Cichlids are Not the Only Radiation

The Congo River catfish Chrysichthys brevibarbis, copyright John P. Sullivan.

With their long barbels around the mouth and lack of scales, the catfish of the Siluriformes are one of most instantly recognisable groups of fishes. They are also one of the more diverse, with close to 3000 species and including a third of the world's freshwater fishes (Diogo & Peng 2010). Within the catfish, the Claroteidae are a distinctly African group of thirteen genera divided between two subfamilies, the Claroteinae and Auchenoglanididae. They are characterised by a moderately elongate body with a distinct adipose fin, and strong spines in the dorsal and pectoral fins (Geerinckx et al. 2003). Distinctive features of the Claroteinae include the presence of a toothplate on the palate. The Auchenoglanidinae have a rounded caudal fin and the anterior nostrils moved to the anteroventral side of the upper lip (Geerinckx et al. 2004). For a long time, the claroteids were included in the catfish family Bagridae before being raised to the level of their own family in 1991. A molecular phylogenetic analysis of the Siluriformes by Sullivan et al. (2006) placed the claroteids within a clade of African catfish that they somewhat whimsically labelled as 'Big Africa'. The Bagridae, meanwhile, were placed within 'Big Asia' (though one true bagrid genus, Bagrus, does occur in Africa). Sullivan et al. (2006) questioned claroteid monophyly, finding Auchenoglanidinae to be sister to a clade grouping the Claroteinae with the family Schilbidae, but other morphological studies have found claroteids as a monophyletic unit (Diogo & Peng 2010).

Lake Tanganyika catfish Lophiobagrus brevispinis, from tanganyikacichlide.nl.

The Claroteinae are notable for having undergone something of an adaptive radiation in one of African Great Lakes, Tanganyika. Though not as dramatic as the famous radiation of cichlids in the same lake, the Tanganyikan claroteines comprise over a dozen species divided between four genera (Bailey & Stewart 1984; Hardman 2008). Seven of these are placed in the genus Chrysichthys which has a wide distribution around Africa; the other three genera are unique to the lake. Molecular phylogeny indicates that the majority of Tanganyikan claroteines represent a single colonisation of the lake; only Chrysichthys brachynema has colonised Lake Tanganyika independently (Peart et al 2014). This indicates that the genus Chrysichthys as currently defined is non-monophyletic (something that had previously been suggested on morphological grounds) but any consequent reclassification is yet to occur. The species of Chrysichthys are mostly larger than the endemic Tanganyikan genera, ranging from 19 to 77 cm within Tanganyika (species elsewhere in Africa may reach up to 1.5 m). Of the endemic genera, the monotypic Bathybagrus tetranema is about 15 cm in length but the other two genera Phyllonemus and Lophiobagrus are even smaller, less than 10 cm in length. Bathybagrus and Lophiobagrus also both have reduced subcutaneous eyes. In Bathybagrus, this possibly reflects their occurrence at greater depths than other Tanganyika fish, occurring down to 80 m (nowhere near the depths reached by Lake Baikal sculpins but still impressive enough in the low-oxygen depths of a tropical lake). Lophiobagrus species are specialised to live in the gaps between rocky rubble on the lake bottom. The species of this genus have also been observed secreting a toxic mucus that can be fatal to other fish; this mucus is believed to be secreted from enlarged glands behind the pectoral fins.

Subcutaneous eyes are also found in two claroteines outside Tanganyika: the species Amarginops platus and Rheoglanis dendrophorus, both found in the Upper Congo (Hardman 2008). These two species are specialised for life in river rapids.

REFERENCES

Bailey, R. M., & D. J. Stewart. 1984. Bagrid catfishes from Lake Tanganyika, with a key and descriptions of new taxa. Miscellaneous Publication, Museum of Zoology, University of Michigan 168: 1–41.

Diogo, R., & Z. Peng. 2009. State of the art of siluriform higher-level phylogeny. In: Grande, T., F. Poyato-Ariza & R. Diogo (eds) Gonorynchiformes and Ostariophysan Relationships: A Comprehensive Review pp. 465–515. Science Publishers.

Geerinckx, T., D. Adriaens, G. G. Teugels & W. Verraes. 2003. Taxonomic evaluation and redescription of Anaspidoglanis akiri (Risch, 1987) (Siluriformes: Claroteidae). Cybium 27 (1): 17–25.

Geerinckx, T., D. Adriaens, G. G. Teugels & W. Verraes. 2004. A systematic revision of the African catfish genus Parauchenoglanis (Siluriformes: Claroteidae). Journal of Natural History 38: 775–803.

Hardman, M. 2008. New species of catfish genus Chrysichthys from Lake Tanganyika (Siluriformes: Claroteidae). Copeia 2008 (1): 43–56.

Peart, C. R., R. Bills, M. Wilkinson & J. J. Day. 2014. Nocturnal claroteine catfishes reveal dual colonisation but a single radiation in Lake Tanganyika. Molecular Phylogenetics and Evolution 73: 119–128.

Sullivan, J. P., J. G. Lundberg & M. Hardman. 2006. A phylogenetic analysis of the major groups of catfishes (Teleostei: Siluriformes) using rag1 and rag2 nuclear gene sequences. Molecular Phylogenetics and Evolution 41: 636–662.

Amphiascus: Can a Copepod be a Friend of Mine?

Amphiascus sp., copyright Alexandra.

The animal shown in the image above is a member of Amphiascus, a cosmopolitan genus of about thirty known species of benthic harpacticoid copepods. Amphiascus is a genus of the family Miraciidae; in older texts, you will find it referred to the Diosaccidae, but this family is now regarded as a synonym of the former. Miraciids are somewhat elongate harpacticoids generally with a fusiform body shape and females with paired egg sacs; as with other copepod taxa, their specific characterisation depends on fairly fine characters of the appendage setation (Willen 2002). Wells et al. (1982) placed Amphiascus in association with a group of related genera in the miraciid family tree on the basis of its retention of a fairly extensive setation on the pereiopods, two inner setae on the endopod of pereiopod II in females, and two articulated claws on that segment in males. However, the proposed phylogeny of Wells et al. provides no apomorphies for Amphiascus itself, implying that it is characterised only by plesiomorphies relative to related genera.

The title of this post refers to the circumstances surrounding the discovery of a relatively recently described Amphiascus species, A. kawamurai Ueda & Nagai 2005. In the cultivation in Japan of nori, the edible alga used (among other things) in wrapping sushi rolls, the conchocelis phase of the life cycle is grown on oyster shells in outdoor tanks of seawater (like many algae, nori goes through an alternation of generations, with its life cycle including two very distinct forms; as well as the familiar large flat alga, the life cycle of nori includes a small filamentous shell-boring stage, initially mistaken for a distinct organism and called Conchocelis). Unfortunately, the oyster shells may also become overgrown with diatoms, retarding the growth of conchocelis. As a result, nori growers may be required to laboriously scrub the shells of diatoms several times over the conchocelis growth period. However, it was noticed in Ariake Bay in Kyushu that some form of copepod would sometimes appear in the nori tanks, presumably brought in with seawater from the bay. When this copepod was present, it would graze on the diatoms, reducing the need for other controls. Study of the nori-tank copepod revealed it to be a previously undescribed species, revealing once more that even the species we are not aware of have the potential to directly improve our lives.

REFERENCES

Ueda, H., & H. Nagai. 2005. Amphiascus kawamurai, a new harpacticoid copepod (Crustacea: Harpacticoida: Miraciidae) from nori cultivation tanks in Japan, with a redescription of the closely related A. parvus. Species Diversity 10: 249–258.

Wells, J. B. J., G. R. F. Hicks & B. C. Coull. 1982. Common harpacticoid copepods from New Zealand harbours and estuaries. New Zealand Journal of Zoology 9 (2): 151–184.

Willen, E. 2002. Notes on the systematic position of the Stenheliinae (Copepoda, Harpacticoida) within the Thalestridimorpha and description of two new species from Motupore Island, Papua New Guinea. Cah. Biol. Mar. 43: 27–42.

The Chromeurytominae: Australo-Asian Mystery Wasps

One of the most diverse groups of micro-wasps is the Chalcidoidea, a bewildering array of intricate little jewels. A number of chalcidoid taxa have been extensively studied due to their roles as parasitoids of insect pests, but there are also many groups of chalcidoids that remain little known. One such group is the Chromeurytominae.

Male Chromeurytoma sp., copyright John Heraty.

The Chromeurytominae are a small group of chalcidoids primarily known from Australia, where they are represented by two genera, fourteen species of Chromeurytoma and the monotypic Asaphoideus niger (Bouček 1988). A single species, Pitayana coccorum, has also been described from Bangladesh (Bouček & Bhuiya 1990). Characteristic features include a relatively large subrectangular pronotum (the first segment of the thorax) and an antenna with six segments between the pedicel and the clava (the club). They are more or less shiny, often with a blue or green metallic gloss, and the gaster is fairly robust and does not collapse in preserved specimens. The affinities of the Chromeurytominae have been rather uncertain and the subfamily was only established by Bouček in 1988. Chromeurytoma itself was originally described in the family Eurytomidae, with which it shares the large pronotum. Other features suggest a relationship with the family Torymidae, such as an occipital carina (a ridge around the back of the head) and prominent cerci. Currently the Chromeurytominae are treated as part of the family Pteromalidae, which is not really saying too much. As our understanding of chalcidoid phylogeny has improved in recent years, it has largely confirmed what many workers had long suspected: that once you account for the other families, the Pteromalidae is pretty much just what's left over. Nevertheless, the broad-scale analysis of chalcidoids by Heraty et al. (2013) places the Chromeurytominae within a cluster of 'pteromalid' subfamilies, closer to the type subfamily Pteromalinae than to either the Eurytomidae or Torymidae.

The chromeurytomines are a bit of a mixed bag in terms of host species, but there is the common thread that their hosts are immobile or semi-sedentary plant-feeding insects. Pitayana coccorum attacks mealybugs and other soft scales, with multiple larvae potentially developing on a single host. Asaphoideus niger attacks the citrus leaf-miner Phyllocnistis citrella. The Chromeurytoma species are associated with galls on trees such as Eucalyptus; presumably they are parasites of the insects forming the galls.

REFERENCES

Bouček, Z. 1988. Australasian Chalcidoidea (Hymenoptera): A biosystematic revision of genera of fourteen families, with a reclassification of species. CAB International: Wallingford (UK).

Bouček, Z., & B. A. Bhuiya. 1990. A new genus and species of Pteromalidae (Hym.) attacking mealybugs and soft scales (Hom., Coccoidea) on guava in Bangladesh. Entomologist's Monthly Magazine 126: 231–235.

Heraty, J. M., R. A. Burks, A. Cruaud, G. A. P. Gibson, J. Liljeblad, J. Munro, J.-Y. Rasplus, G. Delvare, P. Janšta, A. Gumovsky, J. Huber, J. B. Woolley, L. Krogmann, S. Heydon, A. Polaszek, S. Schmidt, D. C. Darling, M. W. Gates, J. Mottern, E. Murray, A. D. Molin, S. Triapitsyn, H. Baur, J. D. Pinto, S. van Noort, J. George & M. Yoder. 2013. A phylogenetic analysis of the megadiverse Chalcidoidea (Hymenoptera). Cladistics 29: 466–542.

Petrosia: The Sexual Life of the Sponges

It has to be admitted that sponges are not one of the best-publicised of animal groups. Even when they are given some grudging mention, there is little reference to the variety of sponges that can be found on our planet. But don't go thinking that all sponges are the same.

Stony sponge Petrosia ficiformis, copyright Véronique Lamare.

Petrosia is a genus of sponges found in tropical and subtropical oceans around the world. Members of this genus come in a variety of forms: branching, cylindrical, globular, lamellate or bowl-shaped. They may reach large sizes, with some species up to a metre or two in diameter, though others may be much smaller. Most species are dark colours such as red, brown or black, though the Sulawesi species Petrosia alfiani is a bright canary yellow (de Voogd & van Soest 2002). The reasons for classifying such superficially divergent forms in a single genus lie beneath the surface. However, it has a high proportion of skeletal spicules to soft tissue, giving Petrosia species a hard, brittle texture (hence they are sometimes known as 'stony sponges'). The spicules of Petrosia are mostly long, slightly curved rods that may be rounded or pointed at the ends; they may be large or smaller, with smaller spicules tending to be more common closer to the sponge's surface. Two subgenera are recognised within Petrosia on the basis of whether the spicules are mostly in a tangential (subgenus Petrosia) or reticulate (Strongylophora) arrangement. The subgenus Petrosia is known from the Atlantic and Pacific Oceans, whereas Strongylophora species are found in the Indian Ocean and the western Pacific (Desqueyroux-Faúndez & Valentine 2002).

Magnified view of surface of Petrosia ficiformis specimen, showing arrangement of spicules, from (Desqueyroux-Faúndez & Valentine (2002).

One of the best-studied species in this genus is the Mediterranean Petrosia ficiformis, which tends towards a cylindrical growth habit in sheltered spots. Like other sponges, P. ficiformis may provide an important habitat for other organisms. Smaller invertebrates live in and around the sponge, and molecular studies have shown that different sponge species tend to host their own distinct communities of bacteria. However, the niche provided by Petrosia in the Mediterranean can be vulnerable to damage: field observations have indicated that stony sponges grow exceedingly slowly. Maldonado & Riesgo (2009) found that in twenty years of diving off the Spanish coast, they saw almost no growth in individual sponges. When they took small (one by one-half centimetre) tissue samples from the sponges, it could take up to three months for the removed patch to regrow. Such a slow rate of growth definitely makes one wonder just how old some of the large Petrosia referred to above must be.

Bowl-shaped Petrosia lignosa, from de Voogd & van Soest (2002).

Maldonado & Riesgo (2009) were taking their samples to study how the sponges reproduced. Petrosia species are free spawners, releasing eggs and sperm directly into the water column. In the case of P. ficiformis, this happens in late autumn. Eggs develop at scattered locations through the sponge, but migrate within the body to form clusters before being released. The sexes are separate, with an individual sponge only producing either eggs or sperm. After fertilisation, the eggs develop into small ciliated larvae that may shift between a spherical and a multilobate form. Whereas the larvae of other sponges may be quite mobile, those of P. ficiformis are not active swimmers, presumably relying on the motion of water currents to carry them to a suitable resting spot. Maldonado & Riesgo (2009) noted that in the two years they observed Petrosia spawning, it occured at times when surge levels had risen immediately prior to the onset of stormy weather. Despite the regular associations of Petrosia with particular microbial populations, the larvae do not carry any sort of culture propagule from their parents, indicating that each individual sponge reacquires its associates from the surrounding waters. Larvae attach themselves to the substrate after two to four weeks of growth, and proceed to grow slowly (though, as is the way of sponges, if multiple larvae settle immediately adjacent to one another they may fuse into a single aggregate individual). Larvae grown in the lab took about one and a half months to develop distinct choanocyte chambers (the ciliated chambers in which a sponge filters water for food particles). They may share their environment with sea hares, but there is no question that Petrosia are sea tortoises.

REFERENCES

Desqueyroux-Faúndez, R., & C. Valentine. 2002. Family Petrosiidae van Soest, 1980. In: Hooper, J. N. A., & R. W. M. van Soest (eds) Systema Porifera: A guide to the classification of sponges pp. 906–917. Kluwer Academic/Plenum Publishers: New York.

Maldonado, M., & A. Riesgo. 2009. Gametogenesis, embryogenesis, and larval features of the oviparous sponge Petrosia ficiformis (Haplosclerida, Demospongiae). Marine Biology 156 (10): 2181–2197.

Voogd, N. J. de, & R. W. M. van Soest. 2002. Indonesian sponges of the genus Petrosia Vosmaer (Demospongiae: Haplosclerida). Zool. Med. Leiden 76 (16): 193–209.

Bizarre 'alien corpse' has idiots stumped

I know we've all become more familiar with 'mystery monster' corpse stories in the last few years, but I think they may have reached a new nadir. Fairfax featured a story today titled 'Bizarre 'alien corpse' discovered in Russia has experts stumped'. This is the corpse in question (image from linked article):

Supposedly, no-one (including a quoted 'biologist') has the slightest idea what this is, and the find has been sent off for extensive testing. Well, I don't know if I can claim to be any kind of expert myself, but even I can recognise the fricking Parrot of King Charles I when I see it.