Malmgreniella dicirra Hartman 1967

“Malmgreniella dicirra, new species

(Plate 11)

Records: 19:1 sta. 1346 (13, TYPE); 19:2 sta. 1343 (85); 19:3 sta. 1345 (2).

Description: The body is white except for black eyes and a fuscous ring about the elytral scar. Length is variable, from 10 to 23 mm, width 3 to 4 mm and segments number 41 to 56. The prostomium (Fig. A) is subhexagonal, has four eyes in trapezoidal arrangement, with the an­terior pair slightly behind the midlength and the posterior pair nearer together. The paired antennae are subterminal and each has a long, coni­cal appendage, more than half as long as the prostomium; the median an­tenna has a thick base; its appendage is of unknown length. Palpi and dorsal cirri are smooth. Elytra number 15 pairs, are inserted on segments 2, 4, 5, then on alternate segments to 23, followed by a pair on 26, 29, and 32; more posterior segments have dorsal cirri. Thick, short dorsal cirri (Fig. B) are first present on setiger 3, then on 6, 8, and more or less alternating regularly thereafter with the slender (Fig. C) cirri-form cirri.

Parapodia are biramous (Fig. D); the notopodium is small, papillar, with 3 to 12 short setae as thick as neurosetae. A single yellow noto­aciculum projects a slight distance from the end of the conical lobe. Neu­ropodia are much longer, directed laterally, taper distally, and have a projecting yellow aciculum overhung by a short, superior lobe. Neuro­setae number 25 to 30 in a fascicle. Notosetae are of one kind, falcate, slightly curved distally (Fig. E), smooth along the cutting edge or with two or three slender denticles. Neurosetae are falcate, distally bifid (Fig. F), with the secondary tooth long and slender, and the cutting edge with a few inconspicuous denticles.

Elytra are rhomboid (Fig. G) to somewhat reniform, the margin en­tire, the surface smooth and the scar excentric. The upper surface is glistening.

Malmgreniella dicirra resembles commensal polynoids in its smooth, unadorned surface. It differs from the harmothoids in having an unlimited number of segments. Parahalosydna sibogae Horst (1917, p. 83) off Sulu Island, in 275 m, also has 15 pairs of elytra but they cover the dorsum. binlmgrenia whiteavesi McIntosh, with which the present spe­cies seems closely related, has long, slender, distally pointed notosetae and neurosetae of two kinds.

The specific name refers to the two kinds of dorsal cirri which char­acterize this species.

Distribution: Pacific Antarctic Ridge, in 549-1153 m.”

(Hartman, 1967)

Malmgreniella dicirra Hartman, 1967

Malmgreniella dicirra Hartman, 1967:37, pl. 11A–D.—Cairns, 1983:130, 140, 145, 151.

Polynoe leioseta Averincev, 1978:65, pl. 7:55–59. [New synonymy.]

MATERIAL EXAMINED.—SOUTHERN OCEAN: Pacific Antarctic Ridge: 54°49′S, 129°48′W, 549 m, Eltanin sta 1346, 7 Nov 1964, 13 syntypes of M. dicirra (USNM 55493-4; BMNH 1986.57; ZMH); 1 specimen with Stylaster densicaulis Moseley (USNM 65951). 51°00′S, 162°01′E, 333–371 m, with Allopora eguchii, Boschma, Eltanin sta 1411, 8 Feb 1965, 1 specimen (USNM 65952). 56°21′S, 158°28′E, 1574–1693 m, with Calyptopora reticulata Boschma, Eltanin sta 1423, 12 Feb 1965, 5 specimens (USNM 65953). 54°09′S, 52°08′W, 419–483 m, with S. densicaulis, Eltanin sta 1521, 30 Jan 1966, 1 specimen (USNM 65954). 54°29′S, 39°22′W, 659–686 m, with S. densicaulis, Eltanin sta 1536, 8 Feb 1966, 1 specimen (USNM 65955). 54°43′S, 55°30′W, 1647–2044 m, with S. densicaulis and Conopora pauciseptata Brock, Eltanin sta 1592, 14 Mar 1966, 4 specimens (USNM 65956). 54°39′S, 170°22′E, 1862–2103 m, with Caltyptopora reticulata and Conopora pauciseptata, Eltanin sta 1991, 2 Jan 1968, 6 specimens (USNM 65957). Weddell Sea: Off Cape Norvegia, 71°50′S, 15°50′W, with Conopora pauciseptata and Lepidopora sp., Deep Freeze IV, USS Edisto TD-2, sta 14, 18 Jan 1959, 2 specimens (USNM 65950). Australia: Off Macquarie Island, 54°56′S, 158°49′E, 320 m, stony bottom, R/V D. Mendeleev sta 1294, 25 Jan 1976, paratype of P. leioseta (ZIASL 2/43284).

DESCRIPTION.—Syntypes of M. dicirra up to 23 mm long, 6 mm wide including setae, with 46 segments. Paratype of P. leioseta 12 mm long, 4 mm wide, with 40 segments. Additional specimens, commensal with stylasterine hydrocorals, 8–18 mm long, 3–5 mm wide, with 34–43 segments. Body colorless except for black eyes. Elytra 15 pairs, small, leaving middorsum uncovered, delicate, oval, without tubercles or papillae (Figure 8B,C; Hartman, 1967, pl. 11G; Averincev, 1978, fig. 7:56).

Prostomium bilobed, with truncate anterior border and 2 pairs of eyes on posterior half; median antenna with ceratophore in anterior notch, and long style with filamentous tip; lateral antennae with distinct ceratophores inserted terminoventrally and short styles; palps stout, tapered; tentaculophores each with pair of dorsal and ventral tentacular cirri similar to median antenna, without setae (Figures 6A, 8A; Hartman, 1967, pl. 11A; Averincev, 1978, fig. 7:55). Second segment with first pair of elytrophores, subbiramous parapodia, and long ventral buccal cirri similar to tentacular cirri; notosetae stouter than neurosetae, with 3–5 spinous rows; neurosetae tapering to slender, blunt, entire tips, with spinous rows (Figure 6A–D).

Parapodium subbiramous, with notopodium shorter and smaller than neuropodium, rounded with projecting acicular lobe on lower side and slightly projecting notoaciculum; longer neuropodium subconical with tapering presetal acicular lobe and short, thick, digitiform supraacicular process above projecting neuroaciculum and shorter, rounded postsetal lobe (Figures 6B, 7A,B,E, 8D,E, 9A,B; Hartman, 1967, pl. 11D). Notosetae short, relatively few in number, slightly stouter than neurosetae, with 2–6 spines along one side (none on posterior segments) (Figures 6C, 7C,F, 8F, 9C; Hartman, 1967, pl. 11E; Averincev, 1978, pl. 7:58). Neurosetae long, more numerous (25–30), with slightly enlarged spinose regions with close-set spines along cutting edges, with bifid tips (Figures 7D, 8G, 9D; Hartman, 1967, pl. 11F; Averincev, 1978, pl. 7:59). Dorsal cirri with short cylindrical cirrophores; styles either short, bulbous basally or longer, cirriform, former type occurring on segments 3, 6, 8, then more or less alternating regularly with latter type; dorsal tubercles slightly developed on anterior parapodia, bulbous on posterior ones; ventral cirri inflated basally on anterior parapodia, gradually tapering on posterior ones (Figures 7A,E, 8A,D, 9A; Hartman, 1967, pl. 11B,C). Pygidium with pair of long anal cirri.


BIOLOGY.—Malmgraniella dicirra was found by Cairns (1983) living commensally with four stylasterine hydrocorals: Conopora pauciseptata Broch, Stylaster densicaulis Moseley, Allopora eguchii Boschma, and Calyptopora reticulata Boschma. According to Caims (1983:130), the polynoid induced Conopora pauciseptata to form a flattened tube about 3.8 × 2.2 mm in diameter (often considerably larger than the branch to which it was attached); the tubes were found on either the anterior or posterior sides and sometimes on both sides of the branch. On Stylaster densicaulis, the polynoid induced the coral to form a broad, flat tube on its anterior side. The tubes were quite long and up to 3 × 5.5 mm in diameter and even bifurcate at various points. The polynoid appeared to induce an anterior rectangular ridge, a preliminary step in tube formation (Caims, 1983:140, fig. 41A). On Calyptopora reticulata, the polynoids induced the coral to form flattened tubes, about 3 × 2.2 mm in diameter, on either the anterior or posterior sides or both sides of the colony (Cairns, 1983:151).

DISTRIBUTION.—Southern Ocean, Pacific Antarctic Ridge, off Macquarie Island, Weddell Sea. In 320–2103 meters.