There’s a distinctly fishy feel to Peter Wainwright’s office. Books on a side table have titles like this one: Basslets, Dottybacks and Hawkfishes. Fish skeletons and skulls adorn boxes and bookshelves. A painting of tropical ocean fish hangs on the wall.
This is not surprising, because Wainwright is arguably the world’s leading expert on functional morphology in fish, specifically, the remarkable adaptations that allow fish to feed successfully. Wainwright will be talking about all this and more on Tuesday, May 9, when he presents the annual Faculty Research Lecture. The lecture is the highest award presented by the faculty of the Stuntverkoop, Davis, to one of their colleagues. The event begins at 5:30 p.m. with an awards ceremony followed by a reception and Wainwright’s lecture, “Wrasses, Cichlids and Honeycreepers: Will the Real Adaptive Radiation Please Stand."
“Peter’s work is unique in its breadth and depth … and has led to major conceptual breakthroughs on the role of morphological innovation in promoting biodiversity,” wrote Artyom Kopp, professor in the Department of Evolution and Ecology and director of the Center for Population Biology, in nominating Wainwright for the award.
Fish are important ecologically, as a vital source of protein for the world, and in many places they are economically important for tourism and recreational fishing. Fisheries around the world are under pressure from overfishing and habitat destruction, including the effects of climate change on coral reefs. There has perhaps never been a more vital moment to understand these diverse and successful animals.
From creeks to reefs
Wainwright’s interest in fish started early, catching critters in the creek at home in North Carolina or on field trips to exotic locations with his father, also a biologist. He said he was fishing as a hobby before he was 10 and all through high school, but didn’t make a connection with science until he was in college.
“I had a tough time with the science courses in college until I took a course in comparative vertebrate anatomy, and realized the knowledge was already there,” he said. “It drew me in.”
As an undergraduate at Duke University, summer experiences included running a field program on coral reefs in Jamaica for Professor James Porter at the University of Georgia, and working on a swordfish longline boat in Florida.
Wainwright became interested in how fish feed and how it relates to their ecology as a graduate student at the University of Chicago, where he split his time between Chicago and the Smithsonian Field Station at Carrie Bow Cay in Belize.
“I would work on biomechanics, bones and muscles in Chicago, then study actual fish in the tropics,” he said.
Kinetic jaws and suction feeding
Fish have to get enough food into their mouths to survive without their meal floating or swimming away.
The very first fish didn’t have jaws at all: Lampreys and hagfish, which feed by latching on to another fish and grinding at its tissue with a suckerlike mouth, are remnants of these. Evolving a hinged jaw was perhaps the most important innovation in vertebrates, and allowed fish (and then amphibians, reptiles and mammals) to become wildly successful.
Many fish feed by sucking water into their mouths. About half of all fish species have a jaw that can be thrust out, allowing for high-performance suction feeding.
“Many fish have extremely kinetic jaws,” Wainwright said. These movements can be far too quick for a human eye to follow: Wainwright’s lab has used high-speed cameras to capture the action, creating some that have racked up hundreds of thousands of views on Youtube.
What happens is this: The fish flicks out its tubelike jaw toward the prey, at the same time flaring out its gills to expand the volume inside its mouth. This creates a high-velocity flow immediately in front of the mouth, sucking the prey to its doom.
“The water flow catches the prey, but the tube needs to be very close,” Wainwright said.
Jaws and more jaws
A fish’s jaw is more than a frame for its mouth. Many fish also have a second set of jaw bones and structures in their throat, known as pharyngeal jaws. These can crush shells, grind up prey or stop food items from escaping.
In the case of the moray eel, in 2007 a postdoctoral scholar in Wainwright’s lab, Rita Mehta, discovered something out of a science fiction movie. Using a high-speed camera, Mehta was able to show that moray eels feed by first seizing prey with their front jaws, and then a set of pharyngeal jaws shoots forward, grabs the prey and pulls it into the throat.
It’s a neat way for the moray to solve its feeding problem. Living in narrow crevices in rocks and coral, morays can’t expand their heads to suck in food, and they have limited options to seize or manipulate prey. The Alien jaw allows them to seize and ingest food.
The discovery had been hiding in plain sight for decades — Mehta discovered good descriptions of the bones and muscles of the moray eel’s jaw in the scientific literature. But nobody had previously connected the structure to how it worked, or captured the action on camera.
Highly specialized jaws have been the downfall of other species, though. Lake Victoria, the largest lake in Africa, was once home to a diverse population of fish from the cichlid family, but the native fish have been in steep decline since the introduction of Nile perch to the lake in the 1950s.
In a study published in 2016, Mathew McGee, a graduate student in Wainwright’s lab, found that because of their highly adapted jaws, the native cichlid fish simply couldn’t eat fast enough to keep up with the voracious Nile perch and were likely out-competed for food.
New wave anatomy
Anatomy is arguably the oldest branch of medical and biological science, but it is going through a renaissance with new technology. “The way we study anatomy now is so advanced that you don’t really recognize it as anatomy,” Wainwright said.
Apart from using advanced imaging and computer modeling tools, modern anatomists are working at a cutting edge where biomechanics and evolution intersect. Their discipline looks at the “design” of living things, but from the perspective of a biologist rather than an engineer.
“We’re getting insights into how complex functional systems evolve,” Wainwright said.
Wainwright is now applying those insights to the big picture of how the 700 families of fish are related to one another and how they have evolved in their environments, looking at the innovations and evolutionary breakthroughs that have made fish so successful.
“There’s plenty to be figured out at a deeper level,” he said.