Locally abundant, endangered Mariana swiftlets impact the abundance, behavior, and body condition of an invasive predator.

Invasive predators are known to have negative consumptive and non-consumptive effects on native species, but few examples show how the abundance of native prey may influence an established invasive predator. We compared invasive brown treesnakes (Boiga irregularis; BTS) found in caves occupied by endangered Mariana swiftlets (Aerodramus bartschi) to snakes found in nearby forests and caves without birds to quantify how the abundance of native avian prey impacts BTS abundance and behavior on Guam. From 2011 to 2017 we removed 151 BTS in caves occupied by swiftlets and never observed BTS in caves without birds. Notable locations included snakes foraging near swiftlets and in holes that allowed cave access and escape from capture. Of 43 BTS with gut contents, 27 (63%) contained swiftlets. BTS in swiftlet-occupied caves had greater fat mass compared to forests, indicating access to swiftlets may increase body condition and promote reproduction. Number of ovarian follicles was significantly greater in female snakes from swiftlet-occupied caves compared to those from ravine, but not limestone forests; evidence of male BTS being more capable of reproduction was limited (i.e., fewer non-discernible but not significantly larger testes in snakes from caves). Assuming other limiting factors are considered, altering the functional response of predators through the modification of caves or interdiction lures to exclude or hinder the largest BTS could bolster swiftlet populations by increasing nesting refugia in currently-occupied caves and facilitate recolonization of historical caves.

Volatile anesthetics activate the human tandem pore domain baseline K+ channel KCNK5.

BACKGROUND: Previous studies have identified a volatile anesthetic-induced increase in baseline potassium permeability and concomitant neuronal inhibition. The emerging family of tandem pore domain potassium channels seems to function as baseline potassium channels in vivo. Therefore, we studied the effects of clinically used volatile anesthetics on a recently described member of this family. METHODS: A cDNA clone containing the coding sequence of KCNK5 was isolated from a human brain library. Expression of KCNK5 in the central nervous system was determined by Northern blot analysis and reverse-transcription polymerase chain reaction. Functional expression of the channel was achieved by injection of cRNA into Xenopus laevis oocytes. RESULTS: Expression of KCNK5 was detected in cerebral cortex, medulla, and spinal cord. When heterologously expressed in Xenopus oocytes, KCNK5 currents exhibited delayed activation, outward rectification, proton sensitivity, and modulation by protein kinase C. Clinical concentrations of volatile general anesthetics potentiated KCNK5 currents by 8-30%. CONCLUSION: Human KCNK5 is a tandem pore domain potassium channel exhibiting delayed activation and sensitivity to volatile anesthetics and may therefore have a role in suppressing cellular excitability during general anesthesia.

TWIK-2, a new weak inward rectifying member of the tandem pore domain potassium channel family.

Potassium channels are found in all mammalian cell types, and they perform many distinct functions in both excitable and non-excitable cells. These functions are subserved by several different families of potassium channels distinguishable by primary sequence features as well as by physiological characteristics. Of these families, the tandem pore domain potassium channels are a new and distinct class, primarily distinguished by the presence of two pore-forming domains within a single polypeptide chain. We have cloned a new member of this family, TWIK-2, from a human brain cDNA library. Primary sequence analysis of TWIK-2 shows that it is most closely related to TWIK-1, especially in the pore-forming domains. Northern blot analysis reveals the expression of TWIK-2 in all human tissues assayed except skeletal muscle. Human TWIK-2 expressed heterologously in Xenopus oocytes is a non-inactivating weak inward rectifier with channel properties similar to TWIK-1. Pharmacologically, TWIK-2 channels are distinct from TWIK-1 channels in their response to quinidine, quinine, and barium. TWIK-2 is inhibited by intracellular, but not extracellular, acidification. This new clone reveals the existence of a subfamily in the tandem pore domain potassium channel family with weak inward rectification properties.