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An Examination of Polymorphism in the Hydroid Hydractinia Echinata

Published online by Cambridge University Press:  11 May 2009

Allison L. Burnett
Affiliation:
Developmental Biology Center, Department of Biology, Western Reserve University, Cleveland 6, Ohio
William Sindelar
Affiliation:
Developmental Biology Center, Department of Biology, Western Reserve University, Cleveland 6, Ohio
Norma Diehl
Affiliation:
Developmental Biology Center, Department of Biology, Western Reserve University, Cleveland 6, Ohio

Extract

Several aspects of polymorphism in Hydractinia echinata (Fleming) have been examined. Polymorphism in Hydractinia appears to be the result of inhibition of the normal developmental sequence and not the result of direct genetic control. The inhibition is mediated by both intrinsic and extrinsic factors. The former are responsible for the formation of reproductive zooids in the colony, but this process may be accelerated by extrinsic factors (crowding, increased pCO2). It is suggested that intrinsic factors consist of an inducer or growth stimulator produced in the hypostomal region of the polyps and an inhibitor of growth and differentiation produced by dividing cells beneath the hypostome. The ratio of these two factors throughout the colony ultimately determines the polyp type which will be formed.

Type
Research Article
Copyright
Copyright © Marine Biological Association of the United Kingdom 1967

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