Research on How Lizard Brains Work During Aggressive Encounters

 

Jaramillo uses a cryostat to process sections of lizard brain as part of her research

From the Trinity University newspage:

Leaping Lizards
Tuesday, March 8, 2016

Student researcher Maria Jaramillo lands Sigma Xi grant studying green anole lizards

by Carlos Anchondo ’14

Two male green anole lizards meet in the forest. One lizard has infringed on the territory of the other, who now feels threatened. In a bout of competition, the lizards extend their dewlaps, the flaps of skin beneath their lower jaw, and a faceoff ensues.

Observing this aggressive act, neuroscience major Maria Jaramillo ’17 pondered how the dewlap is processed as a stimulus in the lizards’ brains. She then compared this hostile social behavior with a non-social interaction, like a lizard’s observation of a leaf. How does the lizard’s brain handle each interaction? At what point and why is the brain more active?

To answer these questions, Jaramillo applied for and was awarded a $1,000 grant from Sigma Xi, The Scientific Research Society. The grant money will be used to purchase antibodies, used for immunocytochemistry, as well as other supplies like microscope slides. Jaramillo studies in the lab of biology professor Michele Johnson, a researcher of the evolution of lizard behavior, and collaborated with Johnson during the grant proposal.

“I find the brain very interesting because it controls everything that we do,” Jaramillo says. “I love to study lizards because the wild environments they live in provide all kinds of stimuli, and I want to understand how they process it all.”

For the study, Jaramillo recorded a video of a green anole lizard exposing its dewlap and edited the video, scrambling the pixels of the lizard but maintaining the exact same colors and movements. After removing the social context, Jaramillo analyzed a lizard’s reaction to the modified video in comparison to its reaction to the original. She also tested two lizards together and then played the video without the lizards as an additional control. The lizards were placed in arenas, and Jaramillo observed them using GoPro cameras.

Jaramillo was notified in December 2015 that she had received funding and couldn’t believe the news. She excitedly called Johnson to share her elation, as Jaramillo had been turned down for the grant during the previous application cycle.

“This was a super cool process because Dr. Johnson and I literally built this project together,” Jaramillo says. “I did a lot of the decision making and, even though lizards are not what I am going to study for the rest of my life, it has given me a lot of research experience where I have worked directly with a professor.”

Applying twice for the grant meant that Jaramillo and Johnson received feedback from Sigma Xi evaluators following the initial application. Jaramillo says she was not discouraged after being rejected, but eager to learn how best to improve her chances. A peer tutor for Johnson’s biology class, Jaramillo encourages other not to give up and to “just keep trying.”

From Katy, Texas, Jaramillo plans to pursue medical school after Trinity. Her motivation is to help others with their medical needs and keep them in good health. She says that she has always loved science, and views medicine as a rewarding way to put her interests to good use.

“Health is the thing everyone needs to survive,” Jaramillo says. “For someone who wants to go into medicine, understanding how to conduct research like this is critically important. Studying at Trinity has made me sure that I want to attend medical school and become a doctor.”

Carlos Anchondo is a writer and editor for University Marketing and Communications. He is a 2014 Trinity graduate and can be found on Twitter at @cjanchondo or at canchond@trinity.edu.

Amazonian Green Anole Fails to See the Cryptic Cricket

punctatusThe caption says: At first look this image may just look like an Amazon green anole (Anolis punctatus) climbing a tree; but look a little closer… there is a cryptically coloured cricket fooling the predatory eyes of the lizard. Jack Mortimer Photography

On the importance of Dorsal and Tail Crest Illumination in Anolis Signals

With a flurry of recent attention investigating how background light may influence the signalling efficiency of Anolis dewlaps (1,2,3,4), particularly those inhabiting low-light environments where patches of sunlight appear at a premium, it occurred to me that extended dorsal and tail crests may fall under similar selection. Below are some photos of Puerto Rican crested anoles (Anolis cristatellus) – a species in which males exhibit an enlarged tail crest and the ability to voluntarily erect impressive nuchal and dorsal crests during aggressive interactions (the mechanisms of which are detailed in this previous AA post) – that show how crests may contribute to signalling.

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I have no doubt this thought has crossed the minds of many anole scientists before, particularly those current graduate students so successfully studying A. cristatellus and familiar with their ecology and behaviour (namely Alex Gunderson, Kristin Winchell, Matt McElroy, and Luisa Otero). Dewlaps are undoubtedly of primary importance to anole signalling and communication, but what are people’s general thoughts on the relative importance of other morphological features?

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Anole Barely Moves While Snail Speeds Past

Anyone who studies animals behaving in their natural environments knows just how long they can spend doing nothing much. This is most definitely true of anoles as well. My colleague Jon Suh learnt this first hand last summer while working with me on Anolis sagrei in Florida. I think his video (from data he collected on lizard display variation, and sped up by 500%) perfectly captures what it feels like to spend a long time watching a lizard doing almost nothing.

Crayons, Anoles, and a College Education

Writing on the blog Cultured Vultures, Karl Koweski reports on a community college classroom exercise that involves coloring in anole ecomorphs and Caribbean anoles with different colored crayons. Surprisingly, he’s not thrilled about it.

Brown Anole (A. sagrei) Surveys in Orange County, CA

Louis Shanghan of the LA Times reports on Greg Pauly‘s field surveys of non-native Cuban brown anoles (Anolis sagrei) and geckos in Orange County neighborhoods

sagrei_california

“The anoles, which are native to Cuba, arrived here about a decade ago as stowaways in nursery plants,” Pauly said as the team strode down a leafy street, methodically scanning sidewalks, brick walls and tree trunks for the stick-like shapes of lizards basking in the sun. “Today, there’s at least 10 to 20 per residential lot in this neighborhood alone.”

“There’s a nice one over there,” he said, nodding toward an anole – about five inches long, adorned with light brown speckles and a bright line running from head to tail – clinging to the side of a front-yard planter box.

Full story here: Scientists survey an Orange County neighborhood’s nonnative lizard populations

As a side note, the details for the original record (as far as I know) of A. sagrei in California are as follows:

The first published documentation was in Herpetological Review 45(4), 2014, an edited version of which you can read below:

ANOLIS SAGREI (Cuban Brown Anole). USA: CALIFORNIA: San Diego Co.: Vista, elev. 158 m) 19 July 2014.
C. Mahrdt, E. Ervin, and L. Geiger. Verified by Bradford D. Hollingsworth. San Diego Natural History Museum (SDSNH 76128–76133).

New county and state record (Granatosky and Krysko 2013. IRCF Rept. Amphib. 20[4]:190–191)
Four adult males and two hatchling specimens were collected on a one-acre parcel landscaped with palms, cycads, and several species of tropical plants and ground cover. Several boulders scattered throughout the parcel were used as perch sites for male lizards. An additional 16 adults and six hatchlings were observed in the two-hour site visit (1030–1230 h). Adults were also observed beyond the property indicating that this population is established and likely expanding through the contiguous tropical landscaping of neighboring properties. According to the property owner, he first observed the species in August 2012 shortly after receiving shipments of palm trees in May–August originating from suppliers located in the Hawaiian Islands.

CLARK R. MAHRDT, Department of Herpetology, San Diego Natural History Museum, San Diego, California 92102, USA (e-mail: leopardlizard@ cox.net);
EDWARD L. ERVIN, Merkel & Associates, Inc., 5434 Ruffin Road, San Diego, California 92123, USA;
GARY NAFIS, (www.californiaherps.com).

More information on A. sagrei in California can be found here

Another Anole Amputee Doing Just Fine

I’m always amazed by the ability of anoles to survive–even prosper!–with dramatic injuries. How could a lizard get by missing half of a hind leg? How does it capture prey or escape predators? Display credibly? But they do. We’ve reported incidents of three-legged lizards before, and are always looking for more examples.

The photo above is a fine example, reported by Karen Cusick on Daffodil’s Photo Blog. The brown anole also had a mysterious dent on its site. Must have been a traumatic event.

Help Identify Herptiles from Roatán

Dear experts, I will be very grateful if anyone could help me identify these three species I found in Roatán, Honduras.

id_1id_2 id_3As reward, I offer this beautiful Allison’s anole (Anolis allisoni) photo. Cheers!Allison's anole/Blue-headed anole (Anolis allisoni)

Lizard Populations Offer Fresh Look at Island Biogeography

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Female Anolis sagrei, Palm Coast, Florida

Any observant individual has noticed and possibly even been astonished by the incredible densities that some insular anole populations (i.e. A. sagrei) can achieve. Islands necessarily create a unique combination of environmental factors, several of which have traditionally been suggested as reasons that insular species are capable of attaining such densities. Species richness tends to be quite low on islands and so the diversity of predators remains low and there are fewer other species with which to compete for resources. A lack of predation pressure and competition can allow a species to more broadly utilize a traditionally occupied niche or even evolve to fill new regions of adaptive space, further utilizing resources in ways that increase population growth. A newly published meta-analysis of lizard densities across the globe confirms some of what we already knew about island biogeography, but also challenges some traditional thinking on the subject.

Seasonality, Activity and Habitat Use of Insular and Mainland Populations of Anolis nebulosus

Seasonal fluctuations in the environment frequently lead to important modifications in the distribution of all kinds of resources in all sorts of ecosystems. Consequently, environmental seasonality has long been known to determine the biology, ecology and behavior of animals. Less known, however, is whether and how seasonality differentially affects populations of the same species inhabiting mainland and island areas.

By conducting field observations on  Anolis nebulosus from a mainland and a nearby island population in the Jalisco coast (Western Mexico), Siliceo-Cantero & Garcia (2015) investigated i) if anoles from these populations experienced similar degrees of seasonality and ii) whether they responded similarly to these seasonal changes. At each of the study sites, the authors conducted a series of transects at three different time blocks of the day within the normal activity range of the species. They collected information on each of the observed anoles including sex, perch height, temperature and humidity. Behavioral information was obtained for males by conducting focal observations in which researchers quantified movement rates, perch height and width, as well as the type of movements (i.e. dedicated to thermoregulation, socialization, and feeding).

Results showed several differences in substrate use and behavior between sexes, sites, and seasons. Overall, females perched lower than males (see Figure below), which could be a strategy of females to minimize competition with males. Interestingly, both sexes tended to perch lower on the mainland site. The authors suggest this could be a way of decreasing niche overlap with the larger lizard Sceloporus melanorhinus, a species that is not present on the island site. The reason why females perched lower during the rainy season whereas males did not remains unclear.

In general, males showed higher movement rates and covered longer distances on the San Agustin island site, maybe due to reduced environmental fluctuation on the island. The explanation for this is that, on the mainland, lizards may have to spend more energy to keep an appropriate body temperature so the costs of being active are higher that the potential benefits. Daily patterns of activity seem to be mainly determined by seasonal fluctuations in temperature and relative humidity (see Figure). The bimodal daily pattern of activity found during the dry season is possibly the consequence of an increased risk of overheating by direct solar irradiation, since the trees have lost their leaves during this time of the year. The lack of such bimodal pattern of activity on the island is compatible with possibility that this environment has less harsh weather conditions (e.g. lower temperatures due to regular wind currents), allowing anoles to be active with a lower risk of overheating.

AnoleAnnals1

Perch height differed among sexes, seasons and sites (means and 95% CI shown). Box shows significant differences among groups. Males (M), females (H), from island (I) and continent (C) during dry (S) and rainy (LI) seasons. (Figure 2 from Siliceo-Cantero & Garcia 2015)

In summary, the behavior of anoles is affected by seasonal fluctuations in their environment, but these effects seem to be the consequence of a complex interaction between several geographic and biotic factors. For instance, an increased seasonality in the environmental conditions of mainland may cause anoles to show a bimodal pattern of activity that does not exist on islands. In addition, the presence of a larger lizard is suggested to influence perch height in mainland anoles. Finally, increased intraspecific competition on islands could explain both increased activity of males (e.g. to defend their territories) as well as increased resource partition on perch height between males and females.

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