Cladonema timmsii, a new species of hydromedusa (Cnidaria : Hydrozoa) from a salt lake in South Australia

Abstract

Cladonema timmsii, sp. nov., is described from Blue Lagoon, an inland saline lake on Eyre Peninsula, near Cactus Beach, due south of Penong, Australia. It is a small medusa with a bell height and diameter of about 2.0mm. It differs from its congeners in having (1) sexually dimorphic gonads, i.e., the males bearing six radially arranged gonadal pouches on the stomach wall, the females lacking gonadal pouches, having instead smooth gonads; (2) different arrangements of nematocyst warts on the main tentacle branches (two rows) and side branches (one row). It is further characterized by having (1) nine simple radial canals, each corresponding with a tentacle bulb bearing a 7-branched stinging tentacle and about six suctorial branches; (2) six oral tentacles with very short stalks, each bearing a terminal nematocyst knob; (3) dark red, lensed ocelli. This is the first report of a species of Cladonema from Australian waters; members of the genus are also reported herein from the Northern Territory and New South Wales.