A technique for preserving pigmentation in some capsalid monogeneans for taxonomic purposes

A technique is described to preserve the pigment found in the bodies and th e intestine of some brightly coloured and darkly pigmented benedeniine caps alid monogeneans. Previous studies of these pigmented capsalids have proven difficult because the pigmentation usually disappears when the worms are f ixed using preservatives containing concentrations of formalin over 5% and/ or ethanol, acetic acid, chromic acid, picric acid and mercuric chloride. T he technique developed here uses a fixative comprising glycerol, acetone an d formalin (GAF). After fixation under light coverslip compression for thre e minutes, specimens are transferred to absolute acetone for three minutes and cleared in a mixture of nine parts cedar wood oil and one part absolute acetone before mounting in Canada balsam. Processing must be carried out q uickly, as these chemicals will cause the pigments to fade if the specimens are exposed to them for too long. Pigmented benedeniines processed using t his technique retain the distribution, intensity and colour observed in liv e worms. The colour and distribution of pigmentation in monogeneans may be of taxonomic importance and this technique aids preparation of whole-mounts suitable for registration as type-material.