Collin Rachel, Spangler Abby
Smithsonian Tropical Research Institute, Balboa, Republic of Panama.
Biol Bull. 2012 Dec;223(3):268-77. doi: 10.1086/BBLv223n3p268.
Adelphophagic development, where embryos consume sibling embryos or nurse eggs, is particularly common in marine caenogastropods and some families of polychaetes. When exogenous nutrition is provided before hatching, egg size and hatching size can be uncoupled, but advantages and constraints of adelphophagic development compared to development from large eggs are unknown. Here we examine temperature-mediated plasticity in offspring size, brooding duration, and fecundity in the adelphophagic marine gastropod Crepidula cf. onyx. We use these data combined with previously published data on two planktotrophic Crepidula and two Crepidula species that develop from large eggs to test hypotheses about the consequences of adelphophagic development and patterns of variation in offspring size. In Crepidula cf. onyx, egg size shows no significant effect of temperature. Hatching size is significantly larger at 28 °C than at 23 °C but proceeds from fewer eggs per capsule at 28 °C. Hatching size is therefore decoupled from both egg size and the number of eggs per capsule. Although development is faster at the higher temperature, broods are produced roughly every 26-27 days at both temperatures. Increased rate of development has been cited as a potential advantage of adelphophagic development in muricids, but the adelphophagic C. cf. onyx did not develop more quickly than C. atrasolea or C. ustulatulina, species that produce similarly sized hatchlings from large eggs. Comparisons across calyptraeid species support the role of adelphophagy in increasing variance in offspring size. This increased variability is primarily expressed within broods or among broods from the same female, not among females.
自相残食式发育，即胚胎会消耗同胞胚胎或吸食卵，在海洋新腹足类动物和一些多毛纲动物家族中尤为常见。当在孵化前提供外源营养时，卵的大小和孵化时的大小可能会脱钩，但与由大卵发育相比，自相残食式发育的优势和限制尚不清楚。在这里，我们研究了自相残食的海洋腹足类动物玛瑙真管螺（Crepidula cf. onyx）在后代大小、育幼持续时间和繁殖力方面的温度介导可塑性。我们将这些数据与之前发表的关于两种浮游性真管螺以及两种由大卵发育而来的真管螺物种的数据相结合，以检验关于自相残食式发育的后果以及后代大小变异模式的假设。在玛瑙真管螺中，卵的大小没有显示出温度的显著影响。在28℃时孵化时的大小显著大于23℃时，但在28℃时每个卵囊中产生的卵较少。因此，孵化时的大小与卵的大小以及每个卵囊中的卵数都脱钩了。尽管在较高温度下发育更快，但在这两个温度下，育幼大约每26 - 27天产生一次。发育速度加快被认为是骨螺科自相残食式发育的一个潜在优势，但自相残食的玛瑙真管螺的发育速度并不比阿特拉索拉真管螺（C. atrasolea）或乌斯图拉蒂纳真管螺（C. ustulatulina）更快，后两种物种从大卵中产生大小相似的幼体。对帆螺科物种的比较支持了自相残食在增加后代大小方差方面的作用。这种增加的变异性主要表现在同一雌性的育幼群体内部或不同育幼群体之间，而不是在不同雌性之间。
