title: The role of cell replacement in benthic-pelagic coupling by suspension feeders.
abstract: Benthic-pelagic coupling through suspension feeders and their detrital pathways is integral to carbon transport in oceans. In food-poor ecosystems however, a novel mechanism of carbon recycling has been proposed that involves direct uptake of dissolved carbon by suspension feeders followed by shedding of cells as particulate carbon. We studied cell replacement rates in a range of cold-water sponge species to determine how universal this mechanism might be. We show that cell replacement rates of feeding epithelia in explants vary from 30 hours up to 7 days, and change during different seasons and life-history stages. We also found that feeding epithelia are not replaced through direct replication but instead arise from a population of stem cells that differentiate and integrate into epithelial tissues. Our results reveal a surprising amount of complexity in the control of cell processes in sponges, with cell turnover depending on environmental conditions and using stem cells as rate-limiting mechanisms. Our results also suggest that for species in cold water with high particulate organic matter, cell turnover is not the mechanism delivering carbon flux to surrounding communities.
authors.affiliation: Department of Biological Sciences , University of Alberta , Edmonton, Alberta , Canada T6G 2E9.
authors.forename: Amanda S
authors.identifier: 0000-0001-6812-9474
authors.initials: AS
authors.lastname: Kahn
authors.affiliation: Department of Biological Sciences , University of Alberta , Edmonton, Alberta , Canada T6G 2E9.
authors.forename: Sally P
authors.identifier: 0000-0001-9268-2181
authors.initials: SP
authors.lastname: Leys
keywords: Porifera; cell turnover; choanocytes; sponge loop; stem cells