Sabellastarte samoensis (Grube, 1870a)

Knight-Jones, Phyllis & Mackie, Andrew S. Y., 2003, A revision of Sabellastarte (Polychaeta: Sabellidae), Journal of Natural History 37 (19), pp. 2269-2301 : 2290-2292

Sabellastarte samoensis (Grube, 1870a)

(figure 8)

Sabella samoensis Grube, 1870a , Samoa (ZMB Q5237 , two syntypes; ZMH V1816), third syntype, both holdings from Samoa .

The largest specimen, maintained in Hamburg, has suffered histolysis (part-lifted cuticle and chaetae) and lacks the posterior part of the abdomen. The following description is therefore made from the larger of two specimens in Berlin ( ZMB Q5237 ), which is complete and has less histolysis. Data in parentheses refer to the larger Hamburg specimen .

Description. Body without crown about 33 (26 +) mm long, 4.5 (5.5) mm wide with about 110 segments of which eight (nine) are thoracic (figure 8A); crown about 25 (24, 30) mm long with fairly shallow base, each side forming nearly a circle, dorsal margins with narrow D-shaped flanges level with interradiolar web (figure 8B), web as long as length of three typical thoracic shields, radioles 36 (34) each side, none interdigitating, subquadrangular in cross-section and without paired ridges (figure 8D, E, F), shape of tips beyond pinnules uncertain (due to histolysis); dorsal lips slender, tapered and with midrib support, 5 (5.5) mm long; thorax about as long as wide (figure 8C), first segment scarcely longer than following thoracic segments (figure 8A, viewed laterally and discounting height of collar); dorsal collar shallow, dorsal lateral margins embayed above shallow pockets, but covering junction of crown and thorax, lateral margins higher and more or less transverse to axis of body (figure 8A), ventral collar forming two small overlapping, subtriangular lappets (figure 8C); first ventral shield with indefinite anterior margin, longer than others in thorax; all thoracic tori indenting sides of ventral shields, anterior tori only slightly longer than posterior ones (15 uncini); chaetae and uncini very similar to those of S. spectabiilis , except for thicker shafted inferior abdominal chaetae (cf. figures 8N and 2M) and shorter shafted uncini (figure 8G, L); there are also fewer chaetae in each thoracic fascicle (e.g. 15 superior and 31 inferior chaetae in 6th fascicle).

Remarks. Grube (1870a) gives no details about habitat. Smallish numbers of chaetae in fascicles and lack of radiolar interdigitations could be considered juvenile characters so comparison was made with the large species Sabellastarte magnifica , especially because of the similarity of their thick shafted inferior chaetae in the abdominal fascicles (cf. figures 8N and 2M). Sabellastarte samoensis , however, has uncini with shorter shafts, a different collar shape and different coloration. In these respects Sabellastarte samoensis is very like S. pectoralis , but S. samoensis has abdominal uncini with thicker shafts (cf. figures 8L and 4S) and the distal parts of the radioles lack longitudinal ridges (cf. figures 8F and 4J).

Sabellastarte samoensis may be endemic to the Samoan region. More material should be sought.