Heterospio peruana Borowski, 1994

Blake, James A. & Maciolek, Nancy J., 2023, New species and records of Heterospio (Annelida, Longosomatidae) from continental shelf, slope and abyssal depths of the Atlantic Ocean, Pacific Ocean, Indian Ocean and adjacent seas, Zootaxa 5260 (1), pp. 1-74 : 53

Heterospio peruana Borowski, 1994

Heterospio peruana Borowski, 1994: 131–136 , figs. 1, 2A–G.

Material examined. Pacific Ocean, SEPBOP, off Western South America, Peru-Chile Trench, R / V Anton Bruun, Cruise 11, Sta. 95, coll. 15 Oct 1965 , R. J. Menzies, 08.517°S, 81.667°W, Menzies trawl, 4332–4423 m, 1 specimen in two parts ( LACM-AHF Poly 13306) .

Description. A single incomplete specimen in two parts, not in good condition; anterior fragment with 12 setigers, 12.5 mm long and a posterior fragment with two segmental setigers and intact bulbous posterior end with five setigers with hooks.

Pre-setiger region with conical, broadly rounded prostomium and two peristomial rings, incomplete dorsally; without dorsal crest; nuchal organs in groove between prostomium and first peristomial ring; dorsal tentacles not present.

Thoracic segments flattened dorsally, rounded ventrally. Thoracic setigers 1–8 short, about twice as wide as long; setiger 9 first elongate segment, about twice as long as setiger 8. Setiger 10 first abdominal segment, as long as entire thoracic region; setigers 11 and 12 equally as long as setiger 10. Branchiae on setigers 2–5 reduced to scars or stubs on this specimen.

All setigers biramous. Thoracic parapodia as rounded pads without postsetal lamellae; with noto- and neuropodia well separated, bearing 20–30 thin capillaries in tight well-defined fascicles. Parapodia of abdominal setigers 10–12 as transverse low ridges, with setae in two rows mostly surrounding body; first row with numerous thickened spinous setae and second row with thin capillaries. Spinous setae of setiger 10 mostly aristate or subuluncinilike with an elongated tapering point. Spines of setiger 12 with those of notopodia mostly aristate, and those of neuropodia mostly acicular.

Bulbous posterior end with five setigers bearing large curved hooks in each ramous.

Methyl Green staining. Not tested due to poor condition of specimen.

Remarks. These fragments from the Peru-Chile Trench agree well with the original account by Borowski (1994) from the abyssal plain of the Peru Basin, except that the abdominal neurosetae tend to be more acicular rather than aristate or subuluncini as in the notopodia.

By having branchiae on setigers 2–5 and setiger 9 as the first elongate segment, ca. 2–2.5 times as long as the shorter thoracic setigers, Heterospio peruana most closely resembles H. hartmanae n. sp. from the North Atlantic Ocean and H. brunei n. sp. from the South China Sea. All three of these widely separated species are from abyssal or lower continental slope depths.

In H. hartmanae n. sp. the abdominal spines in the cinctured abdominal segments are mainly simple spines with narrow rounded tips; only a few have pointed tips and none are aristate. In contrast, the acicular spines of cinctured segments in H. peruana are illustrated by Borowski (1994) as distinctly aristate or subuluncinate-like capillaries where the extended tip is thicker than the smoothly tapering tip of typical capillaries. In the present study aristate spines have been observed, but also acicular spines in some abdominal neuropodia. Heterospio brunei n. sp. has a few aristate spines in the first one or two abdominal setigers, but most are acicular throughout. H. hartmanae n. sp. and H. peruana have two prominent peristomial rings, whereas H. brunei n. sp. has only one.

Distribution. Abyssal Plain, DISCOL manganese nodule site, Peru Basin, 4125–4188 m ( Borowski 1994); Peru-Chile Trench, 4423 m (This study).