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.

Living Larvae and Fossil Fish

Marshall's macristium larva, from Rosen (1971).

Before anything else, a-few-days-belated birthday wishes to Tetrapod Zoology, which has now been going in one form or another for three years. Darren Naish, the author of Tetrapod Zoology, also notes that the number of palaeontology blogs being written that aren't afraid to be technical has increased significantly in recent times - "I don't know if it seems arrogant to think that Tet Zoo was a driving force behind this uber-nerd movement, but I like the idea that it was, so will stick with it". I don't know about other sites, but Darren Naish can pretty much take sole credit (or blame, whichever way you want to look at it) for inspiring yours truly to publish my own ramblings. Of course, I haven't Darren's ability, and I've never achieved his level of following (I'm still waiting for my invite to join ScienceBlogs ;-) ).

In my last post, I briefly alluded to the recent discovery that what have been thought to be three separate species of fish in three different families are, in fact, different life cycle stages (larva, adult male and adult female) of a single species. As remarkable as this discovery is, it can't be called completely incredible - it simply highlights just how little we know about many marine animals. In animals that undergo significant metamorphic changes over the course of development, it is not surprising that the connection between stages should not be initially recognised*. What really struck me about the affair were the low numbers of known specimens - of the three "families" involved, only 65 specimens of "Megalomycteridae" (the adult males) have ever been collected. "Mirapinnidae" (the larvae) are represented by only 120 specimens, while "Cetomimidae" (the adult females) tip the scales at about 600 specimens. To put that into a bit of perspective, the other day I was counting my way through a vial of harvestmen that included some 200 specimens from a single collection.

*Indeed, for those of you familiar with marine invertebrates, this is the reason behind the latin-derived terms for many invertebrate larvae - nauplius, cypris, cercaria. These forms were all initially described as distinct taxa, and after they were recognised as larvae of other taxa their past generic names persisted as terms for that stage in the life cycle.

Because Ed Yong at the link above has already done a bang-up job of explaining the cetomimid situation, I thought I'd dig into the vaults a little and bring up an earlier situation where a family of fish became written off as larvae - the Macristiidae.


Bathysaurus mollis. Photo from here.

"Macristium chavesi" was described by Regan in 1903 from a single specimen collected off the Azores in the North Atlantic (Rosen, 1971). It should be noted that "Macristium" was recognised from the start as a larval form, but supposedly of adults as yet unknown. Initially, Regan regarded Macristium as related to Bathysaurus, a genus of deep-water predatory fish currently in the Aulopiformes, but in 1911 he separated it as its own family that he suggested was related to the Alepocephalidae (other deep-water predators, but now in an entirely different order, the Osmeriformes). Regan's Macristium specimen was in dreadfully poor shape - the lower jaw was damaged, part of the upper jaw was lost entirely, and only one fin (a pectoral) had remained reasonably intact. A second macristiid specimen, in better condition, would not be recognised until 1961, when Marshall described a specimen collected by the ship 'Discovery' in the Bay of Biscay. Marshall's specimen was long and slender, with remarkably elongate fins. On the basis of the new specimen, Marshall reclassified Macristium once again, as a member of the Ctenothrissiformes.

Ctenothrissiformes is a small order of four genera known from England and Lebanon. The type genus, Ctenothrissa resembles Macristium in its elongate fins, but differs from it in being fairly deep-bodied. All three ctenothrissiform genera had one other significant difference from Macristium - they are known only from fossil deposits laid down in the Cretaceous (Patterson, 1964). If Macristium was indeed a member of the Ctenothrissiformes, it was a living survivor of a group long thought to be extinct. As it turned out, though, it was not to be. The relatively few features cited by Marshall as uniting Macristium and Ctenothrissiformes varied from the superficial (fin shape) to the non-existent (supposed similarities in jaw structure). When Berry and Robins described a third macristiid specimen from the Gulf of Mexico in 1967 as a new species, Macristiella lucens, they were sceptical of Marshall's interpretation.


Specimen of Bathytyphlops marionae. Photo from here.

The resolution of the macristiid mystery came in the early 1970s. A third specimen of Macristium was collected by the ship 'Chain' in the mid-Atlantic, allowing Rosen (1971) to convincingly relate it through various meristic characters such as vertebral count, anal position, etc. to members of what is now the order Aulopiformes, and specifically Bathysauridae. Specimens of "Macristiella" from the Pacific Ocean were identified by Okiyama (1972) as belonging to the genus Bathytyphlops in the Ipnopidae (also Aulopiformes). Finally, Johnson (1974) demonstrated using similar characters as in Regan (1971) that a specimen of Macristium from the Gulf of Mexico was assignable to the adult species Bathysaurus mollis. It is perhaps one of ichthyology's great ironies that Regan, as it turns out, had gotten it right in the first place.

As for the Ctenothrissiformes, it may not be a natural group even with the exclusion of Macristium. As indicated in Rosen (1971), while ctenothrissiforms are seemingly related to the modern acanthomorphs (spiny-finned fishes), the characters uniting them as a group are probably all primitive, and Patterson (1964) demonstrated that the genera show different mixtures of primitive and derived features for acanthomorphs. Rosen suggested a relationship to the Beryciformes, but certain features such as the absence of spines in the fins exclude Ctenothrissiformes from the Acanthomorpha (Patterson, 1964). Recent studies suggest that the "Beryciformes" may be a paraphyletic grade near the base of the acanthomorphs (Li et al., 1999), and perhaps the "Ctenothrissiformes" are themselves a paraphyletic outgroup to Acanthomorpha as a whole.


Part and counterpart fossils of Ctenothrissa from Lebanon. Photo from here.

Postscript: They sure don't write scientific articles like they used to. Hay (1903), writing in the American Naturalist, gave an introduction to the diversity of fossil fishes from the Cretaceous of Lebanon (including Ctenothrissa):

To the palæontologist the earth's crust, in its breadth and thickness, is a burial ground from which he may exhume the remains of the animals and plants that once lived on its surface or in its waters. The words of Bryant, spoken of the races of men, might truthfully be applied to other living things,

                     "All that tread
The globe are but a handful to the tribes
That slumber in its bosom."

But there are spots were the carcasses have been sown thicker and have been better preserved than elsewhere; and to such places the scientific birds of prey, who seek for, and must usually be satisfied with, fragmentary bones, and imprints of skeletons, and scattered scales and teeth, are gathered together; and, fed on such booty, they have visions of the swarms of animals, fat, sapid, and comely, that once populated the earth.

REFERENCES

Hay, O. P. 1903. Some remarks on the fossil fishes of Mount Lebanon, Syria. American Naturalist 37 (442): 685-695.

Johnson, R. K. 1974. A Macristium larva from the Gulf of Mexico with additional evidence for the synonymy of Macristium with Bathysaurus (Myctophiformes: Bathysauridae). Copeia 1974 (4): 973-977.

Okiyama, M. 1972. Morphology and identification of the young ipnopid, "Macristiella", from the tropical western Pacific. Japanese Journal of Ichthyology 19 (3): 145-153.

Patterson, C. 1964. A review of Mesozoic acanthopterygian fishes, with special reference to those of the English Chalk. Philosophical Transactions of the Royal Society of London Series B, Biological Sciences 247 (739): 213-482.

Rosen, D. E. 1971. The Macristiidae, a ctenothrissiform family based on juvenile and larval scopelomorph fishes. American Museum Novitates 2452: 1-22.

Perciformes Go Bye-Bye?

Anableps anableps, the four-eyed fish, a member of the newly-named clade Stiassnyiformes. The upper and lower halves of the eyes have different focal distances, allowing the fish to see clearly both above and below the water. Photo from here

Not so long ago, I referred to the unholy taxonomic mess that besets the Acanthomorpha (spiny-finned fishes), the clade that includes (among others) the majority of familiar marine fish, with a large number of acanthomorphs previously dumped in a cluster called "Perciformes". "Perciformes", I'll remind you, was ichthyological code for "morphologically somewhat boring fish that aren't distinctive enough to be called anything else".

Just yesterday, I received notification of a new paper (Li et al., 2009) that identifies a number of the same clades recovered in papers such as Dettai & Lecointre (2005) (which is not entirely surprising because both Dettai and Lecointre are also authors on this one). Where Li et al. (2009) differs from previous studies, however, is that it actually introduces a whole bunch of new names for the clades it finds. (Sadly, they also do something that is a bit of a pet peeve of mine, what I call "stealth taxonomy" - introducing new taxa in a paper without indicating that they're doing so in the title or mentioning their names in the abstract).




The above diagrams from Li et al. (2009) represent a supertree for the Acanthomorpha taken from the results of Li et al.'s analyses. It's been broken into four parts because that's a lot of fish. You may need to click on the images to get a higher resolution picture to follow the next bit.

The clade labelled P at the bottom of the tree doesn't get a name - some studies have found it as monophyletic, some haven't. What does get a name is the clade A uniting the Zeiformes (dories) and Gadiformes (cods) - Zeioigadiformes. That, my friends, is not a name to attempt whilst drunk. The Beryciformes (squirrelfishes and allies) are paraphyletic in the supertree (they're the first three clades leading towards the big P' clade), but some studies (including one of the analyses of Li et al. themselves) still find it to be monophyletic - another watch this space moment. The Ophidiiformes (cusk-eels, etc. - including the Carapidae that are famed for living inside the recta of sea cucumbers) are sister to the P' clade, which is what recent studies have come to call Percomorpha. Batrachoidiformes (toadfishes) are sister to the remaining percomorphs, but as you can see there's still a lot of messiness otherwise. Still, there are a few big clades that can be recognised, most notably the Q, L and X clades.


Sphyraena barracuda, now a member of the Carangimorpha. Photo from here.

The Q clade includes the Atherinomorpha, Mugilidae (mullets), Blennioidei (blennies) and, in most studies, the Cichlidae (cichlids), though in the supertree the cichlids are apparently feeling a bit stand-offish. Li et al. dub this clade the Stiassnyiformes, for reasons sadly unexplained. The L clade, which Li et al. dub the Carangimorpha, includes the big pelagic fish such as dolphins, trevally, marlins, tuna and mackerel, as well as the flatfish. Within the L clade, things are still rather messy, but this is mainly the fault of the flatfish still trying to make themselves look polyphyletic despite all morphological reason.


Unidentified icefish (Notothenioidei). Photo by Uwe Kils.

The X clade is labelled by Li et al. the Serraniformes. I'm guessing that they decided, probably wisely, that "Perciformes" carries just a little to much baggage. Notable members of this clade include the Percidae, Notothenioidei (Antarctic icefishes), Gasterosteidae (sticklebacks) and what were the Scorpaeniformes (now known to be polyphyletic).


Indostomus paradoxus, the armoured stickleback or paradox fish of south-east Asia. Photo from hwchoy.

A couple of smaller clades that rate a mention are the F and G clades. The F clade (now the Anabantiformes) includes the Anabantoidei (gouramis), Channidae (snakeheads), Indostomus (the paradox fish) and Synbranchiformes (swamp eels). The association of these taxa forms an intriguing clade of Old World tropical freshwater fish, with their diversity centred around southern Asia. The G clade includes an assortment of "trachinoid" fishes such as stargazers and torrent fish, but not the Trachinidae themselves. Fittingly, Li et al. label this group the Paratrachinoidei.

Part of the problem with dropping the idea of "Perciformes", to date, has been that to do so would leave a massive pile of unplaced families just flopping all over the place. Hopefully, with the pile of new clade names presented to us by Li et al., a big step has been taken towards allowing us to never have to say "Perciformes" again.

REFERENCES

Dettai, A., & G. Lecointre. 2005. Further support for the clades obtained by multiple molecular phylogenies in the acanthomorph bush. Comptes Rendus Biologies 328 (7): 674-689.

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.

The Bush at the Top of the Tree

Sailfish (Istiophorus albicans) feeding on sardines. Photo by Douglas Seifert.

In an earlier post, I introduced the concept of a wastebasket taxon - a dumping-place for usually largely unspecialised taxa that do not possess the distinctive characters to place them elsewhere. Sadly, the history of taxonomy has no shortage of examples of wastebaskets. Some of them have been progressively cleaned out in recent years; others remain sitting there in a jumbled heap, just daring reasearchers to have the courage (or foolishness) to take them on. Of all the enormous, ugly junk-piles in classification, however, perhaps none is more enormous or more ugly than the Perciformes.

The Perciformes, as pointed out by many a textbook, is the largest by a considerable margin of all orders of fishes, and of vertebrates for that matter. There are over 7000 species of Perciformes of all different varieties, from tiny gobies to gigantic marlin and tuna. Go down to a beach, drop a fishing line into the water, and you can almost guarantee that the first thing you pull up will be a perciform. What makes all this diversity even more of an achievement, though, is that the order Perciformes doesn't really exist. Not in any way that actually makes sense. Not a single distinctive character unites all of the various taxa included in the Perciformes. As Gill & Mooi (2002) put it, "not only are there no synapomorphies to unite the order, it is not even diagnosable on the basis of shared primitive characters". As the saying goes, it's not even wrong.


The oarfish or king of the herrings, Regalecus glesne, a basal acanthomorph. Oarfishes can be over ten metres in length. Photo by Gerry Smith.

So if there's nothing to unite the order, what is it doing there in the first place? "Perciform" fishes belong to a clade called Acanthomorpha, the monophyly of which is well-supported. Among other things, one of the most easily recognisable features of the Acanthomorpha is that the first few rays of the fins have been replaced by hard spines. Within the Acanthomorpha, a number of distinct orders are recognised. The dories of the order Zeiformes have a distinctive telescoping mouth that allows them to function as expert ambush predators. The pufferfishes and triggerfishes of the Tetraodontiformes, in contrast, have the bones of the mouth fused into a powerful beak for crushing hard prey. The flatfish of the order Pleuronectiformes have moved both eyes onto one side of their heads, and spend their days lying on their sides. But once these distinctive taxa have all been isolated - once you've taken out the fish that look like dories and the fish that look like puffers - you're still left with a large pile of fish that, well, just kind of look like fish. This pile is what you label "Perciformes" and pretend that you've somehow done something about it. Needless to say, being the association of acanthomorphs that aren't distinctive enough to be separated off, the Perciformes has varied on content quite considerably over the years.

The very undefined nature of the Perciformes is also exactly what makes it such a difficult phylogenetic problem to solve. The phylogeny of the Perciformes is nothing less than the phylogeny of the Acanthomorpha as a whole - to solve one, you must solve the other. With nearly 15,000 living species of acanthomorphs, that is a colossal task. Still, a number of poor, foolhardy souls have made the attempt over the years. The advent of molecular analyses has improved matters, though there's still a lot of disagreement.



The figure above shows a Bayesian tree from a relatively recent effort (Dettai & Lecointre, 2005). Support for a number of the clades found tended to be on the low side, but this paper and an earlier one (Chen et al., 2003) took the approach of analysing a number of separate datasets from different genes as well as the combined analysis, and seeing which clades were supported in which analyses (the theory being that a clade resulting from a number of different data sources is probably worth consideration even if the numerical support is not high every time). The clades with letters beside them are ones that appeared in a number of analyses.

Though not strongly supported, this analysis agrees with others (both molecular and morphological) in recovering a basal grade within the the Acanthomorpha that includes Polymixia (beardfishes), Zeiformes (dories), Gadiformes (cods) and Beryciformes (squirrelfishes). Members of the "Perciformes" fall in a clade that runs in the tree above from Pomatoschistus (Gobiidae) to Cyclopterus, but this clade also (surprise, surprise) includes members of a number of other orders, and the Perciformes are polyphyletic. Some of the recovered relationships have been suggested before. Clade N, for instance, includes the Tetraodontiformes, Caproidae (boarfishes) and Acanthuroidei (surgeonfishes and allies), and relationships have been suggested on morphological grounds between Tetraodontiformes and either one of the other two groups (though, ironically enough, never both at the same time). Some of the relationships suggested by molecular analyses have been entirely novel - clade N also includes the Lophiiformes (anglerfishes), which might have been just about the last group one would expect to be related to puffers.

The tree is also not without evidence of how far there is yet to go. Both Tetraodontiformes and Pleuronectiformes appear as polyphyletic, a result that is almost certainly complete twaddle in light of the distinctive morphological characters uniting members of these orders. The appearance of the opah Lampris in the middle of the Serranidae seems also pretty suspect to me (offhand, Lampris appears on the tree twice - I suspect the "Lampris" near the bottom of the tree is a misprint for Regalecus, the oarfish or king of the herrings). G. Nelson commented of fish phylogeny in 1989 that "recent work has resolved the bush at the bottom, but the bush at the top persists". That bush still needs a lot of topiary.

REFERENCES

Chen, W.-J., C. Bonillo & G. Lecointre. 2003. Repeatability of clades as a criterion of reliability: a case study for molecular phylogeny of Acanthomorpha (Teleostei) with larger number of taxa. Molecular Phylogenetics and Evolution 26 (2): 262-288.

Dettai, A., & G. Lecointre. 2005. Further support for the clades obtained by multiple molecular phylogenies in the acanthomorph bush. Comptes Rendus Biologies 328 (7): 674-689.

Gill, A. C., & R. D. Mooi. 2002. Phylogeny and systematics of fishes. In Handbook of Fish Biology and Fisheries (P. J. B. Hart & J. D. Reynolds, eds.) pp. 15-42. Blackwell Publishing.