Relative importance of different size food particles in the natural diet of oyster larvae Crassostrea virginica

Abstract

We examined the feeding activity of planktotrophic larvae of the eastern oyster Crassostrea virginica on different size particles suspended in surface waters of 2 subestuaries of Chesapeake Bay, USA. Particle suspensions were characterized uslng particle counters and microscopic observations. At both sites, particle assemblages were dominated (in terms of particle number and volume) by particles (predominantly plankton cells) with equivalent spherical diameters <5 pm. Feeding experiments demonstrated that small (<l50 pm shell length) and large (>200 pm) oyster larvae typically ingested particles between 0.5 and 12 pm. However. in the presence of blooms of large (10 to 30 pm) dinoflagellates, small and large larvae extended their maximum ingested particle size to about 16 and 30 pm, respectively. These results indicate that oyster larvae generally exploit foods within the characteristic particle biomass peak present in these estuaries and opportunistically feed upon periodic blooms of large plankton cells. Larvae derived a large percentage (range 20 to 90%) of the total ingested particle volume from picoplankton-size (here defined as 0.5 to 3 pm) particles. These small particles constituted a larger percentage of the material ingested by small larvae than that ingested by large larvae. By comparison, both sizes of larvae derived about 2 to 4 0 % and about 5 to 20% of total ingested food volume from 3 to 5 pm and 5 to 10 pm particles, respectively. In experiments with abundant dinoflagellates > l 0 pm in size, both sizes of larvae derived 20 to 30% of their total ingested volume from these particles.

Seasonal variations in abundance and biomass of picoplankton in an oyster-farming area of northern Japan

“…Douillet & Langdon (1993) reported that a strain of bacteria enhanced the survival and growth of Pacific oyster larvae. Picoplankton-sized particles (0.5 to 3 mm) constitute a large percentage of the food ingested by small larvae of the Eastern oyster Crassostrea virginica Gmelin (Baldwin & Newell 1995). The relative importance of the bacterial and cyanobacterial biomass in summer implies that picoplankton assemblages play important roles in the survival of planktonic oyster larvae in the study area.…”

Ingestion and assimilation of carbon from cellulolytic bacteria and heterotrophic flagellates by the mussels Geukensia demissa and Mytilus edulis (Bivalvia, Mollusca)

“…Second, Kemp et al (1990) conducted their filtration measurements during August; however, microheterotrophs may comprise a greater proportion of the particulate seston during months when primary production is minlmal . Baldwin & Newel1 (1995) recently demonstrated that veliger larvae of the eastern oyster Crassostrea virginica can ingest and digest heterotrophlc organisms. Although previous studies have shown that bacterivorous nanoflagellates can be ingested by adult suspension-feeding b~valves (for example, see Kemp et al 1990), ours is the first investigation of the ability of adult bivalve molluscs to digest and assimilate these organisms.…”

Consumption of picoplankton by the bivalve larvae of Japanese pearl oyster Pinctada fucata martensii

“…The second is negligible grazing pressure on 2 to 20 pm phytoplankton by the larvae relative to that of other herbivores such as ciliates and crustaceans. Edible food size of the larvae overlaps that of the herbivores (Baldwin & Newell 1995), and grazing pressure on 2 to 20 pm phytoplankton by the herbivores is considerably high (Kamiyama 1994, Kuipers & Witte 1999. Bivalve larvae could grow on bacterial food (Hidu & Tubiash 1963, Douillet & Langdon 1993.…”

“…However, the former method needs skillful technique and sometimes overestimates the actual clearance rates when the estimation was based on the Daro model (Baldwin & Newel1 1991). The latter method also has limitations due to the detection limit for smaller particles using a flow cytometer (Baldwin & Newell 1995). It is difficult to detect particles with sizes < 1 pm using a low-power laser flow cytometer (Olson et al 1990, Baldwin & Newel1 1995.…”