阿根廷滑柔鱼雄性成熟个体的体征和生殖投入

Body condition and reproductive investment of mature male Argentinean shortfin squid Illex argentinus

中文关键词: 阿根廷滑柔鱼  体征  性腺指数  生殖投入  西南大西洋

英文关键词: Illex argentinus  Body condition  Gonadosomatic index  Reproductive investment  Southwest Atlantic Ocean

中文摘要:

      为深入全面地认识阿根廷滑柔鱼(Illex argentinus)的繁殖策略，本研究选取2018—2021年西南大西洋公海海域收集的阿根廷滑柔鱼雄性成熟个体样本，利用残差指标分析法计算体质量–胴长标准差作为个体的体征指标，并利用混合效应模型分析体征和性腺指数与栖息海域主要环境因子之间的关系。结果显示，阿根廷滑柔鱼雄性成熟个体的胴长为143~291 mm，体质量为89~559 g，体型以2020年的最大，2018年的最小。2018年和2020年成熟个体的体质量–胴长幂函数关系b值与匀速生长(b=3)存在显著性差异。体征以2020年的体征最好，2018年和2021年的体征较差；性腺指数则以2020年的最低， 2018年和2021年次之。体征与海表温度和叶绿素a质量浓度存在显著的相关关系，在海表温度为9.0~12.5 ℃时，体征随海表温度的增加呈下降趋势；在叶绿素a质量浓度为1 mg/m3左右，体征处于较佳状态。性腺指数仅与海表温度存在显著的相关关系，在海表温度为15 ℃左右处于较大值。以上结果表明，阿根廷滑柔鱼雄性成熟个体的体征与生殖投入存在权衡，海表温度对体征和生殖投入均有显著影响，且叶绿素a质量浓度也对体征产生显著影响。

英文摘要:

      The Argentinean shortfin squid, Illex argentinus, is an oceanic cephalopod displaying characteristics of short lifespan, fast growth rate, and semelparous reproduction. Here, we aimed to comprehensively understand the squid´s life history strategy by investigating the body condition and gonadosomatic index of mature male squids collected from the high seas of the southwest Atlantic Ocean during the 2018–2021 fishing season. Our evaluations used residual index analysis and mixed-effects models to evaluate the relationships between body condition and gonadosomatic index and the key oceanic variables, including sea surface temperature (SST) and chlorophyll a concentration (Chla). The application of the mixed-effects models allowed us to explore the potential influences of habitat environment on somatic and reproductive growth. Our results showed that mature male I. argentinus had a measured mantle length (ML) between 143 mm and 291 mm and a body weight between 89 g and 559 g. We also noted that the largest individuals were collected in 2020, whereas the smallest were collected in 2018. The b values for individuals from 2018 to 2020, estimated using a power regression of body weight versus mantle length, were significantly different from the assumed isometric growth coefficient b value (equals to 3). The standardized residuals of BW-ML relationships indicated that the individuals collected in 2020 retained the best body condition, whereas the individuals from 2018 to 2021 displayed poor body condition. In contrast, mature male I. argentinus showed the lowest gonadosomatic index in 2020, followed by 2018 and 2021. Mixed-effects model evaluations revealed a significant correlation between body condition, SST, and Chla. The individuals displayed a decreasing trend in body condition in response to increasing sea surface temperature, from 9.0 ℃ to 12.5 ℃, and body conditions improved when the chlorophyll a concentration was around 1 mg/m3. Mixed-effects modeling also revealed that the gonadosomatic index was positively correlated with SST, demonstrating a relatively high value at approximately 15 ℃. Taken together, these findings indicate that there is a trade-off between body condition and reproductive investment, and that SST has a significant influence on body condition and reproductive investment for mature male I. argentinus. Additionally, chlorophyll a concentration also demonstrated a significant influence on the body condition of mature male I. argentines.