There were two species of crayfish
“red-claw” (Cherax quadricarinatus) and “blue-huna” (Cherax albertisii) for
their aquaculture potential. Crayfish were susceptible to fungal (crawfish
plague), parasitic (protozoa and nematodes), and bacterial pathogen. A number
of ectosymbiont Craspedella sp. have been observed on red-claw and blue-huna.
The flatworms were commonly found almost in the whole body, on the upper
exoskeleton behind the head, in the gill cavity and on the claws and underside
of crayfish. Although their number sometimes was very high, they didn’t cause
any problems especially for the new molting crayfish. Micro organisms living on
the crayfish surface body and worms didn’t cause any pathological changes.
Adults Craspedella sp. can be eliminated by a short bath in salt water or formaldehyde
37% solutions for several hours. This treatment didn’t kill worm eggs, so it
needs to be repeated every one week. Moreover, hyposalinity or OST (Osmotic
Shock Therapy) is one of the most effective therapies for ectoparasites on Craspedella
sp. with dose of bath treatment 15 grams per litre of salt (15 ppt) for more
than 3 hours, and dipped in salt water at 30 ppt (or 3.0 ppm, seawater
salinity) for 15 - 20 minutes.