Tag Archives: Invertebrates

The Spineless Gutless Sea Cucumber

Sea cucumbers: those cute log-like animals munching their way along the sea floor. These cylindric invertebrates are part of the phylum Echinodermata which translates to “spiny skin”.

Echinodermata is a completely marine based phylum that includes sea stars, sea urchins and of course, the lovable sea cucumbers. Most days you can find innocent sea cucumbers minding their own business and sucking up sand and mud like a vacuum. The sea cucumber sifts through and feeds on the organic pieces hidden in the sediment. If you have visited CIMI, you may have had the pleasure of holding a sea cucumber that can be found in our cove, Parasichopus californicus, or the warty sea cucumber. A muddy orange-brown color, these guys are named after the wart like bumps that cover their body.

Spineless Sea Cucumber

Sea cucumbers, like the warty sea cucumber, are eaten by a number of different organisms. Predators include types of crabs, fish, sea stars and sometimes sea turtles. How do these spineless logs defend themselves against predators? They can not move very fast, so a quick escape is rarely an option. Sea Cucumbers have evolved a very interesting and gross way to escape possible death by crab or fish. Evisceration!

Spineless Sea Cucumber 2

Evisceration basically means exploding guts. The root word in eviseration, “visera” means “intestines”. When a sea cucumber feels threatened it can spew its intestines and other internal organs at a predator. The predator is distracted by the free snack, allowing the sea cucumber to inch away. Evisceration begins when the attatchment tissues that hold the internal organs, like the intestines or respratory gills, soften. If you’ve ever touched a sea cucumber you’ll have noticed that its body toughens and becomes rigid. Left alone it will losen up and soften again. Like many echinoderms, sea cucumbers can toughen or soften their body texture at will. Once the attachment tissue softens and becomes almost liquidfied, spots on the body where the organs will soon spew out begin to soften too. Depending on the species, the evisteration point can be on the anterior (front) or the posterior (back) end of the sea cucumber. Softening takes between one to three minutes. The sea cucumber muscles contract and expell the internal organs! It can take between 20 minutes to 12 hours to complete the process of eviseration. Now that the sea cuumber has rid itself of most its organs and escaped being eaten, it must begin to regenerate. Regenerating its interal organs can take as long as 145 days and as short as 7 days. It depends on the species, age of the organism and the time of year.

Although evisceration is often associated with defense and escape, this is not always the case. It depends on the species of sea cucumber. Some sepecies, like the warty sea cucumber, eviserate seasonally to get rid of excess waste. In addition, during food shortages, sea cucumbers have been know to eviserate. It is actually a larger metabolic load or energy drain on the sea cucumber to hold onto excess waste than to eviserate and regenerate.

Sea cucumbers are pretty amazing! They can live without their internal organs for weeks and spew their guts at predators. They might be gutless at times, and spineless, but they got a lot of spunk for an animal named after a cucumber.





Leopard sea Cucumber – http://phenomena.nationalgeographic.com/2016/05/10/how-this-fish-survives-in-a-sea-cucumbers-bum/

Catalina Coral & Zooxanthellae

What is a coral?

Corals are not rocks, nor plants. They are animals. Invertebrates, specifically. These sessile organisms are colonial—meaning many individual organisms comprise a single coral. These individual organisms are called polyps. Each polyp is complete with a mouth, a stomach, and multi-purpose tentacles. More on that later.

There are two major types of coral: soft corals and stony corals. The stony corals are considered reef builders, oceanic architects. The polyps that create stony corals secrete a hard skeletal structure made of calcium carbonate. Soft corals, on the other hand, have a different kind of support structure. Their polyps contain something called sclerites—a hard plate of chitin, which is what the exoskeletons of arthropods (think crabs and lobsters) are made of. Recent underwater explorations have discovered a third type of coral: deep sea coral. 20,000 below the surface of the ocean thrive both stony and soft corals. They differ from the shallow water corals in one major respect—they don’t need sunlight to survive.

That Big Ball of Energy

Photosynthesis. The process of converting the sun’s light energy into chemical energy. Many corals have the ability to do this. But polyps cannot complete the task on their own. To create their food source, their energy for survival, they obtain help from zooxanthellae. Put simply, zooxanthellae are microscopic algae. These algae find their home in the surface tissue of coral polyps. In return for shelter, these algae give coral the energy they need to survive. Additionally, these zooxanthellae provide a plethora of colors and patterns for corals. That rainbow of life that paints the iconic coral reefs of the world is much in thanks to zooxanthellae. The relationship between the polyp and zooxanthellae is symbiotic and mutually beneficial. Each one needs the other for its survival. When conditions in the ocean become inhabitable (think: too warm, too acidic), zooxanthellae are kicked out. The polyps, in times of stress, will expel their zooxanthellae—leaving the coral stark white and starving. This is called a coral bleaching event.

The Corals of Catalina Island

Most corals are found in warm tropical waters, near the equator, where there is clear water and ample light for photosynthesis to occur. Catalina lies in a temperate, nutrient rich zone of the ocean—not ideal for a coral reef. Nevertheless, among rocky reefs of Catalina exist a handful of coral. Purple Hydrocoral. Sea Pens. Cup Coral. Gorgonians. Although they are not reef-building corals, they fill their own ecological niche in their home waters.







Mantis Shrimp

Screen Shot 2016-03-29 at 11.20.43 AMMantis Shrimp are neither a shrimp nor a mantis. These odd looking creatures fall under the Subphylum of crustaceans and are in the same class as shrimp, crabs and lobsters. Mantis Shrimp have their own order called Stomatopods, which contains over 450 different species of these animals.

We can separate Mantis Shrimp into two main categories: spearers and smashers. This is in reference to their front appendages. Spearers have an almost spear like appendage that is used to snag soft bodied prey, while smashers have developed a thickened, hammer like appendage used to break shells and exoskeletons. *The Mantis Shrimp seen above is a smashing Mantis Shrimp.

While these animals seem cute and cuddly these are actually one of the most dangerous animals we have the ability to see around Catalina. The Mantis Shrimp will use its smashing and spearing appendages at great speeds to immobilize or kill its prey. The estimated speed at which these animals use their raptorial claws is the same as the acceleration of a .22 caliber bullet or 10,000 times the force of gravity. This movement is so fast that water vaporizes around the claw meaning the Mantis Shrimp’s prey gets hit twice: once by the claw itself and once by the resulting shock wave.

Screen Shot 2016-03-29 at 11.20.19 AMWhile these animals do seem quite dangerous, when seen in the ocean, they will most likely stay hidden within their burrows. Mantis Shrimp create “L-shaped” burrows that conceal their entire body. They will then poke their head out to watch out for predators or to find prey. If you ever observe a Mantis Shrimp the chances are they will retreat into their burrow away from any trouble. However if they do not retreat be wary for the Mantis Shrimp really packs a punch!

Crabs: Crusty or Crustaceans?

Crabs are members of the phylum Arthropoda, which means jointed appendages. Anyone who has picked up a crab, only to have it reach behind and pinch them, knows this is true! Crabs have a thick exoskeleton, or skeleton on the outside of their bodies. Since they are invertebrates, this allows them to have a rigid body shape without a spine. Because of this, when crabs grow they must molt, or shed, their exoskeleton and grow a new one. Most crabs also have a single pair of claws, also called chelae.

It is actually very easy to tell the difference between a male and female crab. On the underside of the carapace, or body, of a crab there is a shape. In male crabs, this shape is a thin triangle. In females, the bottom of the carapace has a large semicircle. Females need this extra space to hold fertilized eggs underneath this flap.

Female Crab (1)

Female Crab

Male Crab

Male Crab

Crabs are omnivores, feeding on algae and other organic material on rocks or the sea floor. On Catalina Island, you can find crabs in a variety of habitats. When tidepooling in the intertidal zone you can often find a Striped Shore crab. While snorkeling near the rocky reef, you might find a Dungeness crab wedged into the rocks. Snorkeling over the sandy bottom in the spring often yields a large Sheep crab.

Striped Shore crabs (Pachygrapsus crassipes) have a dark carapace with thin black and dark green stripes running horizontally. Across the back, they average 3 inches across. Their claws are usually a bright red or pink coloration, and their other appendages are striped or black. They live high in the intertidal zone and spend at least half their time out of water. They must return periodically, however, to wet their gills. They primarily feed by scraping algae off of rocks, but occasionally eat other invertebrates. Their predators include birds and two-spot octopus.

Dungeness crabs are also commonly called Cancer crabs because of their scientific name, Cancer magister. They are common throughout California. They can grow up to 9 inches across, with males averaging 7 inches across the back, and females averaging around 6 inches, making them one of the largest edible Pacific coast crabs. Their backs range from light reddish to purple, and their claws are usually black.

Cancer Crab

Cancer Crab

Sheep crabs are the largest California spider crabs (Majidae). They have long legs and an oval shaped body. The carapace is covered in bumps and, usually, algae and barnacles. Juvenile sheep crabs decorate themselves with algae, barnacles and bryozoans to camouflage themselves. Adults usually have enough built up on their carapace to stop decorating themselves. Sheep crabs spend the winter in deep water, migrating to shallow water in the early spring to mate. While some crab species can molt their entire lives, sheep crabs have a terminal molt. This means that at a certain age, sheep crabs are unable to increase in size or regenerate lost limbs. Males can get up to 10 inches across the back, females to 7 inches. They are scavengers that feed on almost anything.

Sheep Crab

Sheep Crab

Remedies for a Jelly Sting

Animals in the phylum Cnidaria, which means “stinging nettle,” possess stinging cells called nematocysts. Cnidaria includes jellies, box jellies, sea anemones, corals, sea pens and hydroids. Nematocysts are cells that operate like a combination between a spring and a harpoon. A spring with a barbed tip is wound underneath a trap door covering called an operculum. When properly stimulated, this door opens, allowing the poison-coated barbed tip to spiral out towards its target. Only certain species of Cnidarians have springs and barbs strong enough to penetrate human skin, which results in the commonly recognized jelly sting.


The well-known folk remedy for a Cnidarian sting is urine. However, urine has the wrong chemical composition for inactivating the nematocyst, so this method does nothing but supply embarrassment to the involved parties. According to the American Red Cross, the best way to deactivate the stinging cells when stung is to rinse the area with vinegar for 30 seconds. Then, according to the American Heart Association, the best way to relieve the pain of a sting once deactivated is to rinse or soak the area in hot water for 20 minutes.

Navanax: Snail & Slug of the Sea

While most animals found on the sandy bottom areas around CIMI spend most of their time trying to blend in with the sand, the Navanax (Navanax inermis) sticks out like a clown at a camouflage convention. Some head shield slugs like the Navanax and their colorful relatives Nudibranchs have opted out from hiding and instead use colorful displays to send out the message of “yea, I know you can see me, come at me bro…” They spend their time searching the sand for slime trails left by other snails and slugs. Navanax use chemoreceptors on the front of their body to follow these trails of slimy mucous and use their impressive (for a slug) speeds to catch up with, and then devour, their prey.

Navanax will also use this “follow the slime” method to find potential mates. When two of them meet they will first try to eat each other and if that is unsuccessful (usually because they are the exact same size) they will then mate. Scientists have learned a lot about defense mechanisms of other slugs and snails by tracking and recording the eating preferences of the Navanax. Basically, if an eating machine like the Navanax doesn’t want to eat an animal, then that animal is doing something right!

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Writing and Photo Credit: Phil Lemley

Sea Cucumbers: The More You Know

Sea cucumbers are a species of invertebrates under the phylum Echinodermata similar to sea stars and sea urchins. Sea cucumbers live in the benthic zone or ocean floor. They are nocturnal creatures but can be seen in the day as well. Sea cucumber uses their tube feet for locomotion and eating. The mouth is surrounded by twenty retractable tentacles that help them bring food in. They may seem slow, but have a very effective defense mechanism called evisceration in which they can jettison their internal organs to distract or in hopes their prey will eat their organs instead of attacking them. Sea cucumbers can regenerate these organs within days.

Sea cucumbers diets consist of algae, aquatic invertebrates, and waste particles in the ocean. Sea cucumbers are in high demands in Asian markets for their use in medicine and food. Sea cucumbers reproduce by the female launching her eggs in the waters, the male does a similar process with his sperm. Sea cucumbers can also self-reproduce as well.

Sea cucumber’s shape is elongated and is found on the sea floor worldwide. The most common species found on Catalina Island include the warty sea cucumber and the giant California sea cucumber.



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