Body size and trophic level increase with latitude, and decrease in the deep-sea and Antarctica, for marine fish species

The functional traits of species depend both on species' evolutionary characteristics and their local environmental conditions and opportunities. The temperature-size rule (TSR), gill-oxygen limitation theory (GOLT), and temperature constraint hypothesis (TCH) have been proposed to explain the gradients of body size and trophic level of marine species. However, how functional traits vary both with latitude and depth have not been quantified at a global scale for any marine taxon. We compared the latitudinal gradients of trophic level and maximum body size of 5,619 marine fish from modelled species ranges, based on (1) three body size ranges, <30, 30-100, and >100 cm, and (2) four trophic levels, <2.20, 2.20-2.80, 2.81-3.70, >3.70. These were parsed into 5° latitudinal intervals in four depth zones: whole water column, 0-200, 201-1,000, and 1,001-6,000 m. We described the relationship between latitudinal gradients of functional traits and salinity, sea surface and near seabed temperatures, and dissolved oxygen. We found mean body sizes and mean trophic levels of marine fish were smaller and lower in the warmer latitudes, and larger and higher respectively in the high latitudes except for the Southern Ocean (Antarctica). Fish species with trophic levels ≤2.80 were dominant in warmer and absent in colder environments. We attribute these differences in body size and trophic level between polar regions to the greater environmental heterogeneity of the Arctic compared to Antarctica. We suggest that fish species' mean maximum body size declined with depth because of decreased dissolved oxygen. These results support the TSR, GOLT and TCH hypotheses respectively. Thus, at the global scale, temperature and oxygen are primary factors affecting marine fishes' biogeography and biological traits.

Replication of Rift Valley Fever Virus in Amphibian and Reptile-Derived Cell Lines

Rift Valley fever phlebovirus (RVFV) is a zoonotic arthropod-borne virus, which has led to devastating epidemics in African countries and on the Arabian Peninsula. Results of in-vivo, in-vitro and field studies suggested that amphibians and reptiles may play a role as reservoir hosts of RVFV, promoting its maintenance during inter-epidemic periods. To elucidate this hypothesis, we examined two newly established reptile-derived cell lines (Egyptian cobra and Chinese pond turtle) and five previously generated reptile- and amphibian-derived cell lines for their replicative capacity for three low- and high-pathogenic RVFV strains. At different time points after infection, viral loads (TCID₅₀), genome loads and the presence of intracellular viral antigen (immunofluorescence) were assessed. Additionally, the influence of temperatures on the replication was examined. Except for one cell line (read-eared slider), all seven cell lines were infected by all three RVFV strains. Two different terrapin-derived cell lines (Common box turtle, Chinese pond turtle) were highly susceptible. A temperature-dependent replication of RVFV was detected for both amphibian and reptile cells. In conclusion, the results of this study indicate the general permissiveness of amphibian and reptile cell lines to RVFV and propose a potential involvement of terrapins in the virus ecology.

Integrating bioenergetics and conservation biology: thermal sensitivity of digestive performance in Eastern Collared Lizards (Crotaphytus collaris) may affect population persistence

Information on bioenergetics can provide valuable insight into the ecology, life history and population dynamics of organisms. For ectothermic animals, thermal sensitivity of digestion is an important determinant of net assimilated energy budgets. A recent study in the Ozark Mountains indicated that eastern collared lizards (Crotaphytus collaris) restricted to encroached glades (characterized by woody vegetation encroachment) experience reduced environmental heat loads and have reduced age-specific growth and reproductive rates compared to populations in intact glades. To assess the potential impact of reduced body temperatures on assimilation rates of C. collaris in encroached glades, we conducted feeding trials across four temperature treatments (28, 31, 34 and 37°C). We tested for temperature effects on voluntary feeding rates, passage times, apparent assimilated energy (AE) and metabolizable energy (ME). Passage times decreased and voluntary feeding rates increased significantly with increasing temperature. Consumption explained the majority of variance in AE and ME, followed by the effect of temperature treatments. Using data on voluntary feeding rates, passage times and ME as a function of temperature, we estimated over a 10-fold increase in predicted daily assimilated energy across temperature treatments (28°C = 0.58 kJ/day, 31°C = 1.20 kJ/day, 34°C = 4.30 kJ/day, 37°C = 7.95 kJ/day). Thus, lower heat loads in encroached glades may cause reduced body temperature and result in restricted energy assimilation rates. Our study provides a novel approach to the integration of bioenergetics and conservation and shows the efficacy of using information on digestive performance to investigate underlying mechanisms in a conservation context.

Veterinary care of green iguanas (Iguana iguana) part 1: husbandry

The green iguana (Iguana iguana) is a large arboreal lizard with complex environmental requirements, generally making this a poor choice as a companion animal. Husbandry deficiencies are a common contributor to clinical disease, and it is important to be aware of the environmental conditions for this species and relevance of any deficiencies to animal health. This article covers the husbandry of this species. Part 2 will focus on sample collection and common presenting health concerns.

Thermoregulation and habitat selection in wood turtles Glyptemys insculpta: chasing the sun slowly

1. It is widely accepted that reptiles are able to regulate behaviourally their body temperature (T(b)), but this generalization is primarily based on studies of lizards and snakes in the temperate zone. Because the precision of T(b) regulation may vary considerably between taxa and over geographical ranges, studies of semi-terrestrial turtles in climatic extremes are relevant to the understanding of reptilian thermoregulation. 2. We studied thermoregulation in 21 free-ranging wood turtles (Glyptemys insculpta) at the northern limit of their range in Québec, using miniature data loggers to measure their internal T(b) and external temperature (T(ext)) continuously. We simultaneously recorded the available operative environmental temperature (T(e)) using 23 physical models randomly moved within each habitat type, and we located turtles using radiotelemetry. 3. The habitat used by wood turtles was thermally constraining and the target temperature (T(set)) was only achievable by basking during a short 5-h time window on sunny days. Wood turtles did show thermoregulatory abilities, as determined by the difference between turtle T(b) distribution and the null distribution of T(e) that resulted in T(b) closer to T(set). Although most individuals regulated their T(b) between 09.00 h and 16.00 h on sunny days, regulation was imprecise, as indicated by an index of thermoregulation precision (| T(b) - T(set) |). 4. The comparison of habitat use to availability indicated selection of open habitats. The hourly mean shuttling index (| T(ext) - T(b) |) suggested that turtles used sun/shade shuttling from 09.00 to 16.00 h to elevate their T(b) above mean T(e). 5. Based on laboratory respirometry data, turtles increased their metabolic rate by 20-26% over thermoconformity, and thus likely increased their energy gain which is assumed to be constrained by processing rate at climatic extremes.

Scaling the duration of activity relative to body mass results in similar locomotor performance and metabolic costs in lizards

This study examines the physiological response to locomotion in lizards following bouts of activity scaled to body mass. We evaluate this method as a way to compare locomotor energetics among animals of varying body mass. Because most of the costs of brief activity in reptiles are repaid during recovery we focus on the magnitude and duration of the excess post-exercise oxygen consumption (EPOC). Lizards ranging from 3 g to 2400 g were run on a treadmill for durations determined by scaling the run time of each animal to the 1/4 power of body mass and allowing each animal to run at its maximum speed for that duration. This protocol resulted in each species traveling the same number of body lengths and incurring similar factorial increases in V(O(2)). Following activity, EPOC volume (ml O(2)) and the cost of activity per body length traveled (ml O(2) per body length) scaled linearly with body mass. This study shows that the mass-specific costs of activity over an equivalent number of body lengths are similar across a broad range of body mass and does not show the typical patterns of allometric scaling seen when cost of locomotion are expressed on a per meter basis. Under field conditions larger animals are likely to travel greater absolute distances in a given bout of activity than smaller animals but may travel a similar number of body lengths. This study suggests that if locomotor costs are measured on a relative scale (ml O(2) per body length traveled), which reflects these differences in daily movement distances, that locomotor efficiency is similar across a wide range of body mass.

Incubation temperature modifies neonatal thermoregulation in the lizardAnolis carolinensis

The thermal environment experienced during embryonic development can profoundly affect the phenotype, and potentially the fitness, of ectothermic animals. We examined the effect of incubation temperature on the thermal preferences of juveniles in the oviparous lizard, Anolis carolinensis. Temperature preference trials were conducted in a laboratory thermal gradient within 48 hr of hatching and after 22-27 days of maintenance in a common laboratory environment. Incubation temperature had a significant effect on the upper limit of the interquartile range (IQR) of temperatures selected by A. carolinensis within the first 2 days after hatching. Between the first and second trials, the IQR of selected temperatures decreased significantly and both the lower limit of the IQR and the median selected temperature increased significantly. This, along with a significant incubation temperature by time interaction in the upper limit of the IQR, resulted in a pattern of convergence in thermoregulation among treatment groups. The initial differences in selected temperatures, as well as the shift in selected temperatures between first and second trials, demonstrate plasticity in temperature selection. As a previous study failed to find environmentally induced plasticity in temperature selection in adult A. carolinensis, this study suggests that this type of plasticity is exclusive to the period of neonatal development.