Tunicates of St. Eustatius
Tunicates belong to the subphylum Tunicata in the phylum Chordata, which includes all animals with dorsal nerve cords and notocords. Some tunicates live as solitary individuals, but others become colonies, each unit being known as a zooid. They are marine filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. Most adult tunicates are sessile as encrusting or stalked ascidians, which are permanently attached to rocks or other hard surfaces on the ocean floor; whereas others are salps, which swim in the pelagic zone of the sea as adults.
About 3000 described species of tunicates occur in the world's oceans (Appeltans et al. 2012), mostly living in shallow water. The most numerous group is the ascidians, and fewer than 100 species of these are found at depths greater than 200 m. They are found in a range of solid or translucent colours and may resemble seeds, grapes, peaches, barrels, or bottles.
One of the goals of the Statia Marine Expedition 2015, was to contribute to expanding the understanding of the tunicate fauna of the Dutch Caribbean island of St. Eustatius by a base line inventory. Another major goal of the investigation was to obtain DNA subsamples of soft tissue from live individuals of a number of tunicate species for molecular analysis and DNA barcoding. The tunicate fauna of St. Eustatius had been poorly investigated before the expedition. Rocha et al. (2005) reported on tunicates from some islands within 200 km range from St. Eustatius, two species from Saba (30 km) to 96 species from Guadeloupe (200 km). Cole (2012) reported on 32 species in collections from Tobago, which is located 700 km south of Statia.
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