Gnathiidae, Leach, 1814

Gnathiidae View in CoL species

( Fig. 6 View Figure 6 )

Material examined. Mazatlán Bay: Sep. 13, 2023, 12 praniza larvae (TL 2.4–2.6), on gills of H. guentherii ; Oct 8, 2023 29 praniza larvae (TL 1.8–2.1) on gills of E.currani ; Jun 6, 2022 8 praniza larvae(TL 2.2–2.3)on gills of B. polylepis ; Nov. 28, 2023, 153 praniza larvae (TL 2.3–2.6), on gills of Ephinephelus labriformis ( Serranidae ); Oct. 12 2023, 85 praniza larvae (TL 1.9–2.3), on gills of L. guttatus ; Nov 5, 2023, 85 praniza larvae (TL 2.4–2.7), on gills of M. cephalus ; Nov 12, 2023 383 pranizas larvae (TL 2.1–2.6), on gills of Diapterus peruvianus ( Gerreidae ); Feb 07, 2024 33 pranizas larvae (TL 2.0–2.4), on gills of Tylosurus pacificus ( Belonidae ).

Distribution. Mazatlán Bay.

Previous known hosts. In the Eastern Pacific, Caranx caninus , Caranx caballus , Caranx vinctus , Selene brevoortii ( Carangidae ); P. panamensis ; Euthynnus lineatus , and Sarda orientalis ( Scombridae ) (Violante-González et al., 2016; 2020; Miranda-Delgado et al., 2019; Villalba-V á zquez et al., 2018; Santos-Bustos et al., 2020b; and Osuna-Cabanillas et al., 2024). All these records were made as Gnathia sp.

Remarks. At least seven studies on marine fish parasites along the Mexican Pacific coast have reported the presence of the praniza larva of Gnathia sp. (Violante-González et al., 2016; 2020; 2023; Villalba- Vázquez et al., 2018; Miranda-Delgado et al., 2019; Santos-Bustos et al. 2020b; Osuna-Cabanillas et al., 2024). However, we acknowledge that the taxonomic identification of gnathiids is based on the free-living adult forms ( Hadfield et al., 2009). We were unable to associate the praniza and zuphea larvae of the family Gnathiidae with adults of any known species. The identification of these isopods is based on the morphology of the adult males, and this is challenging as males can be difficult to obtain ( Smit and Davies, 2004). Only free-living adults of the species Gnathia steveni Menzies, 1962 have been recorded along the Pacific coast of Mexico, particularly in Bahia San Quintin, west Baja California (Espinosa- Pérez and Hendrickx, 2002). The presence of such larvae in the five species of fish reported in this study in Mazatlán represents new host and locality records for this group of isopods ( Tab. 1).