Taxonomy
- Kingdom: Animalia
- Phylum: Nematoda
- Class: Secernentea
- Order: Ascaridida
- Family: Anisakidae
- Genus: Pseudoterranova (established by Gibson, 1976)
Description
Pseudoterranova is a genus of marine parasitic nematodes commonly referred to as “sealworms.” Members of the genus are elongated, cylindrical roundworms that can reach several centimeters in length in adult form. Morphologically, they possess a well‑developed muscular esophagus, a distinct anterior buccal cavity with three lips, and a tail ending in a small terminal mucron. The cuticle is smooth, and males possess spicules and gubernaculum within the copulatory bursa.
Life Cycle
The life cycle of Pseudoterranova species is indirect and involves multiple hosts:
- Eggs are released in the feces of definitive marine mammal hosts (primarily seals, sea lions, and occasionally cetaceans).
- Larval development occurs in the egg, hatching into free‑living second‑stage larvae (L2) that are ingested by crustacean intermediate hosts (e.g., copepods).
- Third‑stage larvae (L3) develop within the crustacean and are subsequently transferred to fish or squid intermediate/paratenic hosts when they consume the infected crustacean.
- Paratenic hosts (various pelagic and demersal fish species) accumulate L3 larvae in their muscle and viscera.
- Definitive hosts become infected by consuming infected fish or squid. In the stomach of the definitive host, larvae mature to adult worms, completing the cycle.
Species
Recognized species within the genus include, but are not limited to:
- Pseudoterranova decipiens complex (comprising several cryptic species such as P. decipiens sensu stricto, P. azarasi, P. cattani, P. krabbei, and P. bulbosa)
- Pseudoterranova azarasi
- Pseudoterranova cattani
- Pseudoterranova krabbei
Taxonomic revisions based on molecular phylogenetics continue to refine species delimitations within the P. decipiens complex.
Geographic Distribution
Pseudoterranova species have a cosmopolitan distribution in temperate and sub‑arctic marine waters. They are reported in the North Atlantic, North Pacific, and Southern Ocean, reflecting the range of their seal and sea lion definitive hosts.
Clinical Significance
Human infection, termed “pseudoterranovosis,” occurs when raw or undercooked fish containing third‑stage larvae are ingested. Clinical manifestations can include:
- Acute gastrointestinal symptoms (nausea, vomiting, abdominal pain, diarrhea) occurring within hours after ingestion.
- Eosinophilic gastroenteritis in some cases.
- Larval migration to the gastrointestinal mucosa, producing visible “worms” during endoscopy.
Diagnosis is based on endoscopic identification of the larva, histopathological examination, and, increasingly, molecular identification (e.g., PCR of mitochondrial DNA). Treatment generally involves endoscopic removal of the larva and symptomatic care; anti‑helminthic medication may be administered in selected cases.
Public Health and Prevention
Preventive measures focus on proper handling and cooking of marine fish. Freezing fish at –20 °C (–4 °F) for at least 7 days or cooking to an internal temperature of ≥ 63 °C (145 °F) effectively kills Pseudoterranova larvae, reducing infection risk.
Research and Economic Impact
Studies on Pseudoterranova contribute to understanding host–parasite dynamics in marine ecosystems and have implications for fisheries, as larval infestations can affect the marketability of fish products. Ongoing research includes molecular taxonomy, host specificity, and the development of rapid diagnostic assays.
References
(References are omitted here but would typically include peer‑reviewed articles on taxonomy, life cycle, clinical case reports, and guidelines on food safety.)