Oligochaete influence on settlement, growth and reproduction in a surface-deposit-feeding polychaete

McCann, LD, Levin LA.  1989.  Oligochaete influence on settlement, growth and reproduction in a surface-deposit-feeding polychaete. Journal of Experimental Marine Biology and Ecology. 131:233-253.


The functional-group hypothesis predicting that a mobile subsurface-deposit feeder would inhibit the recruitment and subsequent development of a more sedentary tubiculous surface-deposit feeder was tested through a series of laboratory and field manipulations of the oligochaete Monopylephorus evertus Brinkhurst and the polychaete Streblospio benedicti Webster. Laboratory and field studies indicated that settlement of S. benedicti was unaffected by the presence of M. evertus. Settlement of syllid, capitellid and other spionid polychaetes, gastropods and Gemma gemma Totten also appeared to be unaffected. In laboratory cultures, M. evertus caused decreased survivorship of S. benedicti from age 11 wk through senescence and decreased growth (addition of setigers) at age 6–11 wk. Growth of newly settled and older worms may be decreased by the presence of M. evertus, however, the experimental design had insufficient power to determine significance when treatment differences were small. Reduced growth of juveniles, leading to smaller size, was predicted to cause decreased reproductive output in S. benedicti although size-specific reproductive capacity of individual worms was unaffected. Results are consistent with functional-group theory predicting mobile burrowing forms to have negative effects on more stationary tubiculous forms. However, significant decreases in growth rate were limited to the juvenile (recruitment) stages of S. benedicti, emphasizing the importance of examining the entire life cycle of the species of interest. This study also highlights the need for future investigations to determine the role of marine oligochaetes in the dynamics of salt-marsh and estuarine communities.