Observations on Dactylocephala madagascariensis (Vayssière, 1892), a temnocephalan with twelve tentacles from Madagascar

The 12-tentacled Madagascan temnocephalan Dactylocephala madagascariensis is reported on from the first new collections for over 70 years. Previously known from the crayfish Astacoides madagascarensis, it is now reported from A. granulimanus and a further unidentified Astacoides sp. Worms were found in several locations in Madagascar on the cephalothorax, claws and abdomen of the crayfish as well as on pereopods 4 and 5. Using more recent techniques such as de Faure’s mounting fluid, we have photographed the cirrus and shown it to possess a slightly inflated terminal introvert armed with many rows of tiny spines. Furthermore, scanning electron microscopy has revealed an epidermal mosaic unlike any other temnocephalan, viz., one with a dorsal syncytium which covers the tentacles, a ventral syncytium which includes the peduncle of the posterior attachment organ as well as the lateral excretory pores, a unique anterior ventral syncytium just posterior to the base of the tentacles which has a textured surface, and, typical of other temnocephalans, an adhesive field syncytium. The anterior ventral syncytium may be analogous to the post-tentacular (and presumed osmoregulatory) syncytium of higher temnocephalans.