#laevicaudata

One of the mornings for the Great Southern BioBlitz was spent out on Dingo Rock, one of the granite inselbergs in the area. It took me quite a long time to find the gnamma hole I'd seen on a previous trip, but once I did I mostly neglected the rest of the rock, since it was crawling with fascinating species. Gnamma holes are quite important to the local wildlife (and previously, the people), since they're the only freshwater available in the entire district, once the hot weather starts. Groundwater around the Wongan Hills is highly saline, which has become a huge problem after the massive landclearing for wheat farming.

Anyway - one of the species in the pool were these almost grape-sized Clam Shrimp, frantically mating before the shallow parts of the pool dried out completely. The eggs will survived, encysted, in the dry mud at the bottom of the pond until the winter rains come around again. In some species the eggs can wait seven years.

Clam Shrimp have been around since at least the Devonian. Most genera swim using their antennae, but Lynceus can open their bivalved carapace enough to swim with the legs as well.

Clam Shrimp (Orders Laevicaudata,Spinicaudata and Cyclestherida)

Clam shrimp are a group of unique bivalved branchiopods that have no relation to molluscan bivalves. Clam shrimp can be found worldwide, mostly in vernal pools and other small bodies of water, where the filter the water for passing nutrients and food. Like other branchiopods like the infamous Daphnia clam shrimp have several rows of legs which they use to swim trough the water. When threatened the clam shrimp like a true clam can close its hardy shell and will drift to the bottom until it is safe.

Phylogeny

Animalia-Arthropoda-Crustacea-Branchiopoda-Phyllopoda-Laevicaudata (Spinicaudata) (Cyclestherida)