Abstract / Introduction / Summary:
Two ethanol-preserved specimens of argulid branchiuran loaned from the Toyama Science Museum (TOYA, Toyama City, central Japan) are identified as Argulus japonicus Thiele, 1900. These specimens were collected in Toyama Prefecture and represent a new prefecture record for A. japonicus in Japan. One specimen (TOYA-Cr 23793) was an ovigerous female taken from a goldfish Carassius auratus (Linnaeus, 1758) reared in Taikoyama, Imizu City, on 31 August 1982, and another specimen (TOYA-Cr 23794) was an adult female collected in Hongo, Toyama City, on 28 September 1996 without its host record. In both specimens, a single plumose seta is present on or near the posterior margin of each coxa of the first legs, which is a character to distinguish A. japonicus from a morphologically similar, congeneric species, A. coregoni Thorell, 1864 that has 4–9 plumose setae on each coxa. The specimens also have 51 or 52 supporting rods in each marginal membrane of the first maxillae, and these numbers are different from those (60 or more) of supporting rods reported from A. coregoni.
