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The susceptibility of species of lutjanid, lethrinid and serranid fish to infection by either larval or post-larval (juvenile and adult) specimens of the capsalid monogenean Benedenia lutjani Whittington and Kearn (1993) was examined experimentally. Four species of lutjanids became infected when exposed to larvae of B. lutjani, but three species of lethrinids and four species of serranids were not susceptible to larvae under the same conditions. Variability in the intensity of infection by larvae occurred within and between lutjanid species. Few post-larval specimens of B. lutjani transferred between individuals of the specific host Lutjanus carponotatus (Richardson 1842) in 60-l aquaria and none transferred between specimens of L. carponotatus in a 7,500-l concrete tank. These results indicate that transfer of post-larval B. lutjani between individuals of the specific host is unlikely to occur in the wild. Other lutjanid species did not become infected when exposed to specimens of L. carponotatus infected heavily by post-larval B. lutjani, but two lethrinid species were susceptible to infection under the same conditions. These data indicate that different factors may mediate host-specificity for larval and post-larval B. lutjani. [ABSTRACT FROM AUTHOR]

The anterior adhesive areas of Benedenia rohdei from the gills and B. lutjani from the pelvic fins of Lutjanuscarponotatus at Heron Island, Australia, were studied using scanning and transmission electron microscopy. All specimens were fixed when detached from host tissue. Both monogenean species have two disc-like anteroventral attachment organs, each of which has an anterolateral adhesive area divided into three adjacent zones by tegument from the ventral surface of the attachment organ. A rod-shaped secretion and a smaller, roughly spherical secretion are associated with the anterior adhesive areas in both species; a third type of secretion occurs anteriorly but outside these adhesive areas. The electron-dense spherical secretory bodies released onto the anterior adhesive zones in these Benedenia spp. are of a single type and differ ultrastructurally from those previously reported in monogeneans living on teleost hosts. A correlation, therefore, between secretion morphology and host type is not supported. No relationship was found between parasite microhabitat and secretion morphology. [ABSTRACT FROM AUTHOR]