Ahrens, M. J. MSRC, State University of New York, miahrens@ic.sunysb.edu
Lopez, G. R. MSRC, State University of New York, glopez@notes.cc.sunysb.edu

 
BODY LENGTH AND ITS IMPLICATIONS FOR DIGESTIVE AND ABSORPTIVE EFFICIENCY IN THE DEPOSIT FEEDING POLYCHAETE NEREIS SUCCINEA
 
Body size correlates with two important physicochemical parameters--pH and surface tension--in the gut of Nereis succinea, and may be central to explaining the observed variability in the assimilation of sediment-associated organic contaminants among individuals of different size. Smaller N. succinea have shorter gut passage times than larger individuals (by one order of magnitude), which suggests that worms may exhibit compensatory adaptations in ingestive, digestive or absorptive efficiency. To test the hypothesis that small deposit feeders have comparatively more aggressive gut conditions than larger organisms, we measured gut pH and surface tension in N. succinea with body lengths between 1 and 10 cm. pH was determined using a microelectrode or, alternatively, using a newly developed in vivo technique, employing pH-sensitive fluorescent dye fed to live worms (in individuals <2.0 cm length). Surface tension was measured as drop contact angle in extracts of gut fluid. Assimilation efficiency (AE) for hexachlorobenzene (HCB) and tetrachlorobiphenyl (TCB) was measured using C-14 labeled compounds adsorbed to sediment. Gut pH of N. succinea ranged between pH 6.0-7.5, and correlated positively with body length (i.e gut pH was generally higher in larger worms). Surface tension in gut fluids was greatly diminished relative to water, ranging between 25 and 50 degrees, and correlated inversely with body size (i.e. surface tension was generally lowest in large individuals). TCB and HCB were assimilated with efficiencies of 60-80%. AEs were highest in larger N. succinea. Higher AEs for organic contaminants may be attributable to the longer gut passage time and lower surface tension in larger worms, which may result in greater desorption of previously sediment-bound contaminants. Differences in gut pH between worms of different size could have a similar effect on the uptake of sediment-associated trace metals.
 
Day: Wednesday, Feb. 3
Time: 02:15 - 02:30pm
Location: Hilton of Santa Fe
 
Code: SS21WE0230H