Batrachus porosissimus See Toadfishes

Bats Flying mammals belonging to two suborders, the Microchiroptera (small bats) and the Macrochiroptera (large bats, i.e. 'flying foxes'), which appear to have evolved independently from non-flying mammals. Flying foxes of the genus Pteropus, which tend to consume fruits, are important pollinators and seed dispersers for the forest communities of tropical oceanic islands (Banack 1998; Neuweiler 2000).

CD wondered [w]ho would have ever supposed that at the present day there should be a Bat feeding chiefly on frogs & occasionally on fish3; or that the fructivorous Pteropus, when put on a floating raft, should take to the water & 'swimpertinaceously after a boat4'. (Big Species Book, p. 342; n. 3 states: Mr *Blyth gives an account of these habits in the Magaderma lyra in India; Blyth 1845, p. 463; M. lyra is a macrochiropterid; n. 4 refers to Lay 1829).

A fishing bat story is reported by Balon etal. (1988, n. 3), who note that Pteropus, in the Comoro Islands, "catch fish in the sea in a similar way to fisheagles". They also mention that they could not find any mention of fishing bats in the literature, wondering if they were "witness to *evolution in making?" In a sense, they were: organisms are constantly evolving, notwithstanding creationists (see also Punctuated equilibrium). Unfortunately, that evolutionary bit has been part of the literature since 1845. The score is Evolution 1: Balon etal. 0.

Bay of Islands Port of call of the *Beagle in New Zealand, December 21-30, 1835, used by CD, among other things, for sampling of marine organisms (Armstrong 1992b, 1993b); in the nineteenth century "a popular, almost cosmopolitan, place for scientific expeditions" (Roberts and Paulin 1997).

The fish CD collected at this location consisted of specimens assigned in Jenyns' *Fish to Trigla kumu (see Gurnards); Acanthoclinus fuscus (see Roundheads); Tripterygion capito (see Blennies); Eleotris gobioides (see Sleepers); and Mesites attenuatus (see Galaxiidae).

Fig. 1. The voyage of the Beagle (1831-6), with arrival and departure dates. The segments north of Recife (Brazil) and south of Montevideo (Uruguay) and Valparaiso (Chile) are simplified; the dates for the Azores differ from standard accounts.

Beagle H.M.S. Beagle was launched in 1820 as a sloop rigged as a brig (doesn't that sound wonderful?), measuring 90 ft (about 30 m), and displacing 235 tons (Freeman 1978, p. 30). On her first surveying voyage to South America, from 1826 to 1830, her Captain was Philip Parker King, father of Philip Gidley *King (King et al. 1836).

It is the second of her voyages (Fig. 1), captained by R. *FitzRoy, which launched the Beagle into immortality: young CD was on board, though not as her *naturalist (Burstyn 1975). Basalla(1963)reviews aspects of that voyage not related to CD, which involved testing the batteries ofchronometers used to infer longitudes (Sobel 1995), and testing "the new Beaufort scale to reckon wind forces around the world" (MacLeod and Rehbock 1994). Many books for specialist and/or lay persons have been published which retrace all or parts of that voyage, and give emphasis to one or other of its adventures. Examples are Campbell (1997); Keynes (1979); Marks (1991), or the superb volume by

Moorehead (1971). None, however, beats CD's own *Journal of the Beagle, extracted from his *Diary.

Hopkins (1969, p. 201) noted that "the Beagle outlasted both Darwin and FitzRoy. For some years after the voyage to South America, it stayed in service, continuing survey work through the 1870's, when steam replaced sail. The Beagle was finally sold out of the Royal Navy a few years after Darwin's death and ended its sailing as a training ship for the Japanese Navy, finally being broken up in 1888."

The log of the Beagle's years with the Royal Navy is kept in the archives of the Public Record Office at Kew, London, as item ADM 51/5043055.

Beards Fish have beards, just like people, but these beards have different origins.

Agassiz (1835) reports that: "from the bearded *Carps to the bearded *Siluri there appears to be a natural transition by means of the bearded *Loaches; [but] it is important to distinguish that in these latter, as well as in the gv

Fig. 2. Head of female (left) and male (right) Bearded catfish Pseudancistrus barbatus, Family Loricariidae (Plecostomus barbatus in DescentII, p. 339). Based on a drawing by G. Ford, under the supervision of A. Giinther. Note bearded male, presumably a result of *sexual selection.

* Carps and other Cyprinida, the beards, as they are called, are merely processes of the skin; while in the *Siluri, the cirri of the angles of the mouth are actually prolongation of the maxillary bones becoming gradually cartilaginous and tapering into thread-like extremities."

Amazingly, CD knew what to add to this prickly matter: In a siluroid fish, inhabiting the fresh waters of South America, the Plecostomus barbatus18 (Fig. 2), the male has its mouth and inter-operculum fringed with a beard of stiff hairs, of which the female shows hardly a trace. These hairs are of the nature of scales. In another species of the same genus, soft flexible tentacles project from the front part ofthe head of the male, which are absent in the female. These tentacles are prolongations of the true skin, and therefore are not *homologous with the stiff hairs of the former species; but it can hardly be doubted that both serve the same purpose.

What this purpose may be, it is difficult to conjecture; ornament does not here seem probable, but we can hardly suppose that stiffhairs and flexible filaments can be useful in any ordi nary way to the males alone. (Descent II, p. 338; n. 18 refers to Gunther (1868a), p. 232).

CD's own beard poses similar questions. Why did he get one, given that, as his wife wrote on April 28,1866, "[h]e was obliged to name himself to almost all of [his old friends], as his beard alters him so much"? (Litchfield 1915, Vol. II, pp. 184-5).

Browne (2002, p. 302) writes "[a] beard like Darwin's was a visual symbol ofthe real seat of Victorian power, and one of the most obvious outward manifestations ofwhat Darwin would soon be describing as factors involved in *sexual selection among humans."

The Great *Linnaeus had earlier provided a similar answer: "God gave men beards for ornament and to distinguish them from women" (cited in Blunt 1971, p. 157), which is not as silly as it appears: in both cases, catfish and humans, it is sexual selection that did the job Linnaeus assigns to God, i.e. ornament does [...] seem probable. Or put differently: female catfish may share with women a liking for males with beards.

Beauty An attribute of organisms - including fishes - often noted by CD. Here is a typical quote: The males sedulously court the females, and in one case, as we have seen, take pains in displaying their beauty before them. (DescentII, p. 342).

Until recently, such a reference - and the many more strewn throughout this book, and CD's books and *Correspondence - would have been dismissed as hopelessly subjective and/or anthropomorphic. Beauty was perceived as being 'in the eye of the beholder', and not accessible to scientific analysis. Yet, both humans and animals have recently been found to prefer mates with bodies that are highly symmetrical. Symmetry indicates that embryonic development proceeded harmoniously (Reimchen 1997), and remained unaffected by diseases (Haldane 1949b), or *parasites. It further indicates that later interactions with

competitors and potential predators did not lead to injuries (Reimchen 1988,1992; Barlow 2000, p. 131) - all indicative of good genes. Thus, in animals, symmetrical bodies correlate with increased fitness. In humans, facial symmetry is a necessary (though not a sufficient) condition for the perception of beauty (Edcoff 1999).

Except for studies of symmetry, studies devoted to the perception of 'beauty' in fishes do not appear to have been conducted to date. However, its perception is likely, as many species combine a high visual acuity with complexly structured colour patterns on their bodies. (See also Asymmetry; Handicap principle; Reproduction; Sexual selection; Social Darwinism).

Beetles See Water-beetles.

Benthos The plants (phytobenthos, e.g. 'kelp) and animals ('zoobenthos) living in, on or just above the sea bottom.

CD sampled zoobenthos on many of his seashore trips, e.g. Collected some marine animals at Quail Island & spent most part of the day examining them. (Diary, Jan. 25, 1832; 'Cape Verde Islands); Walked to the coast West of Quail Island with 'King, & collected numerous marine animals, all of extreme interest. I am frequently in the position of the ass between two bundles of hay; so many beautiful animals do I generally bring home with me. (Diary, Jan. 30,1832).

The 'ass' in question is often attributed to the French scholastic philosopher Jean Buridan (1300-58), a disciple of William of'Occam (yes, he of the Razor): placed at an equal distance between two equally tempting bundles of hay, the animal would starve, unable to choose where to start munching (Schischkoff 1961, p. 75). Of course, no real donkey would be such an ass.

Bering pike An unidentified fish, mentioned in passing by CD in Notebook C (p. 289): If any one is staggered at feathers & scales. Passing into each other let him look at wing & orbit of'penguin & then he will cease to doubt: Scales into Teeth in Bering Pike (Waterhouse).

I could not find any source identifying this fish; even Jordan and Gilbert (1899), who should have known, failed me. Thus a guess, based on three (weak) arguments: CD's Bering pike is a shark, and specifically the dogfish Squalus acanthias, because (i) sharks can be perceived as having their (placoid) scales 'turning into teeth' (Daniel 1922); (ii) S. acanthias is called piked dogfish in Britain; (iii) it is very common in the Bering Sea.

As for (was it George?) 'Waterhouse, he is of no help, because he wrote on mammals and insects, but, as far as I can tell, not on fishes.

Beroe A free-swimming 'comb-jelly' (Cteno-phora), lacking the tentacles common in its phylum, and feeding predominantly on other comb-jellies.

Beroe are part of the 'zooplankton, and mentioned by CD as food of'flying fishes, in a discussion ofpelagic 'food webs.

Big Species Book One of CD's names for the book he was planning to write (and for which he was accumulating notes) when he received, in June 1858, a letter from Alfred 'Wallace accompanying a little paper (Wallace 1858) neatly summarizing 'his' (Wallace's and CD's!) discovery of 'natural selection.

CD immediately abandoned his plan of publishing a Big Species Book, and, after assembling from pre-existing documents the brief text of Darwin (1858), quickly extracted an abstract from the notes accumulated so far. This 'abstract' is 'Origin. The original notes, whose bearing on 'ecology was analysed by Stauffer (1960), have now been edited and published (Stauffer 1975), and all their references to fishes incorporated into this volume.

Bioluminescence The emission of light by living organisms, called phosphorescence by CD.

Here is what he wrote about this: Near Fernando Noronha the sea gave out light in flashes. The appearance was very similar to that which might be expected from a large fish moving rapidly through a luminous fluid. To this cause the sailors attributed it; at the time, however, I entertained some doubts, on account of the frequency and rapidity of the flashes.

With respect to any general observations, I have already stated that the display is very much more common in warm than in cold countries. I have sometimes imagined that a disturbed electrical condition of the atmosphere was most favourable to its production. Certainly I think the sea is most luminous after a few days of more calm weather than ordinary, during which time it has swarmed with various animals. Observing that the water charged with gelatinous particles is in an impure state, and that the luminous appearance in all common cases is produced by the agitation of the fluid in contact with the atmosphere, I have always been inclined to consider that the phosphorescence was the result of the decomposition of the organic particles, by which process (one is tempted almost to call it a kind of respiration) the ocean becomes purified. (Journal, Dec. 6,1833).

CD was lucky with most of his guesses, but not here: far too little biochemistry was known in his days for him to have figured out the outline of the luciferin-luciferase reactions underlying most instances ofbiolumines-cence in bacteria and higher organisms. Indeed, their complex evolution (reviews in Herring 1978) would have been too much for comfort when added to CD's compilation of *difficul-ties for his theory. Moreover, had CD known about planktonic bioluminescence, he would also have needed to find a reason for the organisms in question to advertise their existence and location, and this too would have been exceedingly difficult. Indeed, it is only recently that the hypothesis of Burkenroad (1943) has been developed to the point where it is compatible with *natural selection.

Burkenroad originally suggested that bioluminescent *phytoplankton produce flashes of light when disturbed (usually by herbivorous zooplankton) in order to attract a second-order predator (as do *minnows with their 'Schreckstoff). As stated, this hypothesis did not make much evolutionary sense, since it postulated a behaviour that would not benefit the specific gobbled-up individuals that displayed it. This would require too much *altru-ism. Wells (1998, p. 96) noted, however, that copepods (and presumably other small grazers) release, unharmed, any cells that flash: ingesting them would make the copepods' small bodies glow, and render them highly visible to predators. This agrees with the observation of Fitch and Lavenberg (1968, pp. 11-12) that predatory deep-sea fishes have black-lined stomachs, useful, as they suggest "to keep the luminous fish which they swallow whole from lighting up' in their death struggle and making the predator an easy meal for a larger fish".

However, alerting second-order predators is not the only, or even the main, reason for bioluminescence in fishes (Hastings 1975). Thus, many species of coastal bioluminescent fishes produce light that is directed downward, and which is thought to match the ambient light, such that their shadows are obliterated, thus foiling first-order predators swimming further below (Hastings 1971).

I once tested this hypothesis, if somewhat crudely, by ranking five species of slipmouth (Leiognathidae), a family of small, coastal bioluminescent fishes, by the size of their light organ, and by the different depths at which they occur, the idea being that large light organs are required to match the stronger light at shallow depths, and conversely. The two ranked lists were similar enough for the resulting paper to be publishable (Pauly 1977), but barely so, and it will not be mentioned again.

Birds A group of vertebrates probably descended from dinosaurs and characterized by feathers, toothless beaks, and egg-laying.

CD reminisced in his * Autobiography that, From reading White's Shelborne, I took much pleasure in watching the habits of birds, and even made notes on the subject. In my simplicity I remember wondering why every gentleman did not become an ornithologist (p. 45; White 1789,1843).

CD, ever a gentleman, did become an ornithologist, as well, but we can't follow him there: the birds considered in this book consist only of species mentioned in *Birds, or in CD's Ornithological Notes (Barlow 1963) and BigSpecies Book, and which feed on, or otherwise relate to fish. (See also Bird's nest soup; Cormorants; Kingfishers; Mother Carey's chickens; Penguins; Petrels; Scissor-beak). Thus, we shall ignore the fishing owl in Richardson's Fauna Boreali-Americana (1829-37) although it was noted in CD's Marginalia.

Birds Short title of The Zoology of H.M.S. Beagle. Part III: Birds (Gould et al. 1841), which presented the bulk of the *birds collected by CD during the voyage of the Beagle, notably the finches (Genus Geospiza), later called 'Darwin's Finches' (Lack 1953).

Bird's nest soup The question arises: what could this entry possibly have to do with fishes, given that [t]he nest is composed of a brittle white translucent substance very like pure gum-arabic or even glass [...]. This dry mucilaginous matter soon absorbs water & softens: examined under the microscope it exhibits no structure, except traces of lamination & many generally conspicuous in small dry fragments, & some bits looked almost like vesicular larva (Big Species Book, p. 499).

The answer is quite simple: Most authors believe that the nest of the esculent swallow is formed of either a *Fucus or of the Roe of fish; others, I believe, have suspected that it is formed of a secretion from the salivary glands of the bird. This latter view I cannot doubt from the preceding observations is the correct one. The inland habits of the Swifts, & the manner in which the substance behaves in flame almost disposes of the supposition of Fucus. Nor can I believe, after having examined the dryed roe of fishes, that we should find no trace of cellular matter in the nests, had they been thus formed. How could our Swifts, the habits of which are so well known, obtain roe, without being detected?

Mr Macgillivray has shown that the salivary crypts of the Swift are largely developed, & he believes that the substance with which the materials of its nest are felted together, is secreted by these glands. I cannot doubt that this is the origin of the similar & more copious & purer substance in the N. American Swifts, & in that of the Collocalia esculenta. We can thus understand its vesicular & laminated structure, & the curious reticulated structure of the Philippine island species. The only change required in the instinct of these several birds is that less & less foreign material should be used. Hence I conclude, that the Chinese make soup of dried saliva! (Big Species Book, p. 500; MacGillivray 1840). This is nearly as revolting as eating insect vomit (i.e. honey).

There are modern authors still believing that bird nests are made of Fucus. One is Keys (1963), who writes that "[s]ome kind of seaweed is gathered by a certain species of*petrel of the Family Procellariidae, which builds its nest in the cliffs of the Malayan Archipelago. The seaweed is predigested by the alkaline fluid of the mouths of these birds before being used to construct the nests. The nests are gathered in the fall, for export to China." So let's use this opportunity to clarify the issue. CD was right, again: these nests are made entirely of the saliva of insect-feeding swiftlets (Family Apo-didae), notably the White-nest swiftlet Aerodra-mus fuciphagus, the Volcano swiftlet A. vulcono-rum, and other species of the same genus, all abundant around the South China Sea. The nests are harvested, dangerously, from cliffs (Summers and Valli 1990), or more safely and sustainably from 'bird houses' constructed for the purpose, notably in Java (Whitten et al. 1996, pp. 234-5), where they have become a profitable, ifsmall, export industry.

However, bird's nest exporters must care about their location. Connoisseurs from Southern China will tell you (at least some have told this author) that bird's nests from coastal areas are far more tasty than those from inland areas. We conclude this by citing Madame Wu (1984, p. 220), who points out that "[b]ird's nest is one of those prized ingredients the Chinese believe add to a woman's femininity."

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