Antarctic Science 23(1), 18–26 (2011) & Antarctic Science Ltd 2010 doi:10.1017/S095410201000060X Biology of the Antarctic dragonfish Vomeridens infuscipinnis (Notothenioidei: Bathydraconidae) KRISTEN L. KUHN 1 , THOMAS J. NEAR 1 , H. WILLIAM DETRICH III 2 and JOSEPH T. EASTMAN 3 * 1 Department of Ecology and Evolutionary Biology and Peabody Museum of Natural History, Yale University, New Haven, CT 06520-8105, USA 2 Department of Biology, Northeastern University, Boston, MA 02115, USA 3 Department of Biomedical Sciences, Ohio University, Athens, OH 45701-2979, USA *author for correspondence: eastman@ohiou.edu Abstract: Nineteen specimens of the rare dragonfish Vomeridens infuscipinnis were evaluated for meristic counts, morphometric measurements, vomerine teeth and the supratemporal canal, anatomical and histological observations of bone, cartilage and lipid, diet, and reproductive status. Seven individuals were measured for buoyancy. All specimens had small vomerine teeth that varied in number. There was also variability in the arrangement of the supratemporal pores and canals. Vomeridens possess a body with little bone and considerable amounts of cartilage and lipid. A mean percentage buoyancy of 1.61% indicated that Vomeridens is nearly neutrally buoyant. Inferences from measurements of buoyancy and from morphological data suggest that Vomeridens lives in an epibenthic water column habitat at 400–900 m. Facilitated by its reduced body density, Vomeridens are likely to forage in the water column by hovering above the substrate. The stomach contents consisted of krill (Euphausia superba), some as large as 46–50 mm.The absolute and relative fecundity in seven female was 1576–2296 oocytes (mean 1889) and 21.3–28.9 oocytes g -1 body weight (mean 25.3), respectively. The reproductive effort in terms of egg diameter, GSI, and absolute and relative fecundity is similar to that for other bathydraconids. Received 22 March 2010, accepted 6 July 2010, first published online 20 August 2010 Key words: bone and cartilage histology, buoyancy, diet, meristics, reproduction, somatic lipid, vomerine teeth Introduction The modern ichthyofauna of the Southern Ocean is dominated by species belonging to a single perciform suborder, the Notothenioidei (Eastman 1993). Of 131 recognized species, ,80% are restricted to Antarctic waters and belong to five families: Artedidraconidae, Bathydraconidae, Channichthyidae, Harpagiferidae, and Nototheniidae. The high degree of Antarctic endemism results from the adaptive radiation of the notothenioids to fill niches vacated by competing, temperate fish taxa, as they became locally extinct due to oceanic cooling during the past 24 million years (Near 2004). At the highest Antarctic latitudes, notothenioids represent 77% of species diversity and 90% of biomass, a level of dominance by a single taxonomic group that is unique among piscine shelf faunas of the world (Eastman 2005). The hallmark of the notothenioid radiation is the evolutionary restructuring of morphology for life in the water column, termed secondary pelagicism (Eastman 1993). The ancestral notothenioid stock was a negatively buoyant, bottom-dwelling perciform that arose , 40–60 m.y.a. (DeWitt 1971, Eastman & Clarke 1998, Eastman 2000). Lacking a swim bladder, the Notothenioidei evolved pelagic or partially pelagic lifestyles by reduction of skeletal mineralization and enhancement of lipid deposition (Eastman 1993). Secondary pelagicism has arisen independently several times in different notothenioid clades (Eastman 1997, 1999, Near et al. 2007) and is based on the retention of traits in the adult that are larval characteristics in outgroups (paedomorphism) (Eastman 1997). Paedomorphic characters in pelagic notothenioids include partial or complete retention of the notochord (Eastman 1997) and persistence of a cartilage-rich skeleton (Albertson et al. 2010). Today, notothenioids occupy cryopelagic, pelagic, semipelagic and benthopelagic habitats in addition to their ancestral benthic habitat (Eastman 1993). The family Bathydraconidae (dragonfishes) includes 16 species in 11 genera (Eastman & Eakin 2000). Dragonfishes are most abundant and diverse in the deep shelf waters of high Antarctic latitudes (Schwarzbach 1988, Ekau 1990, Eastman 1993, La Mesa et al. 2007). They have an elongated body and show only modest diversification in form, which ranges from moderately robust and well muscled (Gymnodraco, Cygnodraco, Parachaenichthys spp., Psilodraco and Acanthodraco) to slender and gracile (most other genera; see Fig. 1a for Vomeridens infuscipinnis). Adults reach 13–59 cm SL, with a median of , 25 cm (Gon 1990). Molecular phylogenetic analyses of notothenioids have shown the Bathydraconidae to be paraphyletic, with some species in the clade (e.g. Gymnodraco acuticeps) appearing to be more closely related to the hemoglobinless icefishes (family Channichthyidae) than to other bathydraconids 18