Fatty acid composition and the evidence for mixed income–capital breeding in female Argentinean short-fin squid Illex argentinus

Abstract

Life histories of organisms are frequently shaped by trade-offs between somatic growth and reproduction. Although previous studies have suggested that sources for reproduction are directly from ingested food in the Argentinean short-fin squid Illex argentinus, recent findings indicate that its reproductive growth probably involves somatic energy use. Therefore, we aimed to determine the reproductive allocation strategy of female I. argentinus, using fatty acids as biochemical indicators. These squid accumulate a substantial amount of fatty acids in the ovary after the onset of sexual maturation. The fatty acid composition in the ovaries was found to have a stronger correlation with that in the digestive gland, a fast turnover tissue reflecting recent dietary information, when compared to the slow turnover mantle tissue, an energy reserve organ. These results suggested that energy for reproduction is primarily from income resources. However, fatty acid composition showed that the ovaries closely resembled mantle tissue during early maturation when the gonadosomatic index increased significantly, and spawning period when the squid showed the lowest feeding activity. This evidence indicated that during these two periods, somatic energy reserve was participating in reproductive growth. Cumulatively, female I. argentinus adopts a mixed income–capital breeding strategy, in that reproduction primarily relies on income resources, coupled with the involvement of storage reserves used during the early maturation and spawning period. This study presents the potential implication of fatty acids to provide insights into the breeding strategies among cephalopods, particularly for oceanic species.