Siphonophores are ocean-dwelling animals, closely related to jellyfish. There are about 175 species known today, with some reaching lengths of 130 feet, making them the longest animals on the planet. Also, these creatures are extremely thin; about the same circumference as a broom handle. Their habitat is deep in the ocean, where they live among many other invertebrates, aenenome, coral, and crustaceans. Some people refer to them as gelatinous strings.
Although it’s amazing how long these animals are, it’s not their measurement that makes them so interesting. Siphonophores are unique because of their physical makeup. Called, Colonial Animals, siphonophores are composed of groups of integrated and highly specialized zooids. A zooid is a single animal that is also part of a colonial animal either through a shared exoskeleton or tissue link. Each is its own organism but is incapable of survival on its own. They do not come together to form a colony, but instead arise by budding from the first zooid, which itself develops from a fertilized egg.
Siphonophores are unique as compared to most other colonial animals. There is a high degree of specialization between the zooids; so high that ones specialized for one function can only do that one function. As an example, the nectophores that specialize in moving the colony through the water can’t eat; likewise, the feeding polyps can’t swim. Each one depends on the others to do what it can’t do.
Siphonophores have evolved into very complicated organisms, just as human beings have, but their own way. Our bodies are made up of specialized cells that are arranged into tissues and organs while siphonophores are made up of specialized zooids organized at the level of the colony.