (Barlow 1933; Porter 1985).

This list, which may be called 'Darwin's Database,' consists of three parts (i.e. red pocket notebooks with soft covers) labelled Catalogue for specimens in spirits of wine (nos. 1-660; 661-1346; and 1347-1529), and three parts labelled Printed numbers (nos. 1-1425; 14263344; and 3345-3907). The numbers, which are the same as in the 'Zoology Notes, refer to the numbers on the labels attached to the specimens, and are arranged in order of their acquisition.

"From this master catalogue and the zoological diary twelve separate classified annotated catalogues were prepared during the summer of1836 so that they could be turned over to naturalists who would be engaged in naming and describing the specimens in their special fields (Sulloway 1982). Some of them were returned to CD when the work was completed, and they are now in the Darwin Archive: DAR 29.1 contains 'Animals,' i.e. mammals; '*Fish in Spirits of Wine'; 'Insecta'; and 'Shells in Spirits of Wine';" (Burkhardt etal. 1985b, p. 547;the words "zoological diary" refer to the 'Zoology Notes, edited by Keynes 2000).

CD's catalogue of specimens, presently on exhibit at CD's family house (Down House), and the annotated lists derived from it provide further illustration ofthe meticulousness with which CD assembled his 'collection, thus justifying his subsequent authorship, in 1859, of a field manual for geologists and biologists.

Catfishes Members of a set of closely related families, all belonging to the Order Siluriformes, formerly a broad 'Siluridae' family. A few species practise *mouth-brooding (and even lower lip-brooding by male armored catfishes, or Loricariidae), some function as *cuckoo-fish, and all species are whiskered, with some South American species sporting *beards as well.

At least four species of catfish were sampled by CD, and three are described in *Fish (p. 11014). One, based on a specimen taken from a running brook near *Rio de Janeiro, was Pimelo-dusgracilis Valenciennes 1836, i.e. it had already been described (see Jenyns' note in Fish in Spirits, no. 180). The other two were new: P. exsudans Jenyns 1840 (also from Rio?) was found in the *collections without labels (Fish in Spirits, after no. 181), and Callichthys paleatus (Fish, p. 11314; Another specimen from same site; Fish in Spirits, nos. 181/182). Of these new species, the former is now called Rhamdella exsudans (Jenyns, 1840), and assigned to the long-whiskered cat-fishes (Family Pimelodidae), along with what is now Pimelodella gracilis. The third, now Carydo-raspaleatus (Jenyns, 1842) is presently assigned to the Callichthyidae, a family of armoured cat-fishes. Additionally, Jenyns noted "One of the Siluridae - very bad & thrown away" (Fish in Spirits, no. 1244). And since we are at it, we may mention item no. 1511 in CD's list of Specimens not in Spirits, consisting of the Pectoral bone from the Armado. Fish (Zoology Notes, p. 393), sampled somewhere near Buenos Aires in August 1833.

After this boring bit, here is what CD has to say about catfish-ing: Owing to bad weather we remained two days at our moorings. Our only amusement was catching fish for our dinner: there were several kinds, and all good eating. A fish called the 'armado' (a *Silurus), is remarkable from a harsh grating noise it makes when caught by hook and line, and which can be distinctly heard when the fish is beneath the water. This same fish has the power of firmly catching hold of any object, such as the blade of an oar or the fishing-line, with the strong spine both of its pectoral and dorsal fin. (Journal, Oct. 12, 1833; also in Fish in Spirits, no. 745; see also Sounds).

CD has more stories about catfishes. Thus, he notes in Notebook B (p. 205) that a Fish which emigrates over lands is a siluris, p. 123 (referring to Kirby 1835); On male fishes hatching the ova in their mouths, see a very interesting paper by Professor Wyman, in Proc. Boston Soc. of Nat. Hist., 15 September 1857; also Professor Turner in Journal ofAnat. andPhys., 1 November, 1866,p. 78.Dr*Gunther has likewise described similar cases. (Descent!,p. 163,n. 30, and p. 345, n. 38; Gunther 1868a).

The item on male fish hatching ova in their mouths may be found on pp. 268-9 of the Proceedings of the Boston Society of Natural History, Vol. VI, pertaining to September 16, 1857, and was presented by its President (i.e. Jeffrey Wyman). There, we read that "some species of fishes from the Surinam River" were exhibited, belonging to a species of 'Bagre' -which indeed practises buccal incubation. However, the original text states that it is the females which incubate the *eggs: "[d]uring the months of June, the females have their mouths filled with eggs, and the young may be seen in all stages of formation, if a large number of individuals is examined. There are at least four species of Siluroids which have this habit."

Turner (1866), based on Wyman (1859), provides more details on Wyman's fishes: they were obtained from a market in Paramaribo (Dutch Guyana, now Surinam) and the "eggs were always in the mouth ofthe males, and were not bruised, and none were found in the stomach". Turner (1866) also cites Gunther (1864, Vol. 5) to the effect that male specimens of 'Arius fissus' - now Cathorops spixii (Agassiz, 1829) -sampled in Cayenne, French Guyana, had about 20 pea-sized eggs in their mouth and gill-chambers. Turner then goes on documenting another case of male *mouth-brooding in 'Arius boakeii' from 'Ceylan' (Sri Lanka), simultaneously describing it as a new species.

Now we should digress a bit: Turner (1866) cites Wyman (1857) as having been presented on the September 15, just as CD cites it. Yet these proceedings are dated September 16, 1857. Hence, it appears that CD did not actually see Wyman (1857), but cited it from Turner (1866). This would explain why CD did not pick up the original (and erroneous) reference to female mouth-brooding Bagre. Turner's error appears to be due to Wyman (1859, p. 5) having given September 15, 1857 as the date in question. Hence, we may have here a case of a chain of authors (including CD and Tort (1996), p. 4709) citing a paper they have not seen (as I sometimes do in this book, as well). Let's add, to complete this story, that the true publication date of Turner '1866' is actually 1867.

Transcription errors often lead to results of this sort, though their specific nature differs among disciplines. Thus, geneticists now can track mutations (a form of transcription error) when these induce diseases in families with well-established genealogies (one of the few instances where aristocrats' exaggerated sense of themselves serves a useful purpose). Similarly, philologists have developed methods for tracking manuscripts through transcription errors (even monks are not perfect!).

Caudal (fin) Of or belonging to the tail (Origin VI, p. 431). In fish, the thing 'of the tail' that comes most readily to mind is the caudal fin, usually homocercal (equal-lobed), but sometimes *het-erocercal, as in larval *Gar-pike, or in *sharks.

This entry could end here, given some witty coda, but won't, as there is more to fish tails than their giving a finish to their owner. Rather, I will use this opportunity to mention that caudal fins can be used to infer the metabolic rate oftheir owners. Thus, the spoon-shaped, broad caudal fins of, for example, *dragonets (Fig. 9) indicate low metabolic rates, whereas more open, forked tails such as in *jacks (Fig. 18) and especially in tuna, indicate high consumption of *oxygen. This difference in shape can be easily quantified (through aspect ratios, as used to describes the wings of airplanes) and used to estimate food consumption and related processes in fish (see Palomares and Pauly 1998; Pauly etal. 2000 - DNA box).

Finis.

Cavefishes Both an ecological group (fishes that live in caves) and a Family, the Amblyopsidae.

Both kinds of cavefishes interested CD, who after having read an article by Silliman (1851) asked for further information: What I want to know is, whether any of the Crustacea, spiders, insects (flies*beetles, crickets &c) & Fish belong to the American type (Has not *Agassiz noticed the Fish?) ie to genera or sections of genera, found only on the American continent. - I shd be most grateful for any, the least, information on this head (Correspondence to J. D. Dana, July 14,1856).

CD felt that the distribution of cave organisms supported his cause: I have little doubt that like the fish Amblyopsis & like Proteus in Europe, these insects are 'wrecks of ancient life' or living fossils,' saved from competition & extermination (Correspondence to C. *Lyell, Jan. 10,1860; see also Extinction).

This opinion later went into print: Far from feeling surprise that some of the cave-animals should be very anomalous, as *Agassiz has remarked in regard to the blind fish, the Amblyopsis, and as is the case with the blind Proteus with reference to the reptiles of Europe, I am only surprised that more wrecks of ancient life have not been preserved, owing to the less severe competition to which the scanty inhabitants of these dark abodes will have been exposed. (Origin VI, p. 112; Agassiz 1851).

Moreover, CD felt that, as in the case of island species, the variety of cave organisms on different continents, in spite of the similarity of their habitat, argued directly against

'creationism: With respect to the cave animals, reflect on the cave-Rat, the fish Amblyopis & Astacus in America - the Proteus in caves of Europe, & you will admit that on creation doctrine, there has been surprising diversity for such similar habitations (Correspondence to A. Murray, May 5,1860).

The Amblyopsis in question, first described from Mammoth Cave, Kentucky, USA, is the troglodyte 'mouth-brooding Northern cave-fish Amblyopsis spelaea DeKay, 1842, one of about a dozen species of Amblyopsidae, the others consisting of epigean, troglophile and more troglodyte species, which thus represent the whole gamut of adaptations for cave life (Poulsen 1963; or Nelson 1994, pp. 221-2). The Family occurs only in North America, and its troglodyte forms have no predators, as CD suggests above. Moreover, they are not anomalous, i.e. they are not the 'aberrant relatives of the 'guppies which Agassiz (1851) suggested they were. However, the amblyop-sids are not a particularly 'ancient' group, i.e. not wrecks of ancient life. The score here is CD 3 :Agassiz 1.

On the other hand, Agassiz' patronizing call for "young American naturalists" to devote their lives to studying the origin of blindness in cavefishes has been followed up (if not only by 'young Americans'), with rather astounding results. This resolved the inconsistencies in CD's uses of the concepts of 'uselessness' and 'simple disuse,' as occurs in the 'BigSpecies Book (p. 295): in the caves of Kentucky there are, also, blind insects crustaceans, fish, & a Rat. The various stages of abortion of the eyes in these Kentucky animals is very curious: some have no trace of an eye, some have a rudiment, & the Crustacean has the footstalk for the eye without the organ, - it has the stand for the telescope without the instrument. Now as the existence of useless eyes could hardly be injurious to these animals, I should attribute their blindness to simple disuse.

As it turns out, maintaining functional eyes in an environment where vision provides no selective advantage is injurious, because this costs metabolic energy, which may better be used elsewhere (see Oxygen), e.g. for olfactory and tactile receptors and the associated parts of the 'brain (Poulsen 1963). Thus, it is not simple disuse that causes the eye of successive generations of cavefish to atrophy, but competitions with variants whose fitness is high because of their atrophied eyes. This is also the reason why the degeneration of the eyes, well studied in Astyanax mexicanus, a 'characin, follows highly predictable steps (G^nermont et al. 1996), and stops when it starts compromising other, ontogenetically related, and still useful organ systems.

Caviller ABritish term for a person who raises irritating and trivial objections (to cavil: to find fault where unnecessary, to complain, criticize, carp).

CD had his fill of those (Ellegard 1958;Kogan 1960; see also the many scurrilous reviews in Hull 1973, itself scurrilously reviewed by Rudwick 1974), and this affected his response even to good news: M.r Walsh has evidently been a close & good observer of Fishes. - What he says about the Sea - 'Trout in the Loch is very curious; & it would be very desirable that some professed Ichthyologist should examine these Trout. - It would make a good case for me. - But until thus examined & pronounced on, cavillers would simply deny that the fish was a sea-trout (Correspondence to G. R. 'Water-house, Nov. 12,1861).

Unfortunately, we do not know who Mr Walsh was, nor what his observations were, which some might cavil about.

CD Abbreviation of'Charles 'Darwin', used by the editors of his 'Correspondence, and other scholars, and also used here.

'CD' is also used for 'CD-ROM' (Compact Disc, Read Only Memory), i.e. a medium for mass storage of digitized text and figures that is eminently suited to making important works, such as Darwin's, accessible to a wide audience.

A 'Darwin CD-ROM,' edited by Ghiselin and Goldie (1997), is available which contains the full text of (i) most of CD's major books ("Journal*Zoology, *CoralReefs, Cirripedia, *Origin, Orchids, *Descent, *Expression), (ii) a few of his shorter papers (including Strickland et al. 1843), and (iii) Ghiselin (1969). The CD-ROM also contains a Darwin Biographical Dictionary, a Darwin Bibliography, pictures, and some fluff (details in Provine (1997) and at www.lbin.com).

I used this CD-ROM extensively when completing this book. On the other hand, I contributed to it the file of*Fish, so there was some give and take.

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