Massive Consumption of Gelatinous Plankton by Mediterranean Apex Predators

Stable isotopes of carbon and nitrogen were used to test the hypothesis that stomach content analysis has systematically overlooked the consumption of gelatinous zooplankton by pelagic mesopredators and apex predators. The results strongly supported a major role of gelatinous plankton in the diet of bluefin tuna (Thunnus thynnus), little tunny (Euthynnus alletteratus), spearfish (Tetrapturus belone) and swordfish (Xiphias gladius). Loggerhead sea turtles (Caretta caretta) in the oceanic stage and ocean sunfish (Mola mola) also primarily relied on gelatinous zooplankton. In contrast, stable isotope ratios ruled out any relevant consumption of gelatinous plankton by bluefish (Pomatomus saltatrix), blue shark (Prionace glauca), leerfish (Lichia amia), bonito (Sarda sarda), striped dolphin (Stenella caerueloalba) and loggerhead sea turtles (Caretta caretta) in the neritic stage, all of which primarily relied on fish and squid. Fin whales (Balaenoptera physalus) were confirmed as crustacean consumers. The ratios of stable isotopes in albacore (Thunnus alalunga), amberjack (Seriola dumerili), blue butterfish (Stromaeus fiatola), bullet tuna (Auxis rochei), dolphinfish (Coryphaena hyppurus), horse mackerel (Trachurus trachurus), mackerel (Scomber scombrus) and pompano (Trachinotus ovatus) were consistent with mixed diets revealed by stomach content analysis, including nekton and crustaceans, but the consumption of gelatinous plankton could not be ruled out completely. In conclusion, the jellyvorous guild in the Mediterranean integrates two specialists (ocean sunfish and loggerhead sea turtles in the oceanic stage) and several opportunists (bluefin tuna, little tunny, spearfish, swordfish and, perhaps, blue butterfish), most of them with shrinking populations due to overfishing

Estradiol modulates effort-based decision making in female rats

Disorders of the dopamine system, such as schizophrenia or stimulant addiction, are associated with impairments in different forms of cost/benefit decision-making. The neural circuitry (i.e. amygdala, prefrontal cortex, nucleus accumbens) underlying these functions all receive dopamine input, which is thought to play a central role in mediating cost/benefit decisions. Estradiol modulates dopamine activity, and estrogen receptors (ERs) are found within this neurocircuitry, suggesting that decision-making may be influenced by estradiol. The present study examined the contribution of estradiol and selective ERα and β agonists on cost/benefit decision-making in adult female Long-Evans rats. An effort-discounting task was utilized, where rats could either emit a single response on a low-reward lever to receive two pellets, or make 2, 5, 10, or 20 responses on a high-reward lever to obtain four pellets. Ovariectomy increased choice on the high-reward lever, while replacement with high (10 μg), but not low (0.3 μg), levels of estradiol benzoate reduced choice on the high-reward lever. Interestingly, both an ERα agonist (PPT) and an ERβ agonist (DPN) increased choice on the high-reward lever when administered independently, but when these two agonists were combined, a decrease in choice for the high-reward lever was observed. The effects of estradiol, PPT, and DPN were more pronounced 24 hr post-administration, suggesting that these effects may be genomic in nature. Together, these results demonstrate that estradiol modulates cost/benefit decision making in females, whereby concomitant activation of ERα and β receptors shifts decision criteria and reduces preference for larger, yet more costly rewards.Arts, Faculty ofPsychology, Department ofNon UBCUnreviewedFacultyResearche