Phenotypic plasticity in the Antarctic nototheniid fish Trematomus newnesi: a guide to the identification of typical, large mouth and intermediate morphs

Abstract

Trematomus newnesi is a common inshore species with a circum-Antarctic distribution. It provides the only known example of phenotypic plasticity in Antarctic notothenioid Wsh, existing as populations of typical, large mouth and intermediate morphs that can be diYcult to identify. Using specimens from both Potter Cove, King George/25 de Mayo Island, and from McMurdo Sound, we found that the morphometric measurements gape width/head length (HL), upper jaw length/HL and, to a lesser extent, orbit diameter/HL reliably separated the morphs. For use in a key, we converted the ratios into the qualitative characters head shape, head width and upper jaw length relative to middle of the eye. To increase the reliability of the key, we also assessed intra-morph variability in these characters. The key is supplemented with colour photographs illustrating the distinctive features for separation of the morphs. We discovered that, in the case of the specimens from Potter Cove, each morph had a distinct pattern of colouration: typical-trunk blotched, with yellow or orange-brown predominating especially on pectoral and caudal Wns; large mouth-trunk blotched, with green predominating especially in pectoral and opercular regions; and intermediate-trunk less blotched, with homogeneous dark brown-grey on trunk, pectoral and caudal Wns. We also discuss the ecological implications of colour in the morphs.

Implications of biological factors on accumulation of persistent organic pollutants in Antarctic notothenioid fish

“…The Antarctic Nototheniids, Notothenia rossii (NOR) and Trematomus newnesi (TRN) are circum-Antarctic and typical representatives of the western Antarctic Peninsula ichthyofauna (Kock et al, 2012). They have similar ecological habits in the fjords, living commonly in shallow inshore waters from 20 to 25 m deep on rocky bottoms with macroalgae beds, to offshore shelf waters down to depths of 450 m (Kock, 1982;Tiedtke and Kock, 1989;Barrera-Oro et al, 2012). Their relative abundance, feeding ecology, and biological characteristics, including size and lipids content among other factors, but mainly their wide Antarctic distribution, support their usefulness as sentinels of pollution in the Antarctic marine environment.…”

Shape, condition and diet of the pike icefish Champsocephalus esox (Teleostei: Channichthyidae): evidence of phenotypic plasticity?

“…Phenotypic plasticity has been previously described for the nototheniid fish Trematomus newnesi (Eastman & DeVries 1997, Piacentino & Barrera-Oro 2009, Barrera-Oro et al 2012). According to these authors, the ecological significance of the phenotypic plasticity in T. newnesi is still unclear, as it has not been related to divergence in habitat or diet, although it has an ontogenetic component (Piacentino & Barrera-Oro 2009).…”

Ecomorphological Differentiation of Feeding Structures within the Antarctic Fish Species Flock Trematominae (Notothenioidei) from Terra Nova Bay (Ross Sea)

“…The eye position of T. newnesi is not well-defined along PC1 compared to benthic and pelagic species. T. newnesi is characterised by a degree of phenotypic plasticity and the occurrence of two morphs (a "largemouth morph" and a "typical mouth morph"), whichpossibly reflects niche partitioning [10,59]. The T. newnesi specimens analyzed in this study are all "largemouth morph", a morphotype known to have more demersal habits [10].…”