Vol. 21, No. 4 | December 1945

https://digitalcommons.bridgewater.edu/bridgewater_magazine/1363/thumbnail.jp

Predator-Prey Interaction between Largemouth Bass and Bluegills as Influenced by Simulated, Submersed Vegetation

Data from the literature suggest that predatory success declines as habitat complexity increases. To explain this phenomenon, we studied the predator-prey interaction between largemouth bass Micropterus salmoides and bluegills Lepomis macrochirus in four laboratory pools (2.4-3.0 m diameter, 0.7 m deep), each with a different density (0, 50, 250, 1,000 stems/m2) of artificial plant stems. Behavior was quantified for both predator and prey during largemouth bass feeding bouts lasting 60 minutes. Predation success(number of captures) by largemouth bass was similar at 0 and 50 stems/m2, then declined to near zero at 250 and 1,000 stems/m2. As stem density increased, predator activity declined due to a decrease in behaviors associated with visual contact with prey. Reduced predation success by largemouth bass in habitats of increased complexity apparently is related to increases in visual barriers provided by plant stems as well as to adaptive changes in bluegill behavior.This research was supported in part by funds from the Federal Aid in Fish Restoration Act under Dingell-Johnson Project F-57-R, the National Science Foundation (DEB77- 16167), and the Department of Zoology

Ecosystem engineering: beaver and the population structure of Columbia spotted frogs in western Montana

Amish, Stephen J. M.S., Autumn 2006 Wildlife Biology ECOSYSTEM ENGINEERING: BEAVER AND THE POPULATION STRUCTURE OF COLUMBIA SPOTTED FROGS IN WESTERN MONTANA Chairperson: Lisa Eby Beavers (Castor canadensis) are considered ecosystem engineers, altering hydrologic regimes, ecosystem processes, and modifying community structure. Effects of beaver on the spatial pattern of lentic habitat and populations using those habitats have not been examined. I used a landscape database and eight microsatellite markers to compare the scale and pattern of lentic sites, their occupancy, and population structure by Columbia spotted frogs (Rana luteiventris) between watersheds with and without beaver activity. Across all watersheds frog breeding sites were more clustered than the underlying pattern of lentic habitat. Beaver watersheds had four times as many lentic and breeding sites than non-beaver watersheds. Non-beaver watersheds often had only one frog breeding site. Frog breeding sites were more dispersed within beaver drainages. In addition, frog breeding sites were evenly distributed across the elevational gradient in beaver watersheds while they were centered above the watershed midpoint in non-beaver watersheds. Columbia spotted frog breeding sites were more dispersed within drainages with evidence of beaver presence than would be expected given the configuration of the underlying lentic habitat and have persisted despite being separated by distances larger than its dispersal ability. The genetic divergence seen within watersheds revealed that landscape configuration affected the fine scale population structure of Columbia spotted frogs. Landscape patterns of breeding sites were reflected in the presence and strength of isolation by distance equilibriums and the overall level of population subdivision within watersheds. Watersheds with beaver presence and an average distance of less than five kilometers between breeding sites showed higher levels of connectivity than did non-beaver watersheds with an average distance of more than five kilometers between breeding sites. More importantly, short beaver watersheds had lower levels of genetic divergence between breeding sites than those in long non-beaver watersheds separated by the same distance, even when distances were within the commonly observed dispersal ability of the frogs. Typical beaver watersheds in southwestern Montana with similar habitat configurations are likely composed of a single population, while non-beaver watersheds likely contain a single or a few isolated population/s. Careful consideration of potential population effects for species dependent upon habitat beaver create is required

Sporadic Infection of Wolbachia

This study examines the distribution and invasion dynamics of Wolbachia in a recently established Formica fusca population. Preliminary data revealed the intermittent infection of Wolbachia across colonies, providing the opportunity to test for ecological factors affecting the acquisition and spread of the parasite. Only 35% of colonies are infected in this population. Both infected and noninfected nests have similar dispersion patterns that approximate a random distribution, suggesting that transmission of Wolbachia between adjacent colonies is not common. There is no difference in the infection rate between workers and brood, indicating that workers are not actively eliminating the infection. Our results show no significant association between Wolbachia infection and nest size; however, infected colonies tend to be larger than noninfected colonies. Finally, Wolbachia infection was not associated with queen number. Overall, our results suggest no large fitness differences between infected and noninfected colonies, although small fitness effects cannot be ruled out for this population

Montana Kaimin, March 1, 1983

Student newspaper of the University of Montana, Missoula.https://scholarworks.umt.edu/studentnewspaper/8519/thumbnail.jp

Entwicklung von chromatographischen Analyseverfahren zur Bestimmung von Neurotoxinen aus Lebensmitteln mariner Herkunft

Durch das vermehrte Auftreten von Intoxikationen, verursacht durch PSP‐Toxine sowie TTX und seinen Analoga, nimmt die Notwendigkeit für deren analytische Bestimmung zu. Grundlage hierfür bilden internationale Rechtsvorschriften, in denen sowohl für PSP‐Toxine als auch TTXs verbindliche Regelungen in Bezug auf den Welthandel mit „Seafood“ festgeschrieben wurden. Die erhöhte Anzahl an PSP‐Vergiftung wird auf die Zunahme von Massenvermehrungen der Dinoflagellaten und Cyanobakterien (harmful algal blooms, HABs), verursacht durch globale Erwärmung, zurückgeführt, wobei die Intensivierung der Aquakulturen sowie eine Überfischung der Weltmeere u.a. das Ausweichen auf andere Arten und damit auch zu einer Zunahme an Belastungen mit bestimmten Toxinen (TTXs) mit den beschrieben Folgen führt. Sowohl die PSP‐Toxine als auch TTXs weisen verschiedene Strukturvarianten auf, die sich vom Saxitoxin (PSP) und Tetrodotoxin (TTXs) ableiten. Dabei sind die strukturellen Gemeinsamkeiten der beiden Toxinklassen mit ihren Guanidinogruppen Ursache für den ähnlichen Wirkmechanismus der Toxine, die Inhibition der Na+‐Kanäle. Jedoch führen unterschiedlichen Funktionalisierungen innerhalb der beiden Toxingruppen zu unterschiedlichen Toxizitäten (LD50) im Tierversuch