Robert B. McCormack

“ The degree of genetic connectivity between populations is not yet known. I suspect that populations have been isolated through habitat fragmentation and may be highly divergent and genetically distinct, containing unique haplotypes. ”

“ Gramastacus lacus has a restricted distribution in ephemeral habitats, being dependent on regular natural flooding and drying cycles, and burrows for survival during temporary dry cycles. Documented are population distributions in lowland habitats (3–48 m, a.s.l.) from Wamberal Lagoon, north along the coastal strip to Wallis Lake. The species is small, reaching a maximum weight of 7 grams and 21.3 mm OCL, and distinguished by a large male genital papilla, large raised post orbital ridges, laterally compressed carapace and elongated chelae.
Introduction
Gramastacus lacus sp. ”

“ Eels and fish may penetrate into and temporarily visit some habitat areas but Gramastacus lacus takes refuge in the periphery, protected within the thick reeds and flooded grasses along the shallow edges, well away from the deeper water.
Larger swamps, such as Boomeri Swamp, the type locality in the Ramsar Wetlands of the Myall Lakes National Park, will dry out completely and then flood with up to 1.5 m of water. Deep water over 1 m is usually devoid of Gramastacus except occasional moulted individuals. ”

“ As the species occurs along the coastal strip in some of the fastest developing areas of Australia, further field surveying to identify isolated populations should also be a priority, with an assessment of the conservation status of each population as currently nearly all are potentially endangered. ”

“ The male genital papilla is large, being a distinguishing character ( [1] ) from other crayfish species in the region. They are opportunistic breeders, starting in early August being reliant on water availability in their ephemeral habitats, only breeding when flooded. Females mature at approximately 12 mm OCL and are very fecund for their size: ACP 2318, 12.3 mm OCL, September 2009, Myall Lakes, 44 eggs; ACP 2387, 13.08 mm OCL, September 2009, Myall Lakes, 29 eggs; ACP 2309, 15 mm OCL, August 2009, Lake Macquarie, 82 eggs; ACP 180, 15.93 mm OCL, August 2005, Myall Lakes, 79 eggs ”

“ General increase in setation along propodal and dactylar cutting edges in populations from the north to the south.
Propodus. Lightly punctated with mesial propodal margin starting as small rolled ridge at carpal articulation, progressing to small rounded mesial propodal spines scattered in twin lines giving a shadow effect to dactylar articulation. ”

“ Size. Maximum OCL 21.32 mm, 7 gram. Maximum size animals extremely rare, mean weight of large adults 4-5 gram.
Rostrum. Long, narrow, reaching midlength or end of 3rd antennal segment, approximately 0.3 × OCL. Rostral apex variable, ranging from very small to a large sharp conical acumen spine; apex upturned at 45–60° angle. Rostral carinae conspicuously raised and sharp, extending well back onto carapace, reaching beyond anterior end of postorbital carina ”