Session 5: ASIH Stoye Physiology & Physiological EcologyRoom: Room 206C2022-07-28 13:30 - 15:00 |
| Moderator: Emily Taylor |
|
1. 13:30 Thermal response of circulating estrogens in an emydid turtle, Chrysemys picta, and the challenges of climate change. Nicholas Topping*, Iowa State University; Nicole Valenzuela, Iowa State University topping@iastate.edu
Maternal hormones such as estrogen deposited into the yolks of turtle eggs follow circulating levels in adult females and may alter the sexual fate of developing embryos in species with temperature-dependent sex determination (TSD). In temperate regions, much of this deposition occurs during the Spring breeding season when estrogen levels increase in adult females, presumably triggered by increasing ambient temperatures, affecting their basking behavior and foraging success. Further, estrogens rapidly decrease after oviposition of the first clutch, and a second peak of circulating estrogens is observed later in the Summer/Fall. Importantly, global warming alters turtle nesting phenology as higher temperatures induce earlier nesting, but whether it may also affect hormonal levels (such as circulating estrogen) or whether females are buffered from such effects remains unknown. This gap hinders our understanding of the full spectrum of challenges posed by climate change and the adaptive potential (or lack thereof) of turtle populations. Here we test the hypothesis that temperature alters circulating estrogen levels in adult female painted turtles. For this, we exposed wild-caught females to 26?C and 21?C in captivity for two months (15 females per treatment) and sampled blood at 0, 2, 7, 14, 28, and 56 days. Estrone and 17-B Estradiol levels were quantified via mass spectrometry. We discuss our findings and their implications for underappreciated potential indirect effects of environmental change in altering sex ratios that may result in an accelerated decline of TSD turtle populations. |
|
2. 13:45 Influence of Temperature on Passage Rate and Metabolizable Energy Intake In Sceloporus consobrinus, With Comparison to a Congener. Allison Litmer*, University of Arkansas; Steven Beaupre, University of Arkansas arlitmer@uark.edu
Variation in energy acquisition, genetics, and environment determine life history traits among individuals, populations, and species. Therefore, influence of climate change may differ by population or even individual. Sceloporus lizards are used as model organisms for thermal biology, and climate modeling. However, it is often assumed that locally-measured thermal and bioenergetic responses apply among broadly similar species, and throughout intraspecific geographic range. The objectives of this project were to quantify the influence of temperature on passage rate and metabolizable energy intake (MEI) in Sceloporus consobrinus from Arkansas, and make comparisons between S. consobrinus, and published data on S. undulatus. Sceloporus consobrinus were assigned to a temperature treatment (30°C, 33°C, or 36°C) and fed crickets ad libitum. Passage rate was assessed by feeding lizards a cricket with a fluorescent marker, and checking feces every 2-4 hours for the marker. Consumption was measured and feces and urates were collected and analyzed with bomb calorimetry to measure MEI. Comparisons of S. consobrinus were made to two S. undulatus populations (NJ and SC) reported in the literature from a study using similar methodology. Results suggest that passage rate is similar among populations, with S. consobrinusbeingslower at 30°C and faster at 33°C and 36°C. Data are currently being analzyed on MEI. While the three populations are comparable in passage rate, MEI may vary. Such data are important for understanding the role of environmental factors and organismal properties, as well as variation among species, when determining response to climate change. |
|
3. 14:00 Cutaneous Evaporative Water Loss in Lizards Changes Immediately with Temperature. Calvin Davis*, California Polytechnic State University; Savannah Weaver, California Polytechnic State University; Emily Taylor, California Polytechnic State University caldavis8@gmail.com
Cutaneous evaporative water loss (CEWL) is one of the primary ways reptiles lose water to their environment. As an adaptive and plastic trait, CEWL is an important area of study as climate change presents new challenges to reptiles' ability to osmoregulate. Lipids are one of the primary barriers to CEWL in snakes and lizards. Given that lipid membrane permeability to water is directly related to temperature, we studied CEWL plasticity in response to acute change in temperature in Western Fence Lizards (Sceloporus occidentalis). To test this, we either cooled or heated lizards to certain body temperatures, and then we warmed up the cold lizards and cooled down the hot lizards while continuously recording CEWL for 15 minutes using a handheld evaporimeter. We found that CEWL was positively related to temperature and is capable of instantaneous change on a second to minute basis. This suggests that the permeability of dermal lipids to water increased or decreased immediately, as a direct effect of the change in temperature. However, at the same body temperature, CEWL for cooling lizards was approximately half CEWL for heating lizards, which indicates that the biophysical properties of lipid membranes are not the only internal physiological mechanisms that may affect acute change in CEWL. These results demonstrate that CEWL is a plastic trait capable of immediate change in response to temperature, which could either help or harm organisms as global temperatures continue to rise. |
|
4. 14:15 Mortality and Metabolic Rate of Larval California Grunion (Leuresthes tenuis) under a Future Climate Change Scenario. Emma Siegfried*, California State University-Long Beach; Darren Johnson, California State University-Long Beach siegfried.emma@gmail.com
Studies investigating the effects of ocean acidification (OA) on larval fish mortality have shown mixed results, suggesting that there is more to the story. To investigate the combined effects of food availability and OA on larval mortality and metabolic rate, larval California Grunion (Leuresthes tenuis) were raised under two pCO2 concentrations (OA: 980 µatm; Ambient: 385 µatm) representing current day and projected scenarios for the study area by the year 2100. These pCO2 levels were crossed with two feeding treatments (80 & 160 Artemia spp. nauplii/individual/day). Mortality data was collected by counting the number of dead larvae daily, and metabolic rates were measured as oxygen consumption over a 20-minute period. Each was analyzed using a linear mixed effects model. For both responses, the interaction between pCO2 concentration and low feeding level had a significant effect (Mortality: p=0.0326, Metabolic Rate: p=0.0097), where metabolic rate was depressed and mortality rates were elevated only under a combination of low food and high pCO2. The synergistic interaction of our two treatments for both mortality and metabolic rate is important to consider as food web dynamics shift in our changing oceans. If larval grunion mortality increases, this could have major implications throughout the trophic web, as adult grunion are an important forage fish species in coastal California ecosystems. |
|
5. 14:30 Food for thought: The effects of feeding on the creation of neurons in the python brain. Hannah Bow*, California Polytechnic State University; Carly Markowski, California Polytechnic State University; Christy Strand, California Polytechnic State University hbow@calpoly.edu
Pythons are a well-studied model of postprandial physiological plasticity. Consuming a meal has been shown by past work to evoke a suite of physiological changes in pythons, including dramatic shifts in stomach pH and intestinal enzyme activity; a five-fold increase in the length of intestinal microvilli; and mass increases of 40% in the heart, 94% in the pancreas, 106% in the liver, and 72% in the kidneys. This systemic upregulation elicits one of the largest documented surges in post-feeding metabolic rates among animals. However, little is known about how this plasticity manifests in the brains of ball pythons, Python regius. Previous work using the cell-birth marker 5-bromo-12’-deoxyuridine (BrdU) has shown that cell proliferation in the python brain increases six days following meal consumption. This study aims to confirm these findings and build on them in the long term by tracking the survival and maturation of these newly created cells across a two-month period. We investigate whether these cells differentiate into neurons using double-immunofluorescence for BrdU and a reptile-specific neuronal marker (Fox-3). This work gives insight into the functional and evolutionary role of neurogenesis in the brain. |
|
6. 14:45 How do garter snakes (Thamnophis) overcome one of the most lethal poisons in the world? Investigating Tetrodotoxin (TTX) sequestration. Kelly Robinson*, University of Nevada Reno; Haley Moniz, University of Nevada Reno; Amber Stokes, California State University Bakersfield; Chris Feldman, University of Nevada Reno kellyrobinson4788@gmail.com
Coevolutionary systems are ideal for studying adaptations because reciprocal selection between interacting partners can lead to arms-races of escalating adaptation and counter adaptation. Pacific newts (Taricha) employ tetrodotoxin (TTX) as a powerful ant-predator defense. Despite this nearly impenetrable chemical defense, garter snakes (Thamnophis) from several populations in western North America prey on newts. These TTX-resistant snakes possess mutant sodium channels, which reduces the ability of TTX to bind to these proteins. However, modified sodium channels are not the whole story—allelic variation in sodium channels genes cannot explain all the variance in TTX resistance. Thus, other mechanisms must contribute to whole animal TTX resistance. We hypothesize that Thamnophis employ an additional physiological mechanism of resistance: TTX sequestration. We test this hypothesis by examining differences in TTX sequestration between TTX-resistant and TTX-sensitive snakes from three species (T. sirtalis, T. couchii, T. atratus) and in contrast to two outgroup species (T. elegans and Pituophis catenifter). Specifically, we quantified the concentrations and retention rates of TTX in various tissues (heart, liver, kidney, muscle) across three time points (24 hrs, 72 hrs, 9 days) following exposure to TTX. We predict that TTX-resistant populations will clear TTX quickly from sensitive tissues (e.g., muscle). Conversely, TTX-resistant populations might also retain TTX in robust tissues (e.g. liver) for longer periods than TTX-sensitive snakes, where the poison might serve as a potential defense for resistant snakes. |