Effects of dissolved mercury on embryo-genesis, survival, growth and metamorphosis of Crassostrea gigas oyster larvae

Abstract

The effects of mercury (Hg) concentrations ranging from 0 (control) to 1024 pg 1-' upon embryogenesis, survival, growth and metamorphosis of Crassostrea gigas (Thunberg) oyster larvae were investigated. Embryogenesis was abnormal in 50 % of the individuals at 11 pg I-' The 48 h LDS" for D-shaped, urnbonate and pediveliger larvae were 33, 115 and 200 pg 1-' respectively. The increase in was partially explained by the larval weight increase, although weight-specific tolerance to Hg was higher in smaller larvae. Growth, the most sensitive physiological process studied, was significantly retarded at 4 pg I-'. The metamorphosis rate was significantly reduced when competent pediveligers were exposed to 64 pg I-' for 48 h prior to the addition of the metamorphosis inducer epinephrine. The implications of the present results for monitoring pollution by utilising different bivalve larval stages are discussed.

Effects of elevated pCO2 on early development in the mussel Mytilus galloprovincialis

“…Other morphological abnormalities include convex hinge and protrusion of the mantle, both of which are typical criteria used to distinguish between normal and abnormal development of veliger larvae in embryotoxicology bioassay (His et al 1997). Although no observations were made on larval behaviour in the present study, Beiras & His (1994) reported swimming inhibition in larvae with protruded mantle, which could reduce environmental fitness.…”

“…Most previous studies on the effect of ocean acidification have dealt with adult individuals; little is known about CO 2 impacts on marine organisms during early development. In addition, several toxicity studies rank bivalve life stages in terms of relative sensitivity to sublethal and lethal effects as: embryos > veligers (D-larvae) > metamorphosing larvae > pediveligers > adults (Beiras & His 1994, His et al 1999. Shell synthesis is significantly suppressed when larvae of the oyster Crassostrea gigas are exposed to seawater equilibrated with CO 2 -enriched (2000 ppm) air (pH 7.4; Kurihara et al 2007).…”

The Impact of Ocean Acidification on Reproduction, Early Development and Settlement of Marine Organisms

“…During later larval development CaCO 3 deposition is converted to aragonite and following settlement and metamorphosis, calcite, the most stable CaCO 3 polymorph, is deposited [72,73]. Rather than earlier stages being more sensitive than later [37] there is an absence of evidence of hierarchical sensitivity and more evidence of sensitivity of larval stages being species specific. The pediveligers of S. glomerata were more sensitive than spat to changes to CO 2 and temperature, but this reversed in C. gigas with newly metamorphosed spat showing greater sensitivity than pediveligers [39].…”

“…Not only has it been suggested that the impact of ocean acidification will be more significant for larvae than adults [14], but it will be most significant for the earlier sensitive life history stages; including egg and sperm production, fertilisation, cleavage, than the later life history stages of larval development and dispersal, settlement and post-settlement survival, especially for molluscs and echinoderms [7,14,[33][34][35][36] (Figure 1). Indeed it has been suggested that the sensitivity of larvae is hierarchical, being most sensitive when embryos and least sensitive as pediveligers and metamorphs, following a linear sequence; embryos>veligers (D larvae)> pediveligers>metamorphs>adults [37]. Such sensitivity may vary among marine groups.…”

Effects of dissolved mercury on embryogenesis, survival and growth of Mytilus galloprovincialis mussel larvae

“…High toxicity and bioaccumulation give Hg a well-known ecotoxicological relevance among the heavy metals (reviewed by Cossa et al 1990). Crassostrea gigas (Thunberg) embryogenesis was found to be abnormal in 50 % of the individuals at 11 pg Hg I-', and larval growth significantly retarded at 4 pg 1-' (Beiras & His 1994).…”