The nutritional ecology of the ctenophore Bolinopsis vitrea: comparisons with Mnemiopsis mccradyi from the same region

Abstract

Bolinopsis vitrea is a warm water lobate ctenophore which does not overlap in its distribution with Mnemiopsis mccradyi in contiguous waters. We examined its feeding ecology on a series of cruises. B. virrea ingested increasingly more prey at higher food concentrations (2–100 prey l ⁻¹ ) but feeding effort (clearance rate) decreased with increasing food availability. On a dry weight basis, smaller tentaculate Bolinopsis ingested several times more than larger lobates, but based on carbon weight, specific ingestion was fairly uniform over the entire size range investigated (6–60 mm total length). Bolinopsis collected during the daytime in the Bahamas rarely had more than three prey items in their guts. These results and laboratory measurements of digestion times (av. = 1.9 h) allowed computation of daily rations, which could not account for the metabolic requirement as measured on the same cruises. Results of feeding experiments, however, implied that prey densities in excess of 11 ⁻¹ were sufficient to sustain a growing population of Bolinopsis. Prey concentrations about an order of magnitude higher were required for M. mccradyi based on similar experiments. These results were in general agreement with observed densities and distributions of ctenophores and their zooplankton prey in the Bahamas and coastal South Florida.