I am interested in the tolerance to low salinity in marine invertebrates early life stages. All the studies I have come across so far always use chronic osmotic stress although organisms in the field are likely to be exposed to episodic osmotic stress. I am inclined to assume that chronic osmotic stress would be worse than episodic stress (in marine species, not estuarine) but would like to know what other researchers think on that subject.
Hello,
Although I am not so familiar with invertebrates' osmoregulation, I think chronic osmotic stress is more detrimental compared to episotic acute one. As a osmoconformer species, these species are not able to regulate their osmotic pressure. So they should necessarily live in an environment with certain osmotic condition ensuring their survivorship. Any change in ambient osmotic pressure may be detrimental to these organisms, and the more prolonged time, the more detrimental effects. In osmoregulators, chronic but not lethal osmotic disturbance may give enough time to adaptation. Therefore, they can adapt to new condition over the time, although, they pay the cost for adaptation for unsuitable medium. However, it is not the case for osmoconformers, I think so.
I hope it is useful.
Have a fun...
The rate of change of the salinity is the most important consideration in my opinion. One way to concentrate marine rotifers in seawater is to suddenly dilute the sample with an equal amount of distilled water. The rotifers stop moving and fall to the bottom of the container where they can be collected en masse. They start moving again after about 10 minutes. Rotifers are microscopic, barely visible to the unaided eye. Larger invertebrates may experience less shock, but an extended acclimation time during which they are likely not feeding and may be more susceptible to predation.
Hi Agnes,
I agree with Seyyed and Ray, if an animal survive the initial salinty stress, a long term salinity challenge will likely have consequences for the energy budget of this animal. The rate of change is crucial, as it will determine the immediate survival of the animal as this must somehow maintain homeostasis within tolerable levels. This is, of course, specie-specific. The magnitude of the salinity change (osmotic gradient) is also important, as some animals (crabs) are able to osmoconform over a wide range of salinities, not investing much energy. Some of our work, might be of interest as we talk about short and long term responses.
Urbina M.A, Schulte P. M, Bystriansky J and Glover C.N. 2013. Differential expression of Na+, K+-ATPase a -1 isoforms during seawater acclimation in the amphidromous galaxiid fish Galaxias maculatus. Journal of Comparative Physiology B. 183(3), 345-357.
Urbina M., Paschke K., Gebauer P & Chaparro O.R. 2010. Physiological energetics of the estuarine crab Hemigrapsus crenulatus (Crustacea: Decapoda: Varunidae): responses to different salinity levels. Journal of the Marine Biological Association of the United Kingdom 90, 267-273.
All the best,
Mauricio
Many thanks for your insightful answers and links, it is very much appreciated. I didn't think of manipulating the rate of change before, but certainly will from now on!
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