PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 110(2): 167-185. 1997. Cnidae of Scleractinia Debora de Oliveira Pires Departamento de Invertebrados, Museu Nacional/Universidade Federal do Rio de Janeiro, Quinta da Boa Vista s/n, 20940-040, Rio de Janeiro, RJ, Brasil Abstract. — Corals and corallimorpharians are considered cnidarians with simple cnidae. This work shows that such a statement is relative, and depends upon the accuracy of the observation. The cnidae of tentacles and mesenterial filaments of 60 species belonging to 17 families of Scleractinia and three fam-ilies of Corallimorpharia were studied using Normarski optics. The diversity of the cnidae (morphological patterns and their varieties) is described and il-lustrated, and their distributions are given: In addition, a new type of cnida from the mesenterial filaments of Agariciidae is recorded. Synonym lists of the names used by other authors for the cnidae of Scleractinia and Corallimorpharia are also included, and aspects of their terminology are discussed. Diversity in the cnidae of Scleractinia confirms the potential of soft tissues as an important source of characters that should be explored in taxonomic studies. When used with other characters, the descriptions of cnidae will contribute to the improve-ment of studies on coral taxonomy and systematics. The knowledge of the cnidae in terms of their diversity, size and distribution, has been considered as a useful taxonomic character for many groups of Cnidaria (see Pires & Pitombo 1992). The nematocysts represent categories that are usually con-stant (Gravier-Bonnet 1987, Pires 1988) and their structural complexity provides many features for comparison (Tilbury & Cameron 1989). The systematics of the Scleractinia, the largest order of the sub-class Hexacorallia (=Zoantharia) (Wells 1956), with approximately 225 recent gen-era and 1500 species (Cairns 1990), is not fully satisfactory (Chevalier & Beauvais 1987), being based primarily on skeletal morphology (Wells 1956). One of the reasons for the neglect of cor-al cnidae studies is the lack preservation of their tissue. It is not routine in most scien-tific collections to preserve scleractinian coral tissues, especially in formalin, be-cause the skeleton is the primary or only taxonomic source of characters. Problems with nematocyst nomenclature, some of which have been recently discussed by En-gland (1991), have also made it difficult to understand and compare studies that have included data on cnidae. The goal of this paper is to describe the diversity of cnidae occurring in tentacles and mesenterial filaments of Scleractinia and to propose a detailed terminology to classify subtypes of coral cnidae. This study is based on a large array of taxa and on features that can be observed through light microscopy, which is easily accessible to most researchers. To help in the understand-ing and interpretating other papers, syn-onym lists of terms used for cnidae by other researchers are included. The cnidae of the Corallimorpharia were also studied here due to their great similarities with the Scler-actinia, as has been previously pointed out (Schmidt 1974, den Hartog 1980). The cnidae are structures unique to the
BioStor
