Meeting Abstract
Euryhaline crustaceans are thought to employ conserved adaptations resulting in hyper-osmoregulation in dilute waters, including a salinity-mediated increase in expression of osmoregulatory genes encoding for ion transport proteins and related enzymes in the gills. However, Halocaridina rubra, an atyid shrimp from the unusual anchialine ecosystem, apparently lacks this response. To further characterize osmoregulatory pathways among crustaceans, RNA-Seq of gill tissue was performed during salinity transfers for 5 additional anchialine shrimp species (Atyidae and Alpheidae). As a control, salinity-mediated RNA-Seq of both osmoregulatory and respiratory gills was performed in the blue crab, Callinectes sapidus, which has traditionally served crustacean osmoregulation model. While “classic” crustacean osmoregulatory genes were up-regulated as expected in C. sapidus, these same genes appear to be ubiquitously expressed in H. rubra at high levels (i.e., top 10% of expressed genes in the gill transcriptome) regardless of salinity. In contrast, H. rubra differentially expressed genes involved in oxygen transport, calcium binding, and mitochondrial genome maintenance during salinity transfer. This atypical pattern was not observed in the 4 other anchialine shrimp. For example, Caridina rubella exhibited a 13-fold increase in expression of Na+/K+-ATPase. This supports metabolic data indicating a trade-off for osmoregulatory function at the expense of gas exchange in the gills of H. rubra and implies a novel osmoregulatory strategy not shared with closely related anchialine crustaceans. Extending these studies to a wider ecological and taxonomic range of taxa will help determine if this strategy is unique among the crustaceans.
