<i>Teraplectanum</i>n. g. (Monogenea: Diplectanidae) from the banded grunter fish,<i>Terapon theraps</i>Cuvier (Perciformes: Terapontidae), off Peninsular Malaysia

<jats:title>Abstract</jats:title><jats:p>A new genus of the Monogenea,<jats:italic>Teraplectanum</jats:italic>n. g., is proposed for two new species of diplectanids found on the gills of<jats:italic>Terapon theraps</jats:italic>Cuvier collected off Carey Island, Peninsular Malaysia. The genus is based on a unique arrangement of the male reproductive system. In the new species spermatozoa stored in the seminal vesicle and secretions stored in the prostatic reservoir are transferred into, and mixed to form semen within, a special sclerotized auxiliary piece (SAP), and not within the copulatory tube as occurs in the majority of monogeneans.<jats:italic>Teraplectanum</jats:italic>species also possess a unique sclerotized vaginal loop through which the vaginal tube passes en route from the vaginal pore to the seminal receptacle. The two new species are<jats:italic>Teraplectanum crassitubus</jats:italic>n. sp. (type species) and<jats:italic>T. angustitubus</jats:italic>n. sp. They differ from each other mainly in the morphology of their copulatory tube: in<jats:italic>T. crassitubus,</jats:italic>the proximal region of this tube is thicker compared to the slender proximal region in<jats:italic>T. angustitubus</jats:italic>, although in both cases the tube tapers and twists distally. Of the known diplectanid species, only<jats:italic>Diplectanum undulicirrosum</jats:italic>Zhang<jats:italic>et al.</jats:italic>, 2000 (currently considered<jats:italic>incertae sedis</jats:italic>) possesses such sclerotized hard parts, which suggests the same type of arrangement of the male reproductive system. Consequently,<jats:italic>D. undulicirrosum</jats:italic>is re-assigned to this new genus as<jats:italic>Teraplectanum undulicirrosum</jats:italic>(Zhang<jats:italic>et al.</jats:italic>, 2000) n. comb. The copulatory tube of<jats:italic>T. undulicirrosum</jats:italic>is similar to the slender, undulating copulatory tube of<jats:italic>T. angustitubus</jats:italic>but does not taper distally as in the latter species.</jats:p>