Endohelminths of a Snake Mackerel, Gempylus serpens (Trichiuroidea: Gempylidae), from the Gulf of Mexico

Endohelminths are reported from a female snake mackerel, Gempylus serpens (Trichiuroidea: Gempylidae), captured from a depth of 61 m in the Gulf of Mexico 140 km south of the mouth of Mobile Bay, AL, in August 1998. A diverse endohelminth parasite fauna was found: 29 plerocercoid type I tetraphyllideans from the lower intestine; 4 didymozoid metacercariae allocated to the collective group Monilicaecum and one didymozoid metacercaria of the collective group Torticaecum from the pyloric cecum; one juvenile Gonocerca phycidis from the stomach; and 5 larvae (L3 stage) comprising 3 species of Anisakis from the pyloric cecum. These nematodes were identified as species of Anisakis due to the presence of an oblong ventriculus lacking an appendix, no intestinal cecum or interlabia, 3 lips with dentigerous ridges, and an excretory pore located between the lateroventral lips. Differences in overall size and in the lengths of the ventriculus and esophagus in relation to total body length were used to distinguish the 3 species of Anisakis collected. Seven specimens of a possibly unnamed species of parasitic copepod representing Bomolochus infected the gill chamber. Stomach contents included 6 early-juvenile flatfish (Pleuronectiformes). All of the helminths are measured and illustrated, and for some of the parasites recovered, we are unaware of any reports from this host species. IntroductIon The snake mackerel, Gempylus serpens Cuvier (Trichiuroidea: Gempylidae), is the sole member of Gempylus Cuvier, representing one of 16 genera within Gempylidae (Nakamura and Parin 1993, Nelson 2006, Froese and Pauly 2009). Like many gempylids, G. serpens reportedly is a cosmopolitan, solitary, meso– or bathypelagic fish that ranges in tropical and subtropical seas to 600 m (Nakamura 1990, Nakamura and Parin 1993, Froese and Pauly 2009). Gempylus serpens exhibits diel vertical migration and feeds on fishes (myctophids, exocoetids, sauries, scombrids), squids, and crustaceans (Nakamura and Parin 1993). The species sporadically appears as bycatch in the tuna longline fishery, but there is reportedly no directed fishery for G. serpens (Nakamura and Parin 1993). Prior to this study, only 5 parasite species have been reported from G. serpens (Table 1). As G. serpens is neither sought after nor kept by fishermen and there are no reports of parasites of G. serpens from the Gulf of Mexico, the purpose of this study was to survey the parasites of a snake mackerel captured in the Gulf of Mexico. MAterIAls And Methods A mature female G. serpens was obtained at a fishing tournament in Destin, FL, and examined for metazoan parasites. The fish was captured 1 August 1998 from 140 km south of Mobile Bay, AL, (29°00’N, 87°50’W; time of capture = 0400 h; depth of fish = 61 m; total length = 78.5 cm; weight = 452.6 g) and placed on ice for 2 days until necropsy and removal of parasites in the laboratory. While fixation of worms in situ is not ideal, we found that the quality of the specimens was good and features of taxonomic importance could easily be identified. Platyhelminths were stained in Van Cleave’s hematoxylin, dehydrated in a graded ethanol (EtOH) series, cleared in clove oil, and mounted in Canada balsam. Nematodes were cleared in a solution of 5 parts glycerin with 95 parts 70% EtOH, and mounted in glycerin jelly. Copepods were placed in 70% EtOH. Drawings were made with the aid of a drawing tube. Measurements are in micrometers (μm), except where indicated in the text, and the mean followed by range and number of measurements (n) follow in parentheses where appropriate. Identification of the fish was based on Nakamura and Parin (1993) and fish systematics and taxonomic authorities follow FishBase 2009 (Froese and Pauly 2009). Endohelminths were deposited in the Harold W. Manter Laboratory of Parasitology (HWML), University of Nebraska–Lincoln, Lincoln, NE, USA. results And dIscussIon We observed 6 early juvenile flatfish (Pleuronectiformes) in the stomach of the snake mackerel; 4 partially digested with lengths of 1.8 cm, 1.9 cm, 2.2 cm, and 2.8 cm and 2 almost completely digested with lengths of 1.8 cm and 2.0 cm, respectively. Small pieces of unidentifiable debris and tissue, including 1 vertebra, were also removed from the stomach.