Somatic energy content and histological analysis of the gonads in Antarctic fish from the Scotia Arc

Abstract

Histological characteristics of the gonads and the energy contents of axial muscle, liver and gonads of Antarctic notothenioid fish collected during the LAMPOS (Latin American Polarstern Study) survey in April 2002 were analysed. Ovaries and testes were staged following histological maturity criteria. Oocyte diameters frequency were established and fecundity values were estimated. The energetic values (kJ/g) of different organs were determined using a microcalorimetric bomb. Ovaries of Chaenocephalus aceratus showed a generalised atretic process. The gonadal histology of Champsocephalus gunnari, Pseudochaenichthys georgianus and Chionodracus rastrospinosus suggests that their spawnings take place in autumn. Gobionotothen gibberifrons and Lepidonotothen larseni females were in the process of maturation, with the ovaries of the former containing yolked and atretic oocytes together. Ovaries of Lepidonotothen kempi showed old postovulatory follicles, which provided evidence of previous spawning. Gonads from both sexes of Dissostichus eleginoides were immature. Absolute and relative fecundity were lower in Channichthyidae than in Nototheniidae. The energy contents of the different organs analysed were: liver > gonads > axial muscle. The highest energy density value (kJ/g wet body mass) was found in Dissostichus eleginoides.