Experimental infection of fish with larval sealworm, Pseudotertanova decipiens (Nematoda, Anisakinae), transmitted by amphipods

Abstract

Larval sealworm (Pseudoterranova decipiens, (Krabbe 1878)) were transmitted sequentially through copepods and amphipods to 12 phylogenetically diverse fish species. Although P. decipiens in amphipods were 0.82–7.08 mm long, only those ≥1.41 mm were infective to fish. Sealworm transmitted at 15 °C migrated to the musculature within 6 h in mummichog (Fundulus heteroclitus) and 12 h in rainbow smelt (Osmerus mordax) but were confined to the bolus in an Atlantic cod (Gadus morhua) stomach at 24 h. All sealworm in smelt, but only 12% of those in cod, occupied the musculature after 7 days. Death of 15 mummichog and a grubby (Myoxocephalus aenaeus) 10–20 days after exposure apparently resulted from damage to the brain, heart, aorta, liver, or spleen by feeding and migrating nematodes. Whereas 100% of the sealworm in grubby and 86–88% of those in mummichog and winter flounder (Pleuronectes americanus) were dead and encapsulated in host connective tissue after 56 days, all P. decipiens in smelt were viable and unencapsulated. With length increasing linearly at 0.421 mm day−1, sealworm larvae reached 27.29 (23.60–30.70) mm after 56 days in smelt at 15 °C. However, P. decipiens, which escaped the host tissue response in mummichog and flounder, were only 10.14 (6.00–21.80) and 12.42 (9.53–14.40) mm in length, respectively.