Self/non‐self recognition in sponges

Abstract

A variety of procedures have been utilized to study the sponge ability to discriminate self-from non-self. In adult sponges, the histocompatibility reaction has traditionally been tested by transplantation techniques or parabiosis. These consist of pushing into contact different species (xenograft) or conspecific individuals (allograft) with their outer pinacodermal layers intact. A fast reaction can be observed when fragments of the inner part of the sponge are tied together. Lack of compatibility generates signals suppressing or activating both exopinacocytes bounding the contact surface and discrete mesohyl cell types (archaeocytes, collencytes, gray and spherulous cells). These cells are involved to different extents according to the species (active migration along the contact surface, cytotoxicity, phagocytosis, synthesis of a collagen barrier). In sponge cell aggregates, species-specific sorting-out expresses the recognition reaction of the mixed cells. Glycoconjugates are key molecules for self/non-self cell discrimination. In the model derived from Geodia cydonium cells, galectin molecules in the presence of Ca 2+ form a bridge between the intercellular multiprotein complex aggregation factor (AF) and the cell surface-associated aggregation receptor (AR). The AF is a soluble and diffusible macromolecule that may play an important role also in self recognition mechanisms occurring in sponges in toto. A new paradigm has recently been suggested for cell recognition: interactions between the most peripheral cell surface specific proteoglycans (glyconectins). These molecules have been purified from three marine sponge species (Microciona prolifera, Halichondria panicea, and Cliona celata). This mechanism of self recognition could represent a remarkable event for the appearance of multicellularity.

Fragmentation, Fusion, and Genetic Homogeneity in a Calcareous Sponge (Porifera, Calcarea)

“…The lack of an allorecognition response upon contact, resulting in fusion of genetically different individuals, yields a chimaera (Pineda‐Krch and Lehtila, ). Graft experiments have suggested that fusion is restricted to genetically identical individuals in adult sponges (Hildemann et al., ; Amano, ; van de Vyver and Buscema, ; Gaino et al., ), maintaining the individual's genetic homogeneity. However, the natural occurrence of chimeric individuals in the demosponge Scopalina lophyropoda Schmidt 1862, a Mediterranean species with high genetic diversity and frequent fragmentation and fusion events, was recently reported (Blanquer and Uriz, ).…”

Innate Immunity, Environmental Drivers, and Disease Ecology of Marine and Freshwater Invertebrates

“…In the sponge Microciona prolifera, calcium ions serve as an intracellular messenger in stimulus-response coupling during cell-cell aggregation (Dunham et al 1983, Weissman et al 1986, and carbohydrate self-recognition mediates cellular adhesion (Haseley et al 2001). Allogenic rejection has a cellular component: Interactions between incompatible sponges activate exopinacocytes (cells forming the external surface of the sponge) and various mesohyl cells, some of which contain the secondary metabolites so common in sponges (Gaino et al 1999).…”

New epizooic symbioses between sponges of the genera Plakortis and Xestospongia in cryptic habitats of the Caribbean

“…Parabiosis experiments using free-living individuals of X. deweerdtae with Plakortis sp. 1 and 2 would help determine how these sponges interact with one another at the interphase (Gaino et al 1999). Characterization of the aggregation factors involved in cellular adhesion of both heterospecifics could also aid in understanding self-to non-self-recognition mechanisms of these sponges (Haseley et al 2001).…”