Les contenus digestifs des holothuries ont des compositions en acides aminés libres différentes en zone abyssale et en zone littorale. Les différences significatives portent sur les acides glutamique et diaminopimélique et sont interprétées comme le reflet d'une prolifération bactérienne particulière au tractus digestif des holothuries abyssales. in

An important turnover of organic matter occurs at the deep sea sediment-water interface, since more than 90% of the sedimentary organic carbon escape burying ([1], [2]). The role played by micro-organisms and by the others members of the benthic community is not clearly understood ([2] to [6]). Holothurians are one of the major groups, of the deposit-feeding benthic megafauna ([7], [8]). In the abyssal zone their digestive tract seemed to be the place of an important bacterial proliferation ([9] to [11]) which is not observed with littoral specimens [12]. Free amino acids in gut contents reflect that situation. Glutamic acid is the major free amino acid. in interstitial water of marine sediments, probably in relationship with the amino acid pool of bacteria ([13] to [17]). In the gut contents of abyssal holothurians, glutamic acid is largely predominant ail along the digestive tract. Total amino acid concentrations are relatively high compared to the surrounding sediment or the gut content of littoral specimens. For littoral species, glutamic acid is only predominant in the sediment just ingested or just to be expeled, as weil as in the feces and the surrounding sediment. Digestive functions of the organisms seemed to govern the free amino acid composition in the major part of the digestive tract except at the extremities. For abyssal specimens, the amino acid composition would be related to the bacterial amino acid pool ail along the digestive tract. Furthemore, significant quantities of fi'ee diaminopimelic acid (0.3 Jlmol/g) are found in gut contents of abyssal specimens only. This is thought to be linked to the occurrence of an important bacterial cell division in the digestive tract of abyssal holothurians.