Abstract
The examination of a species of Japanese gobiid fishes with five branchiostegals and completely separated pelvic fins revealed that it agrees well with the holotype of Riukiuia poecila Fowler, 1946, known only from the holotype.The fact that no specimen has been identified as R.poecila since 1946 is considered to be due to the original description, where R.poecila is described as having five dorsal spines, whereas the holotype actually has six.
Smith (1958) synonymized the genera Leioeleotris Fowler, 1934 (type species: L. zonatus) and Riukiuia Fowler, 1946 (type species: R.poecila) with Hetereleotris Bleeker, 1874 (type species: Gobius diadematus).As a result of our examination of the type species of the genera Hetereleotris, Leioeleotris, Lioteres Smith, 1958 (type species: L.caminatus), Chriolepidops Smith, 1958 (type species: C.nebulopunctatus), Satulinus Smith, 1958 (type species: S.zanzibarensis), and Dactyleleotris Smith, 1958 (type species: D.tentaculatus), and the subgenus Pseudolioteres (type species: Lioteres (P.) simulans which is synonymous with H.diadematus), we conclude that all of these should be included in the genus Hetereleotris, because they all share such common characteristics as protruding anterior and posterior nostrils, the first gill arch with most of the lower limb covered by membrane, broad isthmus and gill membrane attached to the base of pectoral fin, six dorsal spines, segmented caudal fin rays 9+8=17, completely separated pelvic fins without a frenum or a uniting membrane between them, five branchiostegals, vertebrae 10+17=27, first and second pterygiophores of first dorsal fin inserted between neural spines of third and fourth vertebrae and the last between those of sixth and seventh vertebrae, first and second pterygiophores of second dorsal fin spanning neural spine of ninth vertebra, an epural, and four transverse pit organ lines below eye and a longitudinal pit organ line touching the lower tips of the first three transverse pit organ lines and running to the fourth transverse pit organ line.
The relationship between the genus Hetereleotris and the genera Chriolepis, Eleotrica, and Gymneleotris of the seven-spined gobies of the Americas, which are said to be related to the genus Hetereleotris by Smith (1958), is not considered to be close, because, in addition to other differences, the genus Hetereleotris has a membrane covering the first gill slit, which is not found in these genera of the seven-spined gobies.The osteological comparison of H.poecila and H.zonatus with the genera Aruma, Pycnomma, and Gymneleotris of the sevenspined gobies revealed that, although the pelvic girdle of the genus Gymneleotris resembles the genus Hetereleotris, this, characteristic is not consistent in the other closely related genera Aruma and Pycnomma.This characteristic, therefore, does not seem to have any value in considering their relationship.
Pelvic fins without a frenum and with a vestigial condition of the uniting membrane are found in the various phylogenetic groups of gobiid fishes with five branchiostegals, but in these groups pelvic fins without a uniting membrane have been found only in the genus Hetereleotris.
The genus Hetereleotris is thus considered to be unique among the gobiid fishes with five branchiostegals, in having no closely related genera.
