Macroinvertebrates of south Western Australia’s salt rivers 6

Hydrophilidae Berosus discolor

There are several species of water scavenger beetles that are able to tolerate extremes of salinity. The larvae obtain their oxygen through abdominal gills and crawl on the stream bottom feeding on small midge larvae and crustaceans. The adults have heads that bend downward (deflexed) and club shaped antennae tucked under their eyes that help to break the surface film of the water when replenishing their air supply. The hairs on their hind legs assist the beetles to swim. The adults eat plants and organic debris.

Macroinvertebrates of south Western Australia’s salt rivers 3

Cyprididae Mytilocypris mytiloides

The SW is home to a high diversity of seed shrimps (Ostracoda) with over 200 species known. Sixty-five known species live in naturally saline inland waters, however many of them are not found in systems impacted by rising salty groundwater (secondary salinisation). Some species are only found in one or two wetlands and there are still many undescribed species. This makes it difficult to develop protection plans. The eggs of seed shrimps can survive in dried sediments for several years. This species occurs in brackish to saline water and is common in swards of the aquatic flowering plant Ruppia sp. The grid squares are 1mm2.


Macroinvertebrates of south Western Australia’s salt rivers 2

The larval caddisfly, Symphitoneuria wheeleri  shown here is a halophile, i.e. it lives only in saline water. It utilises both sand grains and/or plant material to make its case, depending on what is readily available. The larvae feed on both plant material and small invertebrates and are the longest living stage of its life cycle. The grid squares are 1mm2. The second photo shows the head of a larval Symphitoneuria wheeleri with the head of a midge larvae protruding from its mouth. The adults superficially look like moths, are nocturnal and short lived.

Macroinvertebrates of south Western Australia’s salt rivers 1

Dytiscidae Necterosoma penicillatus

Necterosoma penicillatus is a predatory diving beetle endemic to southern Australia. The adults are able to tolerate extremes of salinity and have been collected in salinities of 130 ppt (over 3 times saltier than the sea), however the larvae require lower salinities to survive. The larvae have long swimming hairs on their legs and feed on their prey by piercing then pumping into them digestive juices with their long mandibles. They then suck up the liquefied food. The adults have long fringes of hair on their hind legs which act as paddles. They feed on their prey by pulling them apart with their strong fore legs and mandibles.