Leitoscoloplos eltaninae Blake, 2017, new species

Leitoscoloplos eltaninae new species

Figure 15

Material examined. South Atlantic Ocean, South Georgia Island, N of Shag Rocks, Eltanin Sta. 22-1527, 0 9 Jan 1963, 63.83°S, 62.60°W, 3742–3806 m, holotype and 3 paratypes (USNM 69403–4).

Description. All specimens posteriorly incomplete; holotype 16 mm long and 2 mm wide for 40 segments; paratypes of similar size. Color in alcohol: brown with darker pigment markings on prostomium and some anterior segments. Body rounded in cross section, with thoracic region slightly depressed; one paratype with mid-ventral line of body inverted, forming long groove. Transition from thorax abrupt, denoted by reduction in number of neurosetae and change in form of neuropodial postsetal lobes.

Prostomium conical, pointed anteriorly (Fig. 15 A); without distinct eyespots, but with several groups of small pigment spots (Fig. 15 B). Peristomium formed of single tapering achaetous ring.

Thorax with 10 setigers (Fig. 15 A). Notopodia of setigers 1–3 inconspicuous, with short triangular-shaped digitiform postsetal lobes from setiger 4 (Fig. 15 C), becoming bilobed in abdominal setigers, with ventral lobes shorter than dorsal (Fig.15 D). Thoracic neuropodia with tapering digitiform postsetal lobes (Fig. 15 C); abdominal neuropodia becoming apically thicker and more erect (Fig. 15 D).

Thoracic setae all long crenulated capillaries. Abdominal notopodia with crenulated capillaries and 3–4 furcate setae; furcate setae with thin needles forming web between subequal tynes; with rows of short barbs on shaft (Fig. 15 E). Abdominal neuropodia with 3–4 thin, non-crenulated capillaries and 2–3 imbedded simple aciculae.

Branchiae from setiger 20, continuing to end of fragment; each branchia short, stubby, barely longer than notopodial lobes (Fig. 15 D). Pygidium unknown.

Holotype and one paratype with large, irregularly shaped ova, measuring 450–500 µm in largest dimension.

Etymology. This species is named for the USNS Eltanin, former research vessel of the United States Antarctic Research Program.

Remarks. Leitoscoloplos eltaninae n. sp. is a deep-sea species that belongs to the L. kerguelensis group in having branchiae first present from anterior abdominal segments. It is closest to L. rankini n. sp., described below, in having a thorax with 10 setigers and branchiae from similar setigers (setiger 18 in L. rankini n. sp.; setiger 20 in L. eltaninae n. sp.). The two species differ in that L. eltaninae n. sp. has bilobed abdominal notopodia and entire neuropodia, whereas L. rankini n. sp. has undivided, fingerlike abdominal notopodia and bilobed neuropodia. In L. eltaninae n. sp. the branchiae are short and stubby, while in L. rankini n. sp. the branchiae are long and thin.

Distribution. South Atlantic Ocean, 3742–3806 m.