Paradiopatra antarctica, (MONRO, 1930), 2011

Budaeva, Nataliya & Fauchald, Kristian, 2011, Phylogeny of the Diopatra generic complex with a revision of Paradiopatra Ehlres, 1887 (Polychaeta: Onuphidae), Zoological Journal of the Linnean Society 163 (2), pp. 319-436 : 348-350

PARADIOPATRA ANTARCTICA ( MONRO, 1930) COMB. NOV. ( FIGS 17 AND 18; TABLE 4)

Leptoecia antarctica Monro, 1930: 133–135 , fig. 50a–i.

Paronuphis antarctica Hartman, 1964: 117 , pl. XXXIV, figs 13, 14; Hartman, 1967a: 96–97, pl. 31; Hartman, 1967b: 208; Averincev, 1972: 179.

Notonuphis antarctica Kucheruk, 1978: 91–93 ,; Orensanz, 1990: 36–38, pl. 6, chart 1C; Paxton, 1986a: 35–36, fig. 21.

Non-type material examined: USNM 058411 , Eltanin St. 428 (20) ; USNM 097890 , Eltanin St. 138 (two) ; USNM 097891 , Eltanin St. 419 (eight) ; USNM 097892 , Eltanin St. 426 (three) ; USNM 097893 , Eltanin St. 432 (three) ; USNM 097894 , Eltanin St. 444 (one) ; USNM 097895 , Eltanin St. 539 (one) ; USNM 097896 , Eltanin St. 1002 (12) ; USNM 097897 , Eltanin St. 1078 (four) ; USNM 097898 , Eltanin St. 1079 (10) ; USNM 097899 , Eltanin St. 1082 (eight) ; USNM 097900 , Islas Orcada St. 115, 60.54°S, 41.38°W, 576–671 m, 17 February 1976 (five) ; USNM 097901 , Hero St. 17-1, 62.16°S, 57.74°W, 618–625 m, 1 April 1983 (one) ; USNM 097902 , Hero St. 18-1, 62.69°S, 56.3°W, 218–248 m, 1 April 1983 (two) ; USNM 097903 , Eltanin St. 428 (15) ; USNM 097904 , Eltanin St. 997 (15) ; USNM, Eastwind St. 9 (33); St. 9A (one); St. 11 (seven); St. 15 (four); St. 31 (eight); St. 44 (three) .

Type locality: Southern Ocean, South Shetland Islands 63.292°S, 61.283°W, 1080 m, mud and stones ( Monro, 1930) .

Diagnosis: First four pairs of parapodia with pseudocompound uni- and weakly bidentate falcigers with moderately long pointed hoods; ventral cirri subulate on first three chaetigers; subacicular hooks starting from chaetiger 9; branchiae absent; frontal lips large and spherical, located ventrally; eyes absent; peristomial cirri absent.

Description: Most specimens lacking posterior regions; two complete specimens 1.3 and 1.5 mm wide consisting of 94 and 104 chaetigers, respectively. Width of all examined specimens varying from 1.2 to 1.6 mm. Colour of alcohol-preserved specimens light brownish, without distinct pattern.

Prostomium rounded with large spherical, slightly flattened, frontal lips located ventrally ( Fig. 17B ). Palps reaching chaetiger 1, lateral antennae reaching chaetigers 6–8, median antenna short, reaching chaetigers 2 or 3. Both palpophores and antennophores with four or five prominent rings; lateral projections absent ( Fig. 17A, B ). Nuchal grooves slightly curved, covered by the anterior fold of peristomium. Eyes absent. Peristomium slightly shorter than first chaetiger. Peristomial cirri absent ( Fig. 17A, B ).

First three pairs of parapodia modified, projecting lateroventrally and directing anteriorly ( Fig. 17B ). Prechaetal lobes rounded; postchaetal lobes digitiform to triangular ( Fig. 17C ), present on first eight chaetigers, later completely reducing. Ventral cirri subulate on first three chaetigers, later replaced by paired broad oval-to-square ventral glandular pads. All cirri and postchaetal lobes on anterior modified parapodia thick, with wide basal parts.

Anterior four pairs of parapodia with pseudocompound uni- to weakly bidentate falcigers with indistinct subdistal teeth ( Fig. 17C–E ). Falcigers with moderately long pointed hoods. First three pairs of parapodia with one or two dorsal simple capillary chaetae and five or six pseudocompound falcigers ( Fig. 17C ). Fourth pair of parapodia with dorsal limbate chaetae, usually with only one pseudocompound falciger and three or four simple stout tapering chaetae. Parapodia with up to three or four dorsal, slender, simple limbate chaetae, and three or four ventral thick and stout limbate chaetae staring from chaetiger 5. Simple paired bidentate subacicular hooks starting from chaetiger 9. Pectinate chaetae with clearly oblique distal margin and up to 13–15 small teeth ( Fig. 17F ). Neuroaciculae pale with pointed tips, between three and five in fascicle. Notoaciculae absent in all parapodia.

Branchiae absent. Mandibles thin with slender shafts. Cutting plates of all examined specimens missing. Maxillary formula of examined material (based on eight specimens): Mx I = 1 + 1; Mx II = 7– 9 + 7–11; Mx III = 8–10 + 0; Mx IV = 5–7 + 5–8; Mx V = 1 + 1. Maxillary formula according to Hartman (1967a): Mx I = 1 + 1; Mx II = 5 + 8; Mx III = 8 + 0; Mx IV = 7 + 8; Mx V = 1 + 1.

Pygidium with two pairs of anal cirri, dorsal cirri longer than ventral ones. Tubes long and rigid; cylindrical, with very tough inner layer and relatively thin external layer of mud particles.

Remarks: Paradiopatra abyssalis comb. nov. and P. minuta comb. nov. are the two other species in the genus known to lack peristomial cirri and branchiae. Paradiopatra antarctica comb. nov. differs from P. abyssalis comb. nov. in having four pairs of anterior parapodia with pseudocompound falcigers rather than three, in having three chaetigers with subulate ventral cirri rather than two, and in lacking lateral projections on ceratophores rather than having them. Paradiopatra antarctica comb. nov. can be distinguished from P. minuta comb. nov. by having pseudocompound rather than simple anterior falcigers.

Distribution: Antarctic and sub-Antarctic waters, north-west of Antarctic Peninsula, South Shetland Islands, Falkland Islands ( Fig. 18). Depth range 218–1427 m.

Figures

Figure 17. Paradiopatra antarctica comb. nov. (USNM Eastwind St. 31): A, anterior end, dorsal view; B, anterior end, lateral view; C, parapodium of chaetiger 1, posterior view; D, bidentate pseudocompound falciger from chaetiger 1; E, unidentate pseudocompound falciger from chaetiger 1; F, pectinate chaeta from chaetiger 9.