Comprehensive DescriptionRead full entry
“Macellicephala eltanina, new species
Record: 15:6 sta. 610 (2, TYPE).
Description: Both specimens are large and broadly depressed. Length attains 56 mm, width with parapodia but not setae is 16 mm, and segments number 37. The 15 pairs of elytral scars are visible as oval depressions; most elytra have been lost. The pale prostomium is broader than long (Fig. A), thrust forward by the partly everted proboscis; it lacks eyes. It is medially divided by the thick base of the median antenna. Prostomial peaks are reduced, visible at the sides of the median antennal base. Paired antennae are inserted ventrally at a level below the median one; each has a cylindrical base and a shorter, conical appendage which is directed forward. Paired palpi are long, pale and smooth; they taper distally and extend beyond all other processes.
The first segment is reduced to acicular lobes with a pair of cirrophores at the sides of the prostomium; its dorsal and ventral cirri are long, cirriform, exceeded in length only by the palpi. The second segment is continuous across the middorsum; its parapodia and neuropodia and its ventral cirrus are slightly hirsute. Each notopodium has five or six thick, short acicular setae which resemble those farther back, and the neuropodium has many slender, spinose hairlike setae directed laterally. From the third segment the parapodia resemble those farther back; notosetae occur in fuller series. Parapodia (Fig. B) are unequally biramous; the notopodium is a short, slender lobe over the neuropodium, with a projecting acicular lobe from which the aciculum extends. Notosetae occur in short, spreading series, number 12 to 15 in a fascicle, and their lengths range from short at the anteroventral end to long at the posterior; their distal ends do not extend to the fleshy ends of neuropodia. Each seta is laterally closely serrated with transverse series of spines (Fig. D). Neuropodia are much larger and broader, distally oblique, and have full fascicles of laterally projecting setae, numbering 40 to 60 in a fascicle. Ventral cirri are long, tapering, inserted on the parapodium about midway between its base and distal end. Neurosetae are slender, taper distally, terminate in an entire tip (Fig. E), and their free length has long teeth along the cutting edge, in double, alternating rows (Fig. F.)
Elytra are inserted on setigers 2, 4, 5, 7, and alternating to 23, then on 23, 26 and 29. Most have been lost but some that remain are nearly smooth. A second one, shown in Fig. A, is long, oval, with a short series of marginal papillae at the postectal edge. Another, loose in the lot, is subquadrate (Fig. C), with excentric scar and marginal fimbriae. The surface has sparse numbers of microtubercles.
Nephridial papillae, at the bases of neuropodia, are cylindrical, first present from segment seven and continued to near the posterior end of the body.
M. eltanina differs from other species of the genus in lacking eyes, in the details of its prostomium and setae, and in elytral details. Its specific name refers to the USNS ELTANIN, which recovered the specimens from great depths.
Distribution: Off South Sandwich Islands, in 2553-2575 m.”