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Biology

Evaluating  the Pollinating Effectiveness of Native and Non-native Visitors to Eriastrum Sapphirinum

Adam Buchholz; ('12); Jennifer Schmidt ('14); Mentor: Frances Hanzawa

Abstract:  Flowering plant reproductive strategies are the product of millennia of co-evolution between a plant and its pollinators, and any disruption can seriously impair a plant’s fitness. Non-native bees such as honeybees (Apis mellifera), can therefore disturb interactions between native plants and their respective pollinators. Eriastrum sapphirinum (Polemoniaceae) is a pollen-limited native annual wildflower that grows at the Bernard Field Station. Our goal was to evaluate the hypothesis that non-native bees are less efficient pollinators than native bees, and therefore disturb the natural reproductive cycle of E. sapphirinum. We isolated flowers, allowing only a single pollinator to visit each one, and counted the seeds produced by each visit. Our data did not indicate any significant difference in per-visit pollination efficiency between visitors to E. sapphirinum, indicating that pollen limitation is not due to inefficient per-visit pollination by invasive bees. It may, however, be due to very high pollen loads on invasive bees.
Funding Provided by: The Schenck Fund  

Drama in the Nest: Research Gets Up Close and Personal with Xantus’ Murrelet

Jamie Canepa ('14); Neha Savant ('14); Molly Shallman ('13); Mentor: Nina Karnovsky

Abstract:  As an IUCN listed threatened species, Xantus’ Murrelet (Synthliboramphus hypoleucus) remains a poorly studied seabird. Researchers on Santa Barbara Island, where 20% of the S. hypoleucus population breeds, supplied us with video footage from in-nest cameras for analysis. We categorized and recorded all behaviors and events observed during the entire breeding season of one nest. We observed two pairs fighting, indicating competition for nest sites that was likely detrimental, as only one of the nest’s three eggs hatched and fledged successfully. S. hypoleucus is considered to be nocturnal, but we found evidence of crepuscular behavior. Finally, we observed a nine-day non-incubation interval between the laying of the first and second egg, which may explain how the eggs of this highly precocious species hatch at the same time. This study is ongoing, and we hope to build on our findings to provide a more detailed description of this crevice nesting species.
Funding Provided by: Montrose Settlements Program Fund(NS, JC) National Parks Service Grant (NK) Faucett Family Foundation (MS)

Sustaining Anaerobic Metabolism: Respiratory Respones to Declining Oxygen Concentrations in Desert and Tropical Millipedes

Ann Dennis ('13); Mentor: Jonathan Wright

Abstract:  Oxygen consumption (VO2) and carbon dioxide production (VCO2) of the millipede Archispirostreptus gigas were examined in response to declining oxygen concentrations (PO2). The animals were contained in a respirometry chamber and perfused with CO2-free air at 3-15% PO2 levels and ambient air (20.95%). An increase in VCO2 was observed at concentrations less than 10% indicating anaerobic respiration and a defined critical oxygen partial pressure (Pcrit) between 10% and 7% O2. At 3% O2, the millipedes sustained elevated VCO2 for multiple hours and increased blood lactate indicating prolonged anaerobic respiration and a need for lactate buffering. We hypothesized that cuticle carbonate buffers lactate. After an exposure to hypoxia, oxygen debt repayment was seen upon return to normoxia. During the initial hours of normoxia, the depressed RQ demonstrated increased VO2 and decreased VCO2 suggesting a CO2 repayment to rebuild cuticle carbonate, and increased VO2 consistent with the oxidation of anaerobic metabolites.
Funding Provided by: Pomona College SURP  

Oxidized Steroids Impact Photosynthetic Electron Transport in Tobacco

Andrew McKinney ('12); Mentor: David Becker

Abstract removed upon request.

Molting Armadillidium Vulgare Use Water Vapor Absorption (WVA) In The Absence Of Water

John David Nako (’12); Mentor: Jonathan Wright

Abstract:  The purpose of this study was to determine whether the terrestrial isopod Armadillidium vulgare could gain the requisite weight during molt solely by water vapor absorption (WVA), as has been demonstrated in several other species.  To test for the isopod’s ability to undergo WVA, the animals were placed in inverted vials in saturated chambers but no direct access to water or food.  They were subsequently weighed throughout molt and their blood osmolality measured daily.  The findings suggest that these isopods do undergo WVA, as they were able to gain mass and complete their molts in their chambers.  The osmolality experiments suggest that parturial molt females also utilize WVA, but regulate their ions differently than the other molting animals. Studying molting and WVA in these organisms can help us gain further insight into their evolutionary history and how some land isopods were able to make the transition from marine to terrestrial habitats.  
Funding Provided by:  Pomona College SURP

Testing the Prenatal Androgen Theory of Transgender Identity

Emmett Radler ('12) Kristin Raphel ('11) Jennifer Franks ('12) Jennie Sweda (’11); Anna Fiastro ('11 SCR); Joss Greene ('11 SCR); Katie Cettie ('11); Ian Hannigan (’08); Jennie Sweda (’11 SCR) Eli Hamilton (’08); Mentor: Rachel Levin

Abstract removed upon request.  

 

It Takes Two to Tango: An Investigation of Cooperative Nest-Care Behavior in Xantus’s Murrelets

Molly Shallman ('13); Mentor: Nina Karnovsky

Abstract:  The purpose of this study was to investigate the distribution of Xantus’s Murrelet (Synthliboramphus hypoleucus) parental care. In other closely related species, both parents incubate and raise chicks but the male takes on late chick-rearing duties. Xantus’s Murrelets differ in that they have two eggs and chicks are in the nest for only two days before fledging. We hypothesized that females spend less time incubating after laying two energy-intensive eggs, but do not leave permanently before fledging due to the presence of two chicks. We analyzed video from inside a nest—calculating the number of egg-turnings, housekeeping behaviors and incubation lengths. We found no difference in responsibility distribution or nest attendance. Compared to other Alcids, Xantu’s Murrelets are similar in that they share incubation duties, but dissimilar in that the female does not leave the nest before the chicks fledge. Directions for future study include looking at post-fledging parental care.

Funding Provided by: Faucett Family Foundation (MS) Montrose Settlements Restoration Program (NK) 

 

Mutation-Selection Balance in Ciliates

Tim Stutz ('12); Mentor: Andre Cavalcanti

Abstract:  Ciliates are a branch of protozoa that possess remarkable genetic architecture.  Each ciliate has two separate types of nuclei: Macronuclei (MAC) are copied during asexual reproduction and are used for transcription during vegetative growth, while micronuclei (MIC) are transcriptionally silent and are only used during sexual recombination to replace the MAC.  However, the MAC possesses thousands of copies of each gene and is effectively immune to mutation, while the lack of transcription makes the MIC invisible to selection.  Hence this architecture produces a disconnect between the genetic forces of mutation and selection.  We have modeled this phenomenon through the use of ciliate-specific mutation-selection balance equations and through stochastic simulation.  Our results indicate that this architecture results in a decreased ability in ciliates to remove deleterious mutations from a population.

Funding Provided by: National Science Foundation ARRA Grant #MCB920697 (AC)  

 

Identifying Binding Partners of Drosophila Syndecan’s Cytoplasmic Domain

Naomi Wagner ('13); Margaret Nguyen ('10); Mentor: Karl Johnson

Abstract:  Syndecan (Sdc) is a transmembrane heparan sulfate proteoglycan (HSPG) involved in nervous system development, both in the CNS and at the neuromuscular junction (NMJ). Previous studies have shown that Sdc promotes synapse growth at the Drosophila NMJ, whereas Dallylike (Dlp), a GPI-anchored HSPG, has opposing effects. We are interested in studying the cytoplasmic domain of Sdc (SdcCD) in order to better understand its specific function at the NMJ. Past lab students conducted a yeast two-hybrid screen and identified five candidate binding partners for SdcCD: Cora, Ced-12, eIF-4a, GRIP, and DAD. Our goal is to confirm these protein interactions using a GST pulldown, an in vitro binding assay. Thus far, we have conducted GST pulldowns with Cora, Ced-12, and eIF-4a. Our results indicate that Cora and Ced-12 are binding partners of SdcCD, although results for eIF-4a are inconclusive. We plan to conduct more pulldowns and test all five potential interactors.

Funding Provided by: National Science Foundation ARRA Grant #IOS-0841551 (KJ) 

 

Research at Pomona