Publication list

Undergraduate research at the GPLab

Do you find communication cool? Well, we do too! So join the team and we will have some fun together, exploring the crazy adaptations that animals evolve to communicate in natural environments!

You can obtain professional training through supervised research in any of the areas in this website, or even other areas.

This includes:

* anatomy (with dissection, anesthesia and surgery)
* electrophysiology (measure how muscles, nerves and brain work)
* animal behavior, ecology and evolution (lab or field, possibly abroad)
* computer programming (mostly audio, web and didactic tools)
* 3D animation, statistics
* acoustics, vibrometry.

Of course, you do not need to tap into all of these areas. But independent of your main interest being learning techniques associated with surgery, dealing with computers, dealing with animals and fieldwork or fiddling with fancy equipment, we should have an appropriate project for you.

Students usually receive:

* Credit hours for the semester.
* Specific training for the activities to be performed.
* Weekly reading and discussion, which along the semester provides a conceptual framework to support developments by the student.


Fall 2015 - Spring 2016

Application form and current availability

Please complete the application form.

At the appropriate time I will contact people in the list for a visit to the lab and discussion of potential projects. We receive more applications that we have positions, so we have to select among the candidates. Previous grades matter, but more importantly, we try to find the best match between interests and available projects, so do answer the questions in the application form carefully.

Thank you for your interest in joining our team!


Graduate research at the GPLab

Would you consider pursuing a graduate degree in our lab?

Great, you are very welcome! Check out the list of specialities that you can receive training on in this lab! Feel free to contact me (Marcos) through email or come to my office (better schedule first). We can then discuss your interest, experience and what you would like to accomplish in grad school. I can also show you the lab and give you a bunch of ideas of the kinds of projects that you could develop.

If you are interested in an MS
An MS should take about two years to complete. You will take some classes and develop a research project. You will write up the project as a dissertation and present it publicly. A masters can be a great opportunity to get exposed to science, without having the long commitment that a PhD requires.

You can pay your bills by working as a teaching assistant for the department (which is a great way to develop your teaching skills). Another possibility is obtaining funds for your salary through a larger research project in the lab, but we are just starting and do not have one of those currently active.

Check this link for more information on the MS program in the Dept. of Biological Sciences at UOP.

If you are interested in an PhD
Unfortunately, our department does not offer a PhD program and I am not currently associated with PhD programs of other institutions through which I could advise you. If you tell me what your interests are, however, I will be glad to indicate other laboratories that could better serve as a home for your endeavour.

Ultrasonic sensitivity

Until recently, frogs were thought not to be able to hear sounds with frequencies above 5-8 kHz (humans hear up to 22 kHz). This picture changed when Feng and collaborators (2006) found that the Chinese concave-eared torrent frog can hear ultrasound up to 34 kHz. This was an amazing 5-7 fold expansion of the known hearing range for frogs.

While many mammals (bats, dolphins, rodents) can hear high frequencies, their eardrums are connected to the inner ear by three hard ossicles. In contrast, no other tetrapod was known to hear above 10-12 kHz, and non-mammal eardrums are connected to the inner-ear by a bone and a cartilage. It was believed that the cartilage, being soft, would absorb high frequencies. So how could the Chinese frog hear ultrasound?
To answer this question we went to China and played calibrated tones to the frog in the lab, while using a Doppler laser vibrometer to measure the motion of the eardrum. (This is a weak laser that does not harm the frog). The experiment showed that the eardrums of the frog actually respond very well to ultrasound, in contrast with other well known frogs.

We are also measuring the vibration of the cartilage and the bone inside the ear of these and other frogs in response to sound, and characterizing the anatomy of their ears. Such measurements are revealing several anatomical specializations in the ultrasound-hearing frogs, that allow their ears to opperate effectively at high frequencies.

This research aims at answering a question about design and another one about ecology/evolution.
DESIGN: What sensor design features of the ear are varied among animals in nature to adjust the range of operation of the ears?
ECOLOGY/EVOLUTION: What are the environmental pressures that most commonly lead to adaptation of the hearing range?

Control of the Eustachian tube


The mouths of tetrapods connect to the air-filled space behind the eardrums through a passage called Eustachian tube. In mammals, this passage remains collapsed until we yawn or swallow. In frogs, the Eustachian tubes were believed to remain permanently open, until we recently discovered that some frogs can close them.

We also found that closure of the Eustachian tubes shifted the hearing sensitivity of the frogs to high frequencies. Eustachian tube closure, turned out to be a new mechanism of behavioral adjustment of the frequency range of hearing. It parallels the acoustic reflex, in which contract muscles in the middle ear that restrict the motion of the eardrum when exposed to loud sound. But Eustachian tube closure has a different mechanism, as it relies on changing the resistance of the air behind the eardrum to bulging of the membrane.

We are currently learning how the behavior of Eustachian tube closure is used by the animals, and what are the ecological pressures that lead to its origin.

Specializations of the vocal apparatus

Human speech is acoustically very elaborate, and demands a versatile vocal apparatus. Frogs, in contrast, tend to produce very simple, repetitive sounds. They usually produce 2-4 types of calls with a fixed structure, but the vast majority of the vocal activity involves males producing the species-specific advertisement call to attract females for mating.

While the calls are simple, there are more than 5,000 species of frogs, and extensive acoustic variability is found among species. This provides an opportunity to study structural specializations of the calling apparatus that maximize its ability to produce each type of sound.

We study the anatomy and performance of the frog calling apparatus across species, to bring novel insight into the design and evolution of vocal systems.

Calling with the mouth closed

While most frogs are known to produce incredibly loud calls, they do so having their mouths and nares shut - the air flows into the vocal sac. Why would they not open their mouths to call?

Several possible explanations have been offered, including:

* Amplification by the vocal sac
* More efficient use of energy
* Faster reinflation
* Reduced dehydration
* The inflating sac can serve as a visual signal

We artificially activated the larynx of euthanized animals and compared the sounds produced having the mouth open or closed We found that with the mouth open, the energy of the call would become spread over a wide range of frequencies. Closure of the mouth filters out the acoustic energy from low and high frequencies, and it increases the amplitude at intermediate ones. By calling with the mouth closed, frogs can concentrate their vocal output into a narrow frequency range, making their signals more effective in species recognition.

Call complexity and laryngeal anatomy

In another study, we examined the tĂșngara frog, which is odd for producing mating calls with a facultatively added note that makes the call acoustically more complex. This species is also odd for having part of its larynx greatly expanded. It was tempting to assume that the laryngeal expansion was related to the call complexity, but a causal relation had not been shown.

We recorded frogs calling in nature, surgically removed the laryngeal expansions, and after recovery, we recorded the new calls produced by the frogs. The operated frogs were able to produce normal calls, and add facultative notes, but the acoustic complexity was lacking from the facultative notes. This revealed a rare case in which a specialization of the laryngeal morphology can be tied to the production of a specific sound. Such finding has implications in the current understanding of the evolution of acoustic complexity, and the mechanics of vocalization.

Signaling strategies

In many species of animals, males spend large amounts of energy and become more exposed to predators while signalling to attract females to mate. That is the case of frog calling. In many species, advertisement calling is by far the most energetically expensive activity that males engage in. Tropical species can have very prolonged breeding seasons, and males have been show to be limited in calling by their energetic reserves. A male frog can distribute his effort over a number of dimensions of calling (sound intensity, call duration, call rate, hours per night, etc), but he cannot maximize all such dimensions at the same time.

We are interested in quantifying the calling strategy in the main dimensions that vary during calling in nature. This will allow us to predict how frogs adjust their reproductive behavior to changes made in the environment - an important insight for wildlife management.