Microplastic contamination in edible marine fishes from the upper Gulf of Thailand.

Seafood consumption is a major source of microplastic exposure for humans. Here, we demonstrated microplastic contamination in marine food fishes from the upper Gulf of Thailand. Microplastics were found in gastrointestinal tracts of 46.9 % of fishes sampled, with a mean concentration of 1.6 ± 0.5 pieces per fish or 0.04 ± 0.01 pieces/g of fish tissue. Demersal fishes had higher contamination rates than pelagic fishes. Fibrous-type and blue-colored materials were the most abundant microplastics, while the most common polymers were polyester and polyethylene. No associations between microplastics and histopathological changes were detected. Estimated daily microplastic exposure for human marine fish consumers was 0.03 to 0.1 pieces per person. Although we expect a low risk of microplastic contamination in fish muscle because of very low calculated transfer rates, we recommend continuing surveillance, including evaluations of contamination in the food chain to ensure future seafood safety in this region.

Predicting Baylisascaris procyonis roundworm prevalence, presence and abundance in raccoons (Procyon lotor) of southwestern Ohio using landscape features.

Raccoon roundworm is a leading cause of a neurological disease known as larva migrans encephalopathy in vertebrates. We determined that roundworm prevalence is significantly lower in Beavercreek Township than other townships surveyed, and that mean patch size and proportion of landscape modified by urbanization or by agriculture are good predictors of roundworm prevalence and abundance in raccoons. The proportion of landscape modified by urbanization was the best predictor of roundworm presence. These data will facilitate predictions regarding roundworm prevalence in areas that have not been previously sampled, and contribute to devising management strategies against the spread of raccoon roundworm.

Investigating the chemical profile of regenerated scorpion (Parabuthus transvaalicus) venom in relation to metabolic cost and toxicity.

We investigated the biochemical profile of regenerated venom of the scorpion Parabuthus transvaalicus in relation to its metabolic cost and toxicity. Using a closed-system respirometer, we compared oxygen consumption between milked and unmilked scorpions to determine the metabolic costs associated with the first 192 h of subsequent venom synthesis. Milked scorpions had a substantially (21%) higher mean metabolic rate than unmilked scorpions, with the largest increases in oxygen consumption occurring at approximately 120 h, 162 h, and 186 h post-milking. Lethality tests in crickets indicated that toxicity of the regenerated venom returned to normal levels within 4 d after milking. However, the chemical profile of the regenerated venom, as evaluated by FPLC and MALDI-TOF mass spectrometry, suggested that regeneration of different venom components was asynchronous. Some peptides regenerated quickly, particularly those associated with the scorpion's "prevenom," whereas others required much or all of this time period for regeneration. This asynchrony could explain the different spikes detected in oxygen consumption of milked scorpions as various peptides and other venom components were resynthesized. These observations confirm the relatively high metabolic cost of venom regeneration and suggest that greater venom complexity can be associated with higher costs of venom production.

The energetic savings of sleep versus temperature in the Desert Iguana (Dipsosaurus dorsalis) at three ecologically relevant temperatures.

One of the proposed ecological functions of sleep is to conserve energy. The majority of studies that support this theory have been done on endothermic animals whose body temperatures drop during sleep due to the reduced neurological control of thermoregulation. In the present study, we examined typical temperatures to which the Desert Iguana, Dipsosaurus dorsalis, is exposed to in the field and found that mean high temperatures ranged from 24-58 degrees C throughout the active portion of the year. We also examined the ecological savings that sleep could provide for this ectothermic iguana using a closed system respirometer. We found that laboratory-acclimated iguanas are able to save significantly more (27.6%) energy by sleeping than by being awake and that field iguanas also had significant savings of energy (69.1%) while asleep. However, iguanas could save more energy by remaining awake at cooler temperatures than by sleeping at warmer temperatures. In addition, we found no correlation for time of night with metabolic rate. Our study supports the hypothesis that one potential function of sleep is to conserve energy.

Cost of venom regeneration in Parabuthus transvaalicus (Arachnida: Buthidae).

Scorpion venom has many components, but is mainly made up of water, salts, small molecules, peptides, and proteins. One can reasonably assume that the production and storage of this complex secretion is an expensive metabolic investment. However, to date, no study has addressed the costs associated with the regeneration of venom by scorpions. Using a closed-system respirometer, we examined the difference in oxygen consumption between milked and unmilked scorpions to determine the metabolic costs associated with the first 72 h of subsequent venom synthesis. During this time period, milked scorpions had a significantly higher (39%) metabolic rate than unmilked scorpions. The regenerated venom from a second milking had significantly lower (74%) protein concentration, suggesting that venom regeneration was incomplete after 72 h. The protein content in the regenerated venom was not correlated with oxygen consumption. The significant increase in oxygen consumption after milking supports existing hypotheses about the metabolic cost associated with venom regeneration and provides further insight on why scorpions appear to be judicious in their stinger use.

Differential tolerance of body fluid dilution in two species of tropical hermit crabs: not due to osmotic/ionic regulation.

The tropical intertidal hermit crabs Clibanarius taeniatus and Clibanarius virescens were examined for differences in survival and physiological responses in low salinity. We found that C. taeniatus survived better in dilute seawater than C. virescens and that these species did not differ in their abilities to regulate haemolymph osmolarity, ionic concentration of the haemolymph or body fluid volume. We also found no difference in oxygen consumption between the species when acutely exposed to a range of temperature and salinity combinations. It is concluded that the greater survival in dilute seawater by C. taeniatus compared to C. virescens is due to a greater tolerance of dilution of body fluids by C. taeniatus. Differences in tolerance to dilute seawater may influence the habitat preferences of these species within the same geographical area.