All about sponges - and more

In the underworld city of the coral reef ecosystem exist thousands of species of plants and animals, all of which co-exist with each other. These living organisms are either dependent on each other for food or for protection from predators, or both. One such animal, the sponge, is the definition of a symbiotic species, one that has working relationships with many plants and animals. Despite the fact that the sponge is the simplest form of a multi-cellular animal, containing no tissues or organs, this often brightly colored animal plays many important roles in the reef ecosystem.

    There are over 5,000 species of sponges throughout the world, the majority of which occur in saltwater. The sheer variety of shapes and sizes in which this animal appears is a unique characteristic - no other invertebrate (animal lacking a backbone) comes close. Some brightly colored sponges are even mistaken for coral. The tube sponge, one of the most common varieties on the reef, is distinguished by long tube-shaped growths, ranging in color from blue to purple. Another species that inhabits the Caribbean is the vase sponge, characterized by a large bell shape, either purple or red, which can grow to two feet wide by three feet high.

Reef Brief is a weekly column published in the San Pedro Sun
    There are essentially two main categories that sponges can be divided into: encrusting or free-standing sponges. Encrusting sponges tend to cover the exterior of rocks, while free-standing sponges, the type most commonly known, grow into odd shapes and tend to be quite large (up to six feet in diameter). Both types of sponges are known to be bottom-dwellers, and most attach to a solid surface in an area where sufficient food exists, allowing it to grow. Covered with pores, by which water is sucked in, sponges feed by filtering out microscopic nutrients of plants and animals and expelling the remaining water through a large opening at the top of their head. While feeding, sponges usually seek out cavities of the reef to avoid predators such as the sea hare. At the same time, sponges often provide an ideal habitat for invertebrates, such as shrimp and brittle stars.

    If sponges don't have organs or tissues, how can they possibly reproduce? Sponges have evolved the ability to mate as either a female or a male, increasing their odds for success. When it comes time to mate, one sponge assumes a female role, while the other plays the role of a male. Throughout their lifetime, sponges are capable of playing both the female and male role. Just like typical reproduction, the male sponge releases sperm, which enters the female sponge. Internal fertilization takes place, and after the larvae is released and has drifted for a few days, they descend onto a surface and begin growing.

    Sponges are commonly observed throughout the coral reef ecosystem. Of the vast amount of species that exist, only 17 species of sponges are commercially valuable, comprised of the colorless variety seen in kitchens and bathrooms around the world. The majority of sponges, however, are vividly colored contributing to the rainbow of life that exists below the sea. And like most other inhabitants of the coral reef ecosystem, the valuable role of sponges cannot be underestimated.

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