Gaping can be either totally harmless--turtles do yawn, or a sign of a serious respiratory problem, including pneumonia. You have to watch the turtle carefully and put all the different signs together. If the animal gapes and yawns frequently, and if there are any other symptoms, like swollen eyes, a runny nose, rasping while breathing, or loss of appetite, have a veterinarian evaluate the turtle immediately. Often a veterinarian will do an X-Ray to determine whether a gaping turtle has pneumonia and water in its lungs. If a water turtle swims lop-sided, mention it to your veterinarian. This is a pretty sure sign, that the turtle does have water in its lungs.
----------
While turtles yawn occasionally just like all animals, frequent yawning combined with wheezing is a pretty good indicator of some respiratory trouble. (Oder potential causes could be obstruction of the airway by a tumor or some other means, but I've never hear this happening in turtles.) There are some simple tests that can be done to get a diagnosis: * Put your turtle into the water. If he floats lopsided at all, then he has fluid in his lungs. * Smear from the throat/airway. This will show a bacterial infection. * Blood test. This will show bacterial infection and inflammation. * X-Rays are often taken to determine the same thing. (If there is fluid in both lungs, the turtle will swim righted, but he may have a harder time adjusting his buoancy.) * Check my website for more information on respiratory infections. * Baytril is a good antibiotic drug to start on. There are other antibiotics than can also be used. You should be injecting it. Make sure you follow the instructions for injection. Make sure the dosage is calculated based on turtle weight MINUS shell weight. Injection must be intra-muscular, twice daily, 2.5-5mg per kg (kilogramm) of body weight. Baytril is not nephrotoxic and you can inject pretty much anywhere. Rear legs are fine. Switch legs for every injection. Be careful not to poke the bone. For respiratory infections, Baytril can be given for several weeks. Minimum, as for all antibiotics, is 7-10 days. 2 weeks is a good time frame for a first time. The turtle may stop eating during treatment and be a bit sleepier from the drug. If there is no improvement after 2 weeks, re-evaluate. The stuff takes a few days to kick in. Remember that I am not a veterinarian and I urge you to double-check all veterinary advice with a qualified veterinarian, in particular calculation of dosage and confirmation of diagnosis.