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SICB 2017: Are Anoles Less Stable When Running Without Using Claws?

Photo courtesy of Catalina Mantilla

Photo courtesy of Catalina Mantilla

This post was written by Brittney Ivanov, research technician in Michele Johnson’s lab at Trinity University.

Catalina Mantilla, a Ph.D. candidate at Florida International University working with Tonia Hsieh of Temple University, is interested in how anoles use their toepads and claws when they run. For most animals, movement on vertical perches such as tree trunks or buildings usually requires specialized morphologies to adhere to these substrates. While many species have evolved adaptations for moving through complex arboreal habits (e.g., prehensile tails or feet, sticky pads, spines), anoles evolved enlarged toepads and distinct claws, presumably to allow for better adhesion. The morphologies of these specialized structures can greatly impact performance; for example, greater toepad area is associated with greater clinging ability. Catalina wanted to better understand how toepads and claws work together to enhance running performance.

Catalina collected 17 males from four Anolis species (A. carolinensis, A. sagrei, A. cristatellus, and A. distichus). Each male was tested in four different running courses to test performance at difference inclines and on different substrates. Two of the courses were positioned at a 45° incline and two at a flat (0°) incline. Plexiglass covered one course at each incline to allow the use of toepads and eliminate the use of claws. Nylon mesh covered the other course at each incline to test the use of both toepads and claws. Performance was evaluated using mean relative sprint speed, relative stride length, and stride frequency.

Catalina found, unexpectedly, that when the lizards ran on the level plexiglass, they ran slower, took shorter strides, and increased their stride frequency compared to when they ran on the inclines. These results suggest that anoles are less stable when they can’t use their claws! in addition, these data support the idea that the combination of toepads and claws is important for their running performance. In the future, Catalina hopes to increase the number of species in this study to determine the effect of ecomorph on claw and toepad interactions during running, and to evaluate limb function changes when running across different inclines.

SICB 2017: How Anoles Climb Trees: Ecomorph Differences in Neuromuscular Function

Kathleen Foster presents her work to a packed room at SICB.

Kathleen Foster presents her work to a packed room at SICB.

Regular readers of AA will be familiar with the differences in microhabitat use that define the Anolis ecomorphs, but do species with such distinct structural habitats move differently on their specialized perches? In other words, does muscle function differ between the ecomorphs? In the very last session at this year’s SICB, Kathleen Foster, currently a postdoctoral researcher at the University of Ottawa studying the biomechanics of fish locomotion (come back to anoles, Kathleen!), presented a portion of her graduate work in Tim Higham’s lab at the University of California, Riverside, to address this question. She used high speed video to film five species of anoles running on broad and narrow perches at two angled inclines, combined with electromyography to record fore- and hindlimb muscle activity during running.

Photo courtesy of Kathleen Foster.

Photo courtesy of Kathleen Foster.

Kathleen found that all five species had greater motor unit recruitment on steeper inclines than on horizontal perches, and that muscle activity is shorter but begins more abruptly on inclines. Further, recruitment of the gastrocnemius (a “calf” muscle) was greater on broad perches, because the way lizards sit on narrow perches limits the function of this muscle. If you’ve seen how anoles position their feet on both sides of narrow perches, it’s easy to understand how this posture prevents effective propulsion by ankle extension. Kathleen also found several intriguing differences that distinguish trunk-ground species’ muscle function from trunk-crown and crown-giant species. The activity of the caudofemoralis (a limb retractor muscle in the hindlimb) changes more in trunk-ground species as a function of incline, and trunk-ground species use the biceps and gastrocnemius more in the early stance phase of propulsion than trunk-crown species.

Overall, these data help us understand how specialization in neuromuscular function can allow different anole species to successfully move through their varying habitats, and offer insight into how behavioral differences depend on the muscles that underlie them.

SICB 2017: Thermal Ecology and Invasion Biology: Anolis cristatellus Invades Dominica

Jeanel Georges with her poster at SICB.

Jeanel Georges with her poster at SICB.

The beautiful island of Dominica used to be home to only one anole (Anolis oculatus), but about 20 years ago, the Puerto Rican crested anole (Anolis cristatellus) showed up. Jeanel Georges, a graduate student in Matt Watson’s lab at Midwestern State University in Wichita Falls, Texas who is originally from Dominica, noticed that while A. oculatus occurs in all the ecological zones of the island, A. cristatellus is absent from the cooler, wetter uplands. With an international group of collaborators, Jeanel examined the thermal habitat use, sprint speed, and bite force of both species to determine what may limit the spread of A. cristatellus across the island.

At a lowland site where the two species co-occur, both species had higher body temperatures that the operative temperatures randomly available in the environment. In the much cooler upland site, A. oculatus had much higher body temperatures than the operative models, but these body temperatures were cooler than that species experiences in the lowland site. Jeanel also found that the two species had stronger bite forces and higher sprint speeds in the lowland site than A. oculatus had in the upland site. These data suggest that A. cristatellus and A. oculatus are partitioning the thermal environment of Dominica, and as climate change alters the temperatures available to lizards on the island, the interactions between these two species may change.

SICB 2017: It’s Getting Hot in Here: How Brown Anoles Respond to Extreme Heat in Greenhouses

Austin Hulbert with his poster at SICB 2017.

Austin Hulbert with his poster at SICB 2017.

This post was written by Brittney Ivanov, research technician in Michele Johnson’s lab at Trinity University.

Austin Hulbert, an undergraduate in Dan Warner’s lab at Auburn University, presented a poster on the behavior of brown anoles (Anolis sagrei) in a novel environment: a few very hot greenhouses in Auburn, Alabama. Brown anoles are an invasive species, most notably in Florida, but some populations have been found farther north in states including Louisiana, Alabama, Mississippi, and Georgia. As ectotherms migrate to higher latitudes, they often have to deal with different thermal environments and must alter their behaviors accordingly. Austin was interested in determining the activity patterns of a population of brown anoles inhabiting a group of greenhouses in Alabama.

During the summer he found that temperatures inside the greenhouses were consistently higher than those outside. Temperatures drastically increased each morning, up to peak temperatures between 11am and 3pm (on average, 45°C inside the greenhouse and 37°C outside). In the evenings, the temperatures again cooled. Austin surveyed the greenhouses and the surrounding areas for anoles during the morning, peak, and evening hours and determined the type of substrate each individual was using (i.e. brick or concrete, ground, metal, or wood). On average, brown anoles were more abundant inside the greenhouses than outside during the morning and peak times. He also found that more of the brown anoles perched on wooden substrate in the morning and evening. During peak hours more lizards perched on the ground. Because temperatures are often cooler closer to the ground, the lizards may be altering their behavior to deal with the extreme heat in the greenhouses during the hottest part of the day. While the visual survey focused on lizards perched in the open areas visible to the surveyor, there may have been individuals hiding under undisturbed objects as a means to keep cool during peak hours. In the future, Austin would like to compare the thermal tolerance of this group of brown anoles to those of populations in Florida to determine if inhabiting these greenhouses has resulted in adaptions to tolerate their more extreme temperatures.

SICB 2017: Is Maternal Stress Transferred to Offspring?

Jerry Husak presenting at SICB 2017.

Jerry Husak presenting at SICB 2017.

This post was co-written by Maria Jaramillo, an undergraduate in Michele Johnson’s lab at Trinity University.

A mother’s experience during gravidity may alter her offspring’s development, particularly through altering hormone levels in the yolk of her eggs. Stress hormones such as corticosterone (CORT) alter various aspects of offspring phenotype following in ovo exposure, and physical exercise elevates CORT in many vertebrates. In the work he presented at SICB, Jerry Husak and colleagues used exercise and food restriction to manipulate female Anolis carolinensis CORT, and to then determine whether the increased CORT was transferred to the females’ egg yolks.

Jerry assigned females to one of four treatments with different combinations of exercise and food restriction: 1) no exercise, regular diet; 2) no exercise, restricted diet; 3) exercise, regular diet; and 4) exercise, restricted diet.  He found that maternal exercise increased maternal CORT (as expected), but surprisingly did not result in higher CORT in the eggs. Further, diet restriction did not affect maternal CORT, but moms with restricted diets laid eggs with reduced CORT.

This study suggests that anole mothers may manipulate the environments of their eggs in ways we don’t yet understand – the mechanisms by which CORT is transferred to eggs is an area ripe for future study!

SICB 2017: Social Hierarchy Influences Green Anole Behavior

Sukalia Miller with her poster at SICB.

Sukalia Miller with her poster at SICB.

This post was written by Miguel Angel Webber, an undergraduate in Michele Johnson’s lab at Trinity University.

An animal’s position in a social hierarchy can influence many aspects of its behavior. In the green anole (Anolis carolinensis), a growing body of literature indicates that dominant males behave differently than subordinate males, and that these behavioral differences may be present even prior to the establishment of a dominance hierarchy. Sukalia Miller, a recent undergraduate in Walt Wilczynski’s lab at Georgia State University, designed an experiment to determine whether subordinate and dominant males differed in their rates of courtship, aggression, and exploratory behavior.

After taking baseline measures of behavior, size-matched green anoles were paired and allowed to establish dominance relationships over the course of six days. Following this pairing, each lizard was then tested again to determine post-pairing measures of behavior. Miller found that subordinate males did not differ from dominant males in their rates of aggression (as simulated in a mirror test) or courtship (tested by placing a female in the habitat) prior to pairing, but that bouts of aggression and courtship practically disappeared in the subordinate group after pairing. Additionally, Miller found that there was a trend in the dominant lizards, such that individuals with higher rates of pre-pairing aggression had higher rates of aggression post-pairing. However, no such relationship was found between pre- and post-pairing rates of courtship in either the dominant or subordinate group, and no Miller observed no differences in exploratory behavior between either group of lizards.

These results suggest that the influence of social status on behavior may be limited to social behaviors in green anoles, and furthermore, that these behavioral differences may not be detectable prior to the establishment of a dominant-subordinate hierarchy.

SICB 2017: Green Anoles, Brown Bodies: Are Brown Lizards “Losers”?

brittneyAnimals frequently compete over resources, and the outcomes of these aggressive interactions depend on a number of factors – one of which is the animals’ previous social experiences. If an animal wins a fight, it may be more likely to win subsequent fights (a “winner effect”), and if it loses, it may be more likely to lose subsequent fights (a “loser effect”).  Garcia et al. (2014, Animal Behavior) previously showed that green anoles exhibit loser effects, but not winner effects. Brittney Ivanov, research technician in Michele Johnson’s lab at Trinity University, wondered whether, since body color in green anoles is associated with social dominance, were color changes in green anoles associated with these loser effects? Could she cause a green anole to be brown if it was forced to lose social contests?

Brittney conducted an experiment using 16 male green anoles. First, in three consecutive days, these focal males interacted with a larger “trainer” male in the trainer male’s home cage for one hour. On the fourth day, the focal males interacted with a size-matched novel male in a cage that was new to both lizards. If the focal males were effectively trained to lose in the first three trials, she predicted that they would lose this fourth trial.

In the series of size-matched trials, 7 of the 16 contests resulted in a clear winner and loser, and 6 of those 7 focal males lost that trial. Further, focal males were less aggressive in the size-matched trial than they were in their previous training trials. These data support the presence of a loser effect in green anoles. Consistent with her previous work, Brittney also found that lizards that were more often green prior to the trials were more likely to win their trials, showing that body color is important in social contests.

brittneycolorgraph2This experiment revealed new findings about loser effects and body color. Focal males who lost their size-matched trial were more likely to be brown in the days after the trials – and not only that, they were more likely to become brown after the trials (so, these weren’t just loser males who had been brown all along).

All together, Brittney’s results show that body color can provide important information about a green anole’s fighting ability or motivation, or its recent social experience, and that dynamic body color influences multiple stages of social interaction in this species.

SICB 2017: How To Make A Lizard With Two Heads, Or Thermal Stress On Eggs Produces Embryonic Abnormalities

Judy Kyrkos presenting her poster at SICB

Judy Kyrkos presenting her poster at SICB

Anole biologists are focusing more and more on thermal ecology and the adaptations associated with heat stress in adult lizards, but what happens when an egg experiences heat stress? Judy Kyrkos, a senior undergraduate in Thom Sanger’s lab at Loyola University, Chicago, presented a fantastic study addressing this question in Thursday’s poster session.

Judy and Thom conducted two experiments to determine the effects of thermal stress on embryonic development in Anolis sagrei. In the first, they incubated 533 eggs at one of five temperatures (ranging from 27-39°C) for 12 days. As predicted, they found that eggs at higher temperatures – and particularly those over 33°C – experienced lower survival and a higher rate of developmental abnormalities, most of which occurred in facial and brain development.  In the second experiment, they heat-shocked 60 eggs at 39°C for one hour on the day they were laid, and then incubated them at 27°C until hatching. 50 of those 60 eggs exhibited abnormal morphologies. Further, overall growth of embryos in heat-stressed eggs was also reduced. Comparing embryos at developmental stage 9-10, lizards incubated at 36°C had smaller SVLs than those heat-shocked in the second experiment, which were in turn smaller than the lizards incubated at 27°C. Altogether, these are a lot of challenges for a vulnerable embryo, and Judy’s results suggest that the rising temperatures anticipated as a function of climate change may affect anoles more dramatically than we’ve yet recognized.

 

 

SICB 2017: Masking the Parietal Eye in Green Anoles

This post was written by Miguel Angel Webber, an undergraduate in Michele Johnson’s lab at Trinity University.

Samantha Adams presenting her poster at SICB.

Samantha Adams presenting at SICB.

The parietal eye, a photosensitive organ located on top of lizards’ heads, has long been thought to play an important role in regulating lizards’ circadian rhythm and body temperature. The eye detects UVB rays, mediating the release of melatonin from the pineal gland and evoking a behavioral response. Samantha Adams, an undergraduate at Marosh Furimsky’s lab at Westminster College, PA, conducted a study on bearded dragons (Pogona vitticeps) and green anoles (Anolis carolinensis) to examine the effects of masking their parietal eye on their thermoregulatory behavior. Adams took individuals from each species and set up a testing arena, placing a UV-B light-only source and an infrared heat-only source on opposite sides. She then tracked the amount of time each lizard spent under either lamp, doing so before masking the parietal eye, while the eye was painted with black non-toxic paint, and again after uncovering it.

Adams found that bearded dragons rely heavily on the eye for thermoregulation – while lizards ordinarily spend less than 20% of their time basking underneath the heat source, lizards with their parietal eye masked spent the vast majority of their time under the heat lamp. Additionally, all of her bearded dragons experienced erratic locomotion in the day post-masking, running so frequently from side to side of the cage that she had trouble characterizing the lizard’s lamp preference. Once the black paint was removed, lizards took one to two weeks to resume ordinary behavioral patterns. However, she found that the green anoles in her study seemed unaffected by the experimental manipulations; lamp preference was unchanged by covering the parietal eye, and anoles spent roughly 25% of their time under the heat lamp in both the control and experimental treatments. The anoles displayed none of the erratic locomotor patterns Adams found in the bearded dragons, and other than a qualitative account of more time spent being brown, the lizards seemed unperturbed by the black paint on their parietal eye.

Adams’ results shine a new light on the parietal eye, long thought to be a structure essential to all lizards that possess it, as a potentially vestigial structure in green anoles. Future work is necessary to understand any other roles the eye could serve in anoles, but the stark difference with bearded dragons in this study helps illuminate the wild evolutionary path of our favorite lizards.

Evolution 2016: Ecomorphology in Caribbean Eleutherodactylus Frogs

Common_CoquíStephen Jay Gould famously claimed that evolution is “utterly unpredictable and quite unrepeatable,” and we Anolis biologists have relished in proving that statement wrong. In his talk in Austin this week, Alejandro Gonzalez Voyer of UNAM (with coauthors Alvaro Dugo Cota and Carles Vilá) showed that anoles aren’t the only Caribbean herps to exhibit the independent, repeated evolution of ecomorphs across islands – Eleuthrodactylus frogs have joined the club!

Among the remarkably diverse Caribbean Eleuthrodactylus species, nine ecotypes exist, including terrestrial, leaf-litter, aquatic, riparian, bromelicolous, arboreal, fossorial, cavernicolous, and petricolous specialists. Gonzalez and his coauthors first determined that these ecotypes evolved repeatedly, and showed that their distribution resulted from both invasion across islands and intra-island speciation. They also found that eight of the nine ecotypes cluster in morphological space and exhibit significant convergence. (The ninth, the fossorial ecotype, is composed of a monophyletic clade from Hispaniola and so convergence could not be tested.)

In sum, it appears that Eleutrodactylus ecotypes are indeed ecomorphs, and that evolution may be utterly predictable and quite repeatable after all.

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