Sea squirt Facts

Sea squirt Facts
Sea squirts are immobile (sessile) marine creatures that belong to the group of tunicates. There are more than 3.000 species of sea squirts that can be found in the oceans around the world. Despite their primitive appearance, sea squirts are chordates (phylum of animals which also includes fish, amphibians, reptiles, birds and mammals). Sea squirts exist on the planet at least 500 to 600 million years. Most species inhabit warm, shallow tropical waters, usually near the coral reefs. Sea squirts are numerous and widespread in the wild (they are not on the list of endangered species).
Interesting Sea squirt Facts:
Sea squirt can reach 0.2 to 4 inches in length.
Sea squirt can be green, yellow, red, orange, pink, blue, brown or white colored, depending on the species and its habitat.
Body of sea squirt is covered with membrane, called tunic, which consists of living tissue with its own blood supply. Tunic is usually smooth and very rigid.
Sea squirt has sac-like, cylindrical (rarely roundish or bell-shaped) body with two siphons on the upper side.
Sea squirts often form colonies that look like grapes or rubbery blobs on the seafloor.
Sea squirt is filter feeder. It absorbs water with edible particles through the siphon and separates plankton and algae from the water in the pharynx and lower parts of digestive system.
Some species of sea squirts use tentacle-like structures to catch jellyfish and small fish.
Sea squirts use second siphon for the elimination of waste products.
Natural enemies of sea squirts are eels, large fish, snails, starfish and crustaceans.
Sea squirt ejects water from the siphon as a response to touch (or when someone tries to pull it out of the water), hence the name "sea squirt".
Sea squirts have both types of reproductive organs. Each animal releases eggs and sperm cells directly into the water, where they mix and merge with sperm cells and eggs of other sea squirts (self-fertilization happens rarely).
Fertilized eggs float as a part of zooplankton from 12 hours to three days. Larvae have numerous anatomical features of vertebrates and they look like tadpoles. Shortly after hatching, larvae migrate to the ocean floor to find suitable spot where they will spend the rest of their life, attached to the substrate.
Larva attaches to the rock or some other solid object and starts digestion of its own body parts: tail, primitive eye, cerebral ganglion (brain-like organ) and notochord (spine-like structure). This process usually lasts 36 hours and leads to creation of sac-like creature equipped with two siphons and circulatory, digestive, and reproductive systems.
Sea squirt undergoes retrogressive metamorphosis, which means that very complex anatomy of larva transforms into very simple anatomy of adult animal. Sea squirts reach sexual maturity at the age of few weeks.
Sea squirt can survive 7 to 30 years in the wild, depending on the species.

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