Tilapia are cichlid fishes that are native to the Great Lakes of East-Africa. Three genera of tilapia are common: Oreochromis, Sarotherodon, and Tilapia. Four species of the genus Oreochromis (O. niloticus, O. mossambicus, O. aureus, O. hornorum) and their hybrids are commonly used for aquaculture. They have spread into aquatic ecosystems world-wide as invasive species. O. mossambicus and O. niloticus are well established models for ecological and biomedical research. The latter and three species of the related genus Haplochromis have been approved for whole genome sequencing.

Like other euryhaline fishes tilapia are capable of living in a wide range of environmental salinity (e.g. freshwater and seawater). They also have high tolerance to other types of environmental stress (cross-tolerance), which is why they are successful invadors of many aquatic ecosystems world-wide. We study the genetic and physiological mechanisms that confer high salinity tolerance to euryhaline tilapia.

Tilapia gills before and after perfusion

Because fish gills are in direct contact with the external aquatic environment and responsible for many vital physiological functions, including osmoregulation, they represent an excellent target tissue for studying mechanisms of osmotic stress adaptation and acclimation. Therefore, most of our studies focus on in-depth analysis of environmental stress response mechanisms in tilapia gills and gill cells. However, when attempting to model whole organisms responses to osmotic stress we also include other tissues in our analyses.

Tilapia gill SEM

Because fishes are aquatic vertebrates abiotic environmental parameters such as osmolality, temperature, pH, oxygen concentration, etc. can be easily controlled during in vivo experiments with gill cells of live fish. This feature represents an important experimental advantage. Much is known about effector mechanisms of osmoregulation in fish gill cells but we know very little about the signaling network that controls these effector mechanisms during osmotic stress. Our research focuses in particular on the stress response network of gill chloride cells and pavement cells because these cell types are in direct contact with the external milieu and they undergo dramatic biochemical and morphological changes in response to osmotic stress and other types of environmental stress.

SEM of tilapia pavement cells

Fish gills are covered by an epithelium that serves multiple major physiological functions: respiration, osmoregulation, acid-base regulation, and nitrogenous waste excretion. Thus, (with the exception of respiration) fish gills functionally resemble mammalian kidneys, which was first realized almost a century ago by Homer Smith. Therefore we use mammalian kidney epithelial cell cultures to compare environmental (in particular osmotic) stress response mechanisms in lower vertebrates to that in higher vertebrates. Such comparison is critical for identifying evolutionary trends and key elements that define environmental stress response networks in vertebrates. The resulting knowledge has direct and profound benefits for biomedical research and human health.