Comprehensive Description

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Description

Paranorthia antarctica, new species

 

(Plate 30)

 

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.”

 

(Hartman, 1967)

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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