Sabellastarte japonica (Marenzeller, 1885)

Knight-Jones, Phyllis & Mackie, Andrew S. Y., 2003, A revision of Sabellastarte (Polychaeta: Sabellidae), Journal of Natural History 37 (19), pp. 2269-2301 : 2288-2290

Sabellastarte japonica (Marenzeller, 1885)

(figure 7)

Sabella pottaei Quatrefages, 1866 , New Caledonia (MNHN A244) original material; Grube, 1870b (same material). Although Sabella pottaei Quatrefages predates Sabellastarte japonica , the name pottaei has not been used since Grube looked at the material in 1870, so according to the International Code of Zoological Nomenclature, ICZN, 1999, article 23.9.1, the rules of priority can be waived. The name ‘ japonica ’ has frequently appeared in publications, if only as a so-called synonym of S. indica .

Laonome japonica Marenzeller, 1885 , Nagasaki, Japan (holotype, NHMW 1959 ).

Paralaonome japonica: Bush (1905, generic revision).

Sabellastarte indica: Fauvel, 1936 , Japan.

Sabellastarte japonica: Imajima and Hartman, 1964 , Japan; Morton and Morton, 1983, Hong Kong [not plate 9E, = Branchiomma , and not Benham, 1916 = S. australiensis ].

Additional material. Japan, Nagasaki (NHMW 1958); China, Xiamen (Amoy, ZMUU 332/3647); Hong Kong, Cape Aguilar (NMMW.Z.1989.117.0043–45, five specimens coll. A.S.Y.M.); south Viet Nam, Iles Condore (coll. by Harmoud in 1877, MNHN A246 as S. indica ); Australia, Northern Territories, Darwin, Fanny Bay (NTM W.3843 as S. indica ) and Coburg Peninsula (NTM W.372 as S. indica ).

The following description is based on the holotype of S. japonica (Marenzeller) . The first data in parentheses are from one of the largest specimens from Hong Kong and the second from the largest of the Australian specimens ( NTM W.3843) .

Description. Body without crown 135 (144, 120) mm long, 14 (13, 9) mm wide with about 170 segments of which eight (eight, seven) are thoracic (figure 7A); crown 50 (27, 42) mm long with short base 5.7 mm long (lateral measurement), involuted ventrally to 1.5 (2, 1.5) whorls, dorsal margins with narrow D-shaped flanges near vestigial interradiolar web, length of web less than length of typical thoracic ventral shield (figure 7B); crown radioles about 140 (130, 80) each side, many interdigitating, round or subquadrangular in cross-section (figure 7E, F) but with paired ridges near web (figure 7D), tips beyond pinnules short and blunt (figure 7G); slender dorsal lips about 15 (15, 18) mm long, each grooved, with midrib support, posterior part of its dorsal lamella joining dorsal-most rachis (no pinnular support); thorax a little longer than wide (Marenzeller, 1885, recorded wider than long), last thoracic torus 0.5 length of first; first segment about twice (2.5, 1.5) as long as following thoracic segments (viewed laterally and discounting height of collar); dorsal and dorso-lateral collar margins flared, undulating and well above junction of crown and thorax, with distinct notch above each deep collar pocket flanking midline (figure 7B, holotype lacks notch above right pocket); ventral collar forming two blunt overlapping lappets and involuted medially (figure 7C); anterior margin of first ventral shield more or less straight, with a medial projection towards collar cleft and embayed each side of midline; first shield about 1.5 times length of others in thorax; all thoracic tori except the first indenting sides of ventral shields; thoracic fascicles short and thick (as in Sabellastarte magnifica ), thoracic parapodium 7 with 97 chaetae and 111 uncini; both superior and inferior chaetae of thorax and abdomen with slender shafts and fine, numerous (dense) surface teeth above narrow knee (figure 7); each abdominal uncinus with more slender neck (figure 7L) than thoracic uncinus (figure 7K), both types of uncini with crest of very fine teeth, and shaft to breast as long as breast to crest; abdominal fascicle 34 with about 60 chaetae and 45 uncini; interramal spots small and round in abdomen, obliquely elongate in thorax; tube not present with holotype but Hong Kong specimens with muco-silt above substratum.

Thorax and abdomen flecked with dark brown throughout, which tends to hide parapodial spots and blotches, such flecks coalescing to give darker areas on thorax and postero-dorsal surface of abdomen; paler areas along crown base, collar edge and uncinal ridges; distal halves of radioles with golden or brown patches across pinnules, together forming very irregular ‘bands’; interramal spots small, more distinct on paler specimen from Nagasaki (NHMW 1958).

Variation. Hong Kong material has narrower and closer pigment bands across the pinnules and is larger than the holotype; material from the Northern Territory is smaller than the Hong Kong material and the holotype, but with 1.5 whorls on each crown ( NTM W.372, NTM W.3843) .

Habitat. Nothing is known about the habitat of the two Nagasaki specimens, but those from Hong Kong were found in a stony area at the lower edges of larger rocks, at 1 m depth in the shelter of a small Island off Cape D’Aguilar. The specimens from northern Australia were also found in shallow water on or near reefs. Quatrefages (1866) gives no information about the habitat of his species, Sabellastarte pottaei .

Remarks and distribution. Marenzeller (1885) compared his new species with specimens of Sabella spectabilis , which he also (mistakenly) put into Laonome . He noted that S. japonica differs from S. spectabilis in having ‘capillary chaetae with a more strongly projecting edge and larger uncini of different form, with coarse grooving on the crest’. The side views of the outer (convex) ‘margins’ of the inferior thoracic chaetae and crests of the uncini have finer, more numerous and more densely packed teeth and these are thus more noticable than those of S. spectabilis or any of the other species described here. The avicular shape of the abdominal uncini is characteristic. The relatively long, slender neck and shaft (figure 7L) makes each uncinus look less compact, hence Marenzeller’s (1885) ‘different form’. He also commented on the shortness of the crown, the length being only three times the width of the thorax, compared with five times in Sabellastarte spectabilis and S. magnifica , and he noted that the outer radioles had thicker ‘shafts’ than the inner ones, but even the outer ones seem to be slimmer than those of S. spectabilis .

Sabellastarte australiensis and S. japonica are similar in having bispiral crowns. Bush (1905) wrongly suggested a new genus, Paralaonome , to accommodate this bispiral character, with Sabellastarte japonica as type species. Sabellastarte australiensis differs from S. japonica in having a shorter first segment, with a shallow dorsal collar and dorso-lateral pockets, more compact abdominal uncini and no pigment flecks over the general body surface.

Fauvel’s Japanese material of S. indica (1936) has not been examined, but he indicated a short crown and speckled body and his record is doubtless Sabellastarte japonica , rather than S. spectabilis , which also occurs there. Sabellastarte japonica also overlaps with S. spectabilis in northern Australia, and also with S. pectoralis in New Caledonia.

New records have extended the distribution of Sabellastarte japonica southwards from Japan to China, Hong Kong, Viet Nam, northern Australia and New Caledonia.