BEACON Researchers at Work: The tale of the tail-less sea squirt

This week’s BEACON Researchers at Work post is by University of Washington graduate student Max Maliska.

Photo of MaxI have found my work as a PhD. candidate in Billie Swalla’s lab at University of Washington in Seattle to be highly integrative; spanning the disciplines of molecular biology, marine biology, evolutionary biology, and computer science. I would have never thought I would have been able to integrate these disciplines and learn a diverse set of training during my PhD. or been able to travel to the places I have been. As a student-researcher member of BEACON since its inception, I have also been able to gain a great amount of knowledge in areas that are becoming necessity in big-data science.

As a kid growing up in the Chicago suburbs, I was a book-worm infinitely interested in the weird and bizarre (I still am). I remember hoping that one day it would become clear that The X-Files actually existed, and I would be hired on and groomed by Mulder and Scully. I would routinely collect frogs and fish at our nearby creek, spending hours wading with a small plastic sand bucket. I remember at the age of 12 being very concerned about what I would do when I grew up. I then came to the quick realization that I would be a biologist, which made perfect sense, and have felt comfortably about being so ever since (X-Files contact me if you are legit).

I moved to University of Florida for college with the specific interest of studying animals in their own element, specifically herps (reptiles and amphibians). It was not until my sophomore year of college that I took a course and discovered a group of animals much crazier, much more alien than I thought would ever exist on this planet: marine invertebrates. I later learned that many movie aliens were actually often based on marine invertebrates (see Alien queen).

At the end of my sophomore year I was encouraged to take a course at UW’s Friday Harbor Labs on marine invertebrate zoology, one of the best courses taught on the subject in the world (go here to check out FHL’s student opportunities). Working in the San Juan Islands of Washington, I fell in love with the temperate waters, lush greenery, and the strange and diverse fauna of the northern Pacific. I knew I had to come back. After completing an undergraduate thesis studying the species relationships of several undescribed species of a tropical sea cucumber in the Florida Museum of Natural History, I applied to University of Washington and was accepted as a PhD. student in the Biology Department.

My dissertation research at UW has been under the advisement of Dr. Billie Swalla. The main interests of my research have been trying to understand how changes in the swimming larval phase of species of sea squirts have occurred and how this affects the evolution of these species. Sea squirts or ascidians are the closest related group of invertebrates to animals with a spine, or vertebrates (fish, reptiles, amphibians, birds, and mammals); understanding their evolution gives us insight into what the common ancestor of invertebrates and vertebrates was like and what kinds of changes have occurred between these groups.

Sea squirtsSea squirts live as adults cemented to the substratum, filter-feeding little particles from the water into a mucous-net inside their pharynx. The only phase of their lives that sea squirts have the ability to disperse, which improves their success of finding a mate or finding a place to grow up favorably as an adult, is when they are a little larva. I have been studying a group of sea squirts, which includes several species that have lost the tail during their larval phase. We have showed that this group has evolved taillessness multiple times independently. As this is the only dispersive phase for these organisms, being tailless results in larvae to often not disperse as far as the tailed species. Therefore, it is somewhat of a conundrum as to why this has evolved many times.

In 2011, I was able to travel to Panama to take a course, involving researchers from all over the world, on sea squirt biology through a National Science Foundation program sponsored by the Pan-American Studies Insititute. I was stationed at the Smithsonian Tropical Research Institute in Bocas del Toro, Panama. The diversity of sea squirts in the Caribbean is quite amazing and we were able to snorkel and SCUBA dive daily and bring different forms back into lab, identify, and understand them.

Tailless and tailed sea squirt larvaeTo understand how genetics and development have played roles in tailless larvae in certain species of sea squirts we have taken advantage of a collaboration through BEACON with Dr. Titus Brown’s lab at Michigan State University. We have taken advantage of recent technological advances to sequence the entire genome scale of data for a species with a normal tailed larva, a species with tailless larva, and the hybrid of these two species, which shows an intermediate of half a tail in its larval phase.

This has been a great collaboration for me because I have been fortunate enough to work with Dr. Brown and also a student in the Brown lab, Elijah Lowe. These two have been patient enough to help me while I have learned computational methods that have advanced my understanding of ascidian and evolutionary biology.

Using these methods, we have been able to determine that species with tailless larvae have changed when they activate the metamorphosis genetic program. This is a program that turns on and allows a larva go through metamorphosis into the very different adult form. These tailless species activate their metamorphosis genetic program earlier and we hypothesize this has been moved earlier and starts “breaking down the tail” before it actually forms.

I will defend my dissertation this spring and I am excited about what is next. I hope to better understand the population scale changes that occur between species of marine invertebrates when they evolve alternative larval forms, which affect their dispersal. While it’s not The X-Files, solving these actual evolutionary mysteries have been exciting to determine.

For more information about Max’s work, you can contact him at mem24 at u dot washington dot edu.

About Danielle Whittaker

Danielle J. Whittaker, Ph.D. Managing Director of BEACON
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