Field Observations of Body Temperature for the Wolf Spider, Rabidosa rabida (Araneae: Lycosidae), Differ From Reported Laboratory Temperature Preference Suggesting Thermoconforming Behavior

Temperature affects all aspects of ectotherm ecology, behavior, and physiology. Descriptions of thermal ecology are important for understanding ecology in changing thermal environments. Both laboratory and field estimates are important for understanding thermal ecology. Rabidosa rabida (Walckenaer 1837) (Araneae: Lycosidae) is a large wolf spider with some natural history, including laboratory estimates of thermal preference, tolerance, and performance, reported in the scientific literature. Laboratory tests suggest the active choice of temperature environment. To test published estimates of thermal ecology from the laboratory, we took body temperature measurements of mature spiders in the field nocturnally and diurnally using a FLIR camera in July 2019. We made comparisons between sexes and activity periods using field observations. We compared these measurements with the published values for thermal preferences and thermal maximum and with mean weather station data. Observed field temperatures differed significantly from published preference, but not from mean temperature from a local weather station. This suggests that this species is thermoconforming rather than actively thermoregulating. Reported thermal preference fell between the diurnal and nocturnal mean measurements closer to the diurnal than nocturnal temperatures. These field observations show how important it is to make field observations for physiology and thermal ecology. Maximum observed diurnal temperatures closely approached the published critical thermal maximum. We observed spiders performing behaviors such as hunting and feeding in conditions well above published thermal preference and near-critical high temperature. These observations suggest that R. rabida is thermoconforming in this limited period but does not rule out that they might thermoregulate in certain situations.

Should One Kind of Freedom Be Restricted to Promote Another?

Due to restraints' consequences for personal liberty and dignity, the threshold to apply restraints is understandably high and heavily regulated. However, there can be clinical scenarios in which restraint use can facilitate a patient's freedom. This article considers such a case and examines conditions under which using restraints offers therapeutic benefit for patients with traumatic brain injuries.

Lipid and phase specificity of α-toxin from S. aureus

The pore forming toxin Hla (α-toxin) from Staphylococcus aureus is an important pathogenic factor of the bacterium S. aureus and also a model system for the process of membrane-induced protein oligomerisation and pore formation. It has been shown that binding to lipid membranes at neutral or basic pH requires the presence of a phosphocholine-headgroup. Thus, sphingomyelin and phosphatidylcholine may serve as interaction partners in cellular membranes. Based on earlier studies it has been suggested that rafts of sphingomyelin are particularly efficient in toxin binding. In this study we compared the oligomerisation of Hla on liposomes of various lipid compositions in order to identify the preferred interaction partners and conditions. Hla seems to have an intrinsic preference for sphingomyelin compared to phosphatidylcholine due to a higher probability of oligomerisation of membrane bound monomer. We also can show that increasing the surface density of Hla-binding sites enhances the oligomerisation efficiency. Thus, preferential binding to lipid rafts can be expected in the cellular context. On the other hand, sphingomyelin in the liquid disordered phase is a more favourable binding partner for Hla than sphingomyelin in the liquid ordered phase, which makes the membrane outside of lipid rafts the more preferred region of interaction. Thus, the partitioning of Hla is expected to strongly depend on the exact composition of raft and non-raft domains in the membrane.

Intraspecific variation in the thermal biology of Rabidosa rabida (Araneae: Lycosidae) (Walckenaer) from the mountains of Arkansas

Temperature affects all levels of biological organization and multiple aspects of ecological performance and fitness. Descriptions of thermal biology are, therefore, essential pieces of information for studying ecology in varying thermal environments. This paper describes the thermal biology of the spider Rabidosa rabida by using three common descriptive measures. Spiders were collected from two populations on mountains in Arkansas that share similar climate and vegetation. Maximum sprint speed across temperature was used to calculate an estimate of thermal sensitivity of locomotor ability. Spiders were placed in a thermal gradient to determine thermal preference. Spiders' body temperatures were increased or decreased until the ability to move was lost. Results were compared between the populations to describe intraspecific variation. Maximum sprint speed increased across temperatures showing moderate sensitivity (Q(10 all spiders) = between 1.74 and 2) except at the highest temperatures in males, and the lowest temperatures in both sexes. Maximum sprint speeds differed between populations (P < 0.05). The critical thermal maximum was shown to be 42.9°C ± 0.70. The critical thermal minimum was estimated at 0°C. Thermal preference of R. rabida was determined to be 31.9°C ± 0.44 showing no significant variation between populations. This study provides a first description of thermal biology in an ecologically important spider, and shows evidence of variation between thermal biology measures between populations with similar climate but no gene flow. Having adapted to various and changing conditions in the past, this spider and others like it can provide many ecologically and evolutionarily interesting lines of inquiry.