Sunday, December 11, 2011

Cherax leckii, Cherax Setousus and Cherax Rotundus

Cherax leckii females appear to begin maturing at a small size. The 24.8 mm OCL female has soft, very swollen and heavily setose gonopores, and was carrying eggs at the time of capture. Relative abdomen width is distinctly higher in this female than in the two smaller female specimens retained (18.0–18.5 mm OCL). The gonopores of these specimens are soft and slightly raised, but with sparse setation. These smaller animals could be classed as adolescent. A 20.0 mm OCL female collected on the return visit to the site had swollen gonopores with moderate setation.  Thus, it appears that females mature as they approach 20 mm OCL. An aberrant animal collected on the return visit to the site (not preserved) bore two male and two female gonopores. This animal had anOCL of 26.5 mm, and the female gonopores were still calcified.

BiologyAside from occasional pools, most of the habitat was generally void of surface water during both collecting trips. Farther upstream, where water was present in a pool overlying a solid bedrock section, a small specimen was observed to be in the process of moulting, directly in the stream body. Animals were caught from beneath rocks in shallow depressions and both simple and multi-chambered burrows. In one case, two animals were retrieved from one burrow. The undeveloped eggs of Leckie's crayfish are soft blue-grey in colour.

EtymologyNamed after Shawn Leckie, who has provided essential support and assistance throughout the broader crayfish research project, including field collection of the specimens of this new species on both collecting occasions.

SystematicsCherax leckii n. sp. perhaps falls closest to C. destructor in general morphology. Among other differences, Cherax leckii has reduced rostral spination, fewer mesial

Propodal tubercles, no setation on the merus and a semi-circular inflation to the antennal squame. In addition, the keel between LPr5 is not produced to a blunt, triangular spine, as it is in Cherax destructor. Given the situation of the type locality in relation to the disputed, original type locality for Cherax rotundus (Severnlea, Qld), it is also worth clarifying differences between Cherax leckii and CHerax setosus from the Newcastle region.

Several useful features readily distinguish Cherax leckii from the only other Cherax in the coastal north of the state, Cherax cuspidatus. In comparison to CHerax cuspidatus, Cherax leckii  has: a more triangular and down turned rostrum, with weakly developed car inae that do not extend posteriorly as far as the postorbital ridges; very poorly developed (almost obsolete) postorbital ridges and spines; a sternal keel much sharper and higher in profile; a broader, more rotund body shape; and fewer mesial propodal tubercles.

Egg colour is a further distinguishing feature: undeveloped eggs of  C. leckii are pale blue-grey, while those of C. cuspidatus are pale green. Cherax leckii can be distinguished from the southeastern Queensland species of Cherax (Cherax depressus, Cherax dispar, C. punctatus and  C. robustus) by, among other things, the setation of the chelipeds and spination of the uropodal basipodite and/or propodus.


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