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2012 Research Showcase
EBE Abstracts
Abstract Title : Comparison of the embryonic cell lineage of C. briggsae x C. sp 9 hybrids to the parental C. briggsae lineage
Abstract : Caenorhabditis briggsae and Caenorhabditis species 9 are unique among Caenorhabditis species because a significant number of their hybrid offspring survive embryogenesis. By comparing the embryonic cell lineages of their hybrids to that of the C. briggsae parental strain we will characterize the differences between the developmental systems of C. briggsae and C. sp 9 and determine which parts of development are most sensitive to incompatibilities between the parents. We used worms with fluorescent nuclei and used fluorescence microscopy to take time courses of developing embryos from the 4-cell stage through the 350-cell stage and are anlyzing them using the programs StarryNite, AceTree, and Matlab. We expect to see characteristic defects in cell movements and in the timing of cell divisions and migrations in the dying embryos and are keenly interested in seeing whether the surviving embryos echo these patterns but still survive. In this poster, I will present data from 1 dying hybrid, 2 surviving hybrids, and 2 C. briggsae embryos.
Abstract Title : The effects of various precipitation patterns on the rates of nutrient mineralization within a chaparral ecosystem.
Abstract : The UCSD Elliot Chaparral Reserve contains a variety of native and invasive plant species. By manipulating the rainfall regime of 30 plots we will be able to model how climate change will affect the local plant species. One such aspect that can be monitored is the rates of nutrient mineralization. Nutrient mineralization is the process that converts organic compounds into inorganic compounds, such as ammonium, that can to be used by plants. This is an important step within nutrient cycling that has a direct effect on an ecosystem's prosperity. By comparing the amount of ammonium in the different plots before and after being exposed to different rainfall patterns we can make predictions as to how climate change may affect the success of the local chaparral ecosystems.
Abstract Title : Mud versus sand: Morphological and behavioral comparison of two species of burrowing orbiniid polychaetes
Abstract : Both morphological and mechanical constraints affect how organisms interact with their environments and consequently their distributions and functional roles. For burrowing animals, the mechanical responses of muddy sediments, elastic materials through which worms burrow by fracture, differ substantially from those of sands, non-cohesive granular materials. We focused on two closely related burrowing orbiniid polychaetes with divergent morphological features to address how morphological and environmental differences affect burrowing behaviors. Naineris dendritica lives in sand, has larger parapodia, and a shovel-shaped head, while Leitoscoloplos pugettensis lives in muddy sediments, has smaller parapodia, and a narrow pointed head. To relate morphological differences to the environments they inhabit, burrowing kinematics were analyzed in transparent analogs for mud and sand: gelatin and cryolite, respectively. Both species slipped backward following each cycle of forward movement but this slip was greater for L. pugettensis compared to N. dendritica. The head of N. dendritica widens following forward movement, and friction around this increased surface area may reduce slipping. Both species twist during peristalsis, further increasing the body thickness, but this is more pronounced and regular in L. pugettensis. Twisting increases the dorso-ventral forces applied to burrow walls, thus facilitating crack propagation in mud, while large parapodia and head widening reduce backward slipping, which in sand could result in collapse of the burrow. These divergent burrowing behaviors along with small morphological differences are consistent with the mechanical constraints on burrowing in the environments that these two species inhabit.
Abstract Title : The effect of long-term parthenogenesis on Drosophila Mercatorum
Abstract : Parthenogenesis is a type of asexual reproduction in which an unfertilized egg can become a viable offspring without being fertilized. Purely parthenogenetic strains of D. mercatorum were established by Templeton (1975) and have been kept in the Drosophila Species Stock Center at University of California San Diego for nearly four decades. These strains have been completely isolated from male flies and have never produced any male progeny. Long term effects of asexual reproduction in Drosophila have never been studied, nor has the basic reproductive biology of D. mercatorum. The existing parthenogenetic strains provide an excellent opportunity to study the some of the aspects of reproduction in parthenogenetic D. mercatorum and allow comparison with the sexual strains.
Abstract Title : Effects of Algal Diversity on Biomass Yield, Grazing Resistance, and Resource Use Efficiency
Abstract : Algae biofuel represents an attractive option to satisfy growing demands for economically viable renewable energy. Commercialization of algae biofuel faces the need to intensify production while minimizing losses to pests. One approach to increasing biofuel yields and reducing consumption is to co-culture multiple algal species. Polycultures may be more efficient than monoculture at capturing and utilizing resources in the environment. They may also may boost biomass and lipids while resisting grazers. We crossed 10 species of algae with zooplankton presence to investigate the benefits of algal diversity in the production of algal biofuel. In this experiment, we found evidence that high algal diversity may provide protection from zooplankton grazing but does not increase yield above that of the most productive single species in the absence of consumers.
Abstract Title : Three New Species of Triplefin Blennies from the Tropical Eastern Pacific
Abstract : The triplefin blennies are cryptic, bottom-dwelling fishes with three dorsal fins that are found worldwide. Three new species of the genus Enneanectes (Teleostei; Tripterygiidae) are described from the Baja California and the Pacific coast of Mexico. These species were identified as distinct from other members of the genus in 1959 using morphological data; however, the species descriptions were never published. Additional morphological analysis including specimens from the Marine Vertebrate Collection (SIO) confirms that two of the three species are easily distinguishable from congeners. Species A is found from the southeastern Gulf of California to southern Mexico, and is distinguishable by brown reticulations outlining scales and 15 pectoral fin rays (with lower 7 unbranched). Species C (common name: chacala blenny) is more elongate and has higher meristic counts in all characters measured than other members of Enneanectes. Its range has been extended through Southern Mexico. Species B was identified as endemic to the Revillagigedos Islands, though its classification as a distinct species is pending molecular analysis. The phylogenetic relationships of the Tripterygiidae of the Tropical Eastern Pacific are poorly resolved. A continuation of this project will attempt to construct a phylogeny of the Tripterygiidae of the Tropical Eastern Pacific using sequence data from the following genes: CO1, Rhodopsin, Cytochrome b, 16S, 12S and 18S. Taxon sampling will cover twelve species from four genera, including those formally described by this project.
Advisor : DR. JAMES NIEH
Abstract Title : The relationship between nectar guides and foraging speed in Bombus impatiens
Abstract : Nectar guides are ubiquitous aspects of flower design, but their function has not been experimentally demonstrated. We presented bumblebees (Bombus impatiens) with two contrasting flower models: one on which nectar guides directed bees to a source of sugar, and one on which the guides misdirected bees. Although not statistically significant (t17 = 1.59, p = 0.13), we found that bees? handling time on congruent-guide flowers is less than that on misdirecting-guide flowers. Future experiments will expand the dataset, as well as identify whether bumblebees use other cues to identify a reward, such as odor.