Harmothoe anderssoni Bergstroem , 1916

Neal, Lenka, Paterson, Gordon L. J., Blockley, David, Scott, Ben, Sherlock, Emma, Huque, Cate & Glover, Adrian G., 2020, Biodiversity data and new species descriptions of polychaetes from offshore waters of the Falkland Islands, an area undergoing hydrocarbon exploration, ZooKeys 938, pp. 1-86 : 1

Harmothoe anderssoni Bergstroem, 1916 Figures 2 , 3 , 4

Harmothoe anderssoni Bergström, 1916: 286; Monro 1930: 57.

Eunoe anderssoni ( Bergström, 1916): Monro 1936: 90; Hartman 1953: 31.

Hermadion anderssoni ( Bergström, 1916): Fauvel 1950: 754.

Harmothoe (Eunoe) anderssoni ( Bergström, 1916): Hartmann-Schröder and Rosenfeldt 1990: 92; Hartmann-Schröder and Rosenfeldt 1992: 89.

Materials.

Sample 40MFC, 442 m, -49.3403947, -59.0845558, coll. 23/04/2012, Ind. 1, NHM.2018.24629. Sample 75MFC, 438 m, -49.3383880, -59.1262342, coll. 22/03/2012, Ind. 1, NHM.2018.21524. Sample 28MFA, 452 m, -49.3044189, -59.0852225, coll. 23/04/2012, Ind. 1, NHM.2018.24377. Sample 30MFB, 456 m, -49.3039703, -59.0302064, coll. 25/04/2012, Ind. 1, NHM.2018.24424. Sample 35MFB, 450 m, -49.3221858, -59.0573711, coll. 15/04/2012, Ind. 1, NHM.2018.24490. Sample 36MFB, 450 m, -49.3219581, -59.0298531, coll. 25/04/2012, Ind. 1, NHM.2018.24508. Sample 38MFB, 434 m, -49.3408178, -59.1396133, coll. 23/04/2012, Ind. 1, NHM.2018.24547. Sample 42MFC, 433 m, -49.3590078, -59.1668389, coll. 14/04/2012, Ind. 1, NHM.2018.24664. Sample 53MFC, 444 m, -49.3751330, -59.1116004, coll. 25/03/2012, Ind. 1, NHM.2018.24908. Sample 67MFB, 442 m, -49.2889470, -59.1102897, coll. 19/03/2012, Ind. 1, NHM.2018.25176. Sample 75MFB, 438 m, -49.3383880, -59.1262342, coll. 22/03/2012, Ind. 1, NHM.2018.21519. Sample 77MFA, 432 m, -49.3511630, -59.1260079, coll. 22/03/2012, Ind. 1, NHM.2018.21547. Sample 19MFA, 443 m, -49.2870544, -59.1680519, coll. 17/04/2012, Ind. 2, NHM.2018.11562-11563. Sample 82MFA, 443 m, -49.2614970, -59.1672448, coll. 16/03/2012, Ind. 2, NHM.2018.12638-12639. Sample 56MFC, 450 m -49.2451170, -59.0544011, coll. 18/03/2012, Ind. 3, NHM.2018.13437-13439.

Description.

Voucher, NHM.2018.24629, a complete specimen (in two fragments) with 35 segments (Fig. 2a ), 7.5 mm long and 2 mm wide, including parapodia, but excluding chaetae. Voucher (SEM specimen on stub), NHM.2018.21524, a complete specimen with 35 segments 5 mm long and 1.5 mm wide, including parapodia, but excluding chaetae (Fig. 2b ).

Prostomium bilobed, with cephalic peaks (Fig. 2b, c ); 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 hind margin of prostomium. Palps papillate, tapering.

Tentaculophores inserted laterally to prostomium, each with notochaetae; styles of dorsal and ventral tentacular cirri papillate, 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 (ventral) cirri.

Fifteen pairs of elytra covering dorsum, on segments 2, 4, 5, 7, on alternating segments until segment 23, then on segments 26, 29 and 32; all elytra present in voucher specimen (NHM.2018.24629) (Fig. 2a ). Outer lateral margin of elytra with dense fringe of long, filiform papillae (Figs 3d ; 4a ), such papillae also cover elytral surface in between tubercles. Elytral surface covered with 3 forms of tubercles (Figs 3e ; 4a-e ): small and conical microtubercules confined to anteriormostmargin of elytra (form 1) begin to increase in size, becoming cylindrical to conical, distally somewhat truncated (form 2) and this form covers most of elytral surface; posteriormost margin of elytra with several (8-10) cylindrical to conical distally multifid macrotubercles (form 3).

Parapodia biramous (Fig. 3a ); notopodia with elongate acicular lobe; neuropodia larger than notopodia, with short slender supracicular process (Fig. 3a , insert) tips of noto- and neuro-acicula penetrating epidermis. Cirrigerous segments with indistinct dorsal tubercules and cylindrical cirrophores, styles of dorsal cirri very long (slightly longer than neurochaetae), slender, papillate, tapering. Ventral cirri from chaetiger 2 where long and basally inserted; on subsequent chaetigers ventral cirri short, smooth, tapering, medially inserted on neuropodia. Nephridial papillae distinct from chaetiger 6 till end of the body.

Notochaetae stouter than neurochaetae. Notochaetae curved, with distinct rows of spines on convex side and blunt, unidentate tip; numerous, arranged in ca. five rows, increasing in length with each row (Fig. 3a ). Neurochaetae uni- and bidentate (Figs 3b, c ; 4f ); lower and mid neurochaetae unidentate, falcate, subdistally with spines; upper neurochaetae few, bidentate with slender secondary tooth (often abraded), subdistally with spines.

Pygidium with a pair of very long (reaching back over ten segments), thin, papillate anal cirri (Fig. 2d ).

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., Barnichand 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.

Figures

Figure 2. Harmothoe anderssoni (voucher NHM. 2018.24629, unless stated otherwise) a complete specimen (in two fragments) in dorsal view b SEM micrograph of the complete specimen in dorsal view (voucher, NHM. 2018.21524) c detail of prostomium in dorsal view d pygidium with pygidial cirri in ventral view. Scale bars: 1 mm (a, d); 2 mm (b).

Figure 3. Harmothoe anderssoni (voucher, NHM. 2018.24629) a mid-body parapodium, insert showing line drawing of supra-acicular neuropodial lobe b bidentate neurochaetae c unidentate neurochaetae d mid-body elytron showing elongated marginal papillae e detail of elytral surface from mid-body elytron showing multifid macrotubercules. Scale bars: 500 µm (a, d); 50 µm (b, c); 200 µm (e).

Figure 4. Harmothoe anderssoni (SEM micrograph), (voucher, NHM. 2018.21524) a detached elytron from mid-body b detail of the multifid macrotubercles c detail of the posterior elytral margin d detail of microtubercules from the mid-section of the elytra e detail of conical microtubercules near the anterior elytral margin f detail of bidentate neurochaetae. Scale bars: 500 µm (a); 100 µm (b, c, e); 50 µm (d); 20 µm (f).