Effect of sexual
maturation on the tissue biochemical composition of Octopus vulgaris
and O. defilippi (Mollusca: Cephalopoda)
R. Rosa, P.R. Costa, M.L. Nunes-2004
Marine
Biology, 145(3): 563-574
Abstract:
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 O'Dor
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.
(Departamento de Inovação
Tecnológica e Valorização dos Produtos da Pesca, IPIMAR, Avenida de Brasília,
1449-006 Lisbon, Portugal, e-mail: rrosa@ipimar.pt)