Acanthoplacatus, Ernst & Jones & Whittington, 2001

Ernst, Ingo, Jones, Malcolm K. & Whittington, Ian D., 2001, A new genus of viviparous gyrodactylid (Monogenea) from the Great Barrier Reef, Australia with descriptions of seven new species, Journal of Natural History 35 (3), pp. 313-340 : 316-317

Acanthoplacatus gen. nov.

Diagnosis. Haptor cylindrical. Sixteen marginal hooks in dorsal lobe of haptor; evenly spaced on posterior margin. Marginal hook handles extend anteriorly parallel to haptoral wall. One pair of hamuli and ventral bar in ventral lobe of haptor. Dorsal bar absent. Ventral lobe of haptor positioned anteriorly on dorsal lobe. Tendons attach to soft tissue caps on dorsal root of each hamulus. Tissue caps also present on anterior of each hamulus. Ventral bar with posterior membranous extension. Anterior of worm bilobed, each lobe bearing area of gland duct openings on ventral surface. Spike sensilla absent. Gland cells in two bilateral groups posterolateral to pharynx, connect to anterior lobes by several ducts. Pharynx bilobed; anterior lobe contains eight protrusible processes that appear to be glandular. Oesophagus short; gut bifurcate, caeca terminate posterior to uterus. Male copulatory organ a non-eversible, muscular bulb bearing spines at distal end. Male copulatory organ immediately posterior to pharynx connects to seminal vesicle by short duct. Uterus central in body between gut caeca; may contain developing embryo folded into inverted U-shape. Egg cell forming region (ECFR) immediately posterior to uterus, contains developing oocyte. Testis posterior to ECFR. Five paired gland cells surround testis and posterior portions of gut caeca. Individual posterior gland cell lies medially near terminations of gut caeca.

Etymology. Refers to the apparently idle nature of hamuli in this genus (from the Latin; Acantho 5 thorn, placatus 5 idle).

Type species. Acanthoplacatus sigani sp. nov.

Other species. A. adlardi sp. nov., A. amplihamus sp. nov., A. brauni sp. nov., A. parvihamus sp. nov., A. puelli sp. nov., A. shieldsi sp. nov.

Comments. The haptoral morphology of this genus is similar super®cially to Archigyrodactylus Mizelle and Kritsky, 1967 and Laminiscus Palsson and Beverley- Burton, 1983. All three genera lack a dorsal bar and none have the Gyrodactylus - type haptor in which the dorsal lobe is circular and has radiating marginal hooks. Acanthoplacatus is clearly distinguishable from Archigyrodactylus and Laminiscus , however, by its muscular, tube-like haptor with anteriorly positioned ventral lobe. This morphology is distinct from the`skirt-like’ haptors of Archigyrodactylus and Laminiscus that do not form a distinct tube and have hamuli located posteriorly, within surrounding marginal hooks. Acanthoplacatus also diOEers by having a ventral bar and membrane rather than the supporting plates of Laminiscus and Archigyrodactylus .