ABSTRACT1. Recreational power boating is growing in popularity in North America. This activity is known to have lethal and sub-lethal effects on aquatic wildlife and freshwater turtles may be particularly sensitive to this activity.2. This study reports on patterns of traumatic injuries inflicted by powerboat propellers to northern map turtles (Graptemys geographica) from two sites differing in boat traffic intensity in Ontario, Canada.3. The relative vulnerability of turtles was assessed, in light of seasonal patterns in boat traffic, as a function of sex-and age-specific movement patterns, habitat use, and basking behaviour obtained by radio-telemetry. Population viability analyses (PVA) were also conducted to evaluate the potential demographic consequences of mortality induced by powerboats.4. The prevalence of propeller injuries was two to nine times higher in adult females than in adult males and juvenile females. Patterns of movement, habitat use, and aquatic basking indicated that adult females are more exposed to collisions with boats. PVA showed that boat-induced mortality in adult females could lead to rapid population extinction if the risk of mortality when hit by a boat is greater than 10%.5. The results of this study showed that recreational power boating is a serious threat to northern map turtles, even under moderate boat traffic. The need to adopt measures restricting boat traffic in areas important to turtles is discussed.
The Cry1A insecticidal crystal protein (protoxin) from six subspecies of Bacillus thuringiensis as well as the Cry1Aa, Cry1Ab, and Cry1Ac proteins cloned in Escherichia coli was found to contain 20-kilobase pair DNA. Only the N-terminal toxic moiety of the protoxin was found to interact with the DNA. Analysis of the crystal gave approximately 3 base pairs of DNA per molecule of protoxin, indicating that only a small region of the Nterminal toxic moiety interacts with the DNA. It is proposed that the DNA-protoxin complex is virus-like in structure with a central DNA core surrounded by protein interacting with the DNA with the peripheral ends of the C-terminal region extending outward. It is shown that this structure accounts for the unusual proteolysis observed in the generation of toxin in which it appears that peptides are removed by obligatory sequential cleavages starting from the C terminus of the protoxin. Activation of the protoxin by spruce budworm (Choristoneura fumiferana) gut juice is shown to proceed through intermediates consisting of protein-DNA complexes. Larval trypsin initially converts the 20-kilobase pair DNA-protoxin complex to a 20-kilobase pair DNAtoxin complex, which is subsequently converted to a 100-base pair DNA-toxin complex by a gut nuclease and ultimately to the DNA-free toxin.Bacillus thuringiensis (Bt) 1 deposits a proteinaceous crystal during sporulation (1). The major component of crystals toxic to lepidopteran larvae is a 130-kDa protein (protoxin) (2). On ingestion, the protoxin is acted on by a trypsin-like gut protease and converted to a 65-kDa toxin derived from the N-terminal region of the protein (3-5). The toxin binds to receptors on the brush border membrane (6 -8) and is inserted into the membrane, leading to disruption of membrane function with subsequent larval death (9, 10). An unusual feature is that activation of the protoxin appears to occur by a sequential series of proteolytic cleavages, starting at the C terminus and proceeding toward the N terminus until the protease-stable toxin is generated (11, 12). As there is no known protein structural motif that would give rise to such a proteolytic process, this phenomenon is indicative of either a novel type of protein structure or the presence of an additional structural component that confers this property to the protein.An unexpected finding was that a 20-kbp heterologous DNA fragment is intimately associated with the crystals from B. thuringiensis subsp. kurstaki HD73 (13). The DNA is not susceptible to nuclease attack unless the protoxin is removed or proteolyzed to toxin. The active toxin is not associated with DNA; however, evidence was obtained which indicated that the DNA was involved in the generation of toxin from the crystal protein. At present, the nature of the interaction of the Bt protein with DNA and the role of the DNA in the generation of toxin are unknown. The present investigation was undertaken to determine the role of the DNA in the structure and function of the Bt crystal protein. EXPERIMENTAL...
In ectotherms, variation in body temperature (T b ) affects physiological performance and, ultimately, fitness. Therefore, reptiles regulate T b behaviourally by choosing habitats of optimal temperature. The main goal of this study was to determine the link between patterns of thermoregulation and habitat selection in Common Musk Turtles inhabiting a thermally challenging region. We expected habitat selection to be based on the fulfillment of thermoregulatory requirements, which can be accomplished by selecting thermally superior habitats. From early May to late August 2007, we tracked 22 Common Musk Turtles with temperature-sensitive radio-transmitters and collected daily T b profiles with automated radio-telemetry data loggers. In addition, temperature data loggers were placed in the study area to measure the range of environmental operative temperatures (T e ) available to musk turtles. The habitats with the highest thermal quality were aquatic habitats with surface cover (i.e., lily pads, macrophytes, etc.) followed by shallow water. As expected, musk turtles used habitats non-randomly and had a strong preference for thermally superior habitats. This is consistent with the typical aquatic basking behaviour observed in musk turtles, suggesting that there is a strong link between thermal quality of habitats and habitat selection, even in this almost entirely aquatic turtle.
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