Colossendeis, Jarzynsky, 1870

Staples, David A., 2019, Pycnogonids (Arthropoda, Pycnogonida) from the Southwest Indian Ridge, Zootaxa 4567 (3), pp. 401-449 : 430

Colossendeis sp.

Plate 5A, B

Material examined. One specimen of indeterminate sex (NHMUK 2018.35), Southwest Indian Ridge, Coral Seamount, 41˚ 21.32.99' S, 42˚.55.033' E, ROV, 863 m, specimen JCO66-578, stn 4.9, parent 971, on dead coral rubble, 14 November 2011.

Distribution. This genus is found world-wide in all deep-sea ocean basins.

Remarks. The leg span of this specimen is about 276 mm. This specimen belongs to a group of morphologically similar species that collectively form the Colossendeis macerrima Wilson, 1881 complex. The four most confused species in the complex are C. macerrima , C. leptorhynchus Hoek, 1881 , C. minor Schimkewitsch, 1893 and C. gardineri Carpenter, 1907 . Probably no other group of pycnogonids has been subjected to such extensive analyses as have those belonging to this complex and yet remain without satisfactory resolution. The most recent analysis of these four species was by Bamber, (2002) who reviewed previous analyses by Stock (1974, 1984 and 1986) and he supported the independent status of the four species. Justification for their independent status was primarily based on proboscis shape, propodal sole spination and palp segment ratios. Bamber did not discuss the earlier work of Turpaeva, (1994) who determined that the ratios of palp segments within the macerrima complex changed and overlapped with age. Her observations supported the earlier findings of Fry and Hedgpeth, (1969) who concluded that owing to differential rates of growth between structures, relative proportions vary continuously through size ranges within species of Colossendeis . As a consequence of her analysis Turpaeva synonymised C. leptorhynchus with C. macerrima and C. gardineri with C. minor .

The strongly-tapered proboscis of this specimen is suggestive of C. minor but based on my reexamination of the C. minor syntypes and the C. macerrima holotype, this species differs in respects which extend beyond regional differences and cause the specimen to not sit easily with any other members of the species complex. Rather than add to the confusion and assign yet another specimen on a tentative or provisional basis to a species in the C. macerrima complex I have left it undescribed. Despite the geographically discrete collection site, the specimen has been included in a morphological and molecular analysis of a large collection of specimens from southern Australia that fall into the species complex. Such analysis is too involved to form part of this paper and the findings of that analysis will be the subject of a separate paper.

Figures

PLATE 5. Colossendeis sp. A, proboscis lateral; B, palp. Colossendeis melancholicus. C, specimen on rock wall. D, specimen with proboscis inserted into Isactinernus quadrilobatus. Hedgpethia filamentus sp. nov., holotype. E, trunk, lateral view; F, trunk, dorsal view. Hedgpethia shalei sp. nov., holotype. G, trunk, lateral view; H, trunk, dorsal view.