Sex‐specific reproductive investment of summer spawners of Illex argentinus in the southwest Atlantic

Abstract

Energy investment in reproduction and somatic growth was investigated for summer spawners of the Argentinean shortfin squid Illex argentinus in the southwest Atlantic Ocean. Sampled squids were examined for morphometry and intensity of feeding behavior associated with reproductive maturation. Residuals generated from length‐weight relationships were analyzed to determine patterns of energy allocation between somatic and reproductive growth. Both females and males showed similar rates of increase for eviscerated body mass and digestive gland mass relative to mantle length, but the rate of increase for total reproductive organ weight relative to mantle length in females was three times that of males. For females, condition of somatic tissues deteriorated until the mature stage, but somatic condition improved after the onset of maturity. In males, there was no correlation between somatic condition and phases of reproductive maturity. Reproductive investment decreased as sexual maturation progressed for both females and males, with the lowest investment occurring at the functionally mature stage. Residual analysis indicated that female reproductive development was at the expense of body muscle growth during the immature and maturing stages, but energy invested in reproduction after onset of maturity was probably met by food intake. However, in males both reproductive maturation and somatic growth proceeded concurrently so that energy allocated to reproduction was related to food intake throughout the process of maturation. For both males and females, there was little evidence of trade‐offs between the digestive gland and reproductive growth, as no significant correlation was found between dorsal mantle length‐digestive gland weight residuals. The role of the digestive gland as an energy reserve for gonadal growth should be reconsidered. Additionally, feeding intensity by both males and females decreased after the onset of sexual maturity, but feeding never stopped completely, even during spawning.

Energy acquisition strategy for reproduction in a semelparous squid

“…The reproductive system of I. argetinus increases dramatically once maturation commences [26], therefore we selected 68 female specimens at maturity stages from physiologically maturing (stage III) to spawning (stage VI) after the scales proposed by ICES [37] and Lin et al [38], for reproductive energy analysis, carbon (δ 13 C) and nitrogen (δ 15 N) stable isotope analysis, and fatty acids analyses. The sample size was 12 at stage III (physiologically maturing), 15 at stage IV (early physiologically mature), 15 at stage V (late physiologically mature), 15 at stage VI (functionally mature), and 11 at stage VII (spawning).…”

“…In addition, the Bayesian standard ellipse The boxplot horizontal line and grey solid point respectively denote the median and mean, while upper and lower hinges respectively represent the 25th and 75th percentiles. The maturity stages were followed the scale proposed by ICES [37] and Lin et al [38]: III physiologically maturing, IV-V, physiologically mature, VI, functionally mature, and VII, spawning. The sample size by maturity stage was 12 at stage III, 15 at stage IV, 15 at stage V, 15 at stage VI, and 11 at stage VII area (SEA b ), a posterior estimate of isotopic matrix using the Bayesian approach [39], was significantly different between maturity stages (Kruskal-Wallis, χ2 = 95.51, p < 0.05; Fig.…”

Environmental influence on life-history traits in male squid Uroteuthis edulis with alternative reproductive tactics

“…Large sex-specific differences in LHTs are common in many squid species (Arkhipkin 1996;Jackson et al 2005). Male squids vary more in somatic growth, while females vary more in reproductive investment, since males tend to invest more energy in somatic growth to fight for mating opportunities, while females invest more in egg production (McGrath Steer and Jackson 2004;Pecl et al 2004;Lin et al 2015). These differences are more complex in coastal loliginid squid species, which typically display male dimorphism associated with two alternative reproductive tactics (ARTs) (Iwata and Sakurai 2007;Iwata et al 2018;Apostólico and Marian 2018;Marian et al 2019).…”

Environmental Influence on Life-History Traits in Male Squid Uroteuthis Edulis With Alternative Reproductive Tactics

“…Large sex-speci c differences in LHTs are common in many squid species (Arkhipkin, 1996;. Male squids vary more in somatic growth while females vary more in reproductive investment, since males tend to invest more energy in somatic growth to ght for mating opportunities while females invest more in egg production (McGrath Steer and Jackson, 2004;Pecl et al, 2004;Lin et al, 2015). These differences are more complex in coastal loliginid squid species, which typically display male dimorphism associated with two alternative reproductive tactics (ARTs) (Iwata and Sakurai, 2007;Iwata et al 2018; Marian, 2018, Marian et al, 2019).…”