Sosane brevibranchiata, Imajima, Minoru, Reuscher, Michael G. & Fiege, Dieter, 2013

Imajima, Minoru, Reuscher, Michael G. & Fiege, Dieter, 2013, Ampharetidae (Annelida: Polychaeta) from Japan. Part II: Genera with elevated and modified notopodia, Zootaxa 3647 (1), pp. 137-166 : 149-150

Sosane brevibranchiata sp. nov.

( Figs. 7 A–J; 16D)

Specimens examined. Holotype: NSMT-Pol. H 564, Bungo Channel, 32°43.0'N, 132°32.3'E – 32°42.9’N, 132°32.0'E, 84–99 m, KT 99-18, St. DG-1, 12.1999, (1cs). Paratype: NSMT-Pol P 565, Off Tsushima Island, 34°15.1'N, 130°15.0'E – 34°15.0'N, 130°14.9'E, 100 m, Soyo-maru, SO 08-D5, 7.2008, (1af).

Description. Length 10 mm, width 1 mm. Prostomium without glandular ridges, with one pair of eyespots ( Fig. 7 A). Buccal tentacles without groove, smooth. Lower lip slightly crenulated ( Fig. 7 B). Four pairs of cirriform branchiae ( Fig. 7 C); 3 pairs of branchiae in transverse row in segment II, 1 pair of branchiae in segment IV; branchial groups separated by wide median gap; branchiae of segment II in median position of transverse row, branchiae of segment III in outermost position of transverse row, branchiae of segment IV in innermost position of transverse row, branchiae of segment V emerging next to notopodia of segment IV ( Fig. 16 D); branchiae of transverse row with ventral tufts of cilia, annulated ( Fig. 7 D); posterior branchiae much shorter, without cilia. Chaetae in segment II of same length and thickness as following notochaetae ( Fig. 7 B, C). Notopodia with limbate capillary notochaetae from segment III, present in 15 segments. Notopodia in third-to-last thoracic unciniger elevated, basally inflated, apically conical, not connected by dorsal ridge ( Fig. 7 E, F); notochaetae of modified unciniger in fan-like arrangement on convex side of notopodia, with hirsute tips ( Fig. 7 G). Neuropodial tori with uncini from segment VI, present in 12 thoracic uncinigers. Cirri and papillae in thoracic parapodia absent. Continuous ventral shields present to thoracic unciniger 10. Two intermediate uncinigers. Ten abdominal uncinigers. Rudimentary notopodia and glandular pads in intermediate and abdominal uncinigers absent. Pinnules without cirri or papillae. Pygidium with terminal anus and one pair of short ventrolateral digitiform anal cirri ( Fig. 7 H). Thoracic and abdominal uncini with crest of numerous teeth above rostral tooth and basal prow ( Fig. 7 I, J).

Remarks. Sosane brevibranchiata sp. nov. differs from the other species of Sosane sensu stricto, S. jirkovi , S. occidentalis , and S. sulcata , by the rudimentary 4th pair of branchiae and the large gap between the groups of branchiae.

The ventral tufts of cilia in the first 3 pairs of branchiae and their distinct annulation have also been observed in other species of the genus Sosane , i.e., Sosane uebelackerae sp. nov. (see below), and other genera, e.g., Anobothrus (see above). The ciliation is probably a juvenile character.

Distribution. Bungo Channel between Kyushu and Shikoku, and off Tsushima Island in the Korea Strait, in 84– 100m.

Figures

FIGURE 7. Sosane brevibranchiata sp. nov. A: prostomium, dorsal view, 30 x, B: anterior end, ventral view, 38 x, C: anterior end, dorsal view, 26 x, D: part of a branchia, 245 x, E: thoracic uncinigers 9 – 12 and intermediate unciniger 1, dorso-lateral view, 30 x, F: modified parapodium of thoracic unciniger 10, posterior view, 64 x, G: modified notochaeta of thoracic unciniger 10, 880 x, H: posterior end, ventral view, 44 x, I, J: thoracic uncini, both 1100 x.

FIGURE 16. ID-cards of reported species with modified notopodia. A: Anobothrus dayi sp. nov., B: Anobothrus fimbriatus sp. nov., C: Anobothrus flabelligerulus sp. nov., D: Sosane brevibranchiata sp. nov., E: Sosane sulcata.