Omnivorous feeding by planktotrophic arvae of the eastern oyster Crassostrea virginica

Abstract

In order to better understand the particle diet of planktotrophic larvae of the eastern oyster Crassostrea virginica (Gmelin) we measured their ingest~on of naturally occurring food organisms. By using a dual radioisotope (3H and I4C) label~ng technique in conjunction w~t h plankton size fractionation procedures we demonstrate that oyster larvae feed upon bacteria, phagotrophic protozoans and phototrophs present in the diverse summer plankton assemblages of Chesapeake Bay, USA. Prodissoconch I1 oyster larvae cleared 0.2 to 30 pm I4C-labeled plankton (primarily phototrophs) at a rate of 0.0825 n~l larva-' h-', and 0.2 to 30 pm 3H-labeled plankton (heterotrophlc bacteria and phagotrophic protozoans) at a rate of 0.0017 m1 larva-' h-' This calculated clearance rate for 0.2 to 30 pm heterotrophs was low due to the predominance of small (0.2 to 0.8 pm), poorly retained bacteria in thls size class. Oyster larvae consumed a wide size range of food part~cles (0 2-0.8 pm to 20-30 pm) and selectively ingested 20 to 30 pm organisms. In other feeding experiments, oyster larvae cleared laboratory cultured heterotrophic flagellates (12 pm) at a rate of 0.0640 m1 larva-' h-' and cultured heterotrophic ciliates (12 X 20 pm) at a rate of 0.1093 m1 larva-! h" The inclusion of heterotrophic food organisms In the diet of C. virginlca may enhance its growth and development by providing energy and nutrients that supplement those of ingested phytoplankton. We suggest that because oyster larvae ingest non-phytoplankton cells, estimates of standing stocks of phytoplankton may not always b e a reliable measure of food supply

Feeding selectivity of bivalve larvae on natural plankton assemblages in the Western English Channel

“…Previous studies have suggested the importance of picoplankton in the diet of bivalve larvae as well as bacteria and detritus (Baldwin and Newell 1991;Raby et al 1997;Sommer et al 2000). However, for this study, the contribution of picoplankton to the carbon ingested by the larvae is extremely small.…”

Variability in responses to nutrients and trace elements, and transmission of stressor effects through an estuarine food web

“…Growth of oysters was always positive, but did not follow the temporal or treatment-related patterns of integrative measures of their phytoplankton prey. Unlike Macoma, growth of the oysters showed no significant relationship to phytoplankton production or biomass, or to particulate N or C. Studies have shown that although oysters can ingest a variety of particle types and sizes, the nutritional value can vary greatly among prey types (e.g., Crosby et al 1990;Newell 1990, 1996;Baldwin and Newell 1991). Growth rates of oysters therefore vary greatly with species and biochemical composition of the available phytoplankton, bacteria, and other particulates.…”

“…The oyster is a key epifaunal species throughout Chesapeake Bay, occurring on and forming hard substrate. It is a suspension-feeder feeding principally on phytoplankton but capable of ingesting other food such as detritus and attached bacteria Crosby et al 1990;Baldwin and Newell 1991;Kennedy et al 1996). Macoma is an infaunal species found in both muddy and sandy environments.…”

Feeding ecology of the mangrove oyster, <i>Crassostrea gasar</i> (Dautzenberg, 1891) in traditional farming at the coastal zone of Benin, West Africa

“…As reported by Newell & Jordan and Newell & Langdon [31,32], by active selection, oysters are able to sort organic material by size before ingestion while rejecting inorganic particles. Baldwin & Newell and Baldwin [50,51] reported that many bivalves like Crassostrea are able to discriminate the nutritional quality of preys and sort foods according to their nutritional needs. Consequently, non-nutritious particles are sorted and rejected before entering the gut, while nutritious foods are retained in the stomach and undergo digestion process.…”