Found in saltwater and freshwater environments worldwide, sponges are an essential part of the environment. While they are commonly mistaken to be a form of plant life, these creatures are actually part of the animal kingdom. With several features in common with one another, there are approximately 10,000 known sponge species, each of which is specialized for life in a specific environment. They add color and excitement to the underwater world, and they help keep water clean. Let’s take a peek.
What are Sponges? The Basics
It’s impossible to describe these animals without providing at least a little scientific information. Part of the phylum Porifera, sponges come in a variety of shapes and sizes, with the largest being bigger than the average diver. All sponges have bodies made up of a jelly-like mesohyl, or endoskeleton, which is sandwiched between two outer layers of cells. Sponges are a very basic life form. They have no digestive or circulatory systems, and they are non-sentient, having no nervous systems. In order to live, sponges rely on maintaining constant water flow through their bodies. From the water, they obtain oxygen, as well as nutrients. While some sponges are carnivorous, preying on tiny crustaceans, most feed on bacteria. Some host tiny plants that use photosynthetic processes to feed them, and all have optimized the shapes of their bodies to maximize efficiency in a specific environment.
You’ll find sponges in tidal zones, and if you could dive to a depth of more than 8,800 meters, you would find sponges there, as well. These amazing animals reproduce by both sexual and asexual means, and while a few species reproduce by budding, the majority of sponges form larvae which swim away from their parents to find a place to settle. Some sponges produce survival pods, which stay dormant until appropriate growth conditions occur.
Sponges are divided into three main classes based on the structure of their endoskeletons. These are the Calcarea, Demosponges, and Glass Sponges. While some sponges are completely stationary, others are capable of moving a few millimeters each day.
Common Sponges
While some tropical sponges can live for 200 years and some of the largest are believed to be thousands of years old, most temperate sponge species only live for a few years. Of these, many different species look much like one another. Some of the most commonly encountered sponges include the following:
-
Tube Sponges – Distinguished by their long tube shaped growths, these sponges are usually purple, blue, grey, or greyish green in color. Tube sponges are one of the few blue colored reef invertebrates.
-
Vase Sponges – Commonly found in the Caribbean and around the east coast of Florida, Vase Sponges can grow to be about 3 feet high and 2 feet across. They range in color from brown to red to purple, and are normally found attached to rocks.
-
Red Tree Sponges – Bright red, and common throughout the Caribbean, the Red Tree Sponge normally grows to about 8 inches high. This species thrives in shadowy places and prefers areas with at least a little current.
-
Yellow Sponge – Ranging in color from light yellow to bright orange, these encrusting sponges are usually found throughout the Pacific Northwest area of the United States and Canada. Sometimes mistaken for coral, these sponges can completely coat rock structures, although growth is normally patchy.
-
Redbeard Sponges – Found in the Chesapeake Bay and other similar habitats, these sponges have thick, intertwining branches. Ranging in color from orange to red, they can grow to be about a foot tall and 8 inches wide.
-
Elephant Ear Sponges – Huge, and bright orange in color, these sponges are found in tropical climates such as Bonaire. They can grow to be several meters across.
-
Rope Sponges – Tree like in form, and also known as Row Pore Rope Sponges, they range in color from shades of purple to shades of red.
-
Barrel Sponges – Found in the Caribbean and other warm waters, barrel sponges are enormous; some are large enough to fit a person inside, although you never want to risk damaging one of these ancient creatures. Take a close look at the rim; this portion of the sponge is very delicate, even though their ridged surfaces tend to be quite hard. About 95 percent of sponge species are classified as Demospongiae, of which barrel sponges are a part.
These are just some of the most common sponges you might encounter while diving. Depending on where you dive, you’ll find different species, for example, Glass Sponges are found primarily in polar regions and in very deep, icy water in other places, so unless you decide to dive the Arctic Circle you may never see one of these animals.
Ecology
While sponges help to keep water clean, many of them also provide homes for crustaceans, fish, and other small creatures. In addition, sponges serve as food for some fish, and sea turtles enjoy grazing on a variety of different sponge species.
To defend themselves, some sponges shed spiny spicules, forming a deep, dense carpet that prevents echinoderms such as sea urchins from preying on them. Some produce toxins that prevent sea squirts and bryozoans from growing on or near them, and others, like the Caribbean fire sponge, cause a severe rash in divers who make the mistake of handling them. Still others, such as the Chondrilla Nucula, or Chicken Liver Sponge, secrete toxins that kill coral polyps, allowing these sponges to take over small segments of a living reef. Others use biocorrosive agents to tunnel into hard coral, mollusk shells, and even rocks.
Still other sponges form alliances with other organisms, sometimes allowing themselves to become overgrown as a means of protection from predation. One of the most interesting alliances that sponges have formed benefits humanity; some sea sponges are an important source of medicines. Luckily, sponge aquaculture, which has been used for centuries to grow sponges deemed important to humans for a variety of reasons, has become even more prevalent, allowing us to take advantage of the many benefits the sponge has to offer, while helping to keep our water clean. A great example of conservation in action, it requires minimum infrastructure and is one way developing countries can continue to make a livelihood based on the ocean, without causing harm; and keeping our reefs healthy helps us all live better lives.