Diversity and biogeography of larval and juvenile notothenioid fishes in McMurdo Sound, Antarctica

Antarctic notothenioid fish larvae and juveniles are pelagic and subject to oceanic transport, influencing species distribution and biogeography. The nature of notothenioid larval/juvenile diversity in the high-latitude McMurdo Sound is virtually unknown to-date. We report here a first assessment of this diversity and its contribution to species richness in the Sound. We collected 151 larvae and juveniles from under ice cover. To overcome uncertainties in identifying larvae by morphology, we used full-length mitochondrial ND2 gene sequences in phylogenetic reconstruction with reference adults and identified 13 species representing four families. Six are nototheniids whose adults are common in the Sound, and a seventh is a cryptic nototheniid that is likely Pagothenia brachysoma, previously unknown to the Sound. The rest included four icefishes, an artedidraconid, and a bathydraconid, all without prior adult record in the Sound. With seven of 13 species previously undocumented, larval/juvenile notothenioid diversity appears to double adult diversity. Published fish surveys show adults of these icefishes and the artedidraconid occur in the nearby Terra Nova Bay and/or western Ross Sea; thus, their pelagic larvae and juveniles could be transported by the Ross Sea circulation into the Sound. The bathydraconid, identified as Psilodraco breviceps, is reportedly endemic to S. Georgia. We found additional unpublished barcode sequences for specimens from the Dumont d’Urville Sea and Ross Sea, and they form a species clade with the McMurdo larval and Marguerite Bay adult P. breviceps in this study, indicating this species has a circumpolar distribution.