Metabolic enzymes are often the targets of selection exhibiting various molecular features related to temperature adaptations. Our group assembled transcriptomic datasets from closely related species of Antarctic and sub-tropical marine invertebrates called bryozoans testing for genes under positive selection using different kinds of bioinformatic tests. Based on these results we compiled a list of genes involved in the metabolic processes of the bryozoans to test for the effects of varying temperatures on their functionality, specifically those involved in the mitochondrial Citric Acid Cycle. With the use of molecular and recombinant expression techniques our lab synthesized orthologous forms of isocitrate dehydrogenase-2 (IDH-2) from both Antarctic and sub-tropical bryozoan species. Using different IDH-2 forms we tested the effect of temperature and substrate concentration on the enzymatic reaction to calculate the maximum reaction rate (V_max) and the Michaelis-Menten constant (K_m) for these enzymes. Our preliminary results indicate that IDH-2 forms from both the warm- and cold-water species function within a wide range of temperatures. IDH-2 forms from Antarctic species may be more cold-tolerant, whereas the activity of IDH-2 forms from warm-water species are more stable at higher temperatures. Our collaborative research group is currently expanding the taxonomic sampling of our transcriptomic datasets leading to more robust tests of positive selection and further experimental tests of potential temperature adaptations among metabolic enzymes. Going forward, these data will shed new insights on the kinds of molecular signatures typical of potential adaptions of genes from Antarctic taxa.