Are life-history attributes, morphology, and metabolic rate linked in the African cichlid, Julidochromis ornatus?

Climate warming and hypoxia, two forms of human-induced rapid environmental change (HIREC), hold great potential to negatively affect aquatic ectotherms (e.g., fish) by respectively increasing their metabolic rate and the energy required to acquire oxygen from the water. Such increases in energy demand, in turn, could have fitness consequences by reducing the amount of energy available for growth and reproduction. As a first step towards allowing us to understand how novel forms of HIREC might influence aquatic ectotherms, we sought to quantify linkages among metabolic rate, morphology, and reproductive life history under unstressed conditions in Julidochromis ornatus, which is a small-bodied fish endemic to, but widely distributed within, Lake Tanganyika (East Africa). In a controlled laboratory setting, we used intermittent-flow respirometry to measure the standard metabolic rate of J. ornatus individuals (n=48 breeding pairs, each with a male and female tested individually). We measured several life-history traits, including the mean duration between reproductive events, batch fecundity (mean eggs per brood), and reproductive rate (mean eggs produced per day). We also took morphological measurements, including individual body mass, total length, and volume. Our analyses showed that many of our traits were strongly correlated, with larger individuals having a lower mass-specific metabolic rate, higher batch fecundity, and longer duration between broods than their smaller counterparts. The findings reported herein will provide important baseline information for an impending long-term experiment that will quantify the impact of climate warming and hypoxia on these attributes in J. ornatus.Division of Mathematical and Natural Sciences - College of Arts and Sciences (Mayers Summer Research Scholarship)No embargoAcademic Major: Evolution and Ecolog

Effects of Lipid Extraction on δ13C and δ15N Values and Use of Lipid-Correction Models Across Tissues, Taxa and Trophic Groups

1. Lipid-rich animal tissues have low δ13C values, which can lead to inaccurate ecological inferences. Chemical lipid extraction (LE) or correction models account for this depletion, but the need for LE or correction is tissue- and species-specific. Also, LE can alter δ15N values, increasing labour and costs because bulk samples must be analysed for δ15N values separately. 2. We studied the effects of LE on δ13C and δ15N values in liver, muscle and skin of common bottlenose dolphins Tursiops truncatus and West Indian manatees Trichechus manatus, two ecologically important species that occupy different trophic levels. We fit lipid-correction models to each species. We also performed a meta-analysis to more broadly determine the effects of LE across taxa, tissues and trophic groups (carnivores, omnivores and herbivores) and to fit lipid-correction models to different taxonomic and trophic groups. 3. Lipid extraction increased the δ13C values in dolphin tissues but had little effect on manatee tissues and no effect on the δ15N values in either species. A mass balance lipid-correction model best fit the data from all dolphin tissues, and a linear model best fit data for manatee liver while null models best fit data from manatee muscle and skin. Across 128 terrestrial and aquatic species, the effects of LE varied among tissues and were lower for herbivores compared to carnivores. The best-fitting lipid-correction models varied among tissue, taxa and trophic groups. Finally, the δ15N values from muscle and liver were affected by LE. 4. Our results strengthen the growing body of evidence that the need for LE is tissue- and species-specific, without a reliable C:N ratio predictive threshold. The prediction errors of lipid-correction models generally decreased with taxonomic and trophic specificity. The smaller effects of LE in herbivores may be due to differences in diet composition or the physiology of lipid synthesis in members of this trophic group. These results suggest that researchers should use the most species-, tissue- and trophic group-specific information on LE available and, if not available, perform LE on a subset of samples prior to analysis to determine effects

Respiratory function and mechanics in pinnipeds and cetaceans

Author Posting. © Company of Biologists, 2017. This article is posted here by permission of Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology 220 (2017): 1761-1773, doi:10.1242/jeb.126870.In this Review, we focus on the functional properties of the respiratory system of pinnipeds and cetaceans, and briefly summarize the underlying anatomy; in doing so, we provide an overview of what is currently known about their respiratory physiology and mechanics. While exposure to high pressure is a common challenge among breath-hold divers, there is a large variation in respiratory anatomy, function and capacity between species – how are these traits adapted to allow the animals to withstand the physiological challenges faced during dives? The ultra-deep diving feats of some marine mammals defy our current understanding of respiratory physiology and lung mechanics. These animals cope daily with lung compression, alveolar collapse, transient hyperoxia and extreme hypoxia. By improving our understanding of respiratory physiology under these conditions, we will be better able to define the physiological constraints imposed on these animals, and how these limitations may affect the survival of marine mammals in a changing environment. Many of the respiratory traits to survive exposure to an extreme environment may inspire novel treatments for a variety of respiratory problems in humans.Funding for this project was provided by the Office of Naval Research (ONR YIP Award no. N000141410563).2018-05-1

Updating and validating a currently-used gas dynamics model using parameter estimates for California sea lions (Zalophus californianus)

A thesis Submitted in Partial Fulfillment of the Requirements for the Degree of MASTER of SCIENCE in MARINE BIOLOGY from Texas A&M University-Corpus Christi in Corpus Christi, Texas.Theoretical models are used to predict how breath-hold diving vertebrates manage O2, CO2, and N2 while underwater. One recent gas dynamics model used available lung and tracheal compliance data from various species to predict O2, CO2, and N2¬ tensions in multiple tissues of diving marine mammals. As variation in respiratory compliance significantly affects alveolar compression and pulmonary shunt, the objective of this thesis was to evaluate changes in model output when using species-specific parameters from California sea lions (Zalophus californianus). I explored the effects of lung and dead space compliance on the uptake of N2, O2, and CO2 in various tissues during a series of hypothetical dives. The updated parameters allowed for increased compliance of the lungs and an increased stiffness in the trachea. When comparing updated model output with a model using previous compliance values, there was a large decrease in N2 uptake but little change in O2 and CO2 levels. Therefore, previous models may overestimate N2 tensions and the risk of gas-related disease, such as decompression sickness (DCS), in marine mammals. Using recently-collected empirical arterial and venous PO2 data, I was able to test the model output against species-specific data for the first time. This showed that lung collapse can be altered by changing physiological parameters and that model input parameters may need to vary between dives. The results of this study suggest that previous models using data that is not species-specific may inaccurately predict the risk of gas-related disease in marine mammals. Future research can use physiological parameters from other marine mammal species as they become available to best estimate the risk of DCS in those species.Life SciencesCollege of Science and Engineerin

High-school Student Teams in a National NASA Microgravity Science Competition

The Dropping In a Microgravity Environment or DIME competition for high-school-aged student teams has completed the first year for nationwide eligibility after two regional pilot years. With the expanded geographic participation and increased complexity of experiments, new lessons were learned by the DIME staff. A team participating in DIME will research the field of microgravity, develop a hypothesis, and prepare a proposal for an experiment to be conducted in a NASA microgravity drop tower. A team of NASA scientists and engineers will select the top proposals and then the selected teams will design and build their experiment apparatus. When completed, team representatives will visit NASA Glenn in Cleveland, Ohio to operate their experiment in the 2.2 Second Drop Tower and participate in workshops and center tours. NASA participates in a wide variety of educational activities including competitive events. There are competitive events sponsored by NASA (e.g. NASA Student Involvement Program) and student teams mentored by NASA centers (e.g. For Inspiration and Recognition of Science and Technology Robotics Competition). This participation by NASA in these public forums serves to bring the excitement of aerospace science to students and educators.Researchers from academic institutions, NASA, and industry utilize the 2.2 Second Drop Tower at NASA Glenn Research Center in Cleveland, Ohio for microgravity research. The researcher may be able to complete the suite of experiments in the drop tower but many experiments are precursor experiments for spaceflight experiments. The short turnaround time for an experiment's operations (45 minutes) and ready access to experiment carriers makes the facility amenable for use in a student program. The pilot year for DIME was conducted during the 2000-2001 school year with invitations sent out to Ohio- based schools and organizations. A second pilot year was conducted during the 2001-2002 school year for teams in the six-state region of Illinois, Indiana, Michigan, Minnesota, Ohio, and Wisconsin. The third year for DIME was conducted during the 2002-2003 school year for teams from the fifty United States, the District of Columbia, and Puerto Rico. An annual national DIME program is planned for the foreseeable future. Presented in this paper will be a description of DIME, an overview of the planning and execution of such a program, results from the first three years, and lessons learned from the first national competition

NASA Microgravity Science Competition for High-school-aged Student Teams

NASA participates in a wide variety of educational activities including competitive events. There are competitive events sponsored by NASA and student teams which are mentored by NASA centers. This participation by NASA in public forums serves to bring the excitement of aerospace science to students and educators. A new competition for highschool-aged student teams involving projects in microgravity has completed two pilot years and will have national eligibility for teams during the 2002-2003 school year. A team participating in the Dropping In a Microgravity Environment will research the field of microgravity, develop a hypothesis, and prepare a proposal for an experiment to be conducted in a microgravity drop tower facility. A team of NASA scientists and engineers will select the top proposals and those teams will then design and build their experiment apparatus. When the experiment apparatus are completed, team representatives will visit NASA Glenn in Cleveland, Ohio for operation of their facility and participate in workshops and center tours. Presented in this paper will be a description of DIME, an overview of the planning and execution of such a program, results from the first two pilot years, and a status of the first national competition