Harmothoe anderssoni Bergström, 1916
Voucher specimen. SEA LION: station 40MFC.
Diagnosis. Voucher is a complete specimen with 35 segments (divided into two fragments). Prostomium bilobed, with cephalic peaks; ceratophore of median antenna in anterior notch, style of median antenna papillate, slightly inflated subdistally, then abruptly tapering; lateral antennae inserted ventrally with styles papillate, tapering. Anterior pair of eyes situated dorsolaterally on widest part of prostomium, posterior pair dorsally near hindmargin of prostomium. Palps papillate, tapering.
Tentaculophores inserted laterally to prostomium, each with notochaetae and a dorsal and ventral tentacular cirrus with styles of cirri slightly inflated subdistally, then abruptly tapering, the dorsal cirri longer than ventral cirri. Second segment with first pair of elytra, biramous parapodia, and long buccal cirri.
Fifteen pairs of elytra, all eytra present. Outer lateral margin and adjacent surface of elytra with dense fringe of long, filiform papillae; elytral surface covered with conical microtubercles, posterior half of elytra with numerous conical macrotubercles; macrotubercules distally mulifid.
Cirrigerous segments with dorsal cirri with cylindrical cirrophore, style papillate, tapering. Ventral cirri with smooth, tapering style. Parapodia biramous; notopodia with elongate acicular lobe; neuropodia larger than notopodia; tips of noto- and neuroacicula penetrating epidermis. Notochaetae stouter than neurochaetae; notochaetae with distinct rows of spines and blunt tip. Neurochaetae uni – and bidentate; unidentate falcate, with rows of spines distally; bidentate with slender secondary tooth (often abraded). Pygidium with a pair of very long (reaching back over 10 segments), thin, papillate anal cirri.
Remarks. During preliminary assessment of Falkland Islands specimens these were assigned to Harmothoe due to presence of bidentate neurochaetae, as well as other generic characters such short body, 15 segments with elytra, prostomium with cephalic peaks and neuropodia with supra-acicular lobes. However, this species did not match any described or recently reviewed species of Harmothoe from the Southern and South Atlantic Oceans (Barnich et al. 2006; Barnich and Fiege 2009; Barnich and Fiege 2010; Barnich et al. 2012; Miranda and Brasil 2014). The form of elytra was, however, consistent with that described for Eunoe anderssoni, a Southern Ocean species, which has a confused taxonomic history. It was originally placed in genus Harmothoe by Bergström (1916), referred to as Eunoe by Monro (1936), moved to Hermadion by Fauvel (1950) and again considered Eunoe by Hartman (1966). Our understanding is that the reports of Polynoe hirsuta from Chile by Ehlers (1901) are misidentified specimens of H. anderssoni, given they were recognised as such by Bergström (1916) and Fauvel (1950). Given that Ehlers’ specimens are not available for examination we prefer not to include these in formal synonymy.
The genera Eunoe and Hermadion share some characters with Harmothoe such as a short body and the presence of 15 elytragerous segments (see e.g., Barnich and Fiege 2009, 2010; Bock et al. 2010), but while prostomial cephalic peaks and neuropodial supracicular lobes are present in Harmothoe and Eunoe, these are lacking in Hermadion (see Barnich and Fiege 2006). However, Eunoe supposed to have only unidentate neurochaetae (see e.g., Barnich and Fiege 2009, 2010), while supra-acicular neurochaetae in Falkland Island specimens are clearly bidentate. Unfortunately, Bergström (1916) did not comment on the form of neurochaetae in detail, but subsequently both unidentate and bidentate neurochaetae were reported in Eunoe anderssoni by Monro (1936), Hartman (1953) and Hartmann-Schröder and Rosenfeldt (1992). Monro (1936) commented that three out of six specimens had unidentate chaetae only, but in our experience, the slender secondary tooth becomes easily abraded, which may erroneously lead to the conclusion that all neurochaetae are unidentate. The original placement of this species in genus Harmothoe is therefore justified and is referred to here as Harmothoe anderssoni. It is important to stress that this decision is driven by practical ease of identification rather than phylogenetic position of this species. Recent molecular work on Polynoidae suggests paraphyly of Harmothoe (e.g., Norlinder et al. 2012) and the current designation of polynoid genera is likely problematic. Here, we do not attempt to solve systematic difficulties, but provide new information on Harmothoe anderssoni with photographs, high quality SEM images (see also Hartmann-Schröder and Rosenfeldt 1992) and detailed description of this species based on material from Falkland Islands.
Distribution. This species is known from Adélie Coast, Kerguelen Islands, South Georgia, South Orkneys and the Antarctic (Hartmann-Schröder and Rosenfeldt 1992). Here, we record this species from the North Falklands Basin, ca. 450 m depth.
