Myxaster perrieri Koehler 1896

Mah, Christopher L., Mercier, Annie, Hamel, Jean-Francois & Nizinski, Martha, 2012, Range Extensions and Taxonomic Notes on Atlantic Myxasteridae (Velatida; Asteroidea), Zootaxa 3572, pp. 55-62 : 56-57

Myxaster perrieri Koehler 1896

( Figures 1 C–E)

Koehler 1896: 48, Fig. 11; Alton, 1966: 1966: 688; Clark and Downey, 1992: 337; Dilman 2005: 456, 460.

Distribution: Bay of Biscay, 1300 m.

Comments: Dilman (2005: 463, 2006: 182) stated that M. perrieri possessed six arms and five primary radial plates compared to eight to ten (typically nine) arms in Myxaster sol with an identical number of radial plates and suggested that M. perrieri should be placed within Pythonaster .

Examination of the holotype of Myxaster perrieri (MNHN EcAh 3840) revealed that this specimen displays the imbricated plates ( Fig. 1 C, E) that characterize Myxaster and lacks the distinct muscular bands observed in Pythonaster ( Fig. 3 B). Dilman’s (2005) conclusion that M. perrieri should be placed in Pythonaster is not supported by morphological evidence. Thus, this species should remain in the genus Myxaster as originally designated.

Based on examination of the holotype, Downey in Clark and Downey (1992) argued that the occurrence of six rays in M. perrieri is unusual for the species, since only five primary plates on the abactinal surface of the disk were observed. However, examination of the holotype shows six pairs of oral plates present. Additionally, the abactinal surface of the holotype is damaged, thus obscuring clear observation of the sixth plate ( Fig. 1 C–D). These observations cast doubt on Downey’s conclusion that M. perrieri is normally five rayed.

Re-examination of the holotype also revealed differences between the specimen and those in Koehler’s (1896) original description. Among the most significant was that his original description indicates that four furrow spines were present per adambulacral plate, when there are actually six to eight. Given that M. sol has between five and eight furrow and the number of arms in M. sol is apparently more variable than has been historically recognized (as outlined below) it is possible that M. perrieri and M. sol are conspecific.

Material Examined: MNHN-EcAh 3840 HOLOTYPE, M. perrieri . Golfe de Gascogne 44˚2’N, 5˚22’W, 1300 m, Coll. Caudan st. 15 (1 wet specimen, R=7.5, r=1.6, but arms disarticulated).

Figures

FIGURE 1. Myxaster sol (long armed variant) A. USNM E 18596. Scale bar = 1.5 cm. B. YPM Y 36040. Scale bar = 1.0 cm. Myxaster perrieri Holotype, EcAh 3840, Scale bar for C – E = 5.0 mm. C. Abctinal surface. D. Actinal surface. E. Arms from holotype.

FIGURE 3. Pythonaster atlantidis USNM E 18842. A. Abactinal surface. Scale bar = 1.5 cm B. Annulations on arm. Scale bar = 5.0 mm. C. Actinal surface showing tube foot groove. D. Oral plate. Scale bar = 5.0 mm.