Otago Museum has recently received its first specimen classed as a new category of type specimen, called a hologenophore. The honour goes to a species of parasite collected near the Catlins! It was donated to us by Dr Bronwen Presswell, a parasitologist at the University of Otago.
A hologenophore is a molecular voucher specimen from which DNA can be directly taken for genetic analysis. It is becoming a common practice for taxonomists to deposit these vouchers in museums as a reference example of a species which can be accessed for future research. These new vouchers are important because they contribute to research that provides an unusually complete revision of this previously poorly-defined species. The findings of this research have recently been published.
The specimen is an Acanthocephalan parasite called Corynosoma hannae. Acanthocephalans are parasitic worms commonly called thorny-headed worms. It’s easy to see why when you see them close up!
A scanning electron microscopy image of Corynosoma hannae showing the detailed spines on its front end.
They have a retractable thorny hook-bearing structure on their front end. They use these fearsome spine-like hooks to attach to the walls of the digestive tracts of their hosts. Lacking their own digestive system, they absorb nutrients from the host’s intestines directly through their body wall.
A scanning electron microscopy image of Corynosoma hannae
The adults of these parasites are found in pinnipeds such as New Zealand fur seals, Arctocephalus forsteri. The life cycle of Acanthocephalans and the number of hosts they exploit varies with different species, but changing hosts as they grow through their stages always involves being eaten!
At the start of the cycle the eggs of the parasites are eaten by an invertebrate like a crab or a shrimp and an infective juvenile stage develops. The parasite then moves to a vertebrate host like a fish that eats the crab or shrimp. The vertebrate host is in turn eaten by the target host, which could be a bird or a mammal. When it reaches this target host the worm mates, produces eggs and thus the life cycle is completed. In this species, the worm must be ingested by a pinniped such as a New Zealand fur seal in order to complete its life cycle.
At only a few millimetres in length, this spiny-headed worm is a contender for one of the smallest objects in the Otago Museum’s collection!