Energy accumulation of both somatic and reproductive tissues and the allocation to reproduction in the dwarf form individuals of Sthenoteuthis oualaniensis in the south China Sea

Abstract:

By the technology of tissue energy density determination combined with residuals analyses, the energy accumulation of somatic and reproductive tissues and the allocation to reproduction in the female and male individuals of dwarf form of Sthenoteuthis oualaniensis in the south China Sea were analyzed. The results showed that:there was a significant difference in the tissue energy density between somatic and reproductive organs; and with the exception of nidamental gland, other tissues showed significant variations in the tissue energy density with the progress of maturation. The tissue energy was accumulated significantly in both somatic and reproductive tissues during the sexual maturation. For a given maturity stage, the proportion of somatic tissue energy was consistently larger than that of reproductive tissues. The relative energy accumulation of reproductive tissues of females increased significantly with maturation, while that in males increased rapidly from maturity stages Ⅰ to Ⅴ followed by a non-significant variation at stages Ⅵ and Ⅶ. At the advanced maturity stages, individuals of the dwarf form of Sthenoteuthis oualaniensis showed a better condition in both somatic and reproductive tissues. Further, residuals analyses indicated that a positive correlation was found between the residuals of each somatic tissue energy accumulation regressed on the mantle length and the residuals of reproductive tissues (combined nidamental gland, oviducal complex and ovary in females, while in males combined spermatophoric complex and testis) energy accumulation on the mantle length, suggesting that there was no energy trade-off between somatic and reproductive tissues during the sexual maturation. In combination, these lines of evidence indicated that energy for reproduction in the dwarf form of S. oualaniensis in the south China Sea is mainly derived from food intake, and there are sex-specific variations in the tissue energy density, energy accumulation and relative energy accumulation of both somatic and reproductive tissues.