ABSTRACT The temporal pattern of juvenile release by two species of viviparous asterinid sea stars that incubate their young in the gonads was documented. Parvulastra parvivipara released juveniles (400–3000 µm diameter) in 1–5 cohorts. Parents produced large juveniles (>1000-µm) irrespective of adult size. Released juveniles were larger than the retained juveniles. Most Cryptasterina hystera offspring were released in one large clutch of similarly sized juveniles (732-µm mean diameter). After this initial release, the presence of large juveniles (944-µm mean diameter) in the gonads of C. hystera indicates that they are supported by matrotrophy, potentially through sibling cannibalism. The degree of parental investment additional to the egg in both species was estimated by using a matrotrophy index (MI, the ratio of juvenile and egg dry mass). As the eggs of P. parvivipara and C. hystera could not be isolated, the eggs of their congeners (P. exigua and C. pentagona, respectively) were used as a proxy to estimate the MI, the first application of this index to a marine invertebrate. The MI ranged from 597 to 55082 in P. parvivipara and 1.7–6.2 in C. hystera for juveniles across the different size classes. Matrotrophy and size variation of offspring may be characteristics of echinoderms that incubate their young.

中文翻译：

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两个胎生海星的后代释放的时间模式和亲本投资的程度，概述了照顾后代的棘皮动物的母体营养和后代大小变化

摘要 记录了两种在性腺中孵化幼体的胎生星形海星释放幼体的时间模式。Parvulastra parvivipara 在 1-5 个队列中释放了幼鱼（直径 400-3000 µm）。父母生产大型幼鱼 (>1000-µm)，而不管成鱼大小。释放的幼鱼比保留的幼鱼大。大多数 Cryptasterina hystera 后代是在一大群类似大小的幼鱼（平均直径 732 微米）中释放的。在首次释放后，癞蛤蟆的性腺中存在大型幼鱼（平均直径为 944 微米）表明它们受到母体营养的支持，可能是通过同胞同类相食。通过使用母体营养指数（MI，幼体和蛋干质量的比率）估计了两个物种中对鸡蛋额外的亲本投资程度。由于 P. parvivipara 和 C. hystera 的卵无法分离，因此它们的同类（分别为 P. exigua 和 C. pentagona）的卵被用作估计 MI 的代理，这是该指数首次应用于海洋无脊椎动物。不同体型的幼鱼的 MI 范围为 P. parvivipara 的 597 至 55082 和 C. hystera 的 1.7-6.2。后代的母体营养和大小变化可能是孵化幼崽的棘皮动物的特征。