Some of the mysterious invertebrates from our blue planet have earned an illustrious association with fruit.

Let’s deeper dive and learn about some of these animals that deserve a closer look. 

Sea Apple

Sea apples are one brightly colored species of sea cucumber! They are aposematic, which means they have warning coloration to signal to predators that they are poisonous, and even produce poisonous eggs. These and other echinoderms like sea stars and sea urchins are not sexually dimorphic, so you cannot tell males and females apart by appearance. But they do reproduce sexually by spawning! When sperm released from males and eggs released from females meet in the water column, they form a planktonic (free-floating) zygote.

When responding to stress, many sea cucumbers can expel their organs to distract hungry predators. Sea apples, however, have an additional ability: typically, adult sea apples get to be at most 8 inches long, but they can inflate to twice their normal size—comparable to a volleyball—to ride the current to safety. While we do not have sea apples on exhibit at the Aquarium, you can still find other kinds of sea cucumbers in the Edge of the Sea exhibit and Northern Waters Gallery.

sea apple
Sea apple | Photo: Bradley Wm. Bowen via Wikimedia Commons
Sea Peach

Sea peaches, also known as sea squirts (not to be confused with our little learners in our Sea Squirts classes!), are a type of tunicate. Tunicates are named for their “tunic,” a protective, tough layer of skin. They are invertebrates with a trait you might not expect. At one phase of their life they have a primitive spine! During their larval phase, tunicates have a supportive rod called a notochord, making these animals the closest relatives to humans of all invertebrates.

While some tunicates are free floating, sea peaches are sessile, meaning they settle at the bottom of the ocean on whatever substrate they can anchor to. Once there, they can filter feed on bacteria and plankton, much like sea anemones! They have the same vulnerabilities as anemones, so poor nutrient levels in the water or fishing practices that damage the substrate can cause problems for these species. You can find them as deep as 100 meters below the surface, and the colder their habitat is, the bigger they tend to grow! Sea peaches hang out in our Northern Waters Gallery—and you might be lucky to see them in our Boulder Reef or Eastport exhibits, too!

Sea peach
Sea Strawberries

Sea strawberries are a species of octocoral, a grouping of corals that have eight feeding tentacles, eight fold symmetry to their bodies, and typically lack a hard calcium carbonate skeleton. All soft corals belong to this subclass along with sea pens, whips, and fans. Although they don’t have a tough exoskeleton like hard corals, octocorals have tiny, stiff calcium carbonate spines called sclerites, which give their bodies shape and help them attach to substrate. If you’ve seen our blue coral skeleton at the coral cart where you can get your learn on with our educators, that is a species of octocoral as well! They are the only exception to the rule as they build expansive skeleton structures. Large groups of sea strawberries are called strawberry grounds and serve as nursery habitats for many other species like lobsters and basket stars.

sea strawberry
Sea strawberries | Photo: Derek Keats via Wikimedia Commons
Sea Grapes

Sea grapes is a nickname for many species of seaweed in the genus Caulerpa. One species, Caulerpa lentillifera, is popular to eat, particularly in the many Asian countries where it grows, including Indonesia, Philippines, Vietnam, Thailand, and Japan. This algae is succulent and prepares well in many styles, providing an array of nutrients and vitamins. Caulerpa lentillifera contains high quantities of vitamin A, vitamin C, magnesium, and iodine. Seaweed in general is known to protect many species of juvenile fish in the wild, making it highly valuable to life above and below the surface.

sea grapes
Seaweed known as sea grapes | Photo: jpatokal via Wikimedia Commons
More Sea Grapes

Cuttlefish eggs also receive the nickname sea grapes! Different species of cuttlefish lay slightly different looking eggs, but they all tend to retain a distinct oval shape. Cuttlefish lay them on substrate in bunches, and here in the Aquarium on plants in their habitat. Pharaoh cuttlefish lay white eggs, but common cuttlefish put a small amount of ink into their eggs, making them black. Eggs take one to two months to hatch depending on the temperature of the water, and our cuttlefish exhibit is on the colder side of that spectrum. Female cuttlefish can continue to lay eggs through their entire lives, so it doesn’t take long to see protective behavior from their mates! Many larval phase marine animals look strikingly different from their adult counterparts. But baby cuttlefish look like miniature versions of their parents right away. There might be some eggs laid by our cuttlefish behind the scenes of the Tropical Gallery right now!

cuttlefish eggs on exhibit
Cuttlefish eggs in the Level 1 exhibit

Come visit the Aquarium the next time you need some fresh, juicy ocean facts! Take a close look at some of the smaller animals, the invertebrates, and plants. Bring your curiosity and questions for our educators. You might just learn something new about our blue planet and what we can do to help protect it. 

This blog post was researched and prepared by Aquarium educator Ruddy Ligonde. Be sure to ask him about the fruits of the flume the next time you visit the Aquarium!