Diversity, Distribution and Phylogeny of Hesionidae (Annelida) Colonizing Whale Falls: New Species of Sirsoe and Connections Between Ocean Basins

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 deepocean 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, Sirsoe Pleijel (1998) and Vrijenhoekia Pleijel 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.

A new species of Euclymene (Maldanidae, Annelida) from Brazil, with new combinations, and phylogenetic implications for Euclymeninae

“…It has become fashionable in polychaete systematics to focus on inferences of phylogenetic hypotheses based only on sequence data (e.g. Struck et al 2011, Borda et al 2012, Glasby et al 2012, Goto et al 2013, Weigert et al 2014, Aguado et al 2015, Goto 2016, Weigert & Bleidorn 2016, Kobayashi et al 2018, Nygren et al 2018, Langeneck et al 2019, Shimabukuro et al 2019, Alves et al 2020, San Martín et al 2020, and often to then comment on other classes of characters in relation to those hypotheses, typically through the process called 'character mapping.' Two significant, interrelated problematic questions arise with these approaches: can inferences of phylogenetic hypotheses causally account for sequence data, and can other classes of characters be explained through mapping on the basis of those inferred hypotheses?…”

Who’s who inMagelona:phylogenetic hypotheses under Magelonidae Cunningham & Ramage, 1888 (Annelida: Polychaeta)

“…We acknowledge that species hypotheses have been previously and separately inferred and are not the focus of this paper. Whilst this distinction between phylogenetic and specific hypotheses has been the typical and inferentially appropriate approach in systematics, exceptions can be found among some publications (e.g., Nygren et al, 2018;Shimabukuro et al, 2019;Radashevsky et al, 2020), in which species hypotheses are simultaneously inferred with phylogenetic hypotheses that only causally account for sequence data, after which morphological characters are incorrectly introduced in a post hoc manner. Notwithstanding the fact that the requirement of total evidence (RTE;Fitzhugh, 2006b; see Sequence data and explanatory hypotheses, below) is violated, such inferences have questionable merits for the fact that explaining shared nucleotides or amino acids requires, at a minimum, discriminating between causes such as genetic drift, and selection via downward causation (see Sequence data and explanatory hypotheses, below).…”

“…Mapping most often involves obtaining phylogenetic trees using sequence data, then ''optimising'' other characters, usually morphological, onto these diagrams, from which are determined vague evolutionary conclusions regarding the mapped characters. This approach has become popular among polychaete phylogenetic studies (e.g., Struck et al, 2011;Borda et al, 2012;Glasby, Schroeder & Aguado, 2012;Goto et al, 2013;Weigert et al, 2014;Aguado et al, 2015;Andrade et al, 2015;Struck et al, 2015;Goto, 2016;Kobayashi et al, 2018;Nygren et al, 2018;Langeneck et al, 2019;Shimabukuro et al, 2019;Radashevsky et al, 2020;Martín et al, 2020;Tilic et al, 2020;Gonzalez et al, 2021). Much credence has been given to mapping, albeit without foundation.…”

“…The present study does not assess the veracity of either the Magelonidae or less inclusive phylogenetic hypotheses in terms of evidential ''support,'' nor are there attempts to use popular methods such as the bootstrap or Bremer analysis to assert that hypotheses are either ''strongly supported'' or ''robust.'' Such perspectives have become all too common in systematics research, including those on annelids (e.g., Struck et al, 2011;Borda et al, 2012;Weigert et al, 2014;Aguado et al, 2015;Andrade et al, 2015;Struck et al, 2015;Gonzalez et al, 2018;Nygren et al, 2018;Shimabukuro et al, 2019;Martín et al, 2020;Stiller et al, 2020;Tilic et al, 2020;Gonzalez et al, 2021). Reasons for not speaking of support in the present study follow from the basics of reasoning described above.…”

Genetic features of the marine polychaete Sirsoe methanicola from metagenomic data

“…First discovered in 1997 in the Green Canyon area of the Gulf of Mexico, USA, S. methanicola creates burrows in methane hydrates and inhabits them mostly with single occupancy (Desbruyères and Toulmond, 1998;Fisher et al, 2000). Members of the Sirsoe genus have also been found in deep-sea whale falls, vents, and seeps, but S. methanicola is the only known Sirsoe species to inhabit methane hydrates (Shimabukuro et al, 2019) and is the only macrofauna known to inhabit deposits in the Gulf of Mexico. Besides S. methanicola, a novel alvinocarid shrimp morphospecies has been found atop exposed methane hydrates in the Blake Ridge Diapir of the South Atlantic Bight (Van Dover et al, 2003).…”