Morphological comparison of black Echinometra individuals among those in the Indo-West Pacific

Y. Arakaki et T. Uehara, Morphological comparison of black Echinometra individuals among those in the Indo-West Pacific, ZOOL SCI, 16(3), 1999, pp. 551-558
Citations number
Categorie Soggetti
Animal Sciences","Animal & Plant Sciences
Journal title
ISSN journal
0289-0003 → ACNP
Year of publication
551 - 558
SICI code
It is almost impossible to discriminate each region's black Echinometra bas ed on appearance, such as the color of spines, milled ring, and skin around the peristome. However, it is possible to divide them into several groups based on such characteristics as the spicules of the gonads and tubefeet, t he pore-pairs, the shape of the sperm, and the pedicellaria. The percentage of spicules of the gonads and tubefeet depends on the region the individua ls inhabit. The five pore-pair percentage of Guamanian individuals is very low, and this is significant compared to the individuals of the other regio ns. The sperm morphology of Guamanian and Hawaiian individuals is significa ntly more compact than that of Mauritian, Indonesian, Okinawan, and Boninia n individuals, while the difference between the Guamanian and Hawaiian indi viduals is also significant. The tridentate pedicellaria of the Hawaiian in dividuals are longer than those of the other regions' individuals, and the difference is significant. The length differences of the ophiocephalous ped icellaria and trifiliate pedicellaria are significant depending on the indi viduals of the region, and it is possible to discriminate individuals of ea ch region into several groups. Guamanian and Hawaiian individuals are separ ated into different groups based on all these characteristics, and it is al so possible to discriminate these two groups from the other regions' indivi duals by several characteristics. Therefore, black Echinometra individuals living in the Indo-West Pacific are divided into three groups, i.e., Maurit ian, Indonesian, Okinawan, Boninian individuals; Guamanian individals; and Hawaiian individuals. The number of pore-pairs and morphology of the sperm in the Okinawan Echinometra species complex reflect species level differenc es, and it is suggested that cross-fertilizations between black Echinometra from Okinawa and Guam as well as Okinawa and Hawaii were not successful. T his indicates that the three groupings based on these characteristics refle ct a species level difference. In other words, the black Echinometra inhabi ting the Indo-West Pacific are a species complex, or a cryptic species comp osed of at least three species.