of the metathoracic ganglion in response to progressive hypoxia in an insect.

Mammals regulate their brain tissue tightly, and only small changes in brain are required to elicit compensatory ventilation. However, unlike the flow-through cardiovascular system of vertebrates, insect tissues exchange gases through blind-ended tracheoles, which may involve a more prominent role for diffusive gas exchange. We tested the effect of progressive hypoxia on ventilation and the of the metathoracic ganglion (neural site of control of ventilation) using microelectrodes in the American locust, .

Responses of threespine stickleback (Gasterosteus aculeatus, L) transcriptome to hypoxia.

Hypoxia is a naturally occurring phenomenon in aquatic systems. Its occurrence is potentiated by eutrophication caused by human actions and it may be made even more severe as a result of increasing temperatures due to climate change. Threespine stickleback (Gasterosteus aculeatus) has previously been used by ecologists and evolutionary biologists, but has great potential also for physiological studies.

Physiological differentiation among nine-spined stickleback populations: effects of copper exposure.

Nine-spined stickleback (Pungitius pungitius) exhibit a very wide geographical distribution and are increasingly used in ecological and evolutionary research. While pronounced morphological and behavioural differentiation among local populations has been shown, physiological differentiation, especially with respect to stress responses, has not been investigated. However, this would be of interest since the increased use of sticklebacks as ecotoxicological sentinel species presumes a uniform response of used populations to stressors.

The copper-induced reduction of critical swimming speed in rainbow trout (Oncorhynchus mykiss) is not caused by changes in gill structure.

In the present experiments, we investigated, if copper exposure causes a decrease in the critical swimming speed, as has been observed earlier, and if such a decrease can be explained by a disturbance in gill structure. The results show that this is not the case. While copper exposure tended to increase the thickness of gill diffusion barrier in resting fish, a similar difference was not seen in swimming animals.

The teleost pseudobranch: a role for preconditioning of ocular blood supply?

The physiological relevance of the teleost pseudobranch as a remnant of a reduced gill arch is still unclear. Numerous hypotheses have been proposed regarding its physiological role, but direct confirmatory evidence is lacking. The close relationship by serial blood flow arrangement with the fish eye's choroid rete has sparked the idea that pseudobranchial preconditioning of blood pH may facilitate initiation of the Root effect and thus support the establishment of high oxygen tensions for retinal diffusive supply.

Molecular and cellular studies in evolutionary physiology of natural vertebrate populations: influences of individual variation and genetic components on sampling and measurements.

Studies combining ecological, genetic and physiological approaches are needed in evolutionary biology. Although the combination of approaches has been emphasized, such studies have been rare with regard to molecular and cellular studies on natural vertebrate populations. The major reasons for this are that the generation time of vertebrates is long and it is difficult to find a molecular or cell physiological measurement that is both relevant for the fitness of the population and can be repeated an adequate number of times to enable estimations of individual variability.

Oxygen delivery to the fish eye: root effect as crucial factor for elevated retinal PO2.

Although the retina has one of the highest metabolic rates among tissues, certain teleost fishes lack any vascular supply to this organ which, in combination with the overall thickness of the organ, results in extremely long diffusion distances. As the only way to compensate for these obstacles, oxygen partial pressure (PO2) in the eyes of such fish is elevated far above atmospheric values. Although not supported by any direct evidence, the enhancement of PO2 is considered to be related to the Root effect, the release upon acidification of Hb-bound O2 into physical dissolution, possibly supported by counter-current multiplication similar to the loop of Henle.

Physiology and biochemistry of the pseudobranch: an unanswered question?

The structure and function of the pseudobranch has long interested scientists, but its overall role has remained a mystery. Previous studies have attributed respiratory, endocrine, osmoregulatory and sensory roles to the pseudobranch, and the present review concentrates on new findings. Perfusion experiments on the pseudobranch of the rainbow trout (Oncorhynchus mykiss) using both erythrocyte suspensions and Ringer solution have shown that this organ is able to generate values for the respiratory quotient (RQ) greater than 1.