Rhopalophthalmus Illig, 1906

Talbot, Suzette, 2009, A survey of Mysida from the Lizard Island area, Great Barrier Reef, Australia, Subfamily Siriellinae (Crustacea, Mysida, Mysidae), Zootaxa 2114, pp. 1-49 : 46

Genus Rhopalophthalmus Illig, 1906

Material examined. 1 juvenile, plankton tow, 5 m depth, open water between Lizard Is. & Eagle Cay, 1951 hrs. Jan. 8 1977 (STL-77-N14). Size: 2.0 mm.

Remarks. The specimen is too badly distorted and immature to identify positively to species, however, of the 3 known Australian species, Rhopalophthalmus dakini O.S. Tattersall, 1957 , R. brisbanensis Hodge, 1963 and R. constrictus Panampunnayil, 1992 , it is most likely to belong to R. brisbanensis , as the anterior margin of its carapace appears to be slightly convex, a feature characteristic of this species. In R. dakini the anterior margin is straight and in R. constrictus it is produced to form a triangular rostrum. The telson of latter species has a marked distal constriction, lacking in the telson of the other two species and also lacking in that of the Lizard Island specimen.

Associated mysid species. Small numbers of Anchialina typica , Anisomysis pelewensis , Hemisiriella pulchra , Doxomysis acanthina and Haplostylus parvus Hansen, 1910 were taken in the same sample as the Rhopalophthalmus juvenile.

Habitat. Estuarine, sublittoral, pelagic.

Distribution. The genus has a widespread estuarine and inshore distribution in tropical and temperate regions. In Australian waters, R. dakini , initially identified as R. egregius Hansen, 1910 , has been found in New South Wales in Lake Illawarra ( W.M. Tattersall 1940). Previously Tattersall (1936a) had recorded the capture of a single small immature specimen outside Trinity Opening in the Great Barrier Reef and had referred it to R. egregius . In her survey of the genus, O.S. Tattersall (1957) transferred the Lake Illawarra specimens to a new species, R. dakini , and she suggested that the Great Barrier Reef specimen should probably be assigned to it as well. The second Australian species, R. brisbanensis was described from the Brisbane River by Hodge (1963) and the third, R. constrictus , from the south-west coast by Panampunnayil (1992).