Feeding adaptations of the pearl oysters Pinctada margaritifera and P. maxima to variations in natural particulates

Abstract

ABSTRACT-The tropical pearl oysters Pinctada margaritifera (Linnaeus) and P maxima Janieson are suspension feeders of malor economic importance. P margaritifera occurs in coral reef waters characterised by oligotrophy and low turbidity. P. maxima habitats are generally characterised by high terrigenous sediment and nutrient inputs, and productivity levels. These differences in habitat suggest that P. margaritifera will feed more successfully at low food concentrations, while P. maxima will cope with a wider range of food concentrations and more silty conditions. The effect of varying concentrations of natural suspended particulate matter (SPM) on clearance rate (CR), pseudofaeces production, absorption efficiency (abs.eff.), respired energy (RE) and excreted energy (EEJ was determined for P. margantifera and P maxlma. The resultant scope for growth (SFG) was deterrmned and related to habitat differences between the oysters. There was no selective feeding on organic particles in either species. P. rnargaritifera had higher CR at low SPM concentration (<2 mg I-'), while P. maxima had higher CR under turbid conditions (SPM: 13-45 mg 1-'). The latter species produced less pseudofaeces in relation to its filtration rates; consequently, this species ingested more SPM than P. margaritifera. P. maxima had positive SFG over a wider range of SPM concentrations (up to 30-40 mg I-') while P. margaritifera maximised SFG under low SPM conditions (<3 mg I-'). Thus feeding responses and energy balance reflected the typical habitats of each species. P, margaritdera retained smaller particles than P. maxima, enabling it to consume a wider particle size range of SPM at low food levels. P. maxima was adapted to its environments of greater SPM load through greater ingestion rates and higher digestive ability. The optimum SPM concentrations and particle size range for P. margaritifera (SPM < 5 mg I-', size > 3 pm) and P. maxima (SPM = ca 3 to 15 mg I-', size > 4 pm) may be used for selection of optimum pearl culture sites.

Phytoplankton composition and selective feeding of the pearl oyster Pinctada margaritifera in the Takapoto lagoon (Tuamotu Archipelago, French Polynesia):in situ study using optical microscopy and HPLC pigment analysis

“…However, the mechanisms involved in this distinction have yet to be determined. On the other hand, the pre-ingestive selection of organic matter has been proved to be low for Pinctada margaritifera when compared to other bivalves (Hawkins et al 1998, Yukihira et al 1999, Pouvreau et al 2000a. Although further evidence is required for making precise conclusions about the processes involved in the selection, our results demonstrate, for the first time, the capability of this bivalve to select the ingested food on a qualitative basis.…”

“…5) is low and may, partly, be attributed to chlorophytes. The low abundance of cyanobacteria in the gut of the bivalve could be related to the low retention of particles < 2 p m demonstrated by the previous studies of Pouvreau et al (1999) and Yukihira et al (1999). This low retention is attributed to the absence of eulatero-frontal cirri on the gill filaments.…”

“…The selective feeding is evidenced by highly significant differences in the alloxanthin concentration-the specific marker pigment of cryptophytesbetween the water column and the gut. Until now, few studies have focused on defining the available food and the feeding behaviour of the pearl oyster Pinctada margaritifera in its natural environment (Hawkins et al 1998, Pouvreau et al 1999, 2000a, Yukihira et al 1999. A positive selection (i.e.…”

“…Because these benthic bivalves are reared in a suspended position they interact with the planktonic food web. In the oligotrophic environment of the atoll lagoons, the structure of the planktonic food web is characterized by a predominance of pico-and nanophytoplankton (Charpy 1996, Niquil et al 1998; the former being weakly retained by the pearl oyster (Pouvreau et al 1999, Yukihira et al 1999. This apparently unfavourable trophic environment currently supports high densities of vigorously growing farm-reared oysters (Pouvreau et al 2000b).…”

Site-related differences in the feeding physiology of the green mussel Perna viridis: a reciprocal transplantation experiment

“…Compared with considerable scientific research on Mytilus spp. in temperate waters, much less work has been done on tropical and subtropical species (Ward & MacDonald 1996, Hawkins et al 1998a, Yukihira et al 1999, particularly the warm-water species Perna viridis (L.), though it is of high ecological significance (Seed & Richardson 1999) and has aquaculture value (Guo et al 1999).…”