Meeting Abstract

77.4  Wednesday, Jan. 6  The epidermal glands of gastrotrichs: ultrastructural insights and hypotheses of function HOCHBERG, Rick; University of Massachusetts Lowell rick_hochberg@uml.edu

Despite more than a century of research, the phylum Gastrotricha remains as enigmatic as ever. Intensive collection efforts by scientists across the globe have uncovered substantial new biodiversity, yet, intra- and interphyletic evolutionary relationships remain shrouded in mystery, and even many aspects of gastrotrich biology are still poorly understood. In particular, the large marine clade, Macrodasyida, contains a wide variety of species with unusual body plans and peculiar organ systems that have yet to be explored in detail. Here, I provide an overview of one of these curious organ systems, the epidermal glandular system, with a focus on gland cell structure and diversity. I use data derived from transmission electron microscopy to show that secretory granules are generated by two sets of cellular organelles: the rough endoplasmic reticulum (rER) and the Golgi apparatus. Mature secretory granules that are synthesized from each organelle and destined for exocytosis are initially formed via one of two pathways. In pathway 1, immature granules are formed in the rER and further processed in the Golgi before condensing into mature granules of heterogeneous chemistry in the cytoplasm. In pathway 2, immature granules are formed solely in the rER and condense into mature granules of homogeneous chemistry in the cytoplasm. Further details on the formation of epidermal glands and the biogenesis of their secretory products are provided, as are hypotheses on the potential functions of epidermal glands. The need for future descriptive research on gastrotrich biology is discussed.