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Ox Heart Tunicate (Polycarpa aurata)

Also known as the ink-spot sea squirt, the ox heart tunicate is a species of styleid tunicate that is distributed throughout the Indo-Pacific. Like all ascidians the ox heart tunicate is a sessile filter feeder and filters any nutrients from the water into its pharyngeal basket and ‘squirts’ it out its atrial siphon.

Phylogeny

Animalia-Chordata-Tunicata-Ascidiacea-Stolidobranchia-Styelidae-Polycarpa-aurata

Image Source(s)

Ascidians | ©billunder   (Bass Point, Wollongong, New South Wales, Australia)

Ascidians are an evolutionary link between invertebrates and vertebrates. They have a primitive backbone at some stage of their life cycle, but in other aspects they resemble invertebrates. Adult ascidians are ‘sessile’ (unable to move around) and filter food particles from the water by pumping water in one siphon and out the other. Their common name of sea squirt arises from their habit of squirting a jet of water when you stand on or near them when they are uncovered at low tide [1].

The photo shows a colony of Botrylloides magnicoecum, commonly known as the Magnificent ascidian. This species, widespread in the Indo-Pacific, forms large colonies in a wide rage of colors from cream, through yellow and brown to dark blue. The Individual zooids are very small, only 1 or 2mm, usually arranged in parallel rows forming lobes. They share an exhalent siphon in centre of the lobe [2]. 

Animalia - Chordata - Tunicata - Ascidiacea - Stolidobranchia - Styelidae - Botrylloides - B. magnicoecum [3]

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Sea Tulip (Pyura spinifera)

…a species of pyurid ascidian (sea squirt) that occurs off the coasts of New South Wales and Victoria, Australia. Like most tunicates P. spinifera is a filter feeder, filtering the water around it for nutrients and expelling out excess. P. spinifera ‘comes’ in a wide range of colors, ranging from white, pink, yellow, orange, and purple. The color is determined by the symbiotic sponge that covers the ascidian’s surface.

Classification

Animalia-Chordata-Tunicata-Ascidiacea-Pleurogona-Stolidobranchia-Pyuridae-Pyura-P. spinifera

Images: Michael McKnight and Richard Ling

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Sea Pineapple (Halocynthia roretzi)

…is a species of sea squirt or tunicate found throughout the waters of the Pacific. Sea pineapples are usually found attached to rocks, corals and man made structures where they filter feed food through their two siphons, they are specially adapted to cold water and can survive in waters as cold as 36 °F. Like Pyura chilensis the sea pineapple is a very popular meal in several Asian countries like Korea and Japan.

Phylogeny

Animalia-Chordata-Tunicata-Ascidiacea-Pleurogona-Stolidobranchia-Pyruidae-Halocynthia-roretzi

Image Source(s)

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