Three species of parasites emerging on the gills of mulloway, Argyrosomus japonicus (Temminck and Schlegel, 1843), cultured in Australia

Abstract

Mulloway is an Indo‐West Pacific sciaenid fish with a short history of commercial culture in Australia. In January 2005, a harvest sample of these fish cultured off South Australia was observed macroscopically with large numbers of a blood‐feeding polyopisthocotylean. Epizootics of this parasite may pose a threat to the economics of farming this species, since it appears to be associated with anemia, as indicated by pale gills. Based on morphological characters, we identify the monogenean as Sciaenacotyle sciaenicola [Murray, F.V., 1932. Correction: note on a microcotylid from Sciaena antarctica. Parasitology 24, 448.] Mamaev [Mamaev, Yu.L., 1989. On species composition and morphological features of the Microcotyle genus (Microcotylidae, Monogenoidea). In: Lebedev, B.I. (Ed.), Investigations in Parasitology . Collection of Papers. DBNTs AN SSSR: Vladivostok, pp. 32–38 [In Russian].]. Maximum likelihood analysis of ITS2 rDNA confirms that the genus Sciaenacotyle is not closely related to two other microcotylid genera also known from sciaenid fishes: Diplostamenides (represented by D. sciaenae (Goto, 1894) Mamaev [Mamaev, Yu.L., 1989. On species composition and morphological features of the Microcotyle genus (Microcotylidae, Monogenoidea). In: Lebedev, B.I. (Ed.), Investigations in Parasitology . Collection of Papers. DBNTs AN SSSR: Vladivostok, pp. 32–38 [In Russian].] from white croaker, Pennahia argentata, in Japan) and Anchoromicrocotyle (represented by A. guaymensis [Bravo‐Hollis, M., 1981. Helminths of fish of the Mexican Pacific. XXXVI. A new genus and subfamily of the family Microcotylidae Taschenberg, 1879 emended. An. Inst. Cienc. Mar Limnol. Univ. Nac. Auton. Mex. 8, 305–313.] from white seabass, Atractoscion nobilis, in California). In more intensive sampling of gills, we detected two other species of metazoan parasites, the monopisthocotylean Calceostoma glandulosum Johnston et Tiegs, 1922; and a copepod we identify as Caligus cf. elongatus, a sea louse very similar to C. elongatus Nordmann (1832), which affects farmed salmonids in the North Atlantic. Praziquantel bath treatment at an initial concentration that removed S. sciaenicola from mulloway gills did not remove C. glandulosum.