Observations on Gastrotricha from a sandy beach in southeastern Australia, with a description of Halichaetonotus australis sp. nov. (Gastrotricha, Chaetonotida)

Several species of Gastrotricha were found among samples of nematodes extracted from a sandy ocean beach, South Broulee beach, in southeastern Australia. One of these Gastrotricha turned out to be a species new to science which is described as Halichaetonotus australis sp. nov. in this study. Although the spines of the hydrofoil scales resemble those of the cosmopolitan H. aculifer, a distinctive feature of the new species is the presence of three prominent posterior dorsal spines. These are exaggerations of the keels found on the dorsal overlapping scales that cover the dorsal surfaces of the head, neck, and trunk. The spines are almost as long as the rami of the terminal furca. H. australis sp. nov. also resembles H. marivagus, but differs in lacking both a cephalion and hypostomion. Freeze drying is introduced as a preparation method for scanning electron microscopy of Gastrotricha.