Scoloplos de Blainville, 1828

Blake, James A., 2021, New species and records of Orbiniidae (Annelida, Polychaeta) from continental shelf and slope depths of the Western North Atlantic Ocean, Zootaxa 4930 (1), pp. 1-123 : 30-31

Genus Scoloplos de Blainville, 1828

Type species: Lumbricus armiger Müller, 1776 , by monotypy.

Synonym: Scolaricia Eisig, 1914 . Type-species: Scolaricia typicus Eisig, 1914 , by monotypy. Fide Day 1973.

Diagnosis. (Emended). Prostomium pointed, usually prolonged; single achaetous peristomial ring. Branchiae first present from middle or posterior thoracic setigers or from abdominal setigers (8–26). Posterior thoracic setigers with 0–2 postsetal lobes and 0–2 subpodial lobes, never more than four lobes of both types combined; not forming ventral fringes. Thoracic neurosetae including blunt, inconspicuous uncini, few or many in distinct rows; accompanied by few to many crenulated capillaries; furcate setae usually present; heavy spear-like spines and bristle-topped setae absent. Abdominal neuropodia with imbedded, non-projecting acicula. Abdominal noto- and or neuropodial flail setae present or absent.

Remarks. Specimens of Scoloplos having thoracic neuropodial uncini or hooks and extra neuropodial postsetal or subpodial lobes have for the most part been identified as S. armiger (Müller, 1776) , resulting in the species being identified from wide geographic areas and thus considered cosmopolitan ( Hartman 1957; Pettibone 1963; Hartmann-Schr̂der 1971, 1996; Blake 1996). Accounts of S. armiger among European investigators, however, suggest that several species are involved. For example, McIntosh (1910) described specimens that have only a few thoracic neuropodial uncini or spines; whereas Hartmann-Schr̂der (1971, 1996) described specimens with numerous thoracic neuropodial uncini. Supporting the view that European S. armiger may represent a suite of species, recent investigations have demonstrated that different populations in shallow and subtidal locations in the North Sea are ecologically and reproductively isolated from one another (Kruse & Reise 2003; Kruse et al. 2003, 2004). Results from molecular sequence data also support these observations ( Bleidorn et al. 2006). Additionally, these authors determined that specimens from the type locality in Norway represented yet a third species. These results suggest that at least three cryptic species are likely present among northern European specimens collectively identified as S. armiger . Bleidorn et al. (2006, 2009) also provided molecular results on some orbiniids from California in the eastern Pacific identified locally as S. armiger that might represent additional undescribed species. To date, none of these various species have been described or redescribed, including specimens from the type locality.

Previous studies along the U.S. Atlantic coast have reported species of Scoloplos as S. armiger , the widely reported European species, and S. acmeceps , an eastern Pacific species (Pettibone 1963; Maciolek-Blake et al. 1985; Trott 2004). The present morphological study of Scoloplos specimens from shelf and slope depths along the U.S. Atlantic coast suggest that several distinct species are present, none of which are either S. armiger or S. acmeceps . Three basic morphotypes are evident: (1) specimens with rows of numerous thoracic neuropodial uncini or hooks and with no extra postsetal or subpodial lobes; (2) specimens with thoracic neuropodial uncini reduced to a single row or a few isolated ventral spines and with extra postsetal and/or subpodial lobes; (3) specimens with 3–4 rows of numerous thoracic neuropodial uncini and with extra postsetal and/or subpodial lobes. Within these three basic morphotypes, there is considerable additional morphology available to separate individual species. These include differences in (a) the pre-setiger morphology with details of the upper and lower lips of the mouth, (b) the shape and form of the thoracic noto- and neuropodia, (c) the presence and form of subpodial flanges with or without internal glands, (d) the shape of the branchiae along the body, (e) the presence or absence of an interramal process or cirrus, (f) the presence or absence of notopodial furcate setae, (g) details of the intersegmental areas, and (h) pygidial morphology. These characters and other aspects of the following five species identified from shelf and slope depths along the U.S. Atlantic coast are reported: