Pyenson Nicholas D, Haasl David M
Department of Integrative Biology, University of California, Berkeley, 3060 Valley Life Sciences Building, Berkeley, CA 94720, USA.
Biol Lett. 2007 Dec 22;3(6):709-11. doi: 10.1098/rsbl.2007.0342.
Whale-fall communities support a deep-sea invertebrate assemblage that subsists entirely on the decaying carcasses of large cetaceans. The oldest whale-falls are Late Eocene in age, but these early whale-falls differ in faunal content and host cetacean size from Neogene and Recent whale-falls. Vesicomyid bivalves, for example, are major components of the sulphophilic stage in Miocene and Recent whale-fall communities, but they are absent from Palaeogene fossil whale-falls. The differences between Palaeogene and Neogene communities led to the hypothesis that the origin of modern whale-fall communities was linked with the evolution of extremely large mysticetes, which provided sufficient biomass and oil to sustain the modern complement of whale-fall invertebrates. Here, we describe a fossil whale-fall community from the Miocene of California, showing vesicomyid bivalves in direct association with a host mysticete smaller than the adult individuals of any living mysticete species. This association, which is the youngest yet reported from the Neogene of North America, demonstrates that body size is not a necessary factor for the formation of modern whale-fall communities. Instead, we suggest that high skeletal oil content may have been a more important factor, which, based on the age of the fossil whale-fall, evolved at least by the Late Miocene.
鲸落群落支撑着一个深海无脊椎动物组合，该组合完全依赖大型鲸类动物的腐烂尸体生存。最古老的鲸落形成于始新世晚期，但这些早期鲸落在动物群组成和宿主鲸类大小方面与新近纪和现代的鲸落有所不同。例如，泡螺双壳类动物是中新世和现代鲸落群落中嗜硫阶段的主要组成部分，但在古近纪的化石鲸落中却没有。古近纪和新近纪群落之间的差异导致了这样一种假说，即现代鲸落群落的起源与超大型须鲸的进化有关，这些须鲸提供了足够的生物量和油脂来维持现代鲸落无脊椎动物的数量。在此，我们描述了一个来自加利福尼亚中新世的化石鲸落群落，其中泡螺双壳类动物与一种宿主须鲸直接相关，这种须鲸比任何现存须鲸物种的成年个体都要小。这种关联是北美新近纪迄今报道的最年轻的例子，表明体型并非形成现代鲸落群落的必要因素。相反，我们认为高骨骼含油量可能是一个更重要的因素，基于化石鲸落的年代，这一因素至少在中新世晚期就已进化形成。
