Pill bugs, sand lice

Code OR999999

See

Crustaceans (with segmented, chitin-encased body and articulated appendages) belonging to the class Malacostraca - that is, possessing a body clearly divided into a 5- segmented head, an eight-segmented thorax and an abdomen of 6 (rarely 7) segments with 'swimmerets' (pleopods). Each segment may bear a pair of segmented appendages unless reduced. The first antenna is two-branched (biramous), the second antenna has its expodite (the outer branch) scale-like.

Isopoda are distinguished amongst the Malacostracans by lacking a carapace, having a distinct head, and with the body dorso-ventrally flattened. The thorax has seven pairs of walking legs, each lacking exopodites. The abdomen is six segmented, each bearing a pair of appendages.

Differentiation from the otherwise quite similar Amphipoda is by the generally dorso-ventrally flattened appearance, by the one pair of uropods, and the 5 pairs of pleopods which are rarely slender and often plate-like.

The Australian freshwater fauna comprises the following families:

CIROLANIDAE (Code OR129999) is differentiated by the telson fused with the last abdominal segment. Both rami of the uropod are inserted laterally and may form a tail fan complex, rather than being positioned laterally or folded dorsally over the pleotelson. The pleon consists of six segments including the pleotelson, in contrast to the two segmented condition in the Sphaeromatidae. The Cirolanidae are predominantly marine, with inland records ectoparasitic on Macrobranchium and Paratya , with one subterranean form.

SPHAEROMATIDAE (Code OR139999) are differentiated by the telson being fused with the last abdominal segment and both rami of the uropod inserted laterally, and may form a tail fan complex, rather than positioned laterally or folded dorsally over the pleotelson. The pleon is in the 1-2-segmented condition in contrast to the Cirolanidae in which the pleon has six segments including the pleotelson. The Sphaeromatidae are predominantly marine, with some estuarine species.

MICROPARASCELLIDAE (Code OR199999) are differentiated amongst the families in which the uropods are neither positioned laterally nor form a tail fan, by the 1 (rarely 2) segmented pleon and the mandible with a palp. They are then distinguishable from the Janiridae by the uropod having a thin protopod that is no longer than the rami and a body which does not broaden posteriorly. The family is known from only one inland locality, some 30km from the southern Queensland coast - all other taxa are intertidal.

JANIRIDAE (Code OR189999) are differentiated amongst the families in which the uropods are neither positioned laterally nor form a tail fan, by the 1 (rarely 2) segmented pleon and the mandible with a palp. They are then distinguishable from the Microparasellidae by the uropod having an elongate, robust protopod that is longer than the rami and having a body which broadens posteriorly.

ONISCIDAE (Code OR259999) are differentiated amongst the families in which the uropods are neither positioned laterally nor form a tail fan, by the pleon comprising several separate segments and the mandibles lacking a palp, the flagellum of antenna 2 having 3 articles and the mandible lacking a grinding surface. The family includes some aquatic species found in inland saline waters of southern Australia.

ANTHURIDAE (Code OR089999) are recognised by the telson being unfused with the last abdominal segment, and the outer ramus of the uropod folding dorsally over the pleotelson. The family is predominantly marine, with undescribed material from a coastal freshwater lake (Timms, in Williams, 1980).

PHREATOICIDAE (Code OR059999) belongs to the suborder Phreatoicoidea, with a six-segmented abdomen and a body that is circular in cross-section (atypical for isopods) and with uropoda that assist in movement by flicking or pushing the animal forward. Distinguished from other Phreatoicoidea by one mandible lacking a lacinia mobilis (both mandibles have a lacinia mobilis in the other families).

HYPSIMETOPIDAE (Code OR049999) belong to the suborder Phreatoicoidea, with a six-segmented abdomen and a body that is circular in cross-section (atypical for isopods) and with uropoda that assist in movement by flicking or pushing the animal forward. Distinguished amongst the Phreatoicoidea by both mandibles having a lacinia mobilis, and amongst the other families of the suborder by the lack of eyes and vermiform body, truncated trunk and generally subterranean habit.

PHREATOICOPSIDAE (Code OR039999) belong to the suborder Phreatoicoidea, with a six-segmented abdomen and a body that is circular in cross-section (atypical for isopods) and with uropoda that assist in movement by flicking or pushing the animal forward. Distinguished amongst the Phreatoicoidea by both mandibles having a lacinia mobilis, and amongst the other families of the suborder by usual possession of small sessile eyes (though some are blind), with a robust/subcylindrical and pigmented body and a relatively long head with a small ridge at the posteroventral corner. Epigeic in habit.

AMPHISOPIDAE (Code OR019999) belong to the suborder Phreatoicoidea, with a six-segmented abdomen and a body that is circular in cross-section (atypical for isopods) and with uropoda that assist in movement by flicking or pushing the animal forward. Distinguished amongst the other families of the suborder by the possession of small sessile eyes, with a robust/subcylindrical and pigmented body and a small head without any ridge at the posteroventral corner but with prominent eyes. Differentiated from the similar Mesamphisopidae by the pleopodal endopods lacking plumose setae, and with the pleotelson being a rounded lobe or emarginate. Epigeic in habit.

MESAMPHISOPIDAE (Code OR029999) belong to the suborder Phreatoicoidea, with a six-segmented abdomen and a body that is circular in cross-section (atypical for isopods) and with uropoda that assist in movement by flicking or pushing the animal forward. Distinguished amongst the other families of the suborder by the possession of small sessile eyes, with a robust/subcylindrical and pigmented body and a small head without any ridge at the posteroventral corner but with prominent eyes. Differentiated from the similar Amphisopidae by the pleopodal endopods with plumose setae, and with the pleotelson being one upturned lobe. Epigeic in habit.

STYLONISCIDAE (Code OR260000) are amongst the families in which the uropods are neither positioned laterally nor form a tail fan, recognised by the pleon comprising separate segments and the mandibles lacking a palp, and the flagellum of antenna 2 having 3-10 articles and the mandible with a grinding surface. Although believed to be solely terrestrial, records from South Australia suggest some taxa may be aquatic.

References:

Horwitz, P., Knott, B. and Williams, W.D. (1995) A Preliminary Key to the Malacostracan Families (Crustacea) found in Australian Inland Waters . Co-operative Research Centre for Freshwater Ecology Identification Guide No. 4., Albury, NSW.

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