Hamasaki Katsuyuki, Kondo Shuji, Dan Shigeki
Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Konan, Minato, Tokyo 108-8477, Japan. E-mail:
Zool Stud. 2021 Aug 6;60:e45. doi: 10.6620/ZS.2021.60-45. eCollection 2021.
Freshwater shrimps in the family Atyidae exhibit one of two life history traits: amphidromy, in which planktonic larvae develop in the sea; and landlocked, in which lecithotrophic larvae develop in freshwater. Temperature and salinity are the most important environmental factors that affect the survival, duration, and growth of decapod crustacean larvae. Larvae of landlocked shrimps are known to retain the ancestral habit of amphidromy, , the ability to develop to the juvenile stage in saline water. Faster development exhibited by large larvae of landlocked shrimps is considered an adaptation that allows the larvae to stay in or near parental habitats. Therefore, information on larval performance under different temperature and salinity conditions is essential to obtain a better understanding of population connectivity through marine larval dispersal in amphidromous shrimps as well as larval adaptation to freshwater environments in landlocked shrimps. We examined the effects of temperature and salinity on the larval performance of two closely related atyid shrimps in the genus : the amphidromous and the landlocked . Larvae were reared under the 25 combinations of five different temperatures (20, 23, 26, 29, and 32°C) and salinity levels (4.25, 8.5, 17, 25.5, and 34 ppt). In , the rate of larvae that survived into the juvenile stage decreased linearly with increasing temperature and the larvae adapted to a wider range of salinity (8.5-34 ppt), though larval mortality increased at the high salinity (34 ppt) under the higher temperature conditions. In , larval survival rates were higher under a wider range of temperatures (20-29°C) in brackish water (4.25-17 ppt). Thus, larvae may disperse broadly under the high salinity conditions of the open sea, but oceanic currents with high temperature and high salinity conditions may act as a barrier to restrict larval dispersion northwards from the southern islands. larvae adapted to a wider range of temperatures in natural freshwater environments and larval duration was shorter in than in under the wide range of temperature and salinity conditions. Our results also highlight the retention strategy by which landlocked larvae stay in or near parental habitats.
洄游性，即浮游幼虫在海洋中发育；以及陆封性，即卵黄营养型幼虫在淡水中发育。温度和盐度是影响十足目甲壳类幼虫存活、持续时间和生长的最重要环境因素。已知陆封虾的幼虫保留了洄游性的原始习性，即在盐水中发育到幼体阶段的能力。陆封虾的大型幼虫表现出的更快发育被认为是一种适应，使幼虫能够留在亲代栖息地或其附近。因此，了解不同温度和盐度条件下幼虫的表现对于更好地理解通过洄游性虾的海洋幼虫扩散实现的种群连通性以及陆封虾幼虫对淡水环境的适应至关重要。我们研究了温度和盐度对匙指虾属两种近缘匙指虾幼虫表现的影响：洄游性的[虾名1]和陆封性的[虾名2]。幼虫在五种不同温度（20、23、26、29和32°C）和盐度水平（4.25、8.5、17、25.5和34 ppt）的25种组合下饲养。在[虾名1]中，存活到幼体阶段的幼虫比例随温度升高呈线性下降，并且幼虫适应更广泛的盐度范围（8.5 - 34 ppt），尽管在较高温度条件下高盐度（34 ppt）时幼虫死亡率增加。在[虾名2]中，在较宽温度范围（20 - 29°C）的半咸水（4.25 - 17 ppt）中幼虫存活率更高。因此，[虾名1]幼虫可能在公海的高盐度条件下广泛扩散，但高温和高盐度条件的洋流可能成为限制幼虫从南部岛屿向北扩散的障碍。[虾名2]幼虫在自然淡水环境中适应更广泛的温度范围，并且在广泛的温度和盐度条件下，[虾名2]的幼虫期比[虾名1]短。我们的结果还突出了陆封性的[虾名2]幼虫留在亲代栖息地或其附近的保留策略。
