Comprehensive DescriptionRead full entry
“Paranorthia antarctica, new species
Records: 14:1 sta. 1009 (1); 14:2 sta. 1025 (10, TYPE).
Description: Large fragments were removed from limp, lightly chitinized, arenaceous tubes measuring 120 mm long by 18 mm wide. An anterior fragment of 53 segments measures 80 mm long and 9 mm wide; a long median and posterior end may be missing. Another anterior fragment of 25 segments is 40 mm long.
The prostomium is short, lacks eyes, and has a pair of short conical frontal processes. The five occipital tentacles are very long, with the longest or middorsal one extending back to about segment 12; the inner lateral pair is nearly as long, and the shortest or outer lateral is about twice as large as the peristomial cirri. Ceratophores of occipital tentacles are annulated, each with four annuli of which the distalmost is the longest. The peristomium is a smooth ring, slightly shorter than the prostomium; it has a pair of dorsal cirri, their length slightly exceeding that of the peristomium.
The maxillary apparatus, seen by dissection, includes a ventral mandible and maxillary pieces from I to V; I is long and falcate; II has 12 small teeth on either side, followed distally by a smooth hiatus separating them from the curved distal fang; III has 13 teeth on the left, and none on the right side; IV has 8 left and 10 right, and V has a single tooth on either side.
The second segment is the first parapodial and has the largest parapodia, directed forward so as to extend beyond the anterior end of the prostomium. Dorsal and ventral cirri, and postsetal lobes are well developed (Fig. A); each parapodium is supported by a transverse series of embedded acicula and four to six simple, falcate spines terminating distally in a few (3-4) shallow teeth (Fig. D) and covered with a rounded hook; some, perhaps torn, lack the hook and lateral teeth; simple limbate setae (Fig. E) are inconspicuous. The second parapodium (Fig. B) is smaller than the first and directed obliquely forward; it is supported by thick, embedded acicula and may have falcigers resembling those in the first parapodia but smaller and smoother. The dorsal cirrus and postsetal lobe are prolonged laterally, and the vental cirri are thicker, shorter. Thereafter the parapodia (Fig. C) are like those in more posterior segments. Setae are long, limbate and slightly geniculate, and subacicular hooks (Fig. F) first present in parapodia nine or ten are obliquely bifid, with a rounded hood; they number two or three in a series. Pectinate setae, numbering 6-9 in a fascicle, occur just below the limbate setae and may be embedded.
Ventral cirri are cirriform on two segments, then padlike and glandular. Branchiae and composite setae are absent.
The tube is semitranslucent, mucoid, covered with oozy silt and has large pieces of Rhabdamnia foraminiferans, measuring to 27 mm long, attached on its outer side, together with disklike pebbles.
Paranorthia antarctica agrees with other species of the genus in having the first two pairs of parapodia enlarged; it differs from them in lacking branchiae. It is the first one reported from the southern hemisphere.
Distribution: Weddell Sea, in 2818-3285 m.”