LABRAL GLANDS OF LEPTESTHERIA DAHALACENSIS (BRANCHIOPODA: SPINICAUDATA): AN ULTRASTRUCTURAL STUDY

Abstract

ABSTRACT The upper lip of Leptestheria dahalacensis contains 3 types of large, polymorphous, and polynucleate gland cells, forming 5 morphologically and topographically distinguishable glandular groups: 2 lateral (A and B) and 1 median (C). In each group the gland cells are arranged in pairs: several of A cells, 2 of B cells, and 1 of C cells. RER, mitochondria, and Golgi complexes are more or less variously shaped in the 3 types of gland cells. The secretion products have different appearances: vesicles, or bodies with dense or variously structured contents. Gland cells of groups A and B show wide intracytoplasmic lacunar areas, but only in the cytoplasm of B cells variously structured secretion bodies are visible close to such lacunar areas. In contrast, each of the 2 C cells surrounds an extracellular funnel-shaped space originating from a deep invagination of the distal part of these cells. Small epidermal cells delimiting a duct are associated with each pair of gland cells. Nerve fibers in contact with the 3 types of gland cells are also seen. The results of the ultrastructural study are discussed in light of the data available on the labral glands of other copepod and branchiopod crustaceans.