A vital stain for studies of behaviour and ecology of the parasitic copepod Lernaeocera branchialis (Pennellidae)

To discriminate between individuals and groups of individuals, the vital stain neutral red was used to mark developmental stages of the parasitic copepod Lernaeocera branchialis (L.). The copepod has a marked ability to accumulate the stain, and the red colour of stained parasites lasts for ca 3 to 4 wk. Experiments demonstrate that exposure to 0.01 g 1-' neutral red for l h does not reduce survival or interfere with mating and host-finding The low toxlcity and persistence of the stain suggest that it may be a useful tool in experimental work with copepods.