Ryukuaster onnae Mah, 2007

Featured Invertebrate Data


Frequency on Okinawa: Collection Data:
[brackets indicate range for all Okinawa-collected specimens of the species]

Species Account:

        Ryukuaster onnae is considered to be uncommon on Okinawa as I have collected a total of twelve individuals over a period of more than twenty years of Okinawa diving, however, the image of the above individual was uncollected. The twelve collected specimens have been received by the NMNH.

        The following attenuated species description (Diagnosis and Description of Ryukuaster onnae) is taken from Mah (2007):

Body form stellate. Approximately 16 marginals per interradius. Lateral edge of marginal plates with granular cover. Tubercular granules, granular spinelets on abactinal, marginal plate surface. Actinal intermediate plates covered by granules at R = 1.5 cm. Furrow spines three to five. Terminal plates enlarged.

Body shape weakly stellate (R/r = 1.3-1.5). Arms short, triangular, disk broad. Arm tips upturned.
        Abactinal plates flat to mildly convex. Some plates, including those on primary circlet and carinal plates strongly convex. Abactinal plates round to polygonal in outline, becoming irregular adjacent to marginal plate contact. Carinal plate series round to hexagonal. Primary circlet interradial plates enlarged (approximately twice as large as carinals). Plates with 8-50 (typically 20-30) peripheral granules, quadrate, angular to polygonal in shape, discretely separate from one another, but tightly arranged. Plates smooth, bare but in larger specimens (R > 1.5) granules identical to peripheral granules form additional rows on plate adjacent to periphery, becoming very dense, sometimes completely obscuring plate. These larger sized specimens sometimes with large nipple-like tubercle positioned centrally on interradial plates.
        Fasciolar channels distinct, but shallow. Papular pores single if present interradially; double on radial regions. Madreporite triangular, commonly bordered by three plates. Four plates are present around more rounded madreporites.
        Marginal plates elongate, swollen, quadrate in outline, decreasing in size distally towards terminal. Fasciolar channels distinctly present between marginal plate series. Peripheral granules 20~60, quadrate, rectangular to polygonal, irregularly angular. Larger plates with additional, similar granules forming second and third irregular rows on plate surface adjacent to periphery.

        I feel fortunate in as much as three of my Okinawa-collected specimens have been given names for local areas. Two opisthobranch mollusks and the above featured asteroid:

        I've added a second page w/ several images of the holotype specimen.

        In addition, there's a page w/ links to misc. phyla including this species phylum, as well as additional resources.


Literature Cited:

Page Date: 15 Apr '17
Page Modification Date: 15 Apr '17
Digitally manipulated photo
Copyright © 2017 Robert F. Bolland