Revising the Definition of the Crustacean Seta and Setal
Blackwell Science, LtdOxford, UKZOJZoological Journal of the Linnean Society0024-4082The Lin- nean Society of London, 2004? 2004 142? 233252 Original Article DEFINITION OF CRUSTACEAN SETAE AND SETAL CLASSIFICATION SYSTEMA. GARM Zoological Journal of the Linnean Society, 2004, 142, 233–252. With 11 figures Revising the definition of the crustacean seta and setal classification systems based on examinations of the mouthpart setae of seven species of decapods A. GARM* Biological Institute, University of Copenhagen, Denmark Received July 2003; accepted for publication June 2004 The crustacean cuticle has numerous projections and some of these projections, the setae, have important mechan- ical as well as sensory functions. The setae display a wide diversity in their external morphology, which has led to great problems separating setae from other projections in the cuticle and problems in making a consistent classifi- cation system. Here, the cuticular projections on the mouthparts of seven species of decapods are examined by scan- ning and transmission electron microscopy. A new definition is given: a seta is an elongate projection with a more or less circular base and a continuous lumen; the lumen has a semicircular arrangement of sheath cells basally. From the details of the external morphology the mouthpart setae are divided into seven types: pappose, plumose, serrulate, serrate, papposerrate, simple and cuspidate setae, which are suggested to reflect mechanical functions and not evolutionary history. This classification system is compared with earlier systems. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 142, 233–252. ADDITIONAL KEYWORDS: functional morphology – mechanical function – setal types. INTRODUCTION paper, the most often used term is setae and it will therefore be used here.
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