Application of a micro-respirometric volumetric method to respiratory measurements of larvae of the Pacific oysterCrassostrea gigas

Abstract

The application of a simple, fast and reliable volumetric microrespirometric method to assess respiration of bivalve larvae is discussed. As a model, C. gigas larvae of various sizes were used. Metabolic activity of veliger larvae was assessed by measuring respiratory rate for use in ecophysiological modelling. As an example of the application of this approach, additional measurements of veliger respiratory rates were carried out to assess the effect on larval metabolism of different concentrations of leachate from wood treated with chromated copper-arsenate (CCA). Veligers of Crassostrea gigas (length from 95 to 331 µm) were fed with a mixture of Isochrysis galbana and Chaetoceros pumilum cells. Experiments were performed in a 20 • C constant seawater temperature. The wet and dry weight of four length (L, in µm) classes of larvae were obtained from which the relationship between total dry weight and veliger length was derived {DW = e (3.27+L×0.0154) } (R 2 = 99%). Moreover, tissue dry weight (TDW; in ng) was calculated according to Gerdes (1983). Since the mathematical model between larval length and respiratory rate explained 88% of the total variability, a more conservative approach using oyster larval dry meat weight (in ng) and respiratory rate (in µlO 2 h −1) was developed to establish a linear model explaining 94.5% of the variability: Resp. = −3.849 × 10 −4 + 5.211 × 10 −6 × TDW. These experiments provided updated figures of C. gigas larval respiratory rates for use in ecophysiological models. The relationship between tissue dry weight and respiratory rate was close to previous estimates obtained by Gerdes (1983) and Hoegh-Guldberg and Manahan (1995) at 25 • C and 20 • C respectively. Our experiments demonstrate that volumetric microrespirometry is suitable for assessing larval respiratory rate and therefore can be used to assess impacts of pollutants on an early larval stage. Oysters exposed to leachates from chromated copper arsenate (CCA) treated timber at 5 kg m −3 showed initially highly variable respiratory rates while those rates decreased drastically for a 15 kg m −3 CCA treatment exposure. Among bioindicators using physiological response to assess pollutant effects, swimming activity and respiratory rates can be compared, the later showing a significant response at a lower pollutant concentration.

Ocean Acidification Has Multiple Modes of Action on Bivalve Larvae

“…Measuring respiration rates on larvae provide several challenges, however our rates were within the range of previously reported values for marine bivalve larvae [47], [51], [76], [77]. We measured respiration on already fully-formed larvae that had been exposed to the treatment conditions from immediately after fertilization, with a reduced treatment matrix.…”

Effects of Glyphosate-Based and Derived Products on Sea Urchin Larval Development

“…Alterations in respiration rates have been widely reported in various life stages and taxa after exposure to anthropogenic stressors, such as pollutants and seawater acidification [71][72][73][74][75]. To our knowledge, no data regarding respiratory alterations due to pollutants in the larval stages of sea urchins are available and a limited number of studies have been carried out in larvae of marine invertebrates [76]. Nonetheless, in a recent study analyzing the effect of ocean acidification on larvae of the sea urchin Heliocidaris crassispina, a decrease in pH caused a gradual increase in oxygen consumption, doubling the value at pH 7.3 compared to the control at pH 8.0 [77].…”

A flow-through rearing system for ecophysiological studies of Pacific oyster Crassostrea gigas larvae

“…In addition, the improvement of rearing methods should allow a new approach for the study of various environmental factors affecting larval physiology. Indeed many studies on C. gigas larvae have generally been focused on assessing larval growth, development, metamorphosis and settlement by varying one or two environmental combined factors (Helm and Millican, 1977;His et al, 1989;Abdel-Hamid et al, 1992), while only limited studies have involved the quantification of physiological functions such as ingestion (Gerdes, 1983a;Baldwin and Newell, 1995) or respiration (Gerdes, 1983b;Mona et al, 1993;Goulletquer et al, 2004). Moreover, most measurement practices in larval physiology have been based on the transfer and handling of larvae from rearing tanks to measurement chambers.…”