西南大西洋巴塔哥尼亚枪乌贼的繁殖生物学特性

Reproductive characteristics of Patagonian longfin squid(Doryteuthis gahi) in the Southwest Atlantic Ocean

作为栖息水域最冷的枪乌贼科头足类,巴塔哥尼亚枪乌贼在西南大西洋生态系统中有着重要的生态作用,但迄今为止,关于该物种的繁殖生物学信息仍较有限。为此,本研究对巴塔哥尼亚枪乌贼的雌雄组成结构、性腺发育及其生殖投入等繁殖生物学特性进行了分析。结果显示,巴塔哥尼亚枪乌贼雌雄比例约为1.79∶1,基本接近雌雄比例1∶1假设。雌雄个体大小以单一峰值区间分布个体为主,雌雄个体之间的生长不存在显著性差异。雌性个体性腺指数为0.11~6.44,缠卵腺指数为10.74~36.51,二者密切相关;雄性个体性腺指数为0.29~5.75,精荚复合体指数为0.06~1.21,二者不存在统计学相关性。随着性腺发育,雌性个体的体征指标呈下降趋势,生殖投入指标呈上升趋势;雄性个体的体征指标随着性腺发育略呈上升趋势,生殖投入指标则下降并处于较差状态。雌雄个体的体征指标与生殖投入指标均呈负相关关系,但是均不存在显著的相关性。研究表明巴塔哥尼亚枪乌贼生殖能量投入以外源性为主,繁殖策略倾向于间歇性产卵。

As the coldest water spawning species among the loliginids, Patagonian longfin squid （Doryteuthis gahi） plays an important ecological role in the Southwestern Atlantic Ocean ecosystem. However, the information on reproductive biology of this species is very limited. So the reproductive characteristics of D. gahi in the southwest Atlantic Ocean, including the sexual structures, gonad development and reproductive investment were studied based on the biological measurement and statistical analysis. The results indicated that the overall sex ratio of females to males was about 1.79 ＂ 1 and the ratio was not significantly away from the hypothesis of 1 ： 1. The size-frequency was unimodal for both sexes in dorsal mantle length and body mass, and no significant difference of growth between females and males was determined according to the length-weight relationship analysis. In females, the gonadosomatic index （GS1） ranged from 0.11 to 6.44, and the nidamental gland index （NG1） ranged from 10.74 to 36.51. There was significant correspondence between these two indices. In males, the GS1 ranged from 0.29 to 5.75, and the spermatohporic complex index （SCI） ranged from 0.06 to 1.21. However, there was no statistical correlation between these two indices. The condition （defined as the residuals from the body weight- dorsal mantle length relationships） of females decreased with maturity, while the reproductive investment （defined as the residuals from the reproductive system weight-dorsal mantle length relationships） increased with sexual maturation onwards. In contrast to females, the condition of males increased with maturity, while the reproductive investment decreased during the course of sexual maturation. Though a slightly negative relationship was found between the condition and reproductive investment for both sexes, the condition was not significantly correlated with the reproductive investment. These findings implied that sourcing energy for reproduction in D. gahi might be mainly on exogenous, and the reproductive strategy was more inclined to the intermittent spawning strategy.