Art. XXIX.—Note on the Parasite (Temnocephala) found on the Freshwater Crayfish of New Zealand.
[Read before the Otago Institute, 11th September, 1888.]
On both species of Paranephrops inhabiting New Zealand an ecto-parasite is found belonging to the genus Temnocephala, an aberrant monogenetic trematode. This has been mentioned by Wood-Mason,† who referred it to the typical species T. chilensis, Gay. Specimens were afterwards sent to Dr. W. A. Haswell, of Sydney, who has lately published a paper on the genus, ‡ and he has given it the name T. novæ-zealandiæ. Similar species are found on other freshwater crayfish of Australia and Tasmania, each having its peculiar species of parasite, viz.,—
T. fasciata, on Astacopsis serratus; streams of New South Wales.
T. quadricornis, on Astacopsis franklinii; northern rivers of Tasmania.
T. minor, on Astacopsis bicarinatus; streams of New South Wales.
[Footnote] † “Ann and Mag. N.H.,” ser. 4, xv., p. 336.
[Footnote] ‡“Q. J. of Micr. Science,” xxviii., part 2, p. 279.
The New Zealand species I have found most abundant on specimens of Paranephrops neo-zelanicus from the Avon and Heathcote; but I have also found it on P. planifrons from Nelson, and I have seen its egg-cases on specimens of the same species from Napier and Greymouth. It is also found on Dunedin specimens of P. neo-zelanicus, but I have not noticed it on specimens of P. planifrons from Roto-iti, the Thames, and Manukau Harbour.
It should perhaps rather be called a commensal than a parasite, for it can scarcely derive any direct nourishment from the hard exoskeleton of its host: according to Haswell, it lives on small Amphipoda, and it is certainly capable of living for months away from the host, as is shown by the following fact: On the 14th September, 1885, some specimens of Paranephrops neo-zelanicus were brought to me with numerous specimens of Temnocephala novæ-zealandiæ adhering to them. I kept the crayfish alive in a glass jar till the 16th, when I put them in spirit, and during this time some of the Temnocephala detached themselves and moved on to some watercress and river-weed in the jar, and here some of them continued to live until the 16th January, 1886, just four months after they had left the crayfish. The specimen seen on this date appeared quite healthy and vigorous; but I lost sight of it, and did not see it again after that day.