New philometrids (Nematoda, Philometridae) from head tissues of two serranid fishes (Epinephelus morio and Mycteroperca microlepis) off Florida, northern Gulf of Mexico

A new species of nematode, Philometra morii sp. nov. (Philometridae), is described from males and gravid females collected from the mouth cavity of the red grouper, Epinephelus morio (Valenciennes) (Serranidae, Perciformes), from the northen Gulf of Mexico, off Florida, USA. The new species is characterized mainly by the length of spicules (84–90 and 72–87 μm) and the length (54 μm) and structure of the gubernaculum in the male, and by the presence of three large oesophageal teeth protruding from the mouth, the number and arrangement of small cephalic papillae (8 papillae in 4 pairs of external circle and 6 single papillae of internal circle), the length (1.09–1.50 mm) and structure of the oesophagus and two large papilla-like caudal projections, and by the length of their bodies (19.34–30.07 mm). Philometra morii is the third species of this genus reported from E. morio in the Gulf of Mexico, differing from the two previously described species, in addition to morphological features, by the site of infection in this host (mouth cavity and sinuses vs oculo-orbits or gonads). From the same region (northern Gulf of Mexico, off Florida), gravid females of Philometra Costa, 1845, morphologically and biometrically similar to those of P. morii, were found in the subcutaneous tissues and sinuses of the head of another serranid fish (gag), Mycteroperca microlepis (Good et Bean). Although their conspecificity with P. morii cannot be excluded, they have been designated as Philometra sp. until conspecific males are discovered and described. Based on light and scanning electron microscopy examination (latter used only for females), both these forms are described.