Physiology, morphology, and biochemical composition of Riftia pachyptila at Rose Garden in 1985

Riftia pachyptila from the central clumps of tubeworms at the "Rose Garden" site on the Galapagos Rift were characterized morphologically, biochemically, isotopically, and to some extent physiologically. There was a large amount of variation between individuals with respect to each of the parameters measured. For example, the heterogeneity in the gross morphology of the individuals is documented by the variation in the relation between body weight and total length of the animals as well as in the variation in the relative proportions of the different body regions among the animals collected. Activities of enzymes involved in sulfur oxidation pathways varied by almost an order of magnitude in samples of trophosome from different individuals. Similarly, the amount of elemental sulfur and extractable lipid varied by over an order of magnitude in the trophosome samples, with elemental sulfur levels as high as 10% of the wet weight reported. Additionally, there was substantial variation in the characteristics of trophosome tissue within individuals. This variation within individuals was often as high as 50% of the total variation found in the population as a whole. There were significant differences in the levels of ATP sulfurylase and sulfide oxidase as well as elemental sulfur, water and extractable lipid contents of trophosome samples removed from the anterior and posterior ends of the worms. The stable nitrogen isotopic composition of Riftia indicate that nitrate and not molecular nitrogen is the most likely source of nitrogen for the intact symbioses, and comparisons between Riftia tissues indicate that the organic nitrogen compounds in the animal tissues are probably synthesized in the trophosome.