17 New Dazzling Species of Sea Slugs Discovered

Hypselodoris violacea. (Photo: Terry Gosliner/California Academy of Sciences)

In a day and age when it seems like so many species are becoming endangered or going extinct, it's a welcome celebration when 17 new species of an animal are discovered — especially ones as bright and colorful as these sea slugs.

These sea slugs, also known as nudibranches, live in coral reefs across the Indo-Pacific region.

A team of researchers led by Terry Gosliner from the California Academy of Sciences analyzed a variety of images of nudibranches from the genus Hypselodoris, detailing their behaviors and mating habits. Studying the color and anatomy of these nudibranches, the research team reorganized the family tree after they determined that there were 17 new species in the Hypselodoris family. They published their findings in the Zoological Journal of the Linnean Society.

"When we find an anomaly in color pattern, we know there’s a reason for it," said lead author Hannah Epstein, former California Academy of Sciences volunteer and researcher at James Cook University in Australia. "It reveals a point in evolution where a selective pressure — like predation — favored a pattern for camouflage or mimicking another species that may be poisonous to would-be predators."

One example of color anomalies are the two Hypselodoris ibas pictured above. For years, scientists believed they were two different species. The lavender iba was believed to be Hypselodoris bullocki until a photographer captured an image of two mating. Gosliner's team studied the image and determined that they were, in fact, the same species but with different color tones and patterns.

"When two different species like H. iba and H. bullocki present in the same color, the simplest explanation is that they share a common ancestor," said California Academy of Sciences Dr. Rebecca Johnson. "These two species, however, are pretty far apart on the family tree: the more likely explanation for their similar appearance is that they reside in the same geographic region where being purple is advantageous for avoiding predators either as camouflage or warning of distastefulness."

The team assembled the rest of the recently discovered species into different "color trees" to better understand how evolution affects their vibrant colors.

"Sea slugs have an arsenal of strategies for surviving, from mimicry to camouflage to cryptic patterns," said Gosliner. "We’re always thrilled to discover new sea slug diversity. Because nudibranchs have such specialized and varied diets, an area with many different species indicates a variety of prey — which means that coral reef ecosystem is likely thriving."

The other nudibranches can be seen below in their full technicolor glory.

Hypselodoris confetti. (Photo: J. Goodheart)
Hypselodoris melanesica. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris variobranchia. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris peri. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris rositoi. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris lacuna. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris alburtuqali. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris cerisae. (Photo: Rie Nakano)
Hypselodoris juniperae. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris katherinae. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris paradisa. (Photo: Vanessa Knutson)
Hypselodoris roo. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris skyleri. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris yarae. (Photo: Terry Gosliner/California Academy of Sciences)
Hypselodoris brycei. (Photo: Nerida Wilson)