Tunicates are characterised by an outer coating known as a tunic, made of a cellulose compound. They are marine animals, fixed or pelagic, whose larva has a typical dorsal nerve cord that disappears in adulthood. Ascidians (Benthic tunicates) only live in marine waters. They live fixed to objects at all depths, from the tidal zone to the ocean trenches.
The Muséum’s ascidian collection is above all a scientific one. The samples are mostly preserved in formalin, and since 2011 part of the recent harvests (Southern Ocean) has been preserved in alcohol for molecular studies. They are all identified at family, genus and species level for the 8,000 bottles and 11,400 microscope slides (dyed dissections and preparations). There are an estimated 600 types. The collection samples come from all the oceans, at all latitudes, from the North Pole to the South Pole. Most of the specimens are from the tropical zone. The value of this collection is also due to the systematic diversity represented there, since it contains preserved specimens of all families and genera. There are several databases for scientists. In the ascidian collection, each record includes the family, genus, species, author, synonyms, and often related publications and place of harvest. The species general file covers all the existing species, listed with their author, publication and synonyms.
Due to a lack of French specialists until 1965, very few ascidians have been harvested and preserved in the Muséum. The oldest specimens date back to Savigny (1816). Then travelling naturalists brought back a few examples. For over 30 years, C. and F. Monniot devoted their entire career to ascidians and accumulated the vast majority of the current collection. The collection of bathyal and abyssal ascidians is unique in the world.
Most of the research concerning the collection is systematic (morphology, anatomy and genetics) but there is also ecological and biogeographical research. Specimens have been used for studies of pollution by heavy metals, hydrocarbons, etc. Ascidians are a major component of biomedical research internationally and the collection includes reference specimens from which chemists have extracted new molecules. The collection is growing all the time thanks to the work of the Muséum’s colleagues and researchers from all countries. The many new species described and simple identifications have been made possible by loans of types by foreign natural history Muséums.