Sabellastarte pectoralis (Quatrefages, 1866)

Knight-Jones, Phyllis & Mackie, Andrew S. Y., 2003, A revision of Sabellastarte (Polychaeta: Sabellidae), Journal of Natural History 37 (19), pp. 2269-2301 : 2280-2282

Sabellastarte pectoralis (Quatrefages, 1866)

(figure 4)

Sabella pectoralis Quatrefages, 1866 , Mauritius (MNHN A246).

Sabella indica: Ehlers, 1897 , in part, Zanzibar (ZMH PE 1343).

Sabellastarte indica: Pruvot, 1930 ; Fauvel, 1930 (in part), both New Caledonia (MNHN A258).

Sabellastarte sanctijosephi: Day, 1967 , figure 37.5G, Natal.

Laonome arenosa Treadwell, 1943 , Hawaii, Pearl Harbour ( AMNH 1925-3262 , holotype).

Laonome ceratodaula: Ehlers, 1904 (ZMH PE1330, western Hawaiian Island, Laysan). [Not Sabella ceratodaula Schmarda, 1861 , New Zealand].

Additional material. Mauritius (ZMA V. Pol. 2394 as S. magnifica ), Maldive Islands, Hulule (NHML unregistered, as Sabellidae , collected by Crossland in 1900); South Africa, Natal, Durban (NHML 1932.12.235, as Sabellastarte indica , collected by Stephenson); Australia, Heron Island (AMS W 9168 as Sabellastarte sp. ); Hawaii (Halape, BZMH 501), Oahu (Pearl Harbour and Fort Kamehameha promontory), Maui (Lahaina) and Molakini (UHM).

The following description is based on Quatrefage’s (1866) original material (cuticle and chaetae lifted by histolysis) with data in parentheses first from Durban and second from one of the larger specimens from New Caledonia.

Description. Body without crown 25+18 (92, 78) mm long, 7 (9.4, 10) mm wide with about 85 segments (figure 4A) of which nine (eight, seven) are thoracic; crown 25 (29, 33) mm long, each side of crown base involuted ventrally to form nearly a circle each side, length of interradiolar web equivalent to length of two or two and a half thoracic segments (figure 4A), narrow flanges on dorsal margins (near web) scarcely D-shaped; radioles about 30 each side, randomly interdigitating (figure 4A insert), outer surface of each rounded for most of length (figure 4F, H), with small blunt longitudinal ridges present distally (figure 4G, J); radiolar tips often long (figure 4K); dorsal lips tapered 8 (9) mm long, with midrib support; thorax about as long as wide; dorsal margins above crown/thorax junction with or without shallow marginal embayments above collar pockets each side of dorsal midline (figure 4B, C), lateral collar margins similar height and transverse to axis of body (figure 4E) leading to small subtriangular lappets (figure 4D) involuted at midline; first ventral shield with indistinct anterior margin (figure 4D); anterior thoracic tori long, at least twice length of last torus, their ventral ends all touching sides of shields (figure 4E); third thoracic fascicle with about 40 chaetae in all, anterior abdominal fascicle with 13 in all, chaetal shapes similar to those of S. spectabilis ; tube muco-silt.

Quatrefages’ material is straw-coloured with darker ventral shields and whitish glandular areas around the abdominal parapodia. Other pigments lost by histolysis. The worm from Mauritius is also pale with darker (light brown) anterior ventral shields, brown lines between uncinal ridges, darker brown longitudinal stripes on crown base and random irregular dark brown flecks and blotches over most of body, these more intense anteriorly and on the ventral shields. There are also small blotches at each side of the parapodia (rather camouflaged by speckled background), and distinct interramal spots.

Variation and habitat. The Indian Ocean populations of Sabellastarte pectoralis show a tendency to lose their crowns and the distal parts of the radioles can be unusually coiled, even when the crown is still attached, possibly a reaction to fixation. This makes it difficult to cut radiolar sections to observe the distal blunt longitudinal ridges characteristic of this species (figure 4G, J). Ehlers (1897) noted that the smaller specimens in his Zanzibar collection (ZMH PE 1343) were ‘irregularly sprinkled and spotted on a light grey background’. These are Sabellastarte pectoralis . His larger specimens ‘uniformly dark violet brown’ except for ‘bands on the crown’ (ZMH PE 1342, distal radioles not coiled) are Sabellastarte spectabilis .

The label of material from Mauritius now identified as Sabellastarte pectoralis notes occurrence with coral in a lagoon at Pte Lafayette (ZMA V. Pol. 2394). This material has shallow dorso-lateral collar emarginations slightly deeper than those from Natal (figure 4E, NHML 1932.12.235) and like those from New Caledonia (MNHN A258, Fauvel, 1930), although they are portrayed as atypically deep by Pruvot (1930, plate II, figure 39). Day’s figure (1967: 37.5g) shows dorsal collar margins without marginal embayments above the pockets.

Remarks and distribution. Laonome arenosa seems to be Sabellastarte pectoralis to judge from collar configuration and size, but surface pigment flecks, parapodial spots and blotches are not apparent perhaps due to histolysis. Ehlers (1904) seemed to think that the Schauinsland material he identified as Laonome ceratodaula Schmarda (ZMH PE 1330) was from New Zealand, yet there is no place called Laysan in that country. Laysan is a small western Hawaiian island. He compared the Laysan material with New Zealand type material of Sabella ceratodaula , which was dark-coloured, shrivelled and much bigger than that from Laysan (type material is no longer with Schmarda’s other types in NHMW; H. Sattmann, personal communication), but he failed to note that Schmarda’s figure of Sabella ceratodaula (1861, plate XXIII, figure 186) shows well-separated dorsal collar margins, like most species of Pseudobranchiomma . So far studies have not found Sabellastarte in New Zealand, but Pseudobranchiomma is represented there by P. grandis Baird (locally known as ‘ serratibranchis ’. Not that of Grube, 1878).

Both Sabellastarte pectoralis and S. spectabilis occur on the islands of Mauritius, Zanzibar and Hawaii and may also co-exist on the Coburg Peninsula of northern Australia, where an anterior thorax, agreeing well with the collar configuration and speckled surface of Sabellastarte pectoralis , is in the same holding as S. spectabilis (NTM W.4229).

A few small specimens in one of the vials from New Caledonia (MNHN A258, Fauvel, 1930) are not Sabellastarte pectoralis , but Pseudobranchiomma punctata (Treadwell, 1906, as Laonome , from Hawaii) redescribed by Nogueira and Knight- Jones (in press). The two species therefore co-exist in both Hawaii and New Caledonia. Fauvel (1930) synonymized Sabella pottaei Quatrefages (1866, from New Caledonia) with Sabellastarte indica , but Sabellastarte pottaei is different from both S. spectabilis and S. pectoralis , being a synonym of Sabellastarte japonica Marenzeller (see below). Sabellastarte pectoralis can therefore be found with S. japonica in New Caledonia.

Sabellastarte pectoralis occurs in Mauritius, Zanzibar, Natal, Maldive Islands, Australia (Northern Territory? and Queensland), New Caledonia and Hawaii.