ABSTRACT
De Blainville originally described two Echinometra species, E. mathaei and E. oblonga in the Indo-Pacific. Recent studies concerning gamete incompatibility, embryology, karyotype, morphology, molecular structure and ecology of Okinawan Echinometra four types have shown that at least four species are represented in what used to be called E. mathaei. Type A with white-tipped spines and spindle-shaped gonad spicules will stay E. mathaei. Type B with unicolor spines and spindle-shaped gonad spicules, newly discovered in Okinawa, will be Echinometra sp.2. Type D with black spines and tri-radiate gonad spicules may be E. oblonga. It was shown that there are disagreements among the phylogenetic trees of the four species based on morphological, embryological, cytogenetical and biochemical studies.
