Page 14 - Abacoa Community News - December '20

Page 14, Abacoa

fAu feAtures

Boo! How Do Mexican dwelling surface fish and multiple populations of cavefish, Wilkes Honors College
but response kinematics and probability differed between
Cavefish Escape Predators? populations. The Pachón population of cavefish exhibited an Receives Top National Rating
increased response probability, a slower response latency and
The ability to detect speed, and reduction of the maximum bend angle, revealing For The Second Time
threatening stimuli evolved differences between surface and cave populations.
and initiate an escape Analysis of the responses of two other independently evolved The Harriet L. Wilkes Honors College of Florida Atlantic
response is critical for populations of cavefish, revealed the repeated evolution of University received a second consecutive top rating among
survival and under reduced angular speed. Investigation of surface‐cave hybrids the country’s best honors colleges and programs in the latest
stringent evolutionary showed a correlation between angular speed and peak angle, edition of Inside Honors: Ratings and Reviews of 40 Public
pressure. To detect suggesting that these two kinematic characteristics are related University Honors Programs.
predators, fish use a number of sensory systems including at the genetic or functional levels.
olfaction (smell) and vision, which contribute to the “These findings show that even the most highly
activation of arousal systems. Surprisingly, little is known conserved behaviors have evolved differences in the cave
about the neural mechanisms through which ecological environment,” said Alex Keene, Ph.D., lead author and an
perturbation shapes the evolution of escape response. When associate professor of biological sciences, FAU’s Charles
startled, do all fish respond the same way? E. Schmidt College of Science. “It puts us in a position
A few fish, like Mexican cavefish, Astyanax mexicanus, to identify the biological causes that underlie the reduced
have evolved in unique environments without any predators. response probability and other changes we observed between
To determine how this lack of predation impacts escape cavefish and surface fish.”
responses that are highly stereotyped across fish species, Keene notes that perhaps most interesting, is the difference
researchers from Florida Atlantic University’s Charles E. in response probability in which Molino cavefish which
Schmidt College of Science and Harriet L. Wilkes Honors diverged from surface fish more recently, were significantly
College explored the tiny A. mexicanus to determine if there more responsive than any of the other populations, with “This wonderful achievement stands as a testament to the
are evolved differences in the species. A. mexicanus exist as Pachón larvae, originating from the more ancestral stock, world-class academic experience and unmatched opportunities
surface fish that inhabit rivers in Mexico and Southern Texas exhibiting the second highest response probability. available to our extraordinary students who are part of an
and as more than 30 geographically isolated cave‐dwelling “The finding that multiple populations independently intimate, ecosystem on the Jupiter campus, across the university,
populations of the same species. evolved similar phenotypes gives us a way to examine how and throughout the region of South Florida,” said Justin Perry,
The ecology of caves differs dramatically from the surface escape circuits can be modified,” said Keene. Ph.D., dean of the Harriet L. Wilkes Honors College.
habitat, resulting in distinct morphological and behavioral Despite having no eyes, cavefish could detect light and Inside Honors is published biannually and rates all honors
phenotypes in A. mexicanus. Cave populations live in sense looming stimuli, raising the possibility that light program components on a five-mortarboard scale (similar to
environments without light, which is thought to contribute modulates their C‐start response. To assess the influence a five-star rating system) and is based on data obtained on
to the evolution of albinism, eye‐loss, and circadian rhythm. of visual input on the C‐start responses of surface fish honors graduation rates, class sizes, course range, and type,
Because they lack predators they might also lack the selective and cavefish, researchers assayed both populations under honors dorms, and other honors benefits, including merit
pressure to avoid predators. Dramatic differences in these light and dark conditions. The presence of light had no scholarships.
cavefish populations combined with the robust ecological detectable effect on response probability, response latency, The Wilkes Honors College is one of seven honors
differences suggest that the startle reflex could indeed differ or angular speed in cavefish or surface fish. It did however, programs to receive a top rating of 5.0 “mortarboards.”
between populations of A. mexicanus. influence peak bend angle. In the dark conditions, surface “Since 2002, more than 100 publications, most of them
To put this theory to the test, researchers elicited “C‐start” fish displayed an increase in peak bend angle compared to in top-tier, peer-reviewed journals, have included a Wilkes
responses using acoustic stimuli and high-speed videography cavefish. Although they were able to perceive light at this Honors College student as a co-author,” said editor John
in multiple cavefish populations and compared responses to age, the presence or absence of light had no observable effect Willingham. “The WHC also has strengths in the humanities
eyed surface fish. The C‐start escape response represents on the responses of Pachón cavefish. and social sciences with 19 concentrations in these areas
a primary mechanism for predator avoidance in fish and To assess differences in responsiveness to acoustic of study and if you are a National Merit Finalist, in or out
amphibians. C-start gets its name from the “c‐shaped” curve a stimuli, researchers quantified the probability of C‐start of state, you will be eligible for a “cost of attendance”
fish’s body forms during the first stage of the escape response, initiation in surface fish and Pachón cavefish at multiple scholarship.”
which is followed by a smaller counter‐bend and then rapid vibration intensities. They found that Pachón cavefish were This is the second time that the Wilkes Honors College
swimming. more likely than surface fish to initiate a C‐start in response has received this distinction. The college also received a top
Results of the study, published in a special issue of to vibrations of higher intensities (31 and 35 decibels, but overall rating in the 2018/19 edition.
the Journal of Experimental Zoology: Molecular and not 28 decibels). “We are extremely proud to have the top-rated Wilkes
Developmental Evolution on the evolution of Mexican “Interestingly, all cave populations analyzed in our Honors College as part of Florida Atlantic University,”
cavefish, support the idea that ecological differences between study exhibited decreased angular speed. Furthermore, said Bret Danilowicz, Ph.D., provost and vice president for
cave and river environments contribute to differences in A. it is likely that a slower latency, such as that of Pachόn academic affairs at Florida Atlantic University. “Through
mexicanus escape behaviors. Findings provide a platform for larvae, decreases the likelihood of successful evasion,” said its distinctive programs and talented faculty, its students are
investigating the evolution of neural circuits contributing to Alexandra Paz, first author, an FAU doctoral student and a provided an incredible education and research experience at
sensory‐motor integration and support using A. mexicanus research assistant in the Department of Biological Sciences. a remarkably low tuition.”
as a model to investigate the evolution of escape behavior. “These data suggest that the C‐start responses of cavefish, Located in Jupiter, Fla., on the John D. MacArthur campus
In diverse fish species, acoustic stimuli activate Mauthner especially from the Pachόn population, may be less effective of FAU, this close-knit, residential, highly-selective liberal
neurons, which initiate a C‐start escape response. Mauthner for successful predator evasion. Because no predators have arts and sciences college offers a distinctive all-honors
cells receive input from multiple sensory modalities been identified in the caves, it is possible that this change is curriculum. Surrounded by world-renowned scientific
including visual, olfactory, and mechanosensory systems. a result of diminished predation in the cave environment.” research institutes, college undergraduates benefit from
To compare C‐start kinematics between surface fish and Co-authors of the study are Brittnee McDole, Ph.D., a unparalleled access to research internships.
cavefish, researchers examined and quantified response post-doctoral fellow at FAU; Johanna E. Kowalko, Ph.D., an The opportunities are elite, especially for students
latency, maximum change in orientation (referred to as “peak assistant professor of biology; and Erik R. Duboue, Ph.D., interested in research at one of the prestigious institutes
bend angle”) and angular speed. They used six-day post- an assistant professor of biology, both in FAU’s Harriet L. nearby, where undergraduates “have unprecedented access
fertilization larvae instead of adult surface fish and cavefish Wilkes Honors College. to working with scientists in all STEM fields.”
to eliminate the confounding variable of learned behavior. This research was funded by the National Institutes of
Researchers found that C-start is present in river- Health (1R21NS105071 and 1R01GM127872). FAU Features on page 16
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