Rhopalophthalminae

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 : 45

Subfamily Rhopalophthalminae

Diagnosis. Eyes prominent, elongate, club-shaped, laterally directed, peduncle not covered by carapace, a pair of post-orbital spines on anterior carapace border with a keel extending posteriorly from each spine towards the cervical groove, posterior 3 thoracic segments exposed. Antennal scale long and slender, outer margin straight, ending in a prominent spine that projects beyond scale apex, terminal lobe small and shallow. Endopod of 8th thoracic limb reduced, sexually dimorphic. Abdominal pleura of males extend ventrally to form epimeral plates in I or more segments. Male pleopods biramous. Uropods slender, both exopod and endopod divided into 2 articles by a transverse suture, inner and outer margins setose. Telson linguiform, elongate, lateral robust setae distally on each margin, 2 pairs of stout, strongly serrated terminal robust setae. This small subfamily is held to be one of the earliest of the Mysidae to emerge ( Meland & Willassen, 2007). It contains16 known species, all belonging to the Genus Rhopalophthalmus . At least 2 of them, R. terranatalis from southern Africa ( Wooldridge & Bailey 1982) and Rhopalophthalmus sp. from the Lane Cove River, N.S.W. (Talbot, aquarium observation) exhibit the unusual behavioural characteristic of swimming with the ventral surface uppermost, a trait otherwise unrecorded among the mysids. According to Wooldridge and Bailey’s observations, the inverted posture of R. terranatalis is associated with the method by which this primarily bottom-dwelling mysid captures its zooplankton prey. This raises the possibility that carnivory, associated with a benthic habit and inverted posture, was a characteristic of the original mysid stock, which subsequently underwent radiation to occupy a great variety of other niches.