An experimental analysis of the water relations of eggs of Blanding's turtles (Emydoidea blandingii)

Eggs of Blanding's turtles ( Emydoidea blandingii ) were incubated in the laboratory under hydric conditions eliciting different patterns of net water exchange between eggs and surrounding air and substrate. Eggs incubated on wet and intermediate substrates increased in mass during the first half of incubation and decreased in mass during the second half, and their mass just before hatching was slightly lower than at oviposition. Eggs incubated on dry substrates and on platforms above substrates declined in mass throughout incubation, with a rate of decline greater in the second half of incubation than in the first. The size of hatchlings was related to the hydric environment in which eggs were incubated and, possibly, to the net flux of water across eggshells. However, variation in size of hatchlings was not as great as has been reported for other species with flexible-shelled eggs, owing presumably to the constraints on water exchange imposed by the more complex eggshells of Blanding's turtles.     

Problems of multiple transfusions

The use of blood infusion in large amounts is increasing sharply. Increased knowledge of blood group antigens has alerted physicians to the possible hazards of hemolytic reactions to subgroups that must be eliminated by proper cross-matching techniques. Multiple transfusions of preserved blood often defeat their purpose in control of bleeding, for thrombocytopenia is enhanced. Careful selection of blood or preparations of plasma concentrates offer increased protection to the recipient.Plastic bag equipment increases the yield of viable platelets and keeps blood in usable condition for longer periods of storage. The use of multiple transfusions has complicated the selection of preserved blood to control pigment metabolism.     

Rats dying for mice: Modelling the competitor release effect

Abstract Introduced vertebrate predators are one of the most important threats to endemic species throughout a range of ecosystems, in particular on islands in biodiversity hot spots. Consequently, the reduction of predator numbers is considered a key conservation action in the management of many native vertebrates vulnerable to predators. It is now established that control attempts may affect non‐target species through trophic interactions, but little is known concerning their consequences on competitive relationships. We study a mathematical model mimicking the effects of controlling introduced species in the presence of their competitors. We used two competing rodents to illustrate our study: black rats, Rattus rattus, and mice, Mus musculus. Analyses of the model show that control of only one introduced species logically results in the dramatic increase of the overlooked competitor. We present empirical data that confirm our theoretical predictions. Less intuitively, this process, which we term ‘the competitor release effect’, may also occur when both introduced competitors are simultaneously controlled. In our setting, controlling both predators can promote their coexistence. This occurs as soon as the inferior competitor benefits from the differential effect of the simultaneous control of both competitors, that is, when the indirect positive effect of control (the removal of their competitors) exceeds its direct negative effect (their own removal). Both control levels and target specificity have a direct influence on the extent of this process: counter‐intuitively, the stronger and more specific the control, the greater the effect. The theoretical validation of the competitor release effect has important implications in conservation, especially for control management.