Book Review: The Amazing World of Flyingfish, by Steve N. G. Howell

In June of last year, I was standing on the deck of a ferry in Taiwan, headed for the island of Lüdao (commonly known as Green Island), keeping an eye out for any interesting sights. I was particularly intrigued by the seabirds that I kept seeing flying away from the ferry. For some time, I couldn't make out exactly what kind of bird they were: they were small, and flew very quickly. Most oddly, they never seemed to rise very far above the water; I kept waiting for one to get higher so that I could get a better idea of its shape, but every time I tried to keep an eye on one individual, it would seem to disappear, as if it had re-entered the water. Eventually, understanding dawned: what I was seeing were not birds at all, but flying fish.

Flyingfish (Exocoetidae) are prominent members of the pelagic ecosystem in tropical waters. For some tropical seabirds (actual birds this time, such as boobies or frigatebirds), they are among the primary source of food. Steve Howell, author of The Amazing World of Flyingfish (Princeton University Press, who were kind enough to send me a review copy), put together a guide to flyingfish after travelling from New Zealand to Australia on the Spirit of Enderby as part of a cruise that was primarily supposed to be for bird-watching. But, as Howell explains, "birds tend to be few in the blue equatorial waters (remember, it's a desert, even though it's full of water), and attention sooner or later shifts to flyingfish".

The Amazing World of Flyingfish is not a large book: all up, it barely makes it over 50 pages. But almost every one of those pages is adorned with spectacular photographs that capture the grace and variety of flyingfish. The images chosen work wonders in expressing the liveliness of their subjects. My favourite image technically doesn't even show the fish at all: on p. 16, a triptych of photographs showing the process of re-entering the water shows first the fish in flight, then closing its fins as it approaches the water's surface, and then simply the splash as it disappears below. The text, geared towards a younger or a lay audience, provides a general overview of flyingfish, with chapters given self-explanatory titles such as, "What is a flyingfish?", "How big are they?", "How do they fly?"

And yet, I also found Howell's book frustrating. The numerous different flyingfish varieties depicted are labelled with vernacular names largely of his own creation, such as Atlantic patchwing, sargassum midget, Pacific necromancer. Zoological names are, for the most part, not provided. As Howell explains, most field guides to marine fish are written for biologists or fisherman, and are oriented around identifying a specimen after it has been caught, often relying on features (such as scale counts) that are not discernible in photographs of live individuals. As a result, the identity of most of Howell's 'field varieties' remains uncertain. But then, in another section of the book, we are told that one juvenile morph "was examined genetically and proved to be a young Atlantic Necromancer" (capitalisation Howell's), implying that the zoological identity of this species, at least, is known.

As Howell points out, "there remains an unfilled niche for a field guide that portrays flyingfish as observers see them in the air". Howell has produced an attractive and engaging introduction to the world of flyingfish, and it should provide an inspiration to fill that niche.

The Sweetest of Lips

Oblique-banded sweetlips Plectorhinchus lineatus, copyright Richard Ling.

In an earlier post on this site, I referred to a fish of the family Lethrinidae being known by the name of "sweetlips". However, as is usually the way with fish vernacular names, there is more than one family of fishes to which this name can be applied. 'Sweetlips' is also the vernacular name for fishes in the Plectorhinchinae.

The Plectorhinchinae is most commonly treated as a subfamily within the family Haemulidae, the grunts (some sources will place 'Plectorhynchidae' as a separate family, and no, that wasn't a typo: read on). Plectorhinchines are distinguished from other subfamily of haemulids, the Haemulinae, by characters including a longer dorsal fin and the presence of at least four prominent lateral line pores under the chin (Johnson 1980). The name 'sweetlips' refers to the prominent lips of mature individuals of two of the genera of plectorhinchines, Plectorhinchus and Diagramma, which are often a distinct colour from the rest of the head. Members of the third genus, Parapristipoma, have the lips not quite so prominent, and are commonly referred to as 'grunts' like the remaining haemulids.

African striped grunts Parapristipoma octolineatum, copyright Juan Cuetos.

The plectorhinchines are found around tropical reefs in the Indo-West Pacific and East Atlantic, with a single species, the rubberlip grunt Plectorhinchus mediterraneus, being found in the in the Mediterranean and Black Seas. No plectorhinchines are found on either side of the Americas. They are nocturnal predators of benthic invertebrates, emerging at night from the secluded crevices and overhangs where they spend the day. Most are medium-sized fish, though the painted sweetlips Diagramma pictum can get up to 90 cm. They are popular with fishers; Smith (1962) referred to them as "among the best if not the best eating fishes of the reef-haunting species". Many species can go through significant changes in coloration as they mature: spotted juveniles may become unicoloured adults, or blotchy babies may mature into stripes. The differences are great enough that juveniles and adults have often been mistaken for separate species.

Juvenile oriental sweetlips Plectorhinchus vittatus, copyright Jan Messersmith. The adult form of this species resembles the oblique-banded sweetlips in the top photo on this post.

But failure to associate parents with their children is not the only way in which this group has been dogged by confusing taxonomy. The name of the type genus has been variously spelled Plectorhinchus or Plectorhynchus, with the family name varying accordingly (it seems that 'Plectorhinchus' is the correct spelling). A surprising number of sources (e.g. Tavera et al. 2012) seem to have it both ways, with the genus being called Plectorhinchus but the higher taxon being called Plectorhynchinae (R. van der Laan et al. confirm the correct family-name spelling). Meanwhile, Smith (1962) argued for the use of the name Gaterin in place of Plectorhinchus, and called the family Gaterinidae. And if you have any interest in the vagaries of taxonomy, settle in: this is going to be a whole thing.

The name 'Gaterin' dates from what is usually known as Forsskål's (1775) Descriptiones animalium, which Fricke (2008) argued should be attributed to Niebuhr (see, right from the first sentence it's confusing). Peter Simon Forsskål and Carsten Niebuhr were members of a Danish scientific expedition in 1761 to 1763 to the Red Sea (though Forsskål himself was Swedish, but that's another story). Forsskål was the expedition's naturalist, while Niebuhr was there as a geographer. The history of the expedition, and of the composition of Descriptiones animalium, has been summarised by Fricke (2008). The expedition was particularly ill-fated; of six original members, Niebuhr was the only one to make it back to Denmark alive. After returning to Denmark, Niebuhr started preparing Forsskål's notes for publication. However, he found this no easy task. Forsskål had not prepared a single manuscript, but made notes on various scraps of paper; in the end, Niebuhr suspected that many of these scraps had gone missing. As an engineer, Niebuhr knew little Latin and even less biology, so he obtained the services of an academic adviser. The identity of this adviser was not divulged in the final publication by Niebuhr himself, but he has since been identified as the Danish naturalist Johann Christian Fabricius. The relationship between Niebuhr and Fabricius was not entirely positive (Niebuhr later stated that his adviser on Descriptiones animalium had been a 'strange fellow'), and Fabricius does not seem to have spent any more time on the Forsskål notes than he absolutely had to. As a result, the final publication that emerged was partly Forsskål, partly Niebuhr, partly Fabricius, and all dog's breakfast.

The name 'Gaterin' is listed by Forsskål/Niebuhr/Fabricius as one of the sub-divisions of the genus Sciaena, and Smith's (1962) revival of the name was based on the assumption that Forsskål intended these subdivisions to represent what we would now call subgenera. As such, Gaterin published in 1775 would clearly be an earlier name than Plectorhinchus published in 1802. Smith further supported this interpretation by pointing out that two names listed by 'Forsskål' as subdivisions of Chaetodon, Acanthurus and Abudefduf, had since been widely accepted as names for separate fish genera. There were no grounds, he claimed, for taking Abudefduf as valid but refusing Gaterin.

As it happens, Forsskål probably never intended either Gaterin or Abudefduf to represent generic names of any kind. It seems that his notes had used local Arabic names to refer to taxa to which he had not yet supplied formal Latin names. When Fabricius compiled these notes, he simply used the Arabic names as formal names, probably because he just didn't care. When 'Forsskål' referred to 'Gaterin' in his introductory paragraph for Sciaena, he was probably referring to the individual species known in Arabia as gaterin rather than any formal group. 'Abudefduf' may have been similarly inadvertent, but long usage as a genus name means that it should probably be retained whatever its original status. No such argument can be marshalled in favour of 'Gaterin', whose usage in place of Plectorhinchus has been minimal.

And I can think of no better response to all that than the expression of this painted sweetlips Diagramma pictum. Copyright John Natoli.

REFERENCES

Fricke, R. 2008. Authorship, availability and validity of fish names described by Peter (Pehr) Simon Forsskål and Johann Christian Fabricius in the ‘Descriptiones animalium’ by Carsten Niebuhr in 1775 (Pisces). Stuttgarter Beiträge zur Naturkunde A, Neue Serie 1: 1–76.

Johnson, G. D. 1980. The limits and relationships of the Lutjanidae and associated families. Bulletin of the Scripps Institution of Oceanography 24: 1–114.

Smith, J. L. B. 1962. Fishes of the family Gaterinidae of the western Indian Ocean and the Red Sea with a resume of all known Indo Pacific species. Ichthyological Bulletin 25: 469-502.

Tavera, J. J., A. Acero P., E. B. Balart & G. Bernardi. 2012. Molecular phylogeny of grunts (Teleostei, Haemulidae), with an emphasis on the ecology, evolution, and speciation history of New World species. BMC Evolutionary Biology 12: 57. http://www.biomedcentral.com/1471-2148/12/57.

Sleepers

Hawaiian sleeper Eleotris sandwicensis, from the Hawaii Biological Survey.

Fishes of the genus Eleotris are a group of gobioids commonly known as the spinycheek sleepers. I haven't found a definite statement as to why they're called sleepers, but presumably it's because, as sit-and-wait ambush predators, they spend a lot of time lying around on the bottom. Eleotris species are found in tropical and subtropical waters around the world, mostly in estuaries and freshwater. They are smallish fish, with most species seeming to be in the ten to twenty centimetre size range. The 'spinycheek' part of the vernacular name refers to the presence of a hook-like spine on the lower corner of the preoperculum (the bone running between the cheek and the gill cover on the side of the head). This spine may be covered with tissue and so not always readily visible, but Pusey et al. (2004) note that it 'can be easily detected by running a thumbnail lightly, and carefully, along the preoperculum margin'. Carefully, I think, is the operative word here.

Eleotris oxycephala, from Chinese Academy of Fishery Sciences.

The species of Eleotris are mostly a conservative bunch appearance-wise, and the genus seems to have gotten a reputation for being difficult to work with taxonomically (it doesn't help matters that for a long time 'Eleotris' was something of a dumping ground for generalised gobioids). The Japanese species were revised in 1967 by Akihito (yes, that Akihito), the West African species have been revised by Miller (1998), and the North and South American species by Pezold & Cage (2002), but species from the remainder of the Indo-Pacific remain unrevised. There has been some disagreement over the status of a group of New World species classified in the genus Erotelis, which resemble Eleotris species but are generally more elongate and have higher numbers of fin rays (Pezold & Cage 2002). Miller (1998) felt that this genus should be synonymised with Eleotris, but Pezold & Cage (2002) argued that its members were distinct enough to be kept separate. A molecular phylogenetic analysis of the gobioids by Thacker & Hardman (2005) suggested that 'Erotelis' is nested within Eleotris, which may support their synonymisation.

Dusky sleeper Eleotris fusca, photographed by C. Appleby.

The sleepers are amphidromous, meaning they spend part of their life in the sea. Sleepers enter the sea as larvae, returning to fresher waters as they mature. As a result of this marine stage in the life cycle, individual species of Eleotris may be widespread and can often be found in places such as oceanic islands that lack populations of permanently freshwater species. It has even been suggested they may cross oceans: Miller (1998), noting similarities between species on either side of the Atlantic, suggested that this may be the result of trans-Atlantic dispersal. Among the evidence cited in favour of this possibility was the record in 1987 of a specimen of the northern South American species Eleotris pisonis from the island of St Helena in the mid-Atlantic. However, Miller also noted that the amount of time it would take to disperse across the Atlantic is greater that the time it would take for the larva to develop to maturity (and mature Eleotris are not known from the open sea). Pezold and Cage (2002) were more skeptical about the possibility of trans-Atlantic dispersal, even though they admitted to being unable to identify any characters distinguishing the Caribbean E. amblyopsis from the West African E. daganensis. They queried whether the St Helena record may have been an individual transported in ship ballast water, rather than an unaided dispersal.

REFERENCES

Miller, P. J. 1998. The West African species of Eleotris and their systematic affinities (Teleostei: Gobioidei). Journal of Natural History 32 (2): 273-296.

Pezold, F., & B. Cage. 2002. A review of the spinycheek sleepers, genus Eleotris (Teleostei: Eleotridae), of the western hemisphere, with comparison to the West African species. Tulane Studies in Zoology and Botany 31: 19–63.

Pusey, B., M. Kennard & A. Arthington. 2004. Freshwater Fishes of North-eastern Australia. CSIRO Publishing: Collingwood.

Thacker, C. E., & M. A. Hardman. 2005. Molecular phylogeny of basal gobioid fishes: Rhyacichthyidae, Odontobutidae, Xenisthmidae, Eleotridae (Teleostei: Perciformes: Gobioidei). Molecular Phylogenetics and Evolution 37: 858-871.

Into the Labyrinth

Climbing perch Anabas testudineus emerging from water, as illustrated by Richard Lydekker.

Amongst the unholy mess that is the Percomorpha, one group that has long been recognised is the labyrinth fishes of the Anabantoidei. The anabantoids are a group of freshwater fishes found in southern Asia and Africa (but not Madagascar) that get their vernacular name from their possession of a distinctive respiratory organ called the labyrinth. This organ, found in a cavity above the gills, is derived from part of the first gill arch; the bone has become expanded and much-folded, and is covered with a layer of respiratory epithelium. So long as the gills do not actually dry out, the labyrinth allows these fish to take in oxygen directly from the air, and they can survive in warm, low-oxygen waters. They can even survive for limited periods entirely out of water (a feature that has helped make some of the larger species popular food fish, due to the greater ease of keeping them fresh in a tropical environment). Recent phylogenetic studies (e.g. Li et al. 2009) have agreed in placing labyrinth fishes as related to a number of other freshwater Indo-Australian fishes, such as the snakeheads of the Channidae and the swamp eels of the Synbranchidae, many of which are also tolerant of air-breathing.

Kissing gouramis Helostoma temminckii, from Peter Bus.

Labyrinth fishes can be divided between three families (Rüber et al. 2006). One of these contains a single species, the kissing gourami Helostoma temminckii of south-east Asia. Kissing gouramis are primarily specialised filter feeders, though they may also graze on algae or insects. The vernacular name refers to their enlarged lips, making them look permanently puckered up. Kissing gouramis even 'kiss', pressing their smackers against one another, though this is regarded as an act not of affection but of aggression (kind of like a 1930s Hollywood melodrama) as the fish push against one another.

A rather unfortunate Cape kurper Sandelia capensis, photographed by Darryl Lampert.

The climbing perches of the Anabantidae include the south Asian Anabas and the African Ctenopominae. These short-bodied carnivores have serrated edges to their gill covers that the Asian species use to pull themselves over land when travelling between water bodies (imagine lying on your stomach and pulling yourself along with your chin). You can see video of some climbing perch Anabas testudineus emerging from water here.

Giant gourami Osphronemus goramy, photographed by E. Naus.

The most diverse subgroup of the Anabantoidei is the gouramis of the Osphronemidae, another south Asian group. The largest of the Osphronemidae, the giant gourami Osphronemus goramy, grows up to 70 cm, but most species are quite a bit smaller. A number of gourami species (as well as the kissing gourami) are popular aquarium fishes; the most popular by far is the Siamese fighting fish Betta splendens, males of which have been bred to exhibit much longer and more ornamental fins than found in the wild. The gouramis are generally omnivorous, with species varying in the extent to which they prefer plant or animal food. The most specialised carnivore of the Osphronemidae is the pikehead Luciocephalus pulcher, a small but elongate species that has been described as having the most protrusible mouth of any fish (and that, by the way, is no small claim). You can see the pikehead in action below:

The pikehead is so divergent from other labyrinth fishes that past authors have regarded it as its own family, possibly the sister taxon to all other anabantoids, or even questioned whether it was a labyrinth fish at all. However, as confirmed by Rüber et al. (2006), Luciocephalus is not only a true anabantoid but nested well within the Osphronemidae as sister to the chocolate gouramis of the genus Sphaerichthys. These and two other genera, Ctenops and Parasphaerichthys, form what is known as the 'spiral egg' clade, named after the presence of spiraling ridges on the egg leading to the micropyle, that have been suggested to act as guides for the sperm.

Siamese fighting fish Betta splendens mating below a bubble-nest, photographed by Stephen & John Downer.

The anabantoids are also known for the bubble-nests constructed by a number of species, in which the eggs are contained within a floating nest of bubbles that is guarded by the male parent (both parents in the Ceylonese combtail Belontia signata). Bubble-nesting has evolved at least twice among the anabantoids: once in the Osphronemidae, and once in the ctenopomine genus Microctenopoma (other anabantids and Helostoma are free spawners that do not construct nests or guard their eggs; the ctenopomine Sandelia capensis digs a nest in the bottom substrate) (Rüber et al. 2006). Though bubble-nesting is probably the ancestral behaviour for Osphronemidae, it has been modified in a number of sublineages. Osphronemus species build submerged nests from vegetation, while members of the 'spiral egg' clade (except Parasphaerichthys) and a number of Betta species are mouthbrooders. Usually the male broods the fry in these species, but the female is the brooder in a couple of Sphaerichthys species.

REFERENCES

Li, B. A. Dettaï, C. Cruaud, A. Couloux, M. Desoutter-Meniger & G. Lecointre. 2009. RNF213, a new nuclear marker for acanthomorph phylogeny. Molecular Phylogenetics and Evolution 50: 345-363.

Rüber, L., R. Britz & R. Zardoya. 2006. Molecular phylogenetics and evolutionary diversification of labyrinth fishes (Perciformes: Anabantoidei). Systematic Biology 55 (3): 374-397.

Empire of the Sunfish

Do you remember when this particular nightmare was vomited forth from the jaws of pop culture hell?


Yes, this was the execrable Billy the Bass, just one more reason we can all be glad that the 90s aren't around any more. But what was it supposed to be?

Smallmouth bass Micropterus dolomieu, photographed by Eric Engbretson.

The bass and sunfishes of the family Centrarchidae are a group of more than thirty species of freshwater fish mostly native to North America east of the Rocky Mountains. A single species, the Sacramento perch Archoplites interruptus, is native to northern California. The family was more widely distributed in the past: the Oligocene–Miocene genera Plioparchus and Boreocentrarchus hail from Alaska, Oregon and the Dakotas (Near & Koppelman 2009). They will also be much more widely distributed in the future: species of the genera Lepomis and Micropterus have been introduced to numerous places around the world as sportfish. The centrarchids are all carnivorous, though the nature of their prey varies from zooplankton to insects to other fish.

White crappie Pomoxis annularis, photographed by D. Ross Robertson.

The molecular analysis of the Centrarchidae by Near et al. (2005) identified the mud sunfish Acantharchus pomotis as sister to all other centrarchids, contrary to its previous inclusion in the subfamily Centrarchinae with other centrarchids possessing more than three spines in the anal fin (Near & Koppelman 2009). Instead, the two genera whose species possess only three anal spines, Lepomis and Micropterus, form a clade that is sister to the remaining 'centrarchine' genera. These are the aforementioned Archoplites, the flier Centrarchus macropterus, the banded sunfishes Enneacanthus, the rock basses Ambloplites and the somewhat unfortunately named crappies of the genus Pomoxis. These are mostly deep-bodied feeders on small invertebrates, though the larger species may also take small fish. Archoplites is a more dedicated piscivore. This latter species is also notable for having less elaborate mating behaviour than other centrarchids: in contrast to the elaborate courtship rituals and nests of other centrarchids, Archoplites males do little more than use the tail fin to dig a small depression (Berra 2007). One can't resist wondering if Archoplites' lax behaviour is connected with its geographic isolation from other species.

Pumpkinseed Lepomis gibbosus, photographed by Cliff.

The genera Micropterus and Lepomis are each more diverse than the centrarchine genera. The black basses of the genus Micropterus are relatively long-bodied compared to other centrarchids, and are all piscivores. Lepomis, with twelve species, is the most diverse centrarchid genus both numerically and ecologically; as well as numerous insectivorous species, it contains the piscivorous warmouth Lepomis gulosus, the specialised planktivorous bluegill L. macrochirus, and two molluscivorous species, the redear sunfish L. microlophus and the pumpkinseed L.gibbosus. Phylogenetic relationships within Lepomis indicate a certain dynamism of ecology as well: a number of species pairs can be identified connecting large and small species, while the two molluscivores are not immediate relatives within the genus (Near et al. 2005).

REFERENCES

Berra, T. M. 2007. Freshwater Fish Distribution. University of Chicago Press.

Near, T. J., D. I. Bolnick & P. C. Wainwright. 2005. Fossil calibrations and molecular divergence time estimates in centrarchid fishes (Teleostei: Centrarchidae). Evolution 59 (8): 1768-1782.

Near, T. J., & J. B. Koppelman. 2009. Species diversity, phylogeny and phylogeography of the Centrarchidae. In: Cooke, S. J., & D. P. Philipp (eds) Centrarchid Fishes: Diversity, biology and conservation, pp. 1-38. Blackwell Publishing.

The Live-Bearing Brotulas

Black brotula Stygnobrotula latebricola, photographed by Thomas W. Doeppner.

The subject of today's post is the Bythitidae, a family of mostly marine fishes referred to as the live-bearing brotulas. Bythitids belong to the Ophidiiformes, a group of more or less elongate fishes with long soft dorsal and anal fins. They differ from most other ophidiiforms in that the males have an external intromittent organ and they are mostly live-bearers rather than egg-layers (though at least one species, Didymothallus criniceps, is potentially an egg-layer: Schwarzhans & Møller 2007). Bythitids do share these features with the deep-water Aphyonidae, which are however particularly elongate, lack scales and a swim bladder, and have loose translucent skin in contrast to the firm skin of bythitids (Nielsen et al. 1999).

Bahamian cave fish Lucifuga spelaeotes, photographed by Joe Dougherty.

Bythitids are often thought of as deep-water fishes, but there is also a reasonable diversity of them in shallower habitats such as coral reefs. The shallower-living species are mostly very cryptic in their habits and may be only rarely encountered; deeper-water species may occupy more open habitats or be found in association with hydrothermal vents. Some species of the genera Lucifuga and Ogilbia are found in freshwater caves in the Caribbean (Lucifuga species), the Yucatan (Ogilbia pearsei) and the Galapagos (O. galapagosensis); other species are found in marine caves such as the 'blue holes' of the Bahamas. New species of bythitid continue to be described at a reasonable rate of knots (over 100 species have been described in the last ten years alone). They vary in size from small (Microbrotula species are about four centimetres in length) to very large (Cataetyx laticeps reaches over 75 cmm; the Fishes of Australia website states that bythitids grow up to 2 m, but I haven't been able to find which species this refers to).

Yellow cuskeel Dinematichthys iluocoeteoides, from here.

Because of their cryptic habits, the lifestyles of most bythitids remain poorly known. They are predators of invertebrates and other fish. The few identified larvae have been collected in the epipelagic zone (Nielsen et al. 1999) but bythitids are believed to have relatively low fecundity rates (presumably as only small numbers of embryos have been found in gravid females). Reef-dwelling species, as far as is known, have only small ranges, and many may be endangered by habitat degradation.

REFERENCES

Nielsen, J. G., D. M. Cohen, D. F. Markle & C. R. Robins. 1999. FAO species catalogue. Volume 18. Ophidiiform fishes of the world. An annotated and illustrated catalogue of pearl-fishes, cusk-eels, brotulas and other ophidiiform fishes known to date. FAO Fisheries Synopsis 125 (18): I–XI + 1–178.

Schwarzhans, W., & P. R. Møller. 2007. Review of the Dinematichthyini (Teleostei: Bythitidae) of the Indo-west Pacific. Part III. Beaglichthys, Brosmolus, Monothrix and eight new genera with description of 20 new species. The Beagle, Records of the Museums and Art Galleries of the Northern Territory 23: 29-110.

Pomfrets of the High Seas

The fanfish Pterycombus petersii, photographed off the Kerama Islands by Kazuo Kayama.

The Bramidae, commonly known as pomfrets, are a cosmopolitan family of pelagic fishes, found mostly in the upper layers of the world's oceans. Pomfrets are teardrop- or elliptical-shaped, deep-bodied and strongly-compressed fish with a single long dorsal fin that is ventrally mirrored by (usually slightly shorter) similar-shaped anal fin. Some species are quite large, with about a metre as the maximum recorded length for the family (McEachran & Fechhelm 2006). Thompson (2002) stated that pomfrets feed on other fish and larger invertebrates such as squid, but García & Chong (2002) found that Brama australis fed primarily on crustaceans such as krill.


Pteraclis aesticola, photographed by Kanno Takayuki.

The Bramidae are divided between two subfamilies, Pteraclinae and Braminae, though the monophyly of the latter in particular does not necessarily appear to have been established. Pteraclinae include two genera, the fanfishes Pteraclis and Pterycombus, with particularly large triangular dorsal and anal fins. Despite their unwieldy appearance, these fins can be completely depressed into a special groove formed by modified scales running on either side of the fins, as is being done by the individual in the photo above (if expanded, the fins of Pteraclis are even more expansive than those of Pterycombus, with the dorsal fin extending all the way forward to the snout). Members of the Braminae (the genera Brama, Eumegistus, Taractes, Taractichthys and Xenobrama) have less flamboyant fins with scales running partway along the rays and unable to be depressed (Thompson 2002).


The large bramine Taractes rubescens, from here.

Phylogenetically speaking, the molecular study using by Li et al. (2009) placed the Bramidae among a clade that they referred to as Stromateoidei (though somewhat different from earlier uses of this name), that also included families such as Stromateidae (butterfishes), Scombridae (mackerels), Trichiuridae (cutlassfishes) and Chiasmodontidae (black swallowers). A comparable clade was also recovered by Yagishita et al. (2009) using different molecular markers (Li et al. used nuclear genes; Yagishita et al. used mitochondrial genes; however, Yagishita et al. sampled a smaller number of families than Li et al.). Though morphologically diverse, all families in this clade are primarily pelagic.

REFERENCES

García M., C., & J. Chong. 2002. Composicion de la dieta de Brama australis Valenciennes 1837 en la zona centro-sur de Chile (VIII región) en Otoño 2000 y Verano 2001. Gayana 66 (2): 225-230.

Li, B., A. Dettaï, C. Cruaud, A. Couloux, M. Desoutter-Meniger & G. Lecointre. 2009. RNF213, a new nuclear marker for acanthomorph phylogeny. Molecular Phylogenetics and Evolution 50: 345-363.

McEachran, J. D., & J. D. Fechhelm. 2006. Fishes of the Gulf of Mexico, vol. 2. University of Texas Press.

Thompson, B. A. 2002. Bramidae: pomfrets. In: Carpenter, K. E. (ed.) The Living Marine Resources of the Western Central Atlantic, vol. 3. Bony fishes part 2 (Opistognathidae to Molidae), sea turtles and marine mammals. FAO Species Identification Guide for Fishery Purposes and American Society of Ichthyologists and Herpetologists Special Publication 5. Food and Agriculture Organization of the United Nations: Rome.

Yagishita, N., M. Miya, Y. Yamanoue, S. M. Shirai, K. Nakayama, N. Suzuki, T. P. Satoh, K. Mabuchi, M. Nishida & Tetsuji Nakabo. 2009. Mitogenomic evaluation of the unique facial nerve pattern as a phylogenetic marker within the percifom fishes (Teleostei: Percomorpha). Molecular Phylogenetics and Evolution 53 (1): 258-266.

Gender's Just a State of Gonads

It didn't take long for Adam Yates to recognise this animal:


Juvenile Pagrus auratus. Photo by Richard Ling.

This is the fish that goes by the name of 'snapper' in New Zealand, though that name is used for different kinds of fish elsewhere. In older references, you'll find this species under the name of Chrysophrys auratus, but the genera Chrysophrys has since been synonymised with Pagrus (Paulin, 1990). However, the molecular phylogenetic analysis of Chiba et al. (2009) failed to recover monophyly for Pagrus, so we may yet see Chrysophrys make a comeback some day.


Mature individuals of Pagrus major, a north-west Pacific species regarded by some authors as a synonym of P. auratus. These two are probably engaging in courtship behaviour. Photo from here.

As this young snapper gets older, its body will change in numerous ways. One is that the blue spots along its side will fade away and it'll become more evenly pink. Its head will become deeper, and if it may develop a large supraorbital boss on its forehead. And one other significant change that it may go through is a reassignment of gender. Members of the marine fish family Sparidae, to which Pagrus belongs, show a bewildering range of sexual development, including forms which show protandrous hermaphroditism (they start life as males before developing into females), protogynous hermaphroditism (starting as females, developing into males) and gonochorism (completely separate males and females, as we have ourselves). Other species start life with the rudiments of both male and female gonads but have only one or the other develop to maturity, without any subsequent sex changes, while a single species has been recorded as possessing simultaneously functional gonads of both sexes (Buxton & Garratt, 1990).

Different species of sparids feed on a variety of different diets, from predators of other fish such as the Dentex species to herbivores on algae such as Sarpa salpa. This variation in diet is reflected in a variety of dental morphologies. Predators such as Dentex possess pointed caniniform teeth while invertebrate feeders such as Pagrus auratus have a combination of pointed teeth in the front and round molariform teeth in the back. Algal feeders have flat-topped incisiform dentition, leading to occassional reports on fish with human teeth:


Teeth of sheepshead, Archosargus probatocephalus. Photo from Nathan Thurston.

In the past, dentition has been used as the basis for dividing sparids into a number of subfamilies, but both molecular (Chiba et al., 2009) and morphological (Day, 2002) analyses indicate multiple polyphyletic origins of the various dentition types. Contrast that to the situation in the possibly related* family Lethrinidae where trophic type and phylogeny show a much closer fit.

*A relationship between the two has been suggested on morphological grounds; molecular analyses have so far not supported such a relationship, but nor have they produced any strong relationships for either family.

REFERENCES

Buxton, C. D., & P. A. Garratt. 1990. Alternative reproductive styles in seabreams (Pisces: Sparidae). Environmental Biology of Fishes 28: 113-124.

Chiba, S. N., Y. Iwatsuki, T. Yoshino & N. Hanzawa. 2009. Comprehensive phylogeny of the family Sparidae (Perciformes: Teleostei) inferred from mitochondrial gene analyses. Genes and Genetic Systems 84 (2): 153-170.

Day, J. J. 2002. Phylogenetic relationships of the Sparidae (Teleostei: Percoidei) and implications for convergent trophic evolution. Biological Journal of the Linnean Society 76 (2): 269-301.

Paulin, C. D. 1990. Pagrus auratus, a new combination for the species known as "snapper" in Australasian waters (Pisces: Sparidae). New Zealand Journal of Marine and Freshwater Research 24: 259-265.

Knocked Off the Perch (Taxon of the Week: Percidae)

The rainbow darter, Etheostoma caeruleum, a representative of the North American radiation of small and often colourful freshwater fish known as darters. This species breeds on fast gravel riffles, where pairs mate with the female half buried in the gravel so the eggs are automatically covered over (Reeves, 1907). Photo by Jim McCormac.

Okay, this post has been delayed again. It's been an unusual week, is all I can say. I'd tell you all about, but I have very good reasons to believe that that would be extremely dull.

In earlier posts, I have ranted in a rather esoteric manner about my distaste with the commonly recognised fish order "Perciformes", really a random multi-paraphyletic assemblage of the more generalised members of the clade Percomorpha. In the recent partial reclassification of the Percomorpha by Li et al. (2009), the name "Perciformes" was ditched entirely, and the clade containing the family Percidae was instead called Serraniformes (suggesting, offhand, that some sort of taxonomic karma is dooming this taxon to be associated with confusing names - the family Serranidae as commonly recognised itself seems likely to be polyphyletic, and a number of "serranids" are not guaranteed Serraniformes). But even before the Perciformes of common use were recognised as a wastebasket assemblage (if, indeed, there ever really was such a time), Percidae was always a slightly odd choice for the type family. The Percidae, the perches and darters, are not particularly average Perciformes.

Among the percomorphs, percids are unusual for one main reason - they're almost entirely freshwater (a few European species stray into brackish waters, but only one species - Sander marinus, the estuarine perch of the Black and Caspian Seas - is a permanent resident in them). While the percomorphs have achieved true world dominance in the upper parts of the ocean, including the vast majority of coastal and surface-pelagic fish species, they have never made such significant inroads into fresh water. A few percomorph lineages have been very successful in fresh water, such as the Cichlidae, the Anabantiformes and various members of the Smegmamorpha*. But in contrast to their surface-marine monopoly, percomorphs have to share dominance of the fresh-water environment with members of the clade Otophysi - Cypriniformes, Characiformes and Siluriformes.

*No, honestly, it's a real name.


The zander, Sander lucioperca, a much larger Eurasian percid. Photo from EoL.

The Serraniformes also include the Trachinidae (weevers), the circum-Antarctic notothenioids and the majority of what were the Scorpaeniformes. Relationships within the Serraniformes are yet to be hammered out, but the Percidae probably divide from the others reasonably basally. Ten genera of living Percidae are currently recognised, with more than two hundred species. Phylogenetic analysis of the family by Sloss et al. (2004) recognised three main clades of unresolved relationships - the Holarctic genus Perca, the mostly Eurasian clade of Gymnocephalus plus Luciopercinae (genera Romanichthys, Sander and Zingel, with three species of Sander in North America), and the North American clade of Etheostomatinae (Ammocrypta, Crystallaria, Etheostoma and Percina). [The tenth genus includes the single uncommon species Percarina demidoffi of rivers running into the Black Sea, and was not analysed by Sloss et al. due to lack of material. Percarina was previously classified in the possibly non-monophyletic Percinae* with Perca and Gymnocephalus and differs from most other Percinae in spawning in brackish waters, so establishing its relationships would be very interesting.] While the greater phylogenetic disparity of Percidae is concentrated in the western Palaearctic and the family is believed to have originated in that area, the greater diversity of species is definitely found in North America. Well over two-thirds of percid species belong to the Etheostomatinae, with the greater part of those in the genus Etheostoma (which, however, may not be monophyletic).

*Though the non-monophyly of Percinae found by Sloss et al. is in contrast to their breeding behaviour - Percinae differ from other percids in laying their eggs encased in long gelatinous strands, while Luciopercinae and (ancestrally) Etheostomatinae are broadcast spawners.


The European perch, Perca fluviatilis. A very similar species, Perca flavescens, is found in North America. Photo from here.

Human interest in the Percidae (as with most matters, really) has usually been related to one of two things - eating or sex. The larger percids of the "Percinae" and Luciopercinae are widely caught for food, and the European perch Perca fluviatilis has been introduced to many localities outside its native range such as New Zealand for the amusement of anglers. Some percids, such as the walleye Sander vitreus, have been recorded reaching lengths of over a metre (though such sizes are, of course, exceptional - a more average walleye would be about twenty centimetres). Species of the Etheostomatinae, known as darters, are not targets of fishing - members of this subfamily (as well as some species of Luciopercinae) are smaller than other percids, less than ten centimetres in length*, and wouldn't offer much in the way of eating. Still, darters more than make up their interest in the other regard of sex. They show a wide diversity of breeding behaviour, from broadcast spawners to some that bury their eggs in sediment or gravel to species that lay their eggs safely hidden on the underside of rocks. Other species may glue their eggs to vegetation (Winn, 1958a, b). During the breeding season, most (but not all) darters move from deeper to shallower waters (many species favour riffle areas) where the males usually establish a breeding territory (as reported by Winn, 1958b, the presence of other males seems to be required to incite the successful establishment of a territory - solitary males tended to lose interest in a potential territory and wander off). Some darter species are fairly relaxed about their territories and only fend off males of their own species, but other darters may be decidedly pugnacious and attack just about anything that moves. Challenging males approach each other with fins held high, and their colours will often become brighter. They may circle each other and butt or bite at each other's tail regions. After a male has mated with a female and she has laid her eggs, he may or may not remain in the area to guard them. Experiments have shown that if the eggs are removed or replaced, the male continues to guard the same spot, so it is the territory that induces guarding behaviour rather than the presence of eggs. Hybrids have been recorded between a number of darter species and seem to be not uncommon, especially where species have been spread outside their native range (Stauffer et al., 1995).

*As a corollary of their smaller size, it is worth noting that darters (and the smaller Luciopercinae) also lack swim bladders.


Percarina demidoffi as illustrated by N. Kondakov in a 1957 Russian textbook. For some reason, I find a certain whimsy in this illustration of what is perhaps one of the more mysterious percids. Image via NOAA Photo Library.

REFERENCES

Reeves, C. D. 1907. The breeding habits of the rainbow darter (Etheostoma cœruleum Storer), a study in sexual selection. Biological Bulletin 14 (1): 35-59.

Sloss, B. L., N. Billington & B. M. Burr. 2004. A molecular phylogeny of the Percidae (Teleostei, Perciformes) based on mitochondrial DNA sequence. Molecular Phylogenetics and Evolution 32 (2): 545-562.

Stauffer, J. R., Jr, J. M. Boltz & L. R. White. 1995. The fishes of West Virginia. Proceedings of the Academy of Natural Sciences of Philadelphia 146: 1-389.

Winn, H. E. 1958a. Observation on the reproductive babits of darters (Pisces-Percidae). American Midland Naturalist 59 (1): 190-212.

Winn, H. E. 1958b. Comparative reproductive behavior and ecology of fourteen species of darters (Pisces-
Percidae). Ecological Monographs 28 (2): 155-191.

Turkey-lion-butterfly-scorpion-zebra

Today marks another first for Catalogue of Organisms - for the first time, the Taxon of the Week post is focusing on a single species. Specifically, the tropical fish Dendrochirus zebra (Cuvier, 1829)*, commonly known as dwarf lionfish, zebra turkeyfish, zebra butterfly-cod and doubtless a whole host of others of which I'm not even aware. And a very attractive animal it is too, as you can see in the photo above by K. Uchino. Dendrochirus zebra is a widespread species on reefs in the tropical Indian and Pacific Oceans. A map, as well as a whole heap of other information, can be found on FishBase.

*Things are a little confusing regarding the authority of this species - some sources (including FishBase) cite Cuvier (1829), while others such as Munro (1958) point to Quoy and Gaimard (1824). I have no idea which is correct.

The lionfishes or firefishes are two genera (Pterois and Dendrochirus) forming the subfamily Pteroinae of the family Scorpaenidae, the scorpionfishes (though Smith & Wheeler, 2006, found the pteroines to be more closely related to the Sebastidae rather than the Scorpaeninae). The differences between the two genera are fairly minimal, and a molecular phylogenetic analysis of seven (of thirteen) species of pteroines by Kochzius et al. (2003) failed to resolve their relative monophyly. Dendrochirus zebra was actually originally described as a species of Pterois (Munro, 1958), and it seems a return might be in order - proving once again that vertebrate workers tend to oversplit their genera. The name Dendrochirus ("tree-hand") refers to one of its supposed distinguishing characters, that some of the upper rays in the pectoral fin are branched. The other distinguishing character is that, unlike Pterois, Dendrochirus never has the upper pectoral rays free from the membrane.



The spectacular coloration of the pteroines makes them instantly recognisable, though the above photo of Dendrochirus zebra by Richard Ling shows quite well how the fish are not quite so obvious against a colorful reef background as one might expect. Like other scorpaenids, lionfish are slow-moving ambush predators. Their somewhat glum expression is the result of their relatively gigantic maws, which open up to inhale just about anything that can fit. Lionfish also resemble other scorpaenids in the presence of painfully venomous spines in the dorsal, ventral and anal fins. This toxicity has not prevented D. zebra from becoming popular in the marine aquarium industry. While D. zebra has spawned in captivity (FishBase), the majority of captive specimens would appear to be wild-caught. Unfortunately, FishBase suggests that this species is a relatively slow breeder and moderately vulnerable to overfishing.

One last thing which, though it relates not to Dendrochirus zebra but to another pteroine, is something I stumbled across while researching this post that is just too cool not to share. Take a look at the two photos below:



The above photos come from Fishelson (2006). The upper photo shows a typical individual of Pterois volitans, the red firefish. The lower photo shows a variant with the supraoral tentacles flattened into feather-like ornaments. Such a variant was first sighted near the southern end of the Sinai peninsula in the early 1980s. Since then, records of variant individuals have slowly spread southwards, and have since been recorded as far south as Kenya and the Comoros. While variant individuals remain extremely rare, they do seem to be slowly increasing in abundance...

REFERENCES

Fishelson, L. 2006. Evolution in action-peacock-feather like supraocular tentacles of the lionfish,
Pterois volitans – the distribution of a new signal. Environmental Biology of Fishes 75: 343-348.

Kochzius, M., R. Söller, M. A. Khalaf & D. Blohm. 2003. Molecular phylogeny of the lionfish genera Dendrochirus and Pterois (Scorpaenidae, Pteroinae) based on mitochondrial DNA sequences. Molecular Phylogenetics and Evolution 28 (3): 396-403.

Munro, I. S. R. 1958. The fishes of the New Guinea region: A check-list of the fishes of New Guinea incorporating records of species collected by the Fisheries Survey Vessel “Fairwind” during the years 1948 to 1950. Papua and New Guinea Agricultural Journal 10 (4): 97-369 (reprinted 1958. Territory of Papua and New Guinea Fisheries Bulletin no. 1).

Smith, W. L., & W. C. Wheeler. 2006. Polyphyly of the mail-cheeked fishes (Teleostei: Scorpaeniformes): evidence from mitochondrial and nuclear sequence data. Molecular Phylogenetics and Evolution 32 (2): 627-646.

The Ugly Stick in Action

Psettodes erumei, as depicted by Sir Francis Day.

I had two things I could have written about this morning, both of them very cool. There's the identification of possible chloroplast-derived genes in ciliates, for one. This is very neat, because ciliates belong to a group of protozoans called alveolates that also includes dinoflagellates. Dinoflagellates have red-alga-derived chloroplasts that contain chlorophyll c, a form of chlorophyll otherwise only found in chromists, the group of algae that includes brown algae and their unicellular relatives. On this basis, it has been suggested that chromists and alveolates together form a superclade called chromalveolates (as opposed, I suppose, to alveomists). See the post I wrote earlier about the discovery of the rather significant little alga Chromera velia for more details. Ciliates have been something of a fly in the ointment for this theory, as they contain nary a trace of a chloroplast, which might support the alternative idea that dinoflagellate and chromist chloroplasts are independently derived. Monophyly of chromalveolates would require that ciliates are derived from chloroplast-carrying ancestors that lost their ability to photosynthesise, something that chloroplast-derived genes in ciliates would make more credible.

The other option to write on was the identification of stem-flatfish. I was leaning towards ciliates, because the stem-flatfish story has already been covered by Ed Yong, GrrlScientist and Carl Zimmer, but I can't access the ciliate paper. So I guess that flatfish it is.

Flatfish are the group that includes such creatures as flounders, sole and halibut. Fish are, of course, the animals that invented ugly. With contenders such as gulper eels, sculpins and dories in action, the title of World's Ugliest Fish is hotly contended. While flatfish are far from being the winners at ugly (that position is quite firmly held by the anglers), they definitely deserve an Honourable Mention.


Flatfish larval development, from Pharyngula.

At some point in their history, both eyes of the ancestral flatfish moved onto the one side of their head. The eyeless side of the body is used by the fish to lie flat on the substrate (hence the name), so left and right have effectively become upper and lower (in most species, right is upper and left is lower, but there are some exceptions). The really odd thing is that flatfish actually hatch out as fairly normal-looking larvae, with the eyes in their usual places on either side of the body, and over the course of maturation one of the eyes migrates over the top of the animal to the other side. How this state of affairs came into being has been a difficult question, and Goldschmidt actually gave flatfish a significant role in his arguments for saltatory evolution (evolution happening by a series of rapid jumps), a theory that has been parodied as the "hopeful monster" position. A paper in today's Nature (Friedman, 2008) adds some crucial data to the debate, as well as confirming that the change took place gradually.

Friedman (2008) establishes that the fossil fish genera Amphistium and Heteronectes show distinctly asymmetrical eye positions on the skull. While the eyes are still on separate sides of the head, one eye is positioned distinctly higher than the other. That these were fully developed adult fish rather than larvae with eyes in the process of moving is indicated by the complete ossification of the skull. Phylogenetic analysis supports the position of the two genera as fossil outgroups to living flatfishes, lying along the stem. This position is supported by characters other than those related to the asymmetry of the skull, so is unlikely to represent convergence. Because the specimens lack distortion in other elements of the skull, Friedman was also able to conclude that the asymmetry was not the effect of post-mortem distortion.

The idea of a gradual development of flatfish asymmetry actually already had support from the living genus Psettodes, generally agreed to the sister taxon to other living flatfish. In Psettodes, the migrating eye moves to the other side, but only as far as just below the dorsal edge. It is also notable that Psettodes apparently spends more time swimming upright than other flatfish. While most flatfish species show a distinct developmental preference for which side the eye migrates to, with opposite-sided individuals as relatively rare mutations, Psettodes individuals may experience eye movement to either side during development. Interestingly, a study by Schreiber, 2006, on larval development in southern flounder (Paralichthys lethostigma) found that while all wild-caught specimens were left-sided, 16% of larvae in the lab developed right-handedly, while 4% of larvae actually developed bilaterally symmetrically, with either the eyes remaining where they were or both moving dorsally. It seems likely that the failure to find such variants in the wild indicates that for some reason or other they do not generally live to adulthood.


From Friedman (2008).

Of course, the identification of these asymmetrical ancestral forms still leaves a lot of questions open. What we still don't know, of course, is why the ancestors of flatfish started lying on their sides, and why they became asymmetrical. The asymmetrical-but-not-one-sided forms Amphistium and Heteronectes are known from two stages of the Eocene, and were contemporary with more derived crown flatfishes, so they were not a short-lived maladaptive form that shuffled off as soon as their better-adapted descendants arrived. It has been suggested that the flattened habitus of flatfishes allows them to better conceal themselves while waiting for other fish as prey, which they are then able to ambush from below, and Amphistium, like living flatfish, does appear to be piscivorous. Side-resting fish may have been subject to selective pressure for eye asymmetry that allowed them to keep an eye out for prey while remaining concealed, and Friedman suggests (in comparison with modern flatfish behaviour) that Amphistium and Heteronectes may have been able to prop themselves up on their pectoral fins, raising the lower eye above the substrate and allowing them to 'squint' for prey. At the moment, of course, this is all speculative. From the aforementioned developmental studies (Schreiber, 2006), though, we can add some details. As well as having the eyes move sides, the larvae also change from swimming vertically to swimming laterally, but the two are independent events. Change in swimming orientation occurs before eye migration, and that small percentage of larvae that did not experience eye migration still changed swimming orientation. In a very small fraction of larvae, swimming orientation actually developed in the opposite direction to eye migration, so they ended up swimming with the eyes on the underside (needless to say, these unfortunate individuals did not live long). Further investigation of how asymmetry develops in living flatfishes - particularly the basal Psettodes - may shed further light on how this remarkable condition arose in the first place.

REFERENCES

Friedman, M. 2008. The evolutionary origin of flatfish asymmetry. Nature 454: 209-212.

Schreiber, A. M. 2006. Asymmetric craniofacial remodeling and lateralized behavior in larval flatfish. Journal of Experimental Biology 209: 610-621.

Sculpins Go Wild

Yokoyama, A., & A. Goto. 2005. Evolutionary history of freshwater sculpins, genus Cottus (Teleostei; Cottidae) and related taxa, as inferred from mitochondrial DNA phylogeny. Molecular Phylogenetics and Evolution 36 (3): 654-668.

Freshwater sculpins of the genus Cottus are a widespread Holarctic group of smallish fishes, belonging to the suborder Cottoidei (the image at top, from Wikimedia, shows Cottus gobio). While most members of the Cottoidei are marine, there are a number of freshwater taxa - about 40 species in Cottus, three in Myoxocephalus (a genus also including marine species), the monotypic genera Mesocottus and Trachidermus, and 33 species divided between three families and 12 genera found in Lake Baikal in central Siberia. Species of Cottus show a wide diversity of life histories, from catadromous (species that live in fresh water before travelling to the sea to spawn) to amphidromous (species that can move between fresh and salt water, but don't do so specifically to spawn - the amphidromous Cottus species are freshwater spawners) to species that are permanently freshwater. As such, Yokoyama and Goto (2005) investigated the phylogeny of this genus using the mitochondrial 12S rRNA and CR (control region) genes to discover its biogeographical history and how the different life histories have evolved.

Previously, the catadromous life cycle has been thought to be ancestral for Cottus, both because freshwater cottoids as a whole are certainly derived from marine ancestors, and because the catadromous Trachidermus fasciatus was identified on morphological groups as the sister group to Cottus. The amphidromous lifestyle was thought to have arisen next, from which increasing specialisation for freshwater habitats had given rise to the purely fluvial (river) or lacustrine (lake) species. The results of Yokoyama and Goto did not contradict the basal position of catadromy, but added a twist - the single catadromous species, Cottus kazika, did not group with the remaining Cottus species, but instead was sister (with high support) to Trachidermus fasciatus, making Cottus polyphyletic (Shedko & Miroshnichenko (2007) have since moved C. kazika out of Cottus as a result, resurrecting an old genus name to label it Rheopresbe kazika). The role of catadromy in the evolution of Cottus therefore becomes a bit more uncertain.

The remaining, freshwater-spawning species of Cottus were supported as a clade, admittedly with low support though the shared life history makes the clade credible. As for whether the amphidromous life style was indeed ancestral to the purely freshwater, Yokoyama and Goto's results seemed to suggest the exact opposite, with the amphidromous species scattered through the various clades of purely freshwater species, and not particular basal within those clades. However, the authors themselves were a little more agnostic about their results - they point out that repeated parallel loss of amphidromy could give a falsely parsimonious appearance of derived amphidromy. Biogeography-wise, their results supported the traditional view of an origin of Cottus somewhere in eastern Eurasia, where the greatest diversity of species is found. Four reasonably well-supported clades of freshwater-spawning species were identified - two restricted to eastern Eurasia and Japan, one found across Eurasia, and one (their clade E) including both Eurasian and North American species.



The non-monophyly of Cottus goes further than just one wayward species, though. You recall that I mentioned the diverse fauna of freshwater cottoids endemic to Lake Baikal? In the past, species of this fauna were divided between three families - some in Cottidae with the other freshwater sculpins, some in an endemic family Abyssocottidae, and a separate family for the unique genus Comephorus. However, molecular analysis (Kontula et al., 2003) had discovered that the Baikal cottoids formed a single clade, and had probably originated from a single colonisation of the lake by an ancestral species. Once in the lake, the cottoids had diversified rapidly (molecular clock calculations, for what they're worth*, estimate an age of 1.2 to 6.2 million years for the Baikal radiation) to occupy a number of niches, including some not occupied by sculpins anywhere else in the world. The pictures above give some indication of the diversity of Baikalian cottoids - the pelagic Cottocomephorus inermis (from here) on the right, an unidentified benthic species reasonably similar to a typical cottid (from here) in the centre, and the highly derived pelagic Comephorus on the left (image from here).

*Okay, so I don't trust molecular clocks as far as I can throw them or the researchers who calculate them. In this case, unfortunately, they're all the evidence we have.

The point where it all becomes really interesting, though, is that not only does this diversity derive from a single point, but it is actually nested within the genus Cottus! This had previously been suggested by Kontula et al. (2003), and so Yokoyama & Goto (2005) took the opportunity to test Kontula et al.'s results against their more extensive dataset by including the data from the earlier study. While support was not impressive, the Baikalian radiation seems to be nested within Yokoyama & Goto's clade E.

As usual, though, I did come away from this paper with a few questions. Yokoyama and Goto used only one marine species and a member of Myoxocephalus as outgroups, and while they did find the Trachidermus + Rheopresbe clade as sister to the freshwater-spawning clade, support was very low and the position was not statistically supported. Is there actually a direct connection between these two clades, or did the catadromous species gain their freshwater lifestyle independently from the freshwater species? Answering this question will be vital to understanding what (if any) role catadromy may have played in the transition of the ancestors of Cottus from marine to freshwater habitats. And what of the untested freshwater Mesocottus haitej? Does this Siberian species represent another independent movement into freshwater, or does the paraphyly of Cottus extend even further?

REFERENCES

Kontula, T., S. V. Kirilchik & R. Väinölä. 2003. Endemic diversification of the monophyletic cottoid fish species flock in Lake Baikal explored with mtDNA sequencing. Molecular Phylogenetics and Evolution 27 (1): 143-155.

Shedko, S. V., & I. L. Miroshnichenko. 2007. Phylogenetic relationships of sculpin Cottus volki Taranetz, 1933 (Scorpaeniformes, Cottidae) according to the results of analysis of control region in mitochondrial DNA. Voprosy Ikhtiologii 47 (1): 27-30 (transl. Journal of Ichthyology 47 (1): 21-25).

Taxon of the Week: Give Us a Kiss!

The fish genus Lethrinus is found in tropical waters of the Indian and western Pacific Oceans, with a single species making an incursion into the eastern Atlantic. The group is commonly known as emperors, though I have heard people here in Australia refer to them as snappers, a confusing piece of terminology for me because they are quite different fish from the one I knew in New Zealand as snapper*. The prominent lips in Lethrinus adults, often a different colour from the surrounding face, have given at least one species the memorable name of "sweetlips" (image above of Lethrinus harak, from Wikimedia). Carpenter & Allen (1989) listed 26 described species and two unnamed species in the genus. One of these undescribed species was named Lethrinus ravus by Carpenter & Randall (2003) (image below of Lethrinus nebulosus from here).



*If you excuse me, I'm just going to have a little rant about the common names of Southern Hemisphere fishes. As with other animals and plants, British settlers in New Zealand and Australia labelled the fish they found in their new country with the names of fish they had been familiar with back in the Old Country. However, when it came to fish the new immigrants seem to have gone to extraordinary lengths to find Northern Hemisphere analogues, with the result that it becomes difficult to see how they ever found a connection. The New Zealand grayling (now unfortunately extinct) was no relation to the Northern Hemisphere grayling. The New Zealand cod is even less like the original. And as I've already indicated, the confusion surrounding the name "snapper" is beyond anyone's ability to sort out. Rant over - please resume normal service.

Emperors are all predators, but are divisible into three ecological groups (Lo Galbo et al., 2002) - low-bodied stalkers with conical teeth that are active hunters of high-speed invertebrates and small fish, high-bodied benthic feeders with molariform teeth that can feed on shellfish and other hard-shelled invertebrates, and high-bodied species with conical teeth that feed on softer-bodied slow-moving invertebrates. The molecular phylogeny of Lo Galdo et al. (2002) recovered a good correlation between trophic type and phylogeny. The high-bodied conical-tooth form appears to be ancestral, with one species (Lethrinus minatus) sister to all the other species, and one species each low down in the two major clades that the other species fell into. Low body-form and molariform teeth both appeared twice, in each case with one clade containing most of the species showing the novel feature, and a single species appearing to have developed it independently.

Of course, what discussion of tropical reef fishes would be complete without a mention of transexuality? Many species of Lethrinus have been shown to be protogynous hermaphrodites - that is, they reach maturity as females before changing sex at a later date to males (Young & Martin, 1982). The mechanism inducing this change in emperors remains unknown. In other protogynous reef fish species, males may maintain harems of females, the largest of which switches sex if the male is removed for whatever reason, but whether emperors have a similar system has not yet been established.

REFERENCES

Carpenter, K. E., & G. R. Allen. 1989. FAO Species Catalogue vol. 9. Emperor Fishes and Large-eye Breams of the World (Family Lethrinidae): An annotated and illustrated catalogue of lethrinid species known to date. Food and Agriculture Organization of the United Nations.

Carpenter, K. E., & J. E. Randall. 2003. Lethrinus ravus, a new species of emperor fish (Perciformes: Lethrinidae) from the western Pacific and eastern Indian oceans. Zootaxa 240: 1-8.

Lo Galbo, A. M., K. E. Carpenter & D. L. Reed. 2002. Evolution of trophic types in emperor fishes (Lethrinus, Lethrinidae, Percoidei) based on cytochrome b gene sequence variation. Journal of Molecular Evolution 54 (6): 754-762.

Young, P. C., & R. B. Martin. 1982. Evidence for protogynous hermaphroditism in some lethrinid fishes. Journal of Fish Biology 21 (4): 475-484.