Abstract
The Monorchiidae Odhner, 1911 are well represented in tropical and subtropical marine fishes worldwide but rarely reported from the Lutjanidae, an important family of tropical fishes that prey mainly on demersal fishes, decapods and cephalopods. Here, we report the first monorchiid from a lutjanid in Australian waters,Retroporomonorchis panshon. g., n. sp. inLutjanus fulvus(Forster), off Lizard Island on the northern Great Barrier Reef. It is morphologically and phylogenetically distinct among known monorchiids, resolves within the Monorchiinae Odhner, 1911, and is characterised by a relatively large ventral sucker, a sinistral genital pore immediately posterior to the ventral sucker, unfilamented eggs, a single testis, and vitelline follicles restricted to the level of the gonads. We assessed all previous records of monorchiids from lutjanid fishes and found only one to be convincing, that ofInfundiburictus overstreeti(Gupta & Gupta, 1990) Wee, Cutmore, Perez-del-Olmo & Cribb, 2020 fromLutjanus monostigma(Cuvier) in the Bay of Bengal. Another,Monorcheides xishaensisShen, 1985, fromLutjanus argentimaculatus(Forsskal) in the Paracel Islands, South China Sea, is here recognised as a cryptogonimid, and is synonymised withSiphoderina asiaticaGu & Shen, 1979. In the remaining reports, the identity of the host is either ambiguous or doubtful, or the identity of the worm is not supported with sufficient evidence.
