UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The limits of osmoregulation : strategies for tolerance and acclimation of 'California' Mozambique tilapia (Oreochromis mossambicus x O. urolepis hormorum) to conditions of the Salton Sea Sardella, Brian

Abstract

The Salton Sea is a large inland lake in southeastern California with salinity currently near 44 g/l that is increasing at a rate of 0.3 g/l annually. Along with salinity, large fluctuations in temperature and dissolved oxygen levels combine to make a very challenging environment that may be responsible for dramatic losses to the Salton Sea's once robust fishery. The dominant species within the fishery is a Mozambique tilapia hybrid (Oreochromis mossambicus x O. urolepis hornorum), which is well known both for euryhalinity and tolerance of extremely high salinities; as such, it provides a unique model for tolerance to hypersaline conditions as well as the interactions of multiple stressors such as those within the Salton Sea. In part one I describe two responses by tilapia to salinities greater than seawater at 25°C. When transfers were conducted below 60 g/l salinity, tilapia maintained osmotic balance without increasing drinking rate, mitochondrial-rich cell (MRC) turnover, or branchial Na⁺,K⁺-ATPase (NKA) activity. With additional increase above 60 g/l, these variables increased in similar fashion to that which has been described in other teleosts during acclimation to elevated salinity. These acclimation responses were defined as response I or response II, with a transition point between the two at 60 g/l. Tilapia exhibiting response I had a reduced whole animal oxygen consumption rate, as well as, liver and brain ATPase activity in proportion to salinity. In part two, I describe how changes in temperature affect the salinity tolerance of this species. Variation in temperature from 25°C to 15 or 35°C resulted in increased plasma osmolality and/or mortality, indicating a combined temperature/salinity stress is more challenging than salinity alone. Using tissue microarrays and laser scanning microscopy, I show that tilapia attempted to respond to the loss of osmotic balance in cold temperatures with MRC hypertrophy and enhanced NKA capacity.

Item Media

Item Citations and Data

License

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.

Usage Statistics