Our team specially focuses on the impacts of environmental perturbations (e.g. ocean acidification and temperature variations) on both embryos and adults of aquatic animals. Integration of molecular genome databases, physiological approaches and biochemical techniques, we try to take advantage of molecular approaches coupled with eco-physiological studies for exploring deeper and practical biological significances behind superficial appearances.
This team scheduled cooperate with several creative groups, including:
Impacts of ocean acidificationand warming on marine animals
Acidification of surface seawater will be accompanied by warming which may significantly affect an organisms thermal window for physiological processes from the molecular to the systemic level. To date there is still a gap in knowledge regarding the effects of environmental hypercapnia within and beyond the limits of the thermal tolerance of marine organisms, which may significantly alter their capacity to acclimate to CO2 induced acid-base disturbances.
We are focusing on the biometric analysis regarding phenotypes, physiological parameters and gene expressions of marine athletic animals such as teleosts (cod and Japanese medaka) and cephalopods (squid and cuttlefish) with low variations of ambient pH (0.4~0.7 units) and temperature . Embryonic development and adult responses are both examining subjects for the global challenging issue.
Physiological genomics of acid-base and ion homeostasis along animal evolution
Mechanisms of ion and acid-base regulation in aquatic animals have become a research focus especially in primitive teleosts and tetrapods. During colonization from open sea to freshwater habitats, maintenance of ionic gradients and even active ion transport are essential for cellular homeostasis and further adaptation to terrestrial life. While in the case of teleosts, progress in molecular physiology research has enabled a detailed understanding of epithelial ionocyte function.
For internal pH homeostasis, the epithelial ionocytes have to secret H+ from the blood, which is acidified due to the metabolic/respiratory acidosis or the impacts of environmental pH fluctuations. Recent molecular physiological studies proposed that the Na+ uptake/acid secretion mechanisms in teleosts epithelium ionocytes are homologous to those in proximal tubular cells of mammalian kidneys. Through the functioning of membrane-bound carbonic anhydrase (CA), ambient HCO3- and H+ secreted by the apical Na+/H+ exchanger (NHE, in SW organisms) or V-type H+-ATPase (VHA, in FW organisms) react to form CO2 and H2O outside of apical membranes of epithelium ionocytes, and this enables the passive diffusion of CO2 into ionocytes. Then the cytosolic CA hydrates CO2 to form HCO3- and H+. In addition, VHA may electrically link to absorption via the epithelial Na+ channel (ENaC) for epithelium apical Na+. Through the investigation of epithelial ion transport machinery in primitive an diverse aquatic animals such hagfish, lamprey, sturgeon, shark and lungfish, we can explore the homeostasis mysteries behind fish terrestrialization.
Energy metabolism and anti-oxidants mechanism in aquatic animals under environmental perturbations
Environmental perturbation, such as cold stress and hypercapnia, triggers a complex program of gene expressions and biochemical responses in different tissues of aquatic animals. In several vital organs increments of mitochondrial properties enhance the metabolic capacity. Nevertheless, raising the mitochondrial respiration rates may lead to deleterious consequences, including reactive oxygen species (ROS) formation, proton leak increment and lipid peroxidation. Among them, mitochondrial ROS overproduction usually results in cellular oxidative stress. Therefore, an antioxidant mechanism through PPAR (peroxisome proliferator-activated receptor) pathways, UCP (uncoupling protein) activations, HIF (hypoxia-induced factor) regulations and the changes in carbohydrates metabolism under environmental stress were observe.
We are focusing on cellular moderate metabolism shift for adequate energy supply and further antioxidant mechanism by studying intact organisms (Japanese medaka and cephalopods embryos) in face of ambient cold stress and CO2 elevation.