Creature Feature: Halloween edition

The Ocean is an incredible place and harbors some of the most fascinating and recognizable animals in the world. However, there are many living things in the ocean that are reminiscent of aliens, mythological monsters, and other frightening creatures. With Halloween approaching there is no better time to shine a spotlight on some of these spooky yet captivating creatures.

Photo of a giant isopod
Giant isopod, photo by FMM staff

Giant Isopod

To begin this list let’s take a look at the giant isopod. This unique creature may look like an extremely large insect but it is actually a crustacean. The giant isopod can grow to over a foot in length making them one of the largest crustaceans and the largest known isopod. While this species may look intimidating, they are not dangerous to humans. In fact, humans are unlikely to cross paths with a giant isopod in the wild because this animal primarily lives at depths greater than 500 ft. When threatened, this species will curl into a ball, similar to pill bugs, in an effort to protect themselves from harm.

Photo of a bobbit worm
Bobbit worm, photo © anemone,

Bobbit Worm

One of the more frightening ocean dwellers isn’t a shark or another species of fish, but rather a species of marine worm. Found living in the sea floor at a depth of 30-130 ft., the bobbit worm uses its 5 antennae to sense potential prey. When prey is sensed the worm will lash out with mandibles so strong and sharp, they sometimes cut their prey completely in half. Once prey is captured the bobbit worm will store the remains in its burrow for future feeding. In addition to their frightening mandibles, the size of the bobbit worm can be incredibly intimidating. While we typically think of worms rarely growing to sizes greater than several inches, bobbit worms often grow to sizes around 4-5 ft. with the largest individuals reaching over 9 ft. in length.

Photo of a decorator crab
Decorator crab, photo © ead72,

Decorator Crab

One group of animals that are more quirky than frightening are the decorator crabs. These crabs live the majority of their life coated in anemones, algae, sea urchins, coral, and other small marine organisms. These crabs wear this costume of critters as a method of camouflage and defense against predation. If covered in the proper material the crab will look nearly invisible on reefs or the seafloor. Decorator crabs are found worldwide and several distinct species of crab are classified as decorators. Because there are several species of decorator crab their size and diets will vary. Typically these crabs grow up to about 5 inches and have a diet consisting of algae, small crustaceans, sponges, and detritus.

Photo of spotted garden eels
Garden eels, photo©Vladimir Wrangel,

Garden Eels

Garden eels are an eerily beautiful species of fish. Their snake-like appearance combined with their tendency to form large colonies is reminiscent of the Greek monster Medusa’s snake hair. However, while one gaze at the face of Medusa would turn you to stone, you would be lucky to come face to face with a garden eel in the wild as they are painfully shy. There are about 35 species of garden eels and they can be found in warm waters around the world. While most other eels swim freely, garden eels have the tendency of burrowing and “planting” themselves into the sand. Swaying in the current, these eels feed on passing plankton and can form colonies of over a thousand individuals.


Author: Andrew Pressly, Education and Engagement Coordinator at FMM


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