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Energy acquisition is of fundamental importance to the survival of any organism. Thus, the morphology, or tools, that an organism uses to capture food can be under intense selective pressure. We studied the prey capture mechanics of the central mudminnow (Umbra limi), a benthic-dwelling fish species with a varied diet. A morphology suited for one specific prey type may not be as well suited for another prey type. Thus, we might expect that mudminnow are more successful at capturing one sort of prey over another. Specifically, we sought to determine if there were any changes in prey capture success and underlying prey capture mechanics when faced with highly elusive prey, live feeder fish (guppies), versus a non-elusive invertebrate larvae (midges of the family Chironomidae), commercially known as “blood worms.” Our results indicated that the more elusive prey caused mudminnow to have a slightly slower but a slightly more extreme premaxillary protrusion and expansion events. However, these differences were so small that they were not significantly different, and likely not biologically significant. These findings suggest that mudminnow do not modulate their prey-capture kinematics in response to these experimental food treatments.
Current dense forests in the Spring Mountains, Nevada, attributed to land management practices including fire exclusion, are considered to provide sub-optimal habitat for the rare endemic Mount Charleston blue butterfly (Plebejus shasta charlestonenesis). To reduce fuel loads in these forests, managers have used various treatments, including tree thinning and mechanical mastication. This study analyzed potential negative and positive effects of deposition of masticated slash (post-tree thinning material such as branches and logs) on host plants within Mount Charleston blue habitat. We manipulated depth of woodchip beds in 1-m2 quadrats at a Pinus ponderosa (ponderosa pine) site and monitored understory vegetation and butterfly host-plant response to the treatments. We also performed a germination experiment on seeds of the butterfly larval host plant Astragalus calycosus var. calycosus (Torrey's milkvetch) by applying various treatments combinations which included shading, liquid smoke, cold stratification and scarification. We found no significant effect (P>0.05) to any of the plant community variables (e.g., species richness, plant cover, and A. c. var. calycosus density, cover, and flowering) from forest-floor treatments during the first reproductive season after treatments. Cover and leaf number of A. c. var. calycosus declined over all treatments, suggesting that the pine tree canopy inhibited butterfly host plants, despite thinning of the pine canopy, or other factors limited the host plant. In the germination experiment, scarification significantly increased germination but all other treatment effects were not significant (P>0.05). The lack of a short-term response of the plant community to forest-floor manipulation is consistent with experiments in other P. ponderosa forests (including longer-term research) and indicates that these treatments did not substantially alter the vegetative characteristics of butterfly habitat. Given the potential detrimental effects of wood chip deposition on butterfly habitats, this small-scale experiment indicates that such effects will not result in short-term changes in Mt. Charleston blue butterfly host plants in wood chips layers less than 5 cm in depth.
Few people today appreciate the contributions of Dr. Charles T. Vorhies, who at one time was Arizona's foremost naturalist and nongame wildlife expert. A man of varied interests and extraordinary talents, Dr. Vorhies not only excelled as a research biologist and ecologist, he published his work in numerous scientific and popular articles. Equally at home in the field or on the campus, Vorhies, notwithstanding his early training in entomology, was the foremost authority on Southwest mammals, birds, reptiles and insects. He was also an ardent conservationist, sharing his knowledge with fellow scientists, bird watchers, and sportsmen so that all might benefit from a more knowledgeable outdoor community. A co-founder with Dr. Walter P. Taylor of the Tucson Natural History Association and Arizona Game Protective Association (AGPA) the forerunner of the Arizona Wildlife Federation, Vorhies was in the words of a colleague, “the Arizona Wildlife Federation in person.”
The molly (Poecilia sphenops) has an unusual feeding mechanism among fishes in that its jaw is essentially “doublejointed”. They possess an extra joint within the lower jaw, or mandible, called an Intramandibular Joint (IMJ). Because of this joint, these fish are capable of opening their mouths to extreme angles. We wanted to understand how this mechanism functions during feeding and if the joint angles could be actively altered by the fish in different feeding situations. We asked specifically if there was a difference in the gape angle (the angle formed by the tip of upper jaw, the jaw joint, and the tip of the lower jaw) and intramandibular joint angle when offered food in the water column versus on the substrate, as well as with different food types in the water column. Feeding events were captured using high-speed video and the resulting footage analyzed using the software Image J. The average gape angle produced during midwater feedings was significantly larger than that produced during benthic feedings. Similarly, the average IMJ angle produced during midwater feedings was significantly larger than that produced during benthic feedings. This suggests that the joint angles are actively modulated in response to different feeding scenarios. Observations of benthic-feeding habits, including number of feeding attempts per hour, were also recorded to understand how often the jaws are experiencing bending at the IMJ. This speaks to the potential for subsequent longer-term deformation of the underlying cartilage and muscle based upon the stress and strain that the cartilage is undergoing daily. When observing benthic-feeding habits, it was found that most feeding, and therefore IMJ bending, occurred at midday and during the last two hours of the day and could exceed over 100 attempts per hour.
Hoxworth Springs are one of several natural spring systems located within the Lake Mary Watershed in northern Arizona. The springs serve as critical water resources and contribute to the overall water budget for Lake Mary. Lake Mary is an artificial reservoir that supplies municipal drinking water for Flagstaff, Arizona, and surrounding communities. This area is therefore important to overall water security in the region and necessitates prioritization of its natural integrity. Springs that feed into the greater Lake Mary watershed form wetlands in the immediate area, which provides wetland habitat in an otherwise arid ecosystem matrix. Wetlands provide numerous benefits and ecosystem services including water purification, increased biodiversity and ecosystem health. However, these important wetlands and spring systems are in danger of disappearing due to increased demand for groundwater and mismanagement of land surrounding these streams. Activities that lead to changes in land use include fire suppression, climate change, and increased grazing along the fragile stream channels. These activities lead to increased risks of bank erosion and other structural stream degradation. To ameliorate the situation, restoration efforts such as stream re-channelization and construction of elk exclosures were implemented to minimize grazing in and around Hoxworth Springs in the late 1990s and early 2000s. This study examined the current state of Hoxworth Springs and assessed the effects of restoration on surface soil aggregate stability, vegetation cover and channel width. We found that restoration efforts significantly improved surface soil aggregate stability and stabilized stream width and water retention structure. Native sedge vegetation cover was indicative of restored areas, indicating that initial efforts to establish this important wetland species were successful. In untreated areas, soil stability was significantly lower, groundwater was absent and stream width was significantly wider. This study concluded that restoration efforts in the Hoxworth Springs system were successful, but further restoration needs be implemented to restore further areas in the watershed.
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