Shield shrimps, tadpole shrimps

Code OE999999

See Key to Families of Australian Aquatic Crustacea

An order of Crustacea (with segmented, chitin-encased body and articulated appendages). The Notostraca are placed with the orders Conchostraca, Anostraca and Cladocera in the Branchiopoda. Notostraca are distinguished from other Branchiopoda by the dominance of the carapace development, which is broad, shield-like and although attached only to the head, covers the head, thorax and much of the abdomen. The paired compound eyes are on the anterior carapace (head), the first antennae are single-branched and unsegmented. The second antennae become reduced through development, such that they are small or vestigial in adult notostracans. The body posterior to the head is relatively undifferentiated, being composed of body rings. The first 11, each with a pair of ventral appendages, comprise the thorax - a variable number of rings posterior to this comprise the abdomen.

All extant forms are represented by one family - the Triopsidae (Code OE019999) . There are two Australian genera, with Triops more common in the arid areas, and Lepidurus the southern and south-western parts where winter rainfall is more predictable. Some species are bright red with haemoglobin. Notostracans can be found in water bodies ranging from permanent farm dams, ditches etc to very impermanent rain-filled pools, with salinities varying from oligotrophic to modestly saline. One species has desiccation-resistant eggs that are easily dispersed on air currents, allowing rapid colonisation of ephemeral habitats.

Reference:

Williams, W.D. (1980) Australian Freshwater Life: The Invertebrates of Australian Inland Waters. The Macmillan Company of Australia, Melbourne.