The surface topography of a monogenean, Diclidophora merlangi revealed by scanning electron microscopy

The body surface of adult Diclidophora merlangi is characterized by an annular array of irregularly-shaped ridges, with the intervening troughs of tegument invested with microvilli. The microvilli measure approximately 0.5 micrometer in length and 0.06 micrometer in diameter and at maximum density (10.8/micrometer 2) increase the body surface area by a factor of two. On the anterio-dorsal surface of each peduncle the ridge-like structures consolidate as a distinct area of ornamentaltion some 100 micrometer in diameter. A frontal pit opens just inside the mouth and is thought to provide the outlet for the buccal gland secretions. The tegument surrounding the gonopore and paired excretory pores is unmodified in morphology. Presumed sensory endings are of at least two types: (1) uniciliated structures, projecting from a pit or supported by a collar of tegument, and distributed either singly over the general body surface and in the buccal cavity, or in groups around the mouth; and (2) large numbers of non-ciliated papillae localized on the opisthaptor. A number of these papillae occur on a wart-like outgrowth of tegument positioned on the ventral surface of each peduncle and have obvious significance in contact communications.