Biology Projects

Projects are subject to change without notice.

Title: The role of stress on tetrodotoxin production in rough-skinned newts (Taricha granulosa)

Newts of the genus Taricha have tetrodotoxin (TTX) in the glands of their skin, which is used to defend them from predation.  Tetrodotoxin is a small neurotoxin, that is most well known in puffer-fish, but is found in a wide array of other species.  Much is known about TTX in these species, but very little is known about the physiological constraints of TTX production by these species.  Stress has been shown to impact toxin/venom production in other species due to energetic costs, so it seems likely that this will also be the case in newts.  Students will learn to extract and quantify the stress hormone corticosterone in rough-skinned newts.  Further, students will learn to extract and quantify TTX in the tissues of newts.  This project will give students experience with basic lab skills like pipetting, as well as immunoassays, and solid phase extraction as means of quantifying biological chemicals in the lab. 


Title: Legume-rhizobium mutualisms affected by nitrogen-deposition

Anthropogenic nitrogen deposition as a result of increased industrial and agricultural activities is having profound effects on terrestrial ecosystems. Regionally in the San Joaquin Valley, surrounding mountains combined with stagnant airflow and an atmospheric inversion layer tend to concentrate pollution particulates in the valley. This causes species interactions that are dependent on nitrogen, such as the mutually beneficial interaction between legume plants and nitrogen-fixing bacteria, to be susceptible to ecological and evolutionary changes. Our research explores how changes in nitrogen deposition along an elevation gradient affects the interactions between mutualistic legumes and nitrogen-fixing rhizobia bacteria. We will sample both plant and bacteria populations across an elevation gradient to isolate and culture rhizobia bacteria in the lab. These strains will then be used in a greenhouse experiment to determine the effects of these changes on plant populations. Students will learn a mixture and field and laboratory techniques, such as: measuring plant traits and fitness to quantify the costs and benefits of these symbiotic associations; isolating and culturing bacterial strains; and performing DNA sequencing of these isolated strains to identify the rhizobia. This research will provide substantial insight into the potential long-term consequences of nitrogen deposition on species interactions that have been shown in to be keystone mutualists within ecological communities.


Title: Microplastic abundance in ponds and interactions with aquatic macroinvertebrates

 The increase in global plastic production has led to an accumulation of plastic pollution in aquatic ecosystems worldwide. One specific type of plastic debris is microplastic (particles < 0.05 mm) and is a contaminant of emerging concern globally. There is significant concern about the potential effects of microplastic on aquatic organisms since plastic has toxic additives and can become entangled in the digestive tract, irritating animal digestive tissues. Microplastic sources to the environment can come from fragments from large plastic litter, waste water treatment plant effluent, atmospheric deposition, and consumer products with microbeads (i.e., tooth paste, face wash). Recent studies have shown that microplastic is abundant in freshwater ecosystems, but assessments of microplastic sources and biological interactions in freshwaters are lacking. Summer 2019 REVS UP students will investigate microplastic contamination in ponds and the aquatic macroinvertebrate communities. Students will learn how to sample different habitats within ponds (surface, benthic, margins) and for aquatic invertebrates, become familiar with microscopy, learn macroinvertebrate and microplastic identification. Furthermore, students will learn how to work as part of a research team while meeting project goals.


Title: Predatory behavior of a local aggressive mimic, the Pirate Spider Mimetus hesperus**

I study organisms that use a resemblance to attractive stimuli (e.g. food, mates) to lure their prey to where they can be more easily attacked and killed, a form of aggressive mimicry.  This summer’s project extends this work in two ways.  1) We will study the predatory behavior of a local aggressive mimic, the Pirate Spider Mimetus hesperus.  This spider preys on web-weaving spiders, using a vibratory signal to lure their victims from the safety of the center of the web to the periphery, where they are vulnerable to attack.  We will collect spiders and stage predatory interactions in the laboratory, where they will be recorded & analyzed.  2) We will also conduct a pilot experiment using fruit flies (Drosophila sp.) to determine if artificial selection in the laboratory can modify fruit flies’ habitat choices.  This pilot experiment is the first step towards understanding the evolution of prey discrimination when under threat by aggressive mimics. 

**Please note that Pirate Spiders can only be reliably collected at night, so this project will require working on several nights.  The number of nights we will work will depend to some extent on our success in collecting spiders.