For a snail crawling around the ocean floor, finding a mate is a bit more difficult than going to a party on a Friday night. Because snails can perceive light but not clear visual images and don't have any hearing, simply finding a suitable partner for reproduction is a challenging task.
Tufts professor of biology Jan Pechenik and graduate student Olivia Ambrogio are currently researching the reproductive patterns of several snail species native to New England waters and attempting to answer, among other questions, how two lonely gastropods pair up.
Pechenik has been working with the Crepidula genus of snails since he received his Ph.D. from the University of Rhode Island in 1978. Shortly after obtaining his doctorate, Pechenik started to investigate how temporary stresses that animal larvae experience - such as short periods of food deprivation - might affect how fast the organisms grow after metamorphosis or how many offspring they eventually produce.
According to Pechenik, this sort of examination of the long-range effects of short-term events is unusual, since most biologists who study the larval stages of organisms rarely study those same animals after metamorphosis.
"They're really two different classes of biologist," Pechenik said.
Luckily for Pechenik, the Crepidula genus is easy to keep in the laboratory since it has a very low mortality rate, can produce larvae on command and is relatively sedentary.
"They don't move around much at all, and so they don't waste any energy doing anything but having sex, really," Pechenik said.
Of course, finding a suitable partner for sex might be a bit problematic for an animal with such limited sensory capabilities; Ambrogio is conducting experiments to see whether chemical cues called pheromones help lead male snails to their female counterparts.
She has set up variations of what is called a Y-maze to help accomplish this task. In its simplest form, the Y-maze consists of clear plastic walls that form a Y-shape on the bottom of a shallow tank of water. At the top of one branch of the Y is a female snail tied in place, at the top of the other branch is an empty shell and at the base of the Y is a male.
Ambrogio has a photograph of this set-up taken every ten minutes to track the movements of the male snail, looking to see whether he goes for the empty shell or for the lone female in the tank.
If [the male] goes right away to [the female's] side, it's using a chemical cue," Ambrogio said.
If a chemical helps male Crepidula find females, this might make the snails particularly sensitive to changes in the environment. A chemical accidentally released into the ocean that happens to mimic the pheromone released by female snails could potentially interrupt breeding for these animals.
And although Crepidula may appear insignificant, they are in fact vitally important to marine ecosystems.
"Most of these animals that don't get the kind of attention that penguins and polar bears get are really at the basis of all these marine ecosystems," Pechenik said. "They're strange to most people, but they're the things that keep these systems running. Every marine bird or sea otter or sea turtle ... ultimately depend[s] for their food, one way or another, directly or indirectly, on invertebrates."
Another reason to pay attention to the snail Crepidula fornicata is the impressive success it has had as an invasive species.
Although native to the Atlantic Ocean along the coast of North America, the snail has spread as far as Scandinavia and Japan.
The potential explanation of this species' extraordinary spread might lie in two facts related to its reproductive pattern. First, the snails begin life as microscopic larvae that can travel hundreds of kilometers in the water before they undergo metamorphosis. Second, all snails in the Crepidula genus undergo a sex change during their lives. All start out as males and at some point become females.
"If you have just two animals that invade, you have a potential mated pair. In fact, you will have a mated pair if the animals are near each other," Pechenik said.
Although most male snails will choose females to mate with if they are given a choice of gender, some Crepidula fornicata males will choose other males - who then transform into females - as partners.
"With these animals, a male could choose another male and that would sort of be like a female on delay," Ambrogio said.
Ambrogio said she was drawn to study these creatures by their unique traits that seem so foreign in comparison to land animals.
"In their shapes, in terms of their lifestyles, in terms of their life history, their behaviors, all of these aspects of what they do [are] so different from what we usually think of," Ambrogio said.
Not only do these seemingly bizarre characteristics of life lend themselves to investigation, but they also put a new twist on old questions typically posed about terrestrial organisms.
"By looking at these systems this can sort of broaden our understanding of how these really vital behaviors ... mate finding, mate choice ... are really going on in a large majority of animals that haven't even been looked at all," Ambrogio said.
