Sand fleas

Code OP999999

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.

Amphipods are distinguished amongst the Malacostracans by lacking a carapace, having a distinct head, and with the body laterally 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 Isopoda is by the generally laterally flattened appearance, by the usual 3 pairs of uropods, and the 3 pairs of pleopods being slender, rather than plate-like.

The Australian freshwater fauna comprises nine families:

COROPHIIDAE (Code OP059999) are distinguished from other families of Amphipoda by the mandible possessing a palp, by the slight dorso-ventral flattening of the body and urosome and the conspicuous elongation of the merus of the second gnathopod.

HYALELLIDAE (Code OP099999) are distinguished from other families of Amphipoda in which the mandible lacks a palp (ie. Talytridae) by the rapid swimming, the two antenna being subequal in length , and the usual presence of a third uropodal ramus.

EUSIRIDAE (Code OP039999) are distinguished from other families of Amphipoda in which the mandible has a palp by characters of the rami of the uropod, which are subequal, the urosomites 2 and 3 are separate, and the accessory flagellum of the first antennal segment is conspicuous and usually bi-articulated.

PARACALLIOPIIDAE (Code OP040000) are distinguished from other families of Amphipoda in which the mandible has a palp by characters of the rami of the uropod, which are subequal, the urosomites 2 and 3 are fused, and the accessory flagellum of the first antennal segment is conspicuous and usually bi-articulated.

PARAMELITIDAE (Code OP069999) are distinguished from other families of Amphipoda in which the mandible has a palp by characters of the rami of the uropod, which are unequal, the accessory flagellum of the first antennal segment inconspicuous, uni-articulate or absent, and by the sausage-shaped sternal gills (in some taxa they are absent).

TALITRIDAE (Code OP019999) are distinguished from other families of Amphipoda in which the mandible lacks a palp (ie. Hyaleliidae), by the clumsy swimming or crawling , the relative lengths of the two antenna being highly unequal, and the absence of a third uropodal ramus.

NEONIPHARGIDAE (Code OP079999) are distinguished from other families of Amphipoda in which the mandible has a palp by the rami of the uropod, which are unequal, the accessory flagellum of the first antennal segment which is inconspicuous, uni-articulate or absent, and by:

i) the dendritic or lumped sternal gills,

ii) the small rugose gnathopods,

iii) antenna 1 being significantly longer than antenna 2.

PERTHIIDAE (Code OP089999) are distinguished from other families of Amphipoda in which the mandible has a palp by the rami of the uropod, which are unequal, the accessory flagellum of the first antennal segment which is inconspicuous, uni-articulate or absent, and by:

i) the dendritic or lumped sternal gills,

ii) the large non-rugose gnathopods,

iii) antenna 1 being not significantly longer than antenna 2.

Reference:

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.