What are Tunicates?

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Why in news?

The new fossil, named Megasiphon thylakos, revealed that ancestral tunicates lived as stationary, filter-feeding adults and likely underwent metamorphosis from a tadpole-like larva.

About Tunicates:

These are commonly called sea squirts which are a group of marine animals.
They spend most of their lives attached to docks, rocks or the undersides of boats.
About 3,000 species of tunicate exist in the world’s oceans, living mostly in shallow water.
They are a species of marine invertebrates with an evolutionary history from atleast 500 million years ago.
Researchers are interested in them as they are the closest relatives of vertebrates, which includes fish, mammals, and people.
There are two main tunicate lineages namely;
- Ascidiaceans: They are often called “sea squirts and most ascidiaceans begin their lives looking like a tadpole and mobile, then metamorph into a barrel-shaped adult with two siphons. They live their adult life attached to the seafloor.
- Appendicularias: They retain the look of a tadpole as they grow to adults and swim freely in the upper waters. These seem extremely far removed from vertebrates.
Features
- Tunicates are truly strange creatures that come in all shapes and sizes and have a wide variety of lifestyles.
- An adult tunicate’s basic shape is typically barrel-like, with two siphons projecting from its body.
- One of the siphons draws in water with food particles through suction, allowing the animal to feed using an internal basket-like filter device.
- The other siphon expels the water.

Q1) What are Invertebrates?

Invertebrates are characterized by their lack of a backbone or vertebral column. Instead, they have other structural features that support and protect their bodies. Invertebrates comprise a vast array of animal groups, including insects, spiders, crustaceans, mollusks etc

Source: Science for All | What are tunicates?