Comaster L. Agassiz, 1836

Summers, Mindi M., Messing, Charles G. & Rouse, Greg W., 2017, The genera and species of Comatulidae (Comatulida: Crinoidea): taxonomic revisions and a molecular and morphological guide, Zootaxa 4268 (2), pp. 151-190 : 171

Comaster L. Agassiz, 1836

Table 1, Figs. 8–9

Type species. Alecto multifida Müller, 1841 .

Other included taxa (2). Actinometra schlegelii Carpenter, 1881 ; Comaster audax Rowe, Hoggett, Birtles & Vail, 1986 .

Diagnosis. Mouth excentric in fully developed individuals; up to 180 arms; centrodorsal small, discoidal or pentagonal; cirri absent or present; aboral surface with irregular plates between bases of adjacent rays; IBr2 united by synarthry; IIBr and beyond 2 or 4(3+4), usually with IIIBr of 2 ossicles exteriorly and 4(3+4) interiorly; first syzygy on undivided arms always 3+4; distal intersyzygial interval 4; distalmost pinnule comb at least P2 (usually P3–P8), sometimes at intervals to P14; combs arising gradually and tapering to a sharp point distally; pinnules on brachitaxes and sometimes P1 with comb of single, nonconfluent teeth; combs on brachial pinnules of paired, confluent, erect, more or less equal-sized and well separated teeth; pairs sometimes joined to form a transverse bar ( Fig. 8 D, M). Paired comb teeth may be absent on juvenile specimens (10–13 arms).

Distribution. Tropical Indo-western Pacific from northern Australia (Perth, WA, to Solitary Is., NSW), west to the Maldives, east to Fiji, and north to Sagami Bay, Japan. Depth range: 2– 183 m. All but a very few records are from depths shallower than 50 m.

Molecular results. Specimens identified as Comaster nobilis and C. schlegelii are less than 1.6% divergent in uncorrected distances of COI. As a clade, specimens of nobilis / schlegelii were at least 4% divergent in uncorrected distances of COI from C. audax ( Fig. 9 ). A more comprehensive molecular and morphological analysis of Comaster is in preparation (Owen et. al. in prep.)

Remarks. Species of Comaster are most easily distinguished from other comatulids by the irregular plates between the bases of adjacent rays, which give the aboral surface a solid, paved appearance. Because specimens identifiable as C. nobilis or C. schlegelii exhibit such minimal sequence divergence, we reinstate the former as a junior synonym of the latter, in agreement with AH Clark (1911b, 1911c, 1912b, 1931). Nevertheless, substantial morphological variation exists. Smaller C. schlegelii with numerous cirri are easily distinguished from larger cooccurring “ C. nobilis ” on the Great Barrier Reef. The distinction may be ontogenetic, although accompanied by distinct and consistent color pattern differences. Specimens attributed to “ C. nobilis ” lose cirri with growth. At Raja Ampat, Indonesia, C. schlegelii and “ C. nobilis ” with similar centrodorsal diameters have ~20 versus 1 (plus a few tiny buds) cirri, respectively, whereas a smaller “ C. nobilis ” with the same color pattern as the large specimen has ~20 cirri. Specimens attributed to C. schlegelii from Micronesia, where “ C. nobilis ” has not been collected, retain well-developed cirri, reach a larger size, and perch in the open instead of nestling in crevices as C. schlegelii typically does elsewhere ( Messing 1998b).

Figures

FIGURE 8. Comaster. (A – G) Comaster schlegelii— (A) live, exposed on sediment; (B) aboral surface, showing pentagonal centrodorsal lacking cirri; (C) live, exposed on reef; (D) paired comb teeth of equal shape, well separated and confluent with edge of pinnular, tapering to pinnule tip; (E) aboral surface, showing pentagonal centrodorsal with row of cirri; (F), live, tucked within coral structure; (G) aboral surface showing centrodorsal with ring of cirri. (H – M) Comaster audax— (H – I) live, exposed on reef, (J – L) aboral surface showing centrodorsal with few cirri, yellow distally; (M) paired comb teeth of equal shape, well separated and confluent with edge of pinnular, tapering to pinnule tip. Madang, Papua New Guinea: A – B. MNHN-IE- 2013 - 8147; C. MNHN-IE- 2013 - 8178; E. MNHN-IE- 2013 - 8071. I, L. not vouchered, SIO-BIC E 5998 (DNA subsample). Raja Ampat, Indonesia: D, F. SIO-BIC E 6260; G. SIO-BIC E 6261; H. not vouchered. K, M. SIO-BIC E 6258. Lizard Island, Australia: J. AM J 17567, holotype.

FIGURE 9. Maximum likelihood tree of Comaster inferred from COI. Symbols and labels as in Figure 2. Location abbreviations — Madang, Great Barrier Reef, Australia (GBR); Papua New Guinea (PNG); Raja Ampat, Indonesia (Raja); Goodwyn Island, Western Australia (WA). New COI sequences are Genbank KR 010330 - KR 010347.