Limits to the Prolonged Planktonic Life Among Larvae of Tropical Benthic Invertebrates and Its Biogeographic Consequences

在中太平洋、大西洋和印度洋的热带上层水域广泛存在着沿海下无脊椎动物的远生或“远距离”幼虫，这支持了这样一种假设，即幼虫不仅对海洋岛屿最初的定居，更一般地说，对这些物种目前的连续或间断的活动范围作出了重要贡献，岛屿之间甚至岛屿与遥远大陆人口之间持续的基因交流也是如此。然而，还没有人以任何系统的方式证明，在公海收集的时候，端跖幼虫能够变形。我们还不知道，浮游幼虫是否在生理上适应了长时间的浮游生活，还是已经记录的缺乏进一步生长的原因是开放海洋中浮游植物浓度低。未来的研究将解决这两个问题：1)在开阔的海洋中获得幼虫，并通过实验确定这些幼虫是否有能力变态；(2)在实验室中维持幼虫，以确定在海洋中不能变态的个体最终是否有能力变态；3)确定在浮游植物浓度足够的情况下，浮游幼虫在生理上是否有能力进一步生长，或者是否达到生长停滞，即准全浮游状态。

The widespread existence of teleplanic or "long distance" larvae of sublittoral invertebrates in the tropical epipelagic waters of the central Pacific, Atlantic and Indian Oceans supports the hypothesis that larvae contribute importantly not only to initial colonization of oceanic islands and, more generally, to the present continuous or disjunct ranges of such species, but also to the continuing genetic exchange among islands or even between islands and far distant continental populations. However, no one has yet demonstrated in any systematic way that teleplanic larvae are capable of metamorphosing at the time of their collection in the open sea. We do not yet know whether teleplanic larvae are physiologically adapted for remaining planktonic over long periods of time or whether the lack of further growth already documented instead is due to low phytoplankton concentrations in the open ocean. The future research will address these two questions 1) by obtaining larvae in the open ocean and ascertain experimentally whether or not these larvae are competent to metamorphose, (2) by maintaining larvae in the laboratory to determine whether individuals that would not metamorphose in the sea eventually become competent to metamorphose, and 3) by determining whether or not teleplanic larvae are physiologically capable of further growth given adequate phytoplankton concentrations or alternatively whether growth stasis, i.e., a quasi-holoplanktonic state, is achieved.