Sicydium 属とSicyopterus 属の相違について

抄録

The genus Sicydium was established by Valenciennes (1837) with Gobius plumieri Bloch as its type species. Sicyopterus was first established by Gill (1861) as a subgenus of the genus Sicydium with Sicydium stimpsoni Gill as its type species, and later raised to a generic level by Bleeker (1874).Since then the two generic names, Sicydium and Sicyopterus have been used for the type species of the genus Sicyopterus.
Sicydium and Sicyopterus were insufficiently diagnosed by Gill (1861), Bleeker (1874 and 1876).and Koumans (1931), so that the characteristics given by them do not agree.
Our comprehensive study of the type species of the two genera, Sicydium cocoensis (Heller et Snodgrass), Sicyopterus japonicus (Tanaka), Sicyopterus macrostetholepis (Bleeker), Sicyopterus parvei (Bleeker), and Sicyopterus pugnans (Grant) revealed that the characteristic differences of these species are divided into three levels as follows.The two species of the genus Sicydium and the five species of the genus Sicyopterus are distinguishable at level I.The characteristic differences between them are shown as A and B in Table 3.At level II on the one hand the two species of the genus Sicydium are distinguishable in that their characteristic differences are the presence or absence of a median cleft in the upper lip, of a fleshy tubercle behind the cleft, of the middle pore N of the preopercular canal, and of the ctenoid scales, which are expressed as C and D in Table 2.On the other hand Sicyopterus pugnans and the four other species of the genus Sicyopterus are distinguishable by the presence or absence of a median cleft in the upper lip, of the projections lining the edge of the upper lip, of a fleshy tubercle behind the cleft, of the ridge with protuberances inside the upper lip, by the tips of the teeth in the upper jaw being divided into two or three, by the presence or absence of the flapped lateral lower lip, and by the row of labial teeth being extended or not beyond the last tooth of the upper jaw, which are expressed as E and F in Table 2.At level III the four species of the genus Sicyopterus are distinguishable by the widely or closely set papillae between the band of papillae on the lower lip and the labial teeth, and the differences of fin ray and scale counts, which are expressed as G, H, I, and J in Table 2.Since the differences at level I are sufficiently remarkable to be of generic level, the genus Sicyopterus should be separated from the genus Sicydium, so that A and B in Table 3 become the diagnostic characters of the two genera.However, some of the characteristic differences shown in Table 3 might have to be omitted when more species of the two genera are examined.