Syncarids

Code ON999999

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.

The super-order Syncarida is recognised by the absence of a carapace, the presence of exopodites on the walking legs, and the lack of any limbs modified as gnathopods.

Syncarids are represented in Australian freshwaters by the orders Bathynellacea and Anaspidacea, differentiated by the number of trunk segments (8 free trunk segments against 7 respectively). The six families are interstitial in habit.

ANASPIDIDAE (Code ON019999) belong to the order Anaspidacea, distinguished by the 7 free thoracic segments (13 body segments). The rostrum is a simple lobe, the maxillula has a palp, the telson is rounded and the uropods form a flattened tail fan. The otherwise similar Koonungidae have the eyes sessile or are blind, rather than having the eyes stalked. There are three Australian genera: Anaspides , Allanaspides and Paranaspides .

KOONUNGIDAE (Code ON029999) belong to the order Anaspidacea, distinguished by the 7 free thoracic segments (13 body segments). The rostrum is a simple lobe, the maxillula has a palp, the telson is rounded and the uropods form a flattened tail fan. The otherwise similar Anaspididae have the eyes stalked rather than sessile or absent. There are two Australian genera: Koonunga and Micraspides.

PSAMMASPIDIDAE (Code ON059999) belong to the order Anaspidacea, distinguished by the 7 free thoracic segments (13 body segments). The rostrum is bilobed, the maxillula lacks a palp and the telson does not form a flattened tail fan with uropods. Separated from the Stygocarididae by the third and fourth abdominal segments possessing small pleopods, and the uropod exopodite being two- segmented. Interstitial crustaceans, up to 10mm long. There are two Australian genera: Psammaspides and Eucrenonaspides.

STYGOCARIDIDAE (Code ON049999) belong to the order Anaspidacea, distinguished by the 7 free thoracic segments (13 body segments). The rostrum is bilobed, the maxillula lacks a palp and the telson does not form a flattened tail fan with uropods. Separated from the Psammaspididae by the third and fourth abdominal segments lacking pleopods, and the uropod exopodite being one-segmented. Interstitial crustaceans, up to 2mm long.

PARABATHYNELLIDAE (Code ON089999) belong to the order Bathynellacea, distinguished by the 8 free thoracic segments (14 body segments). Separated from the Bathynellidae by the first pleopod being 1-segmented or absent, and the expodite of the second antenna being absent or replaced by a seta. There are four Australian genera: Notobathynella, Chilibathynella, Atopobathynella, and Hexabathynella . Small, interstitial crustaceans, up to 3mm long.

BATHYNELLIDAE (Code ON079999) belong to the order Bathynellacea, distinguished by the 8 free thoracic segments (14 body segments). Separated from the Parabathynellidae by the first pleopod being 2-segmented, and the expodite of the second antenna being 1-segmented. One Australian genus: Bathynella. Small interstitial crustaceans, up to 1mm long.

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.