It takes some effort to get brittle stars in the mood to reproduce in captivity. They must be well fed, in total darkness and convinced that the world is coming to an end.
“It’s like a battle of attrition,” said Augie Davis, a senior honors student at William & Mary. Davis had just finished kicking a pushcart full of tiny bowls of brittle stars around the second floor of William & Mary’s Integrated Science Center. “After we take them for a few laps, we turn them upside down in their bowls, but they turn themselves over again, so we have to turn them upside down again and turn off the lights. It’s scientific, but there’s also some voodoo involved.”
Every year around Valentine’s Day, W&M biologist Jon Allen’s lab plays starfish matchmaker by cleverly mimicking nature to study the animals’ incredible life cycles.
Research in the Allen Lab focuses on the life histories of marine invertebrates. Students, both undergraduate and graduate, study the ecology and evolution of the larval stages of various organisms, including sea urchins, snails, flatworms, starfish and, in rare cases, brittle stars.
Allen explained that brittlestars are hard for researchers to find. The animals are abundant in the deep sea, but are rare and cryptic near the coasts, avoiding light and living under rocks with only the tips of their fragile arms exposed. With any luck, Davis’s state of mind efforts would result in baby brittlestars for the lab to study.
“It depends on how you want to anthropomorphize it,” Allen said. “You either tire them out and convince them that the world is going to end, so they have to spawn — or you wind them up somehow, because they might like that sort of thing.”
One thing that obviously doesn’t turn on embroidery stars are other embroidery stars. In the wild, male and female brittle stars rarely interact, Allen explained. But while there are no brittlestar meet cutes, a complicated breeding process still takes place just below the surface of the water.
“In nature, starfish and brittle stars just throw their eggs and sperm in the water, so mom and dad never really see each other,” says Allen. “It’s their gametes, the sperm and the eggs, that have the most fun.”
Allen explained that there is a very intimate communication system between starfish eggs and sperm. The eggs are highly attuned to certain qualities in the sperm, most notably a species-specific protein called bindin, and are selective in their choice of which sperm is allowed to enter the egg’s cytoplasm. The sperm is just as selective, actively swimming only when the precise egg match is present and following a trail of chemicals captured by mature eggs.
“That’s what fascinates me about these animals,” Allen said. “There’s a whole chemical ecology, a whole world of fertilization and selection, and the parents aren’t even involved.”
He added that climate change-induced variations in water temperature and currents could have the potential to alter population outcomes for a species whose survival literally depends on going with the flow.
For example, the brittle star is an arctic species, which means that the animals enter spawning condition around mid-February when the water is relatively warm for them. The female brittle star takes cues from certain changes in her environment, such as water temperature, that let her know it’s time to release eggs. And although husband and wife never meet, the brittle stars still have some form of mating dance.
“When they do their thing, they stand on all fives and twist their waists back and forth,” said Allen, who described the movement male and female brittle stars make when releasing gametes. “They stand on their feet to get above what’s called the boundary layer, where the water doesn’t go up to where the water does move. Then they squirm around and release eggs and sperm from their armpits.”
With brittle stars and sea stars, the math works against the survival of nearly all animals produced during a spawning event, Allen explained. Imagine a stable population of starfish, where mom and dad produce just enough offspring to replace themselves for their lifetime. In a large-bodied species, such as some of the West Coast starfish Allen is working on, a reproductive female can produce 50 million eggs a year. That same female can live for decades, and if she reproduced at that level for 20 years, she would produce a billion eggs in her lifetime — only two of which survive on average.
“That means every adult starfish we find is almost literally a one-in-a-billion event,” Allen said.
While pressure is high for a successful spawning season, Allen is quick to add caveats to any romance analogy in the phylum Echinodermata (breeding stars, starfish, sea urchins, etc.). The beings do not have a brain or central nervous system. They have thousands of eyes that have been determined to be sensitive to light, but brittle stars do not have a sophisticated system for processing visual stimuli.
“Well, we can probably rule out love at first sight,” Allen joked. “Because the jury is still out on whether these animals can see at all.”
Ultimately, the brittlestar novel was successful at the Allen Lab, with multiple animals spawning over the course of two days and nights. Each reproductive female produced tens of thousands of eggs, so Allen and his students will have more than enough frail babies to work with for their research. They will use the newly produced animals to study how environmental factors, such as changes in temperature and salinity, affect cloning during the larval stage. Each larval brittle star has the ability to asexually produce genetically identical clones of itself. Understanding that process is the focus of the lab’s most recent work.
While the frail babies mark a successful spawning season for one species, another lab’s spawning attempt was less of a triumph. As Davis shuffled and flipped brittlestars, a team of college students (Caroline Vanduzer ’23, Alexis Reece ’22, and Nhu-Lan Pho ’25) used a more scientific, chemical induction method to spawn. asterias forbesic, a type of starfish native to the East Coast and found along the beaches of Virginia. The students injected six male and six female starfish with a hormone proven to stimulate spawning.
The goal was to mix the gametes and study the resulting larval-stage starfish, which, as a previous lab student accidentally discovered, cannibalize each other in an expanded, micro-sized Darwinian display. Unfortunately for this year’s researchers, the female starfish didn’t respond to the hormone and held onto their eggs.
“Those were the star-crossed lovers,” Allen laughed. “We made all the right moves of romance, if we want to call it that, but fate got in the way. Of course, our goal in the end was to figure out why they eat each other, so let’s be honest about the science here. In nature sometimes gets a little crazy.”
Adrienne Berard, Assistant Director for Research, News and Analytics