Two new monorchiids infecting Mulloidichthys flavolineatus (Lacépède) and Mulloidichthys vanicolensis (Valenciennes) (Perciformes: Mullidae) from off Lizard Island, northern great barrier reef.

We report two new monorchiids from two species of goatfishes (Mullidae), Mulloidichthys flavolineatus (Lacépède) and Mulloidichthys vanicolensis (Valenciennes), from off Lizard Island, northern Great Barrier Reef. Morphological and molecular analyses indicate that the two species belong in the previously monotypic genera Obscuromonorchis Wee, Cribb, Miller & Cutmore, 2025 and Lobucirruatus Wee, Cribb & Cutmore, 2022. Obscuromonorchis brittanyae n. sp. is reported from both mullid species and differs from Obscuromonorchis ranae Wee, Cribb, Miller & Cutmore, 2025, in the possession of a less-developed ventral sucker, a noticeably shorter oesophagus, and an ascending uterine coil that enters the terminal organ in the anterior half rather than at its posterior end. Lobucirruatus hasturi n. sp. is also reported from both mullid species, and differs from Lobucirruatus infloresco Wee, Cribb & Cutmore, 2022 in the possession of an unlobed or single-lobed ovary and less prominent lobation of the cirrus. Morphological distinctions for both species are supported by significant differences in three gene markers, the ITS2 and 28S ribosomal DNA regions, and cox1 mitochondrial DNA region. Ovarian form is typically considered a genus-level character for monorchiid genera; the two species of Lobucirruatus differ in this character and the generic diagnosis is thus amended.