First valid record of Astacilla Cordiner, 1793 in Australia, with description of a new species (Crustacea: Isopoda: Arcturidae)

Abstract

A new species of arcturid isopod, Astacilla lewtonae, is described from Western Australia. Although other Australian species have been attributed previously to this genus, this is the first record for the genus as currently diagnosed. The Arcturidae Dana, 1849 are a specialised group of marine isopods, which use the anterior four pairs of pereopods as a setose filtering complex extending from a cylindrical body usually elevated above the substrate. The family belongs to the isopod suborder Valvifera, which has recently been restricted by Poore (2001) who removed many genera traditionally placed in it to other families, Antarcturidae Poore, 2001 in particular. The first description of an Australian arcturid isopod was of Areturus brevieornis Haswell, 1881 from New South Wales. The types of this species are lost but it is probably a species of Neastaeilla. Further species of Areturus were described from New South Wales by Whitelegge (1904), Arcturus aleieornis, A. dentatus, A. nodosus, A. serratulus, A. simplieissimus, the types of all of which are also lost. All probably belong in the Antarcturidae. The first review of Australian arcturid taxa was that of Hale (1924), who examined many specimens and established the endemic genus Parastaeilla for two very distinctive species. He also described two other species and placed them in Neastaeilla Tattersall (Neastaeilla algensis and Neastaeilla deducta). In a further, more comprehensive, review Hale (1946) described five arcturid species from the Southern Hemisphere and placed them all in Astaeilla (Astaeilla attenuata, A. maeilenta, A. sheardi and A. vicaria from Australia and A. fusiformis from New Zealand) arguing that the genus Neastaeilla Tattersall was poorly differentiated from Astacilla and should not be recognised. Hale (1946) re­ examined his two previously described Australian species, Neastacilla algensis Hale, 1924 and Neastacilla deducta Hale, 1924, moving both to Asta cilIa, and included Astacilla marionensis Beddard, 1886 and Astaeilla kerguelensis Vanh6ffen, 1914 from the Southern Ocean in his discussion. Guiler (1949) was also reluctant to confirm the genus Neastaeilla and described five new Tasmanian species of Astaeilla (Astaeilla monoseta, A. inaequispinosa, A. unieornis, A. derwenti, and A. oeulata). Of these, only A. monoseta and A. inaequispinosa are currently valid species (Poore et al., 2002).