February 12, the anniversary of Charles Darwin’s birthday, is affectionately known as “Darwin Day” in the scientific community. From solar-powered slugs to sea star stomachs, MBL scientists are highlighting some of their favorite adaptations in the animal kingdoms this Darwin Day.

collected specimens of the Dead leaf butterfly (Kallima inachus). Credit: Nipam Patel
Collected specimens of  the dead leaf butterfly (K. inachus). Credit: Nipam Patel

A Leafy Look-Alike

Kallima inachus, aka the dead leaf butterfly, have evolved to resemble dead leaves, which help them avoid predators. The level of mimicry is remarkable, including patterns that look like leaf veins, stems, and “holes,” actually transparent windows, in the wings surrounded by dark spots that resemble mold damage. There is also extensive genetic variation in the population so that no two individuals look exactly alike, and individuals show variations that match different types of leaves.”

  • Nipam Patel
    MBL Director
Bee orchid (Ophrys apifera). Credit: Hans Hillewaert, Wikimedia Commons
Bee orchid (Ophrys apifera). Credit: Hans Hillewaert, Wikimedia Commons

Orchid Mimicry: Animals are Fooled by Plants

“Darwin got a few things wrong in his theories about sexual selection, but one thing he got right was the concept of co-evolution between insects and plants. Orchids have evolved ways to make sure their pollen (containing male sperm) reaches other flowers (containing eggs) so that cross-fertilization, or intercrossing, between two different plants could occur.

One amazing adaptation in five sentences: Intercrossing benefits organisms. Orchids have evolved along with insects to make sure pollen from one orchid gets transferred to another. The flower of the orchid Ophrys apifera evolved petals that smell and look like a female bee to attract the male bee to mate. After an unsuccessful mating with the flower petals, the bee gets some sweet nectar, then travels to the next flower, bringing with it pollen from the first in a win-win for orchid and bee. Together the showiest sweetest flowers get the most pollination from bees and the two are naturally selected for their mutual success.”

  • Anne Sylvester
    Director of Research


Elysia chlorotica (eastern emerald Elysia) in the MBL's Marine Resources Center. Credit: Lisa Abbo
Eastern emerald Elysia (Elysia chlorotica) sea slug in the MBL's Marine Resources Center. Credit: Lisa Abbo

Solar-Powered Sea Slugs

“The mollusk Elysia chlorotica (eastern emerald Elysia) is an amazing little sea slug. It’s a member of Sacoglossa (also known as "solar-powered sea slugs") that has adapted to suck out the chloroplasts from a species of algae, Vaucheria litorea, and retain the chloroplasts in its own body, which it then uses for photosynthesis to generate energy for itself! The Elysia can then go many months without eating, surviving on the energy generated from the chloroplasts. They are also able to regenerate their entire bodies from their heads! Plus, they are just beautiful little creatures.”

  • Lisa Abbo
    MBL Veterinarian


Two photos side by side. One of an orange sea star, the other of that sea star flipped over. In the second image, the sea star has expelled its stomach out of its mouth. It does this to eat prey larger than itself!
A sea star that expelled its stomach out of its mouth. Credit: Margherita Perillo

External Stomach of Sea Stars

“Sea stars are a great example of animals that developed unique characteristics to adapt to their environment. One example is the way they eat their prey—mostly snails, mussels, or even large dead seals!

To adapt to their food source, sea stars hold their prey by the suction of the tube feet, which are tiny protrusions on their legs that also allow them to move. The hungry sea star then pushes its stomach outside its body to engulf prey bigger than its mouth. The snails you see in this picture will be digested where they are, right while they are peacefully living inside their shells. Thanks to this feeding adaptation, sea stars can eat everything they find on their way—a skill that helped them colonize and survive in every ocean of our planet!”

  • Margherita Perillo
    Research Scientist, Bell Center for Regenerative Biology and Tissue Engineering
Aeolid nudibranch, Hermissenda opalescens. Yellow tipped, finger-like projections (cerata) on the animal’s back store the stinging cells. Credit: A.M. Kuzirian
Aeolid nudibranch, Hermissenda opalescens. Yellow tipped, finger-like projections (cerata) on the animal’s back store the stinging cells. Credit: A.M. Kuzirian

Nudibranchs: You Are What You Eat

“Aeolid nudibranch mollusks that feed on cnidarian hydroids like sea anemones and jellyfish have adapted the unique ability to use the stinging cells (nematocysts) from the hydroids they eat for their own defense against predators. The nudibranch can ingest the nematocysts without triggering them to explode and emit their toxin, pass them through the gut, and store them in a special pouch at the tips of their cerata. 

The animal’s skin and the lining of the entire gut secretes a specific mucus (mucopolysaccharide) that keeps the nematocysts intact. Fish or crustacean predators receive a massing dose of stinging cells if they try to munch on and eat the nudibranch!”

  • Alan M. Kuzirian
    Senior Scientist, Emeritus
A huge flock of starlings in the sky at dawn. Starling Murmations. Credit: Albert Beukhof Freepik.com
A huge flock of starlings move together in murmuration in the Netherlands. Credit: Albert Beukhof, Freepik.com

Murmuration Magic

“Birds have many amazing adaptions, but I am simply amazed by their ability to fly in a coordinated way in huge numbers. Many types of birds flock when foraging or migrating. Starlings (Sturnus vulgaris) are known for their 'murmurations', which can include hundreds of thousands of birds in a rapidly changing mass. Each bird's flight path is based on its observation of its nearest neighbors.”

  • Hilary G. Morrison
    Senior Scientist, Josephine Bay Paul Center