Hagfishes are living representatives of the earliest-diverging vertebrates and are thus useful for the study of early vertebrate physiology. It has been previously postulated that digestive enzymes account for the majority of digestion because hagfish are agastric with notable zymogen granules in specialized cells of the hindgut. While the presence of some digestive enzymes (amylase, lipase and leucinaminopeptidase) have been confirmed with histochemistry, quantification of enzymatic activity is limited. This study sought to biochemically quantify the tissue activity of six digestive enzymes (α-amylase, maltase, lipase, trypsin, aminopeptidase and alkaline phosphatase) along the length of the Pacific hagfish ( Eptatretus stoutii ) alimentary canal. In addition, the effect of feeding on the rate of enzyme activity was examined. Overall, maltase and trypsin activities were unchanging with respect to location or feeding status, while the activities of α-amylase and alkaline phosphatase decreased substantially following feeding, but were consistent along the length. Lipase and aminopeptidase activities were elevated in the anterior region of the alimentary canal in comparison to the more posterior regions, but were not altered with feeding. This study indicates hagfish have an assortment of digestive enzymes that likely are the result of a varied diet. The differential expression of these enzymes along the tract and in regards to feeding may be indications of early compartmentalization of digestive function.

Municipal wastewater is a large source of pollution to Canadian waters, yet its effects on Arctic marine ecosystems remains relatively unknown. We characterized the impacts of municipal wastewater from a growing northern community, Iqaluit, Nunavut on the Arctic truncate soft-shell clam, Mya truncata. Clams were sampled from six locations that varied in proximity to the wastewater treatment plant and shell biogeochemical analysis revealed that clams nearest the wastewater treatment plant had slower growth rates, lower carbon and oxygen stable isotope ratios, and elevated concentrations of copper and lead. A parallel analysis on mRNA expression profiles characterized M. truncata's physiological response to wastewater effluent. Clams nearest the wastewater treatment plant had significantly lower mRNA expression of genes associated with metabolism, antioxidants, molecular chaperones, and phase I and II detoxification, but had heightened mRNA expression in genes coding for enzymes that bind and remove contaminants. These results demonstrated a biological response to Iqaluit's wastewater effluent and highlight M. truncata's potential to act as a biomonitor of municipal wastewater along Canadian Arctic coastlines.

Hagfish are an excellent model species in which to draw inferences on the evolution of transport systems in early-vertebrates owing to their basal position in vertebrate phylogeny. Glucose is a ubiquitous cellular energy source that is transported into cells via two classes of carrier proteins: sodium-glucose linked transporters (Sglt; Slc5a) and glucose transporters (Glut; Slc2a). While previous pharmacological evidence has suggested the presence of both sodium-dependent and -independent transport mechanisms in the hagfish, the molecular identities were heretofore unconfirmed. We have identified and phylogenetically characterized both a Slc5a1-like and Slc2a-like gene in the Pacific hagfish (Eptatretus stoutii); the latter sharing common ancestry with other glucose-transporting isoforms of the Slc2a family. To assess the potential post-prandial regulation of these glucose transporters, we examined the abundance and localization of these transporters with qPCR and immunohistochemistry alongside functional studies using radiolabeled 14C-D-glucose. The effects of glucose- or insulin-injection on glucose transport rate and transporter expression were also examined to determine their potential role(s) in the regulation of intestinal glucose carrier proteins. Feeding prompted an increase in glucose uptake across the hindgut at both 0.5 mM (~84%) and 1 mM (~183%) concentrations. Concomitant increases were observed in hindgut Slc5a1 protein expression. These effects were not observed following either of glucose- or insulin-injection, indicating these post-prandial factors are not the driving force for transporter regulation over this timeframe. We conclude that Pacific hagfish utilize evolutionarily-conserved mechanisms of glucose uptake and so represent a useful model to understand early vertebrate evolution of glucose uptake and regulation.