Effect of sexual maturation on the tissue biochemical composition of<Emphasis Type="Italic"> Octopus vulgaris</Emphasis> and<Emphasis Type="Italic"> O</Emphasis>.<Emphasis Type="Italic"> defilippi</Emphasis> (Mollusca: Cephalopoda)

Changes in the protein, lipid, glycogen, cholesterol and energy contents, total amino acid and fatty acid profiles of Octopus vulgaris and O. defilippi tissues (gonad, digestive gland and muscle) during sexual maturation (spermatogenesis and oogenesis) were investigated. Both species showed an increase of amino acids and protein content in the gonad throughout sexual maturation (namely in oogenesis), but allocation of these nitrogen compounds from the digestive gland and muscle was not evident. The major essential amino acids in the three tissues were leucine, lysine and arginine. The major non-essential amino acids were glutamic acid, aspartic acid and alanine. With respect to carbon compounds, a significant increasing trend (P<0.05) in the lipid and fatty acid contents in the three tissues was observed, and, consequently, there was also little evidence of accumulated lipid storage reserves being used for egg production. It seems that for egg production both Octopus species use energy directly from food, rather than from stored products. This direct acquisition model contrasts with the previous model for Octopus vulgaris proposed by ODor and Wells (1978: J Exp Biol 77:15–31). Most of saturated fatty acid content of the three tissues was presented as 16:0 and 18:0, monounsaturated fatty acid content as 18:1 and 20:1 and polyunsaturated fatty acid content as arachidonic acid (20:4n-6), eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n-3). Though cholesterol is an important precursor of steroid hormones, this sterol content exhibited variations that do not seem to be related with the maturation process. Moreover, significant differences (P<0.05) were obtained between genders, suggesting that perhaps there is a greater physiological demand for cholesterol during spermatogenesis than oogenesis. If the component sterols of octopus are of a dietary origin, considerable variation in the cholesterol content between species might be expected on the basis of the sterol composition of their prey. The glycogen reserves increased significantly in the gonad and decreased significantly (P<0.05) in the digestive gland and muscle of O. vulgaris (these trends were not evident in O. defilippi). Glycogen may play an important role in the maturation process and embryogenesis of these organisms, because carbohydrates are precursors of metabolic intermediates in the production of energy. It was evident that sexual maturation had a significant effect upon the gonad energy content, but the non-significant energy variation (P>0.05) in the digestive gland and muscle revealed no evidence that storage reserves are transferred from tissue to tissue. The biochemical composition of digestive gland and muscle may not be influenced by sexual maturation, but rather by other biotic factors, such as feeding activity, food availability, spawning and brooding.Communicated by S.A. Poulet, Roscoff