Sea cucumbers are echinoderms from the class Holothuroidea (/ˌhɒləˌθjʊəˈrɔɪdiə, ˌhoʊ-/ HOL-ə-thure-OY-dee-ə, HOHL-). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. They are found on the sea floor worldwide. The number of known holothurian (/ˌhɒləˈθjʊəriən, ˌhoʊ-/ HOL-ə-THURE-ee-ən, HOHL-) species worldwide is about 1,786, with the greatest number being in the Asia-Pacific region. Many of these are gathered for human consumption and some species are cultivated in aquaculture systems. The harvested product is variously referred to as trepang, namako, bêche-de-mer, or balate. Sea cucumbers serve a useful role in the marine ecosystem as they help recycle nutrients, breaking down detritus and other organic matter, after which bacteria can continue the decomposition process.