Description and Relationships ofChaetopterus pugaporcinus, an Unusual Pelagic Polychaete (Annelida, Chaetopteridae)

Abstract

MBL Biological Discovery in Woods Hole CoverChaetopterid polychaetes, distinctive members of nearly all benthic marine communities, have larvae that may spend months in the plankton before settling to live their adult lives in parchment-like tubes attached to the sea floor. The cover image shows an extraordinary new species, Chaetopterus pugaporcinus, that may have relinquished the benthic portion of its life and made itself permanently at home in the pelagic realm. Chaetopterus pugaporcinus possesses the same combination of larval and adult features regardless of the size of the specimen (1 to 2 cm), and it has lost features associated with benthic life that were previously thought to be characteristic of the family. The species is reliably found off the coast of California at about 1000 m, regardless of the seafloor depth. One of its 15 segments is greatly expanded, while the others are compressed to the anterior and posterior poles of the decidedly non-vermiform body.On pages 40-54 of this issue, Osborn et al. describe this new species and its ecology. On the basis of three genes, they provide the first hypothesis for a Chaetopteridae phylogeny. The new species is a recently derived member of Chaetopterus, a genus fraught with taxonomic controversy yet used repeatedly in developmental, ecological, and physiological research. The authors provide molecular support for morphological research showing that Chaetopterus variopedatus is a species complex, and they provide evidence that unrestricted dispersal ability does not necessarily lead to cosmopolitan species. Chaetopterus pugaporcinus may represent a logical step in the evolution of a group with long-lived pelagic larvae and may be a modern representative of the many historic invasions of the oceans' midwaters by benthic invertebrates. Abstract. An extraordinary new species, Chaetopterus pugaporcinus, is described from eight specimens collected from deep mesopelagic waters off Monterey Bay, California, by remotely operated vehicles. All specimens exhibit a consistent combination of both adult and larval characteristics, leaving in question the maturity of the specimens. All specimens lack ciliated larval bands and the stout, modified chaetae (cutting spines) typically found in segment A4 of chaetopterids. If the specimens described here are larvae, they are remarkable for their size, which ranged from 10 to 21 mm total length, nearly twice the length of the largest polychaete larvae previously reported and 5 to 10 times larger than known chaetopterid larvae. Then too, their lack of segment addition prior to settlement would be atypical. If adult, they are particularly unusual in their habitat choice and body form. Morphology of the uncini and comparison to larval morphology indicated a close relationship to either Chaetopterus or Mesochaetopterus. However, the lack of cutting spines and typical adult morphology made it impossible to determine to what genus this species should be allied. Thus, we carried out the first molecular phylogenetic analysis of the Cha...

Multiple origins of pelagicism within Flabelligeridae (Annelida)

“…Additionally, the two holopelagic lineages show convergence in reduced segment number. This is also observed in a holopelagic chaetopterid (Osborn et al, 2007) and some tomopterid species (a holopelagic lineage of Phyllodocida). Further examination of morphological transitions associated with pelagic habit requires increased taxon sampling and better resolution of the flabelligerid tree.…”

“…Genomic DNA was extracted from specimens using DNAzol Ò Genomic DNA Isolation Reagent (Molecular Research Center, Inc., Cincinnati, OH) with modifications to the manufacturer's instructions (Osborn et al, 2007).…”

“…There are a few non-phyllodocid pelagic polychaetes, notably, Poeobius meseres Heath, 1930, and Chaetopterus pugaporcinus Osborn et al, 2007. Recently, Burnette et al (2005) placed P. meseres firmly within Flabelligeridae.…”

Description of a new species of Eulepethus (Annelida, Eulepethidae) from the northern South China Sea, and comments on the phylogeny of the family

“…The most suitable molecular evolution model for each gene and the concatenated sequences were determined using jModeltest2 (Darriba et al, 2012) based on the Akaike Information Criterion (AIC), resulting in the use of GTR+I for 16S, 18S and COI, and GTR+G for 28S and the concatenated data. Maximum Likelihood (ML) analysis and Maximum Parsimony (MP) analysis were conducted with RaXML GUI1.3 and PAUP* V4.0, respectively, using settings reported by Osborn et al (2007). Etymology.…”

A new species of Chaetopterus (Annelida, Chaetopteridae) from Hong Kong

“…variopedatus' represents a species complex containing at least ten species. The concept that C. variopedatus is a single cosmopolitan species was also refuted by a phylogenetic analysis based on molecular data (Osborn et al, 2007). Indeed, recent studies of Chaetopterus have recognised many more species, and their distribution ranges may well be more limited.…”