Description and Comparison of Eggs and Yolk Sac Larvae of Greenland Cod (Gadus ogac), Atlantic Cod (Gadus morhua) and Arctic Cod (Boreogadus saida) from West Greenland Waters

摘要

Laboratory reared eggs and yolk sac larvae of Greenland cod (Gadus ogac) from West Greenland are described and compared to wild-caught larvae from West Greenland presumed to be G. ogac, to wild-caught larvae of Atlantic cod (Gadus morhua) from West Greenland waters and in the literature, to larvae of Arctic cod (Boreogadus saida) in the literature and wild-caught in West Greenland waters and to a literature description of larvae of toothed cod (Arctogadus borisovi). The almost total absence of external pre-anal pigmentation with none dorsally in late stage embryos and yolk sac larvae of G. ogac up to 5.2 mm notochord length (NL) distinguishes them from the other species, where extensive external pre-anal pigmentation is always present, at least dorsally. Also, a larger maximum yolk sac larval size of at least 5.2 mm NL (based on reared specimens) compared to a maximum of 4.0-4.5 mm NL and post-anal length/total length ratios of 0.55-0.59 compared to 0.51 respectively in G. ogac and G. morhua distinguish these species. Concerning the post-anal pairs of dorsal and ventral pigment bars and ventral and dorsal caudal melanophores posterior to these, in G. ogac the first dorsal bar is usually shorter than the ventral bar, while the second dorsal bar is usually the longer of the pair, and there are 2-6 ventral and 0-1 dorsal melanophores. In G. morhua the ventral bars are the wider and there are 1-2 ventral melanophores. In B. saida both of the dorsal pigment bars are wider than the ventral ones, and there are 0-1 ventral and 0-2 dorsal melanophores. Three 6-12 mm NL G. morhua larvae from West Greenland have a 24-38% greater horizontal eye width than larvae of similar sizes from boreal North Atlantic waters