New records of Philometra spp. (Nematoda: Philometridae) from marine perciform fishes off Florida, USA, including descriptions of two new species

New record of Philometra species from the marine edible fish Terapon jarbua collected from the Sindh, Arabian Sea, Pakistan

Diseases in fish due to helminth parasites, especially Philometra species, are the primary worry in aquaculture. Philometra are responsible for health problem in fishes they directly affect fish growth and population parameters. A comprehensive survey was conducted involving the examination of the marine fish species Terapon jarbua, gathered from the coastal waters of Sindh, Pakistan In this research different Philometra species from marine fish Terapon jarbua during 2021 and 2022. Philometra nematodes, belonging to the family Philometridae, are common parasitic organisms inhabiting both marine and freshwater environments. Their prevalence, particularly when existing in high numbers within host organisms, can lead to severe and potentially lethal consequences. Employing light microscopy techniques, diverse species of Philometra were identified, including Philometra teraponi, P. jarbuai, P. arabiai, P. karachii, and P. awarii, localized primarily within the ovaries of the host fish. A total of 140 fish samples were examined and 76 were infected. The intensity of infected fish was 54.28%. The identification process encompassed meticulous analysis of crucial parameters, such as body size, esophagus length, positioning of the nerve ring, dimensions of the ventriculus, and ligament size. Intriguingly, the parasites were found in varying contexts; while some were free within the ovaries, others were embedded within tissues, inducing severe muscular dystrophy. This research presents novel findings of Philometra nematodes in the marine waters of Pakistan, extending their host and geographical distribution records. Future studies are needed to better evaluate and describe the dynamics and the epidemiology of Philometra infection in wild and cultured fish species.

Review of the parasitic nematodes of marine fishes from off the American continent

The ichthyofauna of the Atlantic and Pacific coasts off the American continent is very rich. Consequently, a high biodiversity of nematodes parasitizing these vertebrates is also expected. Currently, data on nematode parasites of marine fish off the Americas are fragmented. A review of all adult nematode species reported parasitizing marine fish from off the American continent is herein presented, as well as comments on their patterns of diversity, life cycles and advances in the taxonomic and phylogenetic knowledge. A total of 209 valid species, 19 species inquirendae and 6 dubious records have been recorded, the majority from the fish taxa Eupercaria and Perciformes. The families Sciaenidae, Serranidae and Lutjanidae, as well as the tropical and temperate Atlantic waters, exhibited the highest records of parasitic nematodes. The Cucullanidae, Philometridae and Cystidicolidae were the most speciose families of nematodes, which may be related to technological advances and relatively recent efforts of taxonomists, resulting in description of new taxa and the resolution of taxonomic problems. Numerous taxonomic questions still need resolution and, even though genetic data have been important for this process, the database is very scarce. This is the first review on all currently known nematode species parasitizing marine fish off the Americas and may serve as an important basis of reference for future approaches on these organisms.

Philometra longa n. sp. (Nematoda: Philometridae), a new parasite from the abdominal cavity of the eastern sea garfish Hyporhamphus australis (Hemiramphidae, Beloniformes) off Australia

A new nematode species, Philometra longa n. sp. (Philometridae), is described from male and female specimens collected from the body cavity of the marine fish, Hyporhamphus australis (Steindachner) (Hemirhamphidae, Beloniformes) from off the south-eastern coast of Australia. Based on examination by light and scanning electron microscopy, the new species differs from those parasitising other beloniform hosts mainly in the body length (4.69 mm), the length of spicules (141 µm) and the structure of the caudal end and the distal tip of gubernaculum in the male, and in the conspicuously long body (455-560 mm) of the gravid female. Philometra longa n. sp. is the first species of philometrids described from fishes of the family Hemiramphidae. It is the 26th nominal species of philometrids and the 19th species of Philometra so far recorded from Australian marine and brackish waters. Re-examined museum specimens of Philometra sp. from Hyporhamphus melanochir (Valenciennes) off Tasmania, as well as those previously reported from the same host species off the Australian coast, were found to be identical with P. longa sp. n.