ENDOHELMINTH PARASITES OF SOME MIDWATER AND BENTHOPELAGIC STOMIIFORM FISHES FROM THE NORTHERN GULF OF MEXICO

Mesopelagic fishes represent significant ecological links between mesozooplankton and the larger pelagic squids, fishes, and marine mammals. As such, these fishes also play a significant role as intermediate or paratenic hosts for parasites that require a crustacean intermediate host and mature in marine mammals or pelagic fishes. We examined a total of 208 individuals representing 5 species of Sternoptychidae and 88 individuals representing 2 species of Phosichthyidae from 20 locations in the northern Gulf of Mexico (nGOM). Six of the 7 species we examined are mesopelagic and one species was benthopelagic. We found the larval stages of Anisakis brevispiculata, Anisakis typica, Hysterothylacium fortalezae (all Nematoda: Ascaridoidea); Bolbosoma sp. (Acanthocephala: Polymorphidae); and Tetraphyllidea (Cestoda) plus an immature specimen of Brachyphallus sp. (Digenea). Molecular sequencing was used to identify the ascaridoids and Bolbosoma sp. and to confirm the identification of 3 host sternoptychid species. The mesopelagic fishes hosted Anisakis brevispiculata (that matures in pygmy and dwarf sperm whales) and Hysterothylacium fortalezae (that matures in pelagic fishes, primarily mackerels), whereas the benthopelagic species was parasitized by Anisakis typica (that matures in dolphins). We suggest this pattern of infection indicates a pelagic life—cycle for Anisakis brevispiculata and Hysterothylacium fortalezae and a demersal life—cycle for Anisakis typica. Our study represents the first published sequences from the nGOM for the fishes Argyropelecus aculeatus, Maurolicus weitzmani, and Polyipnus clarus and the first molecular identification of larval ascaridoids from mesopelagic fishes in the nGOM.