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Variation in green hydra. A description of three cloned strains of Hydra viridissima Pallas 1766 (Cnidaria: Hydrozoa) isolated from a single site

McAuley, PJ.

Biological Journal of the Linnean Society 231: 1-13

1984


ISSN/ISBN: 0024-4066
DOI: 10.1111/j.1095-8312.1984.tb00801.x
Accession: 022076695

Three different strains of green hydra were isolated in successive years from a single site in the River Frome, Bristol. England UK . The strains resembled each other in important taxonomic characters, and were identified as H. viridissima by their possession of smooth-walled single-chambered embryothecas, but were smaller, possessed smaller nematocysts and produced fewer eggs per individual than the Western European holotype. It is possible that English green hydra-represent a geographical subspecies. The 3 strains could be distinguished from each other by differences in rates of bud production and in characters associated with their symbiotic algae. These differences are considered varietal, and it is suggested that H. viridissima is a polytypic species. The possible origins of these variations and their significance is discussed.

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