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Disseminated neoplasia (DN) is a form of cancer in bivalve molluscs that can be transmissible between individuals and in some cases across species. Neoplastic cells are highly proliferative, and infection is usually lethal. Commercially valuable bivalve species (mussels, cockles, softshell clams, and oysters) are affected by outbreaks of DN, making disease diagnosis and mitigation an important issue in ecological restoration efforts and aquaculture. Basket cockles (Clinocardium nuttallii) are native to the North American Pacific coast from California to Alaska. Recent concern from some Coast Salish Tribes regarding an observed long-term decline in basket cockle populations in Puget Sound, WA has increased interest in monitoring efforts and subsequent collection for aquarium-reared broodstock. Disseminated neoplasia was detected in Puget Sound basket cockle populations, delaying aquaculture efforts so that potential broodstock could be assessed for the presence of DN. This study details a minimally invasive, inexpensive, nonlethal method for high-throughput screening for DN in adult basket cockles. The hemolymph smear screening method to diagnose DN in C. nuttallii can be applied at field sites at low financial cost. Results of the hemolymph smear technique were validated against whole tissue histology, the standard method for DN diagnosis. Due to the similar cellular morphologies of DN in different bivalve species, it is proposed that hemolymph histology can likely be applied for diagnosing DN in other bivalves. 

Abstract The formation of extracellular DNA traps (ETosis) is a first response mechanism by specific immune cells following exposure to microbes. Initially characterized in vertebrate neutrophils, cells capable of ETosis have been discovered recently in diverse non-vertebrate taxa. To assess the conservation of ETosis between evolutionarily distant non-vertebrate phyla, we observed and quantified ETosis using the model ctenophoreMnemiopsis leidyiand the oysterCrassostrea gigas. Here we report that ctenophores – thought to have diverged very early from the metazoan stem lineage – possess immune-like cells capable of phagocytosis and ETosis. We demonstrate that bothMnemiopsisandCrassostreaimmune cells undergo ETosis after exposure to diverse microbes and chemical agents that stimulate ion flux. We thus propose that ETosis is an evolutionarily conserved metazoan defense against pathogens. 

Cell suspension fluidics, such as flow cytometry (FCS) and fluorescence-activated cell sorting (FACS), facilitates the identification and precise separation of individual cells based on phenotype. Since its introduction, flow cytometry has been used to analyze cell types and cellular processes in diverse non-vertebrate taxa, including cnidarians, molluscs, and arthropods. Ctenophores, which diverged very early from the metazoan stem lineage, have emerged as an informative clade for the study of metazoan cell type evolution. We present standardized methodologies for flow cytometry-mediated identification and analyses of cells from the model ctenophoreMnemiopsis leidyithat can also be applied to isolate targeted cell populations. Here we focus on the identification and isolation of ctenophore phagocytes. Implementing flow cytometry methods in ctenophores allows for fine scale analyses of fundamental cellular processes conserved broadly across animals, as well as potentially revealing novel cellular phenotypes and behaviors restricted to the ctenophore lineage.