Abstract
Whale falls are important environments contributing to biodiversity, connectivity and evolutionary novelty in deep-sea ecosystem. Notwithstanding, most of this knowledge is based in studies from NE Pacific basin. Interestingly, the only known natural whale fall on the SW Atlantic has faunal composition affinities with carcasses from other deep-ocean basins. In this carcass, annelid worms belonging to Hesionidae are abundant and species-rich, and include some shared species with NE Pacific Ocean. Here we evaluate the diversity of Hesionidae on the SW Atlantic using new information of implanted whale bones and explore whether some species have interbasin distribution or if they represent cryptic species in different basins. We described, using morphological and molecular data, a total of 10 new hesionid species and report of a new lineage Sirsoe ‘BioSuOr,’ not formally described herein. Two hesionids found exclusively in deep-sea chemosynthetic environments, SirsoePleijel (1998) and VrijenhoekiaPleijel et al. (2008), are primarily distinguished from each other by the presence of a median antenna on the former and its absence on the latter. However, our analyses showed that Vrijenhoekia should be synonymized with Sirsoe and for this reason we emended the diagnosis of Sirsoe. We also emphasized the presence of Sirsoe balaenophila comb. nov. and S. sirikos in SW Atlantic whale falls confirming their interbasin distribution. Moreover, COI and 16S rDNA data reveal that S. balaenophila comb. nov. also comprises cryptic species on the SW Atlantic (S. pirapuan sp. nov. and S. ypupiara sp. nov) and perhaps also in the Pacific Ocean (herein named as S. balaenophila lineage-2). The new species, S. maximiano, is shared between whale falls from SW Atlantic and vent sites from Mid-Cayman Spreading Center. Our data adds to the growing literature showing species are shared between deep ocean basins and among cognate deep-sea environments. Zoobank registration publication LSID - urn:lsid:zoobank.org:pub:7E891B1D-DCE4-45C8-83F4-8586D286B327.
Highlights
Whale carcasses impact the food-limited deep sea (>200 m) creating remarkable island-like habitats considered hotspots of biodiversity and evolutionary novelty (Smith and Baco, 2003; Smith et al, 2015)
We aim to evaluate (a) the diversity of Hesionidae in whale falls from SW Atlantic Ocean using traditional and molecular taxonomy; (b) the phylogenetic relationships between Sirsoe and Vrijenhoekia species relative to the diagnosis of Vrijenhoekia and Sirsoe; and (c) whether V. balaenophila presents an interbasin distribution ranging from the NE Pacific to the SW Atlantic Ocean or, alternatively, if it is a cryptic species-complex
Notwithstanding, both datasets highlight that V. balaenophila and our morphotype Vrijenhoekia sp. 4 contain cryptic species (Supplementary Figure S1)
Summary
Whale carcasses impact the food-limited deep sea (>200 m) creating remarkable island-like habitats considered hotspots of biodiversity and evolutionary novelty (Smith and Baco, 2003; Smith et al, 2015). Whale falls become chemosyntheticbased habitats, similar to hydrothermal vents and cold seeps in which part of the faunal composition is reliant on chemosynthetic production (Smith et al, 1989, 2015; Smith and Baco, 2003; Alfaro-Lucas et al, 2018). In this scenario, organisms dependent on chemosynthesis could use whale falls as intermediate habitats facilitating dispersion among spatially isolated cognate habitats (Smith et al, 1989). Addressing patterns of whale-fall biodiversity is crucial for the effective protection and understanding of these hotspots of deep-sea biodiversity
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