Some animal species are a breeze to identify. That plump masked mammal lurking in your backyard? Clearly a raccoon. That large dark bird with a white head and bright-yellow beak soaring overhead? Definitely a bald eagle. But other groups of animals can confound even the most experienced naturalist.
That’s the predicament Hakai Institute scientist Matt Lemay recently found himself in. A trio of summer bioblitzes, conducted on British Columbia’s Calvert Island between 2017 and 2019, had left Lemay and his colleagues with a considerable collection of sea stars belonging to the genus Henricia, otherwise known as blood stars for their sanguine hues. These sea stars are notoriously difficult to identify, since they include many examples of what biologists call cryptic species—related organisms that look alike, but are actually separate species.
Without the help of genetics, it’s nearly impossible to tease apart cryptic species. So though it’s tempting to organize blood stars by looks—grouping them by color, skin texture, or arm length, for example—you’ll almost certainly come away flat-out wrong.
Lemay recently demonstrated how perplexing these species can be when he posted a collage of blood stars to Twitter and invited people to guess how many species were pictured. One respondent speculated they were all distinct species—a whopping fifteen in total. Another estimated they all belonged to one species.
“The actual number of species? I wasn’t sure how many we’d get until we sequenced their DNA,” says Lemay.
