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Polymorphism and pore signature patterns in the copepod genus Oncaea (Cyclopoida)

Published online by Cambridge University Press:  16 October 2009

S. J. Malt
Affiliation:
Department of Zoology, British Museum (Natural History), Cromwell Road, London, SW7 5BD

Abstract

Species of the cyclopoid copepod genus Oncaea are commonly polymorphic. Using material from several localities, forms of O. venusta Philippi, O. mediterranea Claus and O. conifer a Giesbrecht are described, and specimens of two closely related and morphologically similar species, O. ornata Giesbrecht and O. englishi Heron, are compared. The integumental pore signature patterns of all these species are mapped from stained, tissue-free integuments. Each species has its own characteristic pore signature pattern and sexual dimorphism is confined to the urosomal pore pattern. Similarly the prosomal pore patterns of female copepodid 5 do not usually differ from those of adult females, but urosomal patterns are distinct. Juveniles of O. conifera are exceptional in this respect; their prosomal pore pattern lacks the detail of the adult pattern. Differences in the pore signatures of O. ornata and O. englishi confirm their status as separate species. Signatures in the O. conifera ‘group’ may also prove to be distinct. Whereas intraspecific variation in pore signatures may exist at a level below the resolution of this technique, such small morphological differences should be considered to be taxonomically insignificant.

The implications of polymorphism in the process of speciation, and the mechanisms by which the polymorphic forms are maintained are discussed.

Scanning electron microscopy and light microscopy are used to examine the morphology of pores and their associated sensilla. Three types of sensilla are described, peg, short-hair and long-hair sensilla.

Type
Research Article
Copyright
Copyright © Marine Biological Association of the United Kingdom 1983

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