Effects of body size on suspension feeding and energy budgets of the pearl oysters Pinctada margaritifera and P. maxima

Abstract

This study compared suspension f e e d n g , assimdation efficiency, respiration and excretion, and energy budgets (= scope for growth, SFG) in relation to body size in 2 pearl oysters, Pinctada maryaritifera and P. maxima, at a low food concentration (ca 5000 cells ml-l Tahitian Isochrysis galbana). Clearance rate (CR), respiration rate (K) and ammonia excretion rate (E) were strongly correlated with body size ( p < 0 001) in both species, wlth exponents of 0.60 and 0.61 (CR), 0.44 and 0.56 (R), and 0.64 and 0.78 (E), respectively, for P margaritdera and P maxima. CR did not differ significantly between the species, but absorption efficiency, which was unrelated to size, was significantly greater in P maxima (57 5 vs 51 %, p < 0.05). There was, however, no significant difference in absorbed energy (AE) between the species. Respired energy (RE) and excreted energy (EE) as proportions of AE were slgniflcantly lower ( p < 0.01) in P. maxima of 0.1 g dry soft tissue wt (ca 36 mm shell height, SH). The former was 0.36 compared to 0.58 in P. margaritifera of the same size. Thus, P. m a x m a of 0.1 g dry soft tissue wt exceeded P. margaritlfera of the same size in SFG, which accords with the former species' more rapid early growth. Both species of pearl oysters have a high abihty to acquire energy under low phytoplankton conditions. Both species are exceptional bivalves in terms of energy fluxes, with clearance rates of 50 to 100 1 h-' in large oysters of 150+ mm SH. They show among the highest CR, R, E and SFG values recorded for blvalves (using 1 g dry soft tissue wt as a standard size). The largest g a n t clam, Tridacna gigas, is one tropical bivalve with comparable SFG. It, however, 1s dependent on energy from autotrophy as well as heterotrophy to achieve its high SFG.

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

“…Their soft tissues were dried at 60°C and then weighed. CR and rejection rate (RR = mg total pseudofaeces ejected h-', mg h-') were size-standardised to those for a n equivalent individual of 10 g dry soft tissue wt as follows: (Navarro et al 1991) where Ys is the size-standardised physiological rate, Ws is the standard size (10 g dry tissue weight), We is the dry tissue weight of experimental oyster, b is the size exponent: 0.61 (Yukihira et al 1998a), and Ye is the uncorrected physiological rate.…”

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

“…Assessing the carrying capacity of the lagoon for pearl oyster farming implies determining the food resource available to the oysters. It is generally assumed that filter-feeding species rely on phytoplankton as their main source of energy, but only a few studies have been concerned specifically with the feeding behaviour of the pearl oyster (Chellam 1983, Nasr 1984, Hawkins et al 1998, Yukihira et al 1998a, Pouvreau et al 1999, 2000a. Because these benthic bivalves are reared in a suspended position they interact with the planktonic food web.…”

Growth and survival of the blacklip pearl oyster Pinctada margaritifera (Linnaeus) spat reared with various combinations of microalgae in different stocking densities

“…This was supported by the findings of Mondal (2006) that the clearance rate of P. fucata reduced considerably at water temperature above 28°C. In P. margaritifera, it reportedly declined over 28°C to 32°C but in P. maxima the clearance rate remained steady under the same conditions (Yukihira et al, 1998). During the present experiment wide fluctuation in temperature (27°C to 25°C) was observed from 9 to 21 DOC, the period which also recorded the highest mortality (10 -40%) in all feeding types irrespective of the stocking density.…”

“…Similarly, del Rio-Portilla et al (1992) reported that, the growth of Pteria sterna was influenced by a synergistic effect of temperature and food concentration. Yukihira et al (1998) reported that scope for growth (SFG) of P. margaritifera spat peaked at cell concentrations from 10-20x10 3 cells.ml -1 of Tahitian Isochrysis sp. (T-Iso).…”

“…According to Yukihira et al (1998), scope for growth (SFG) is very dependent on environmental conditions, especially food availability. In farming system many species of microalgae along with particulate organic matter are available to pearl oysters so the probability of nutritional deficiency is negligible.…”