Mysterious Creatures and Their Powerful Impact on Habitats


Seeing dolphins at the bow, colorful corals, soaring sea birds and lively fish never gets old. Yet, new encounters with unique species are also a wonderful part of boat life. As boaters who frequent marinas, beaches and waterways, we have all either heard or uttered out loud, “What IS that?”

While a lot of marine life could illicit this response, a brief look at some of the usual suspects — the sea hare, sea cucumber, sea pork and horseshoe crab — can help us appreciate and protect the marvelous mysteries of our marine ecosystems.

Not Batman

Sea Cucumber
Sea cucumber | Credit: plovets

We were at a marina in Key West when a dark, undulating creature was swimming at the surface of the clear blue water. A small crowd gathered, none of whom had ever seen anything like it. The soft-bodied creature had two small horn-like structures and “wings” spread out like a Batman cape. Before long, imaginative guesses were replaced with researched confirmation that we’d encountered a sea hare.

Sea hares are mollusks named for the large tentacles on their head that remind some of the ears of a hare. Their small interior skeleton is covered by a soft mantel with external wing-like extensions the length of their body. Their color, ranging from dark maroon to browns and greens, is dependent on the color of the algae they eat.

As an important food source for many marine predators, they are also valuable in neuro research. Sea hares do not have an abundance of neurons, but they do have some of the largest neurons in the animal kingdom. This distinct anatomy makes it easy for researchers to isolate individual nerve cells and identify which are responsible for specific behaviors. The sea hare is an important contributor to the study of memory, behavior and learning in human neurology.

Not a Vegetable

Nature has no shortage of marine specimens whose names do little to help us understand them. A fitting example is the sea cucumber. This species may have the general shape of a cucumber, but that is where the resemblance ends and the question, “What IS that?” begins. While swimming or snorkeling in shallow waters, you may happen upon what appears more like an ugly potato.

Though harmless to humans, disturbing them is not recommended as they have a startling method of defense. When concerned for their life, they expel their internal organs. Known as evisceration, the tubular organs are unappealing, sticky and toxic to predators.

Living on the sea floor, usually near grass beds and coral reefs, sea cucumbers tend to burrow or be covered in sand, much like earthworms. Like worms, they provide nutrient cycling as they take in sediment, absorb food particulates and expel clean sand. This process releases nitrogen and calcium carbonate, key components for healthy coral reefs. One study showed a sea cucumber population produced over 70,000 tons of this valuable excrement a year.

Surprisingly, these unsung heroes of our coral reefs are overharvested. They might not taste like their namesake, but they are a luxury food item, prominently featured on menus for festive and formal dinners in many Asian countries. Fortunately, like their namesake, sea cucumbers are relatively easy to farm, and aquaculture farms may play a pivotal role in their conservation.

Not a Brain

As odd as the sea cucumber may seem, it is far from the most queried. That honor probably goes to the equally poorly named sea pork. Beachgoers who happen upon sea pork washed ashore inundate local fish and wildlife organizations, aquariums, police and even television stations with calls asking, “What IS that?”

The inquiries are understandable. When found on beaches or in seagrass beds after storms, the rubbery sea pork can resemble brains, chicken cutlets, waterlogged organs or petroleum byproducts. When alive, sea pork, the common name for tunicates, are stationary filter feeders. Spending their lives siphoning water and feeding off bacteria, they are considered our oceans’ best purifiers.

Horseshoe Crab
Horseshoe crab | Credit: aimintang

Not a Crab

Gliding along in shallow water or creeping along the shore, the prehistoric-looking horseshoe crab is a frequent recipient of “What IS that?” proclamations. More closely related to spiders than crabs, the armor-domed, spike-tailed horseshoe crab is falsely intimidating. This harmless bottom feeder’s carapace is its primary defense, and its tail is used as a rudder or to help right itself if it gets turned on its back.

Horseshoe crabs and their eggs are a primary food source for many coastal predators and migrating shore birds. The horseshoe crab’s blue blood has made a significant impact on the biomedical industry. Its copper-based blood contains a substance that will clot in the presence of toxic bacteria. This agent is used to test for bacteria in injectables and to verify the sterility of medical devices.

Encounters that pique our curiosity and inspire us to ask, “What IS that?” are part of what makes boating a mighty adventure. Witnessing strange yet beautiful, weirdly impactful, and small but powerful marine life helps to remind us that our aquatic environment is vast, valuable and worthy of protection.

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