alimentary canal trophosome tissue BTO:0001396 BrendaTissueOBO Various chemolithotrophs have been found to live in symbiotic association with animals of the thermal vents. For example the 2-m-long tube worms lack a mouth, gut or anus but contain a modified gastrointestinal tract consisting of spongy tissue called the trophosome. Making up about 50% of the weight of the worm, trophosome tissue is loaded with sulfur granules and large numbers of symbiotic prokaryotic cells (average of 4 X 109 cells per g of trophosome tissue). Trophosome tissue also shows activity of the enzyme RubisCO and other enzymes of the Calvin cycle, the pathway by which most autotrophic organisms fix CO2 into cellular material.