Morphology, ultrastructure, and implied function of ciliated sensory structures on the developmental stages of Merizocotyle icopae (Monogenea : Monocotylidae)

Abstract

<jats:title>Abstract</jats:title><jats:p>Experimental infections were used to track the fate of the dorsal sensilla of <jats:italic>Merizocotyle icopae</jats:italic> (Monogenea: Monocotylidae) from nasal tissue of the shovelnose ray, <jats:italic>Rhinobatos typus</jats:italic> (Rhinobatidae). Scanning and transmission electron microscopy revealed that 3 types of uniciliate dorsal sensilla exist at different times in the development of the monogenean. Type 1 sensilla have little or no invagination where the cilium exits the distal end of the dendrite and possess a ring of epidermis surrounding the cilium distal to the invagination. Type 2 sensilla have a deep invagination where the cilium exits the dendrite. Type 3 sensilla can be distinguished from the other types by the shape of the dendrite. The larvae have predominantly Type 1 dorsal sensilla, most of which are lost approximately 24 h after infection and a few Type 2 sensilla, which are retained. Additional Type 2 sensilla (termed Adult Type 2 sensilla), which are slightly different morphologically from the Type 2 sensilla of the larvae, form in later stages of development. Numerous Type 3 sensilla are unique to the dorsal surface of adults. Loss of all Type 1 sensilla upon attachment to the host, <jats:italic>R. typus</jats:italic>, suggests that these may be chemo‐ or mechanoreceptors responsible for host location by the swimming infective larvae. Type 2 sensilla appear to be important in the larvae, juveniles, and adults whereas the modality mediated by Type 3 is specific to adults. Microsc. Res. Tech. 62:267–276, 2003. © 2003 Wiley‐Liss, Inc.</jats:p>