A light microscope study of the attachment organs and their role in locomotion ofCraspedellasp. (Platyhelminthes: Rhabdocoela: Temnocephalidae), an ectosymbiont from the branchial chamber ofCherax quadricarinatus(Crustacea: Parastacidae) in Queensland, Australia

Abstract

The five anterior tentacles and the single posterior attachment organ of the temnocephalan flatworm Craspedella sp. perform important roles in locomotion and attachment. Craspedella sp. moved using a low ‘looping’ motion by alternately attaching the ventro-distal regions of the central three tentacles and the ventral surface of the posterior attachment organ. Secretion from the tentacles is by rod-shaped rhabdites produced in rhabditogen cells. There are more rhabdites and pores in the region of the distal concavity on each of the central three tentacles. It was not possible to determine the presence or not of suction at the distal concavities. The posterior attachment organ has true suctorial ability, can create a reduced pressure and a marginal valve appears to prevent influx of water. However, the ‘sucker’ is also supplied with a granular secretion from posterior gland cells which can leave a conspicuous, annular footprint on glass surfaces. The posterior secretion enables the worms to attach to surfaces by only a small proportion of the surface area of the ventral surface of the posterior disc. The musculature of the anterior tentacles and the posterior attachment organ is described. These means of attachment provide Craspedella sp. with the ability to attach to various surfaces inside the branchial chamber of Cherax quadricarinatus such as the flat, smooth body wall and also irregular and often moving substrata like the gill filaments and associated structures (gill cleaning setae and branchiostegite).