Bull trout See Trout

Burbot Common name of Lota lota (Linnaeus, 1758), a freshwater gadid with a circum-arctic distribution, and an affinity for the bottom of deep lakes and large rivers (Cohen et al. 1990, p. 53).

CD discussed the eyes and swimbladder of this fish: In the depths of the ocean, & in deep & dark wells some Crustaceans [...] are blind.4 Now though I am not aware that any Fish inhabiting very deep water is normally blind, yet it seems to bear on the above facts, that the Gadus lota5 at the depth of 100 fathoms has its air-bladder frequently atrophied, often accompanied by total blindness. (Big Species Book, p. 296; n. 4 refers to Forbes (1851), p. 254; n. 5 to Jurine (1825), p. 149).

Note that CD defines 'atrophied' as Arrested in development at a very early stage (Origin VI, p. 431), which completely overlaps with his definition of'aborted'; see Lungfishes.

Burrfishes (I) Fishes of the Family Diodontidae, also known as porcupine fishes, the latter name referring to the spines covering their bodies, which stand erect when their owners are inflated.

Quoy and Gaimard (1824, pp. 2012) reported that the widely distributed

Indo-Pacific Birdbeak burrfish Diodon caeruleus [now Cychlichthys orbicularis (Bloch 1785)] was not consumed, and that in Guam, people considered it "venomous". They also speculated that this may be due to its consumption of coral, confirmed by opening the stomach of what must have been a large specimen, containing "one pound of rocky debris". CD summarized their account by stating that it has sometimes been thought (vide Quoy in Freycinet's Voyage), that coral-eating fish were poisonous, then used a 'parrotfish to test the generality of the proposition. We now know that burrfishes are indeed dangerous, owing to toxins in their gonads and intestine (Halstead 1978; see also Puffers).

CD collected three species of burrfish himself. One was the Globefish Diodon nicthemerus (Cuvier, 1818, p. 135), misspelled nycthemerus in Fish (p. 150). As the label of the specimen was lost, the sampling locality is unknown, but it can be assumed to have been 'King George's Sound, as the species is 'endemic to southern Australia (Coleman 1980, p. 296), and CD collected Australian fish only at that location.

Next are the Striped burrfish, Cyclichthys schoepfi (Walbaum, 1792), formerly Diodon rivu-latus, collected by CD on the shore of the Rio Plata, at 'Maldonado, Uruguay (Fish, p. 150; Fish in Spirits, no. 723), and the Bridled burrfish Cyclichthys antennatus (Cuvier, 1816), formerly Diodon antennatus.

C. antennatus is a shallow-water species, found mainly on seagrass beds (Randall 1996). CD collected a specimen of this species in 'Bahia, Brazil (Fish, p. 151; Fish in Spirits, no. 132), and upon his return to England, wanted it identified: Will you ask Leonard 'Jenyns whether he can tell me the genus of little fish, which I believe is a Diodon (132). - It is the only fish I care about the name; but I am far from certain, whether it is one of those preserved or whether it was thrown away (Correspondence to J. S. 'Henslow, July 12/13,1837).

The reason CD was pressing Jenyns for the name of his 'Diodon' was his wish to include a story, presented below, in the 'Journal of the Beagle, the book he was then working on. Also, true to his habit of recycling the same story through his various publications (see, for example, entries on Megatooth shark, or Pike), CD suggested to Jenyns he could incorporate elements of his Diodon story into Fish: You willfind in my Journal p. 13 & 14 some account of the habits of the Diodon (Nor. 132) - & I send the notes, I made at the time, which very briefly relate to 'colour. - You can extract shorten, & alter anything you think worthy of insertion. -I would have corrected a copy, but I really do not know whether any, or how much, is worth repeating. - Please use your own judgement. -& bring with you, when you come to town, the three original pages ofnotes (Correspondence Nov. 1841).

Burrfishes (II) Here are the notes CD wanted Jenyns to use:

March 10th a Diodon was caught swimming in its unexpanded form near to the shore. -Length about an inch: above blackish brown, beneath spotted with yellow. On head four soft projections; the upper ones longer like the feelers of a snail. - Eyes with pupils dark blue; iris yellow mottled with black. - The dorsal 'caudal & anal fins are so close together that they act as one. These as well as the Pectorals which are placed just before branchial apertures, are in continuous state of tremulous motion even when the animal remains still. - the animal propels its body by using these posterior fins in same manner as a boat is sculled, that is by moving them rapidly from side to side with an oblique surface exposed to the water. - The pectoral fins have great play, which is necessary to enable the animal to swim with its back downwards. -

When handled a considerable quantity of fine "Carmine red" fibrous secretion was emitted from the abdomen & stained paper, ivory &c of a high *colour. - The fish has several means ofdefence it can bite & can squirt water to some distance from its Mouth, making at the same time a curious noise with its jaw. - After being taken out of the water for a short time, & placed in again, it absorbed by the mouth (perhaps likewise by the branchial apertures) a considerable quantity of water & air, sufficient to distend its body into a perfect globe. - This process is effected by two methods: [swallowing the air and water] & then forcing it into the cavity of the body, its return being prevented by a muscular contraction which is externally visible [and] by the dilatation of the animal producing suction. - The water however I observed entered in a stream through the mouth, which was wide open & motionless; hence this latter action must have been caused by a kind of suction. When the body is thus distended, the papilla with which it is covered become stiff, the above mentioned tentacula on the head being excepted. - The animal being so much buoyed up, the branchial openings are out of water, but a stream regularly flowed out of them which was constantly replenished by the mouth.

After having remained in this state for a short time, the air & water would be expelled with considerable force from the branchial aperture & the mouth. - The animal at its pleasure could emit a certain portion of the water & I think it is clear that this is taken in partly for the sake of regulating the specific gravity of its body. - The skin about the abdomen is much looser than that on the back & in consequence is most distended; hence the animal swims with its back downwards. Cuvier doubts their being able to swim when in this position; but they clearly can not only swim forward, but also move round. -this they effect, not like other fish by the action of their tails, but collapsing the *caudal fins, they move only by their pectorals. - When placed in fresh water seemed singularly little inconvenienced. (Zoology Notes, pp. 25-6, which also give details on CD's corrections of his notes, not reproduced here).

Jenyns did follow CD's suggestion to include some of his field notes, and included in Fish (p. 151) a paragraph on the behavior of 'Diodon antennatus', and a reference to pp. 13-14 of CD's Journal, both rare features in taxonomic books, then even more than presently devoted almost exclusively to the cataloguing of pickled corpses.

Note, however, that burrfishes are unlikely to have developed the ability to blow water as a defence tactic. [Which shark would be impressed by having water blown at its face?] Rather, this behaviour is a foraging technique, used to excavate invertebrates from sandy or muddy bottoms (Wainwright and Turigan 1997). Moreover, it is this behaviour, and its anatomical correlates, which provided the basis for the evolution ofinflation in burrfishes.

Burrfishes (III) And here is the story CD was so eager to tell:

One day I was amused by watching the habits ofa Diodon, which was caught swimming near the shore. This fish is well known to possess the singular power of distending itself into a nearly spherical form. After having been taken out of water for a short time, and then again immersed in it, a considerable quantity of both water and air was absorbed by the mouth, and perhaps likewise by the branchial apertures. This process is effected by two methods; the air is swallowed, and is then forced into the cavity of the body, its return being prevented by a muscular contraction which is externally visible; but the water, I observed, entered in a stream through the mouth, which was wide open and motionless: this latter action must, therefore, depend on suction.

The skin about the abdomen is much looser than that of the back; hence, during the inflation, the lower surface becomes far more distended than the upper; and the fish, in consequence, floats with its back downwards. Cuvier doubts whether the Diodon, in this position, is able to swim; but not only can it thus move forward in a straight line, but likewise it can turn round to either side. This latter movement is effected solely by the aid of the pectoral fins; the tail being collapsed, and not used. From the body being buoyed up with so much air, the branchial openings were out of the water; but a stream drawn in by the mouth, constantly flowed through them.

The fish, having remained in this distended state for a short time, generally expelled the air and water with considerable force from the branchial apertures and mouth. It could emit, at will, a certain portion of the water; and it appears, therefore, probable, that this fluid is taken in partly for the sake of regulating its specific gravity. This diodon possessed several means of defence. It could give a severe bite, and could eject water from its mouth to some distance, at the same time it made a curious noise by the movement of its jaws. By the inflation of its body, the papilla, with which the skin is covered, became erect and pointed.

But the most curious circumstance was, that it emitted from the skin of its belly, when handled, a most beautiful carmine red and fibrous secretion, which stained ivory and paper in so permanent a manner, that the tint is retained with all its brightness to the present day. I am quite ignorant of the nature and use of this secretion. [I have heard from Dr. Allan of Forres, that he has frequently found a Diodon, floating alive and distended, in the stomach of the *shark; and that on several occasions he has known it eat its way not only through the coats of the stomach, but through the sides of the *monster, which has thus been killed. Who would ever have imagined that a little soft fish could have destroyed the great and savage shark?] (Journal, Feb. 29, 1832. Cuvier doubts is an understatement: Cuvier (1829) asserts that inflated Diodon cannot control their movements, but his authority is another author, as unlikely as Cuvier himself to have seen the fish when alive. So we should trust CD's direct observations. Dr J. Allen of Forres provided much information to CD when he completed *Coral Reefs, which cites his MS thesis, based on coral transplantation experiments along the east coast of Madagascar, in 1830-2.)

Randall (1996) describes for this species, as well, "a curious red secretion [which] may colour large regions ofthe body, especially ven-trally" (p. 348). At my request, he amplified his description as follows: "I remember the red secretion of C. antennatus, but I do not know the function. If I were to have a live one in my hands today and it produced the secretion, I would taste it. In this way I and Japanese colleagues first determined the skin toxin ofsoap-fishes and clingfishes" (John E. Randall, Bishop Museum, Hawai'i, pers. comm., May 1997). I have not followed up on this matter, as I did not want to put Jack at risk.

Finally, I must confess that I have been so far unable to corroborate the Jonahesque story about a burrfish chomping its way out of a shark's stomach.

Butterfishes Members of the Family Stromatei-dae, with about a dozen species. These coastal, smooth-looking fishes are very tasty (pers. obs.), which may be the reason for their common name (or maybe it is because their flesh is somewhat soft?). One of two species sampled by CD, Stromateus stellatus Cuvier, 1829 was, at *Chiloe, at the extreme southern end of its *range. Jenyns described it as Stromateus macula-tus, a *synonym (Fish, p. 74; see also Fish in Spirits, nos. 788,1146).

Butterflyfishes Members of the Family Chaeto-dontidae, known for their lively colours, and for the complete dependence of many of their long-snouted species on specific, live corals for their food, just as some butterflies with a long "proboscis" rely on specific flowers for their food (see Darwin 1877a).

The Threadfin butterflyfish, Chaetodon auriga Forsskal, 1775, which complements its diet of corals with other small *zoobenthos organisms (Hobson 1974; Sano et al. 1984), was collected by CD in April 1836 in the *Cocos Islands, and described as Chaetodon setifer in Fish (pp. 61-2).

Calendar Short title of A Calendar of the Correspondence ofCharles Darwin, 1821-1882, a list of all the letters so far identified that were authored or received by CD.

The annotations in the Calendar, compiled by Burkhardt etal. (1985a) as a first step toward their monumental * Correspondence of Charles Darwin, were used here to infer the contents of letters not included in the twelve volumes of the Correspondence so far published, and the total number of *words in CD's letters. Letters not seen, but cited from the Calendar, are identified here by their number.

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