Studies on Nematode Parasites of New Zealand Fishes: A Systematic and Parasitological Study of the Nematodes Occurring in New Zealand Marine and Fresh-Water Fishes, Including Biological Studies on the Genus Anisakis Dujardin, 1845

Abstract

Nine hundred and ninety-one marine and fresh-water fishes, distributed in 68 families, have been examined for adult and larval nematodes. Nematodes were present in 83 species of 78 genera. A further 27 species of 27 genera were examined and found to be negative. The total overall infestation was 56.7%. The total number of fish examined were divided as follows: Marine--564 representing 98 species of 59 families; fresh-water--427 representing 12 species of 9 families. The incidence of infestation in marine and fresh-water fishes was 58.2% and 54.6% respectively. It is pointed out that in parasitological surveys the figure for the overall incidence of infestation can be misleading. From the above fishes 47 species of nematodes are recorded. Four of the five nematode orders are represented: O. Ascaroidea, O. Filarioidea, O. Dioctophymoidea and O. Trichinelloidea. Of the 47 species recorded here, five had been described from New Zealand prior to 1953--Anisakis sp. larva, Hedruris spinigera, Cucullanus antipodeus, Eustrongylides sp. larva and Cucullanus robustus. Twelve species described from New Zealand, in an earlier, unpublished work by the author (Brunsdon, 1953) have been recorded in the present study. Four of the above twelve species, which were recorded in 1953 but on which positive identification was withheld, have now been identified as new: Cucullanus rhombosoleae, C. polyprionis, C. genypteri and C. anguillae. The following 16 new species are described and figured: Ascarophis anguillae, A. chelidonichthydis, A. gnathophidis, A. helicoleni, A. lepidorhynchi, A. lepidotriglae, A. macruroni, A. plagiogenionis, Cucullanellus peltorhamphi, Cucullanus helicoleni, C. morae, C. mugilis, Paraquimperia novae-zelandiae, Spiro-camallanus anguillae, Terranova scymnodontis and T. dalatiatis. Positive identification of a further nine species (four of Capillaria, two of Philometra, one of Cucullanus, one of Cucullanellus and one of Terranova) was not reached, principally because of inadequate material but also because of difficulties in obtaining relevant literature in the case of Capillaria. Nineteen new host species are recorded for the cosmopolitan larval parasite, Anisakis sp. This teleost parasite has been found regularly infesting the common New Zealand squid, Notododarus sloanii. Evidence is presented showing that, contrary to previous opinion, larvae of the genera Anisakis and Porrocaecum can be distinguished. An account is given of the parasitic ecology and life history of the cosmopolitan larval parasite of marine fishes, Anisakis sp. The experimental infestation of the two species of fresh-water eel, Anguilla dieffenbachii and A. australis, with Anisakis larvae from the barracouta, Thyrsites atun, is described. This has yielded information on the behaviour of the larvae in fish hosts, i.e. method of and location for penetration of the alimentary canal, migration in the body cavity and time taken for and method of encapsulation. Evidence collected from the examination of a large number of hosts strongly suggests the presence of two intermediate hosts in the life cycle of Anisakis sp. and the results of the experimental infestations have indicated the existence of paratenic hosts. Eggs of Anisakis simplex have been hatched in seawater. Attempts to experimentally infest various planktonic invertebrates and some teleosts, with the first infective stage of this parasite, were not successful. The degree and incidence of infestation in the fishes examined, and the various host-parasite relationships encountered, are fully discussed.