Two Types of Nematocysts in Campanulariidae (Cnidaria, Hydrozoa) Studied by Light and Scanning Electron Microscopy

Abstract

The cnidom was found to consist of several morphologically distinct types of nematocysts in six investigated species of Campanulariidae. Descriptions are provided for b‐rhabdoids (micro‐basic b‐mastigophores) of two sizes, occurring in the polyps of Campunulariu Integra and Clytia hemisphaerica of the johnstoni and gracilis forms, respectively. The smaller nemato‐cyst is the most frequent type and is also abundant in the polyps of Laomedea flexuosa, L. geniculata, L. longissima and L. dichotoma as well as in the medusae of Campanulariidae. Structural details of the two nematocyst types, as revealed by scanning electron microscopy, permit discussion of the classification of the nematocysts. The tube in the two types tapers almost unnoticeably from base to tip. No distinct, proximal enlargement of the tube was discernable in either type, as earlier light microscopical observations have suggested. The proximal armature consists of a right‐handed, triple helix of three separate strands of long, closely‐set, paired spines. In the small nematocyst the distal part of the tube is armed with medium sized spines and the discharged tube forms an obtuse angle to the long axis of the capsule. The discharged, wider tube of the large nematocyst roughly forms a right angle to the long axis of the capsule and is distally armed with minute spines.