Revising the definition of the crustacean seta and setal classification systems based on examinations of the mouthpart setae of seven species of decapods

Abstract

The crustacean cuticle has numerous projections and some of these projections, the setae, have important mechanical 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 classification system. Here, the cuticular projections on the mouthparts of seven species of decapods are examined by scanning 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.

SEM study of Sandersiella chilenica sp.nov. (Cephalocarida), with a review of the Integumentary Structures and Functional Adaptations in the Group

“…He also points out that "setules may have a lumen distally, but it never continues through the entire projection". Although these two general classifi cations (Felgenhauer 1992 andGarm 2004) attempt to make the terminology applicable to sensory structures associated with the body cuticle in Crustacea more precise, the study of Cephalocarid species disclose differences. These are blind and minute animals of the infaunal benthos, whose setation and sensorial tegumentary structures become particularly important to understand general behavior, interactions with the environment and niche differentiation.…”

“…The last revision of this problem by Garm (2004) based on the external morphology and ultrastructure of the setae found in the mouthparts of seven species of Decapoda led him to propose a reconsideration of the basic types differentiating setae (two types), setules and denticles as basic major types and grouping the setae in the following seven types: pappose, plumose, serrulate, serrate, papposerrate, simple and cuspidate. He optimizes this classifi cation identifying the different names proposed by Thomas (1970) and ensuing authors since the 70s onwards with each of his seven types.…”

First zoeal stage of the crab Domecia acanthophora (Desbonne, in Desbonne & Schramm, 1867) (Decapoda, Brachyura) and revision of the larval morphology of superfamily Trapezioidea

“…Larval description and terminology of setae are based on Clark et al (1998) and Garm (2004). The parental females of D. acanthophora were deposited in the crustacean collection of the Museum of Zoology of the University of São Paulo (MZUSP-16705).…”

Drawing setae: a GNU way for digital scientific illustrations

“…Th ere are also some other defi nitions for these structures and they are generally meant to be homology-based (Garm, 2004). As a matt er of fact, setae can be divided into diff erent types according to their mechanical functions.…”

“…As a matt er of fact, setae can be divided into diff erent types according to their mechanical functions. Garm (2004) defi ned setae based on their mechanical functions rather than homology.…”