Osawa Yumiko, Aoki Masakazu N, Thiel Martin, Bauer Raymond T
Shimoda Marine Research Center, University of Tsukuba, Shimoda 415-0025, Japan;
Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan;
Biol Bull. 2015 Apr;228(2):125-36. doi: 10.1086/BBLv228n2p125.
The hypothesis of protandrous (male to female) sex change was tested for the first time in a rhynchocinetid shrimp, Rhynchocinetes uritai, with an analysis of life-history traits. Samples were taken monthly for 2 years in Oura Bay, Japan, using a combination of bait and refuge traps. Breeding was seasonal but extended from spring through autumn, with female-phase individuals (FPs) producing broods successively, with their ovaries maturing for a new spawn during incubation of a previous brood. Females incubated numerous (∼500-4000) embryos that suffered insignificant mortality before hatching. Recruitment of juveniles after planktonic larval development began in summer and peaked during the autumn, with negligible recruitment during winter and spring. Cohort analysis confirmed the hypothesis of protandric sex change in this species, with juveniles maturing into the male phase (MP) during their first reproductive season at an age of 6-10 mon, depending on the time of recruitment. Sex change occurred during the following winter when transitional individuals matured into FPs during their second reproductive season at an age of ≥18 mon. Two cohorts were followed from recruitment until the end of the study, indicating a life span of 21-25 mon. Aside from its sexual system, this sex-changing species showed no obvious differences in reproductive and other life-history traits from those of gonochoric species from similar latitudes and habitats.
首次在一种鼓虾（Urita鼓虾）中对雄性先熟（从雄性转变为雌性）的性别转变假说进行了检验，分析了其生活史特征。在日本大浦湾，使用诱饵陷阱和避难所陷阱相结合的方法，连续两年每月采集样本。繁殖具有季节性，但从春季持续到秋季，处于雌相的个体（FPs）相继产卵，在前一窝幼体孵化期间，它们的卵巢会成熟以便进行新一轮产卵。雌性孵化大量（约500 - 4000个）胚胎，这些胚胎在孵化前死亡率很低。浮游幼体发育后的幼体补充在夏季开始，秋季达到峰值，冬季和春季的补充量可忽略不计。群组分析证实了该物种雄性先熟性别转变的假说，幼体在6 - 10个月大时，根据补充时间，在其第一个繁殖季节成熟进入雄相（MP）。性别转变发生在接下来的冬季，过渡个体在≥18个月大时，在其第二个繁殖季节成熟为FPs。从补充开始跟踪了两个群组直到研究结束，表明寿命为21 - 25个月。除了其性别系统外，这种具有性别转变的物种在繁殖和其他生活史特征方面与来自相似纬度和栖息地的雌雄异体物种没有明显差异。
