Collaborative Research: Energy Sources for Reproduction and Development in a Cold-Seep Mixotrophic Mussel

异养深海动物需要向下流动的物质才能生存和繁殖，而在热液喷口或冷渗漏处具有化学自养共生体的动物理论上应该能够或多或少地连续产生配子，而不需要来自表面的碎屑。混合营养贻贝在冷渗漏是这两种情况的中间。它们可以仅使用甲烷或硫化物作为能量来源生长和生存，但也能够以底栖边界层的碎屑颗粒或浮游生物为食。现有证据表明，为了给贻贝提供足够的氮，浮游细菌的补充过滤可能是必要的。生活在路易斯安那州斜坡上甲烷渗漏处的冷渗贻贝（Bathymodiolus childressi）表现出周期性而非连续性的繁殖，这种模式并没有被普遍接受的模式所预测，即深海中食物限制控制着繁殖时间。因此，混合营养贻贝提供了一个独特的机会来研究碎屑输入在深海配子发生时间控制中的作用。脂质生物标志物和化合物特异性稳定同位素将用于确定来自表面来源的碎屑的能量在B. childressi性腺和体细胞组织之间是否有差异分配。在深海巨型动物中，季节性繁殖者实际上总是产生供食的幼虫，这表明在海面繁殖和幼虫成功之间可能存在机制或进化联系。克里斯普定律就是这样一种可能的联系。克里斯普定律预测，有浮游营养性幼虫的动物会选择繁殖时间，以确保幼虫获得最佳营养。本研究将通过在不同深度的自然水中饲养幼体来检验Crisp’s Rule。

Heterotrophic deep-sea animals require a downward flux of material in order to survive and reproduce, whereas animals with chemoautotrophic symbionts at hydrothermal vents or cold seeps should theoretically be capable of producing gametes more-or-less continuously without the benefit of surface-derived detritus. Mixotrophic mussels at cold seeps are intermediate between these two situations. They can grow and survive using only methane or sulfide as an energy source, but are also capable of filter-feeding on detrital particles or plankton in the benthic boundary layer. Available evidence suggests that supplemental filtration on bacterioplankton may be necessary to provide sufficient nitrogen to the mussels. The cold-seep mussel Bathymodiolus childressi, which lives at methane seeps on the Louisiana slope, demonstrates periodic rather than continuous reproduction, a pattern not predicted by the commonly accepted paradigm that food limitation controls reproductive timing in the deep sea. Thus, mixotrophic mussels present a unique opportunity to investigate the role of detrital input in the control of gametogenic timing in the deep sea. Lipid biomarkers and compound specific stable isotopes will be used to determine if energy from surfacederived detritus is differentially partitioned between the gonads and somatic tissues of B. childressi. In the deep-sea megafauna, seasonal breeders virtually always produce feeding larvae, suggesting a possible mechanistic or evolutionary link between surface production and larval success. Crisp's rule, the prediction that animals with planktotrophic larvae will time their breeding to assure optimal nutrition for the larvae, is one such possible link. Crisp's Rule will be examined in this study by rearing the larvae of B. childressi in natural water collected at various depths.