Short communicationEffects of salinity on fertilization and larviculture of the mangrove oyster, Crassostrea gasar in the laboratory
Introduction
According to the Food and Agriculture Organization of the United Nations, Latin America, Africa and the Caribbean present high and increasing potential for bivalve production. However, cultivation in these areas is limited mainly due to the small number of hatcheries and the lack of proper methodologies for domesticating native species (FAO, 2014).
Brazil is a representative example of the Latin America scenario. Along its 7.370 km of coastline, Brazil has only two established hatcheries and another two under construction. Furthermore, laboratory techniques for native species seed production are still under development, and studies to determine optimal conditions for each culture stage are required.
Brazilian oyster culture focuses on Pacific oyster, Crassostrea gigas, with smaller scale production of the native oysters, Crassostrea gasar (= Crassostrea brasiliana) and Crassostrea rhizophorae. Since higher seawater temperatures can compromise growth and survival rates of C. gigas (Poli, 2004), the expansion of oyster farming in the Brazilian tropical regions is linked to the domestication of native species. Among indigenous oysters, C. gasar is the most cultivated species because it reaches greater size than C. rhizophorae (Christo and Absher, 2006) and presents satisfactory performance at cultivation sites (Baldan and Bendhack, 2009, Galvão et al., 2009, Lopes et al., 2013).
The use of artificial collectors to obtain C. gasar seeds from the environment is difficult due to the occurrence of overlapping settlement periods with other oyster species. In South Brazil, Paraná State, 31% of the individuals collected by Montanhini-Neto et al. (2012) were Crassostrea sp., 36% C. rhizophorae and 33% C. gasar. When obtaining seeds from the environment using artificial collectors is not viable, production in hatcheries is the most efficient approach, and offers the additional advantage of minimal impact on natural populations (Ferreira and Oliveira-Neto, 2007).
The present study evaluated the effects of salinity on fertilization and larval development of the native oyster C. gasar aiming to contribute for the development of hatchery techniques for seed supplies of this species.
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Materials and methods
The broodstock of C. gasar used for the fertilization (1) and larviculture (2) experiments was produced (sixth generation) at the Laboratory of Marine Molluscs of the Federal University of Santa Catarina (LMM-UFSC) (27°35′S, 48°26′O). The animals were kept in lantern-net floating systems at the experimental culture area of LMM, at Sambaqui Beach, Florianópolis (27°35′S, 48°32′O). From December 2013 to April 2014 adult animals were transported from the culture area to the laboratory in thermal
Effects of salinity on fertilization and embryonic development
Fertilization conducted in salinity 28 resulted in a significantly (p < 0,0001) higher number of normal shape D-larvae in comparison to other salinities (7, 14, 21 and 35) (Fig. 1). There was no difference in numbers of normal D-larvae between the salinities 21 and 35, although this last treatment (salinity 35) presented significantly more deformed shaped D-larvae in comparison to the other treatments.
Successful embryonic development did not occur in salinities 7 and 14, in these salinities there
Discussion
Regarding the influence of salinity on embryonic development of C. gasar in the laboratory, results presented in this study indicate that fertilization and D-larvae development occurs from salinity 21 and optimal conditions occur around salinity 28. At higher salinity (35) the success of fertilization declines. Optimal salinity ranges for fertilization in other oyster species of the genus Crassostrea are presented in Table 2.
In fertilization tests conducted at LMM-UFSC (unpublished data) using
Acknowledgments
The authors would like to thank Paul Gailey, Paola Tomaselli and Leticiaà Legat for reviewing the English version of the manuscript. To Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), for scholarship granted to the last author.
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2022, Journal of Experimental Marine Biology and EcologyCitation Excerpt :Similar observations have been reported in other marine mollusks subjected to salinity stress; for example, embryos of the mangrove oyster, Crassostrea rhizophorae incubated at lower salinities (19, 16, 13 and 10 psu) exhibited a high proportion of abnormal development at the D-larval stage (Dos Santos and Nascimento, 1985). In addition, a recent study conducted on the oyster, C. gasar revealed that the proportions of abnormal larvae maintained at 14 psu were significantly higher compared to those at 21, 28 and 35 psu (Legat et al., 2017). A possible explanation could be due to changes in cellular osmotic balance, which can cause changes in form (Sayco et al., 2019).
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2021, Encyclopedia of Smart MaterialsInfluence of the proximity to the ocean and seasonality on the growth performance of farmed mangrove oysters (Crassostrea gasar) in tropical environments
2018, AquacultureCitation Excerpt :In this context, physical-chemical variables of the water, in particular salinity, pH, temperature, and dissolved oxygen, interfere with the osmotic balance of the organism and its absorption of nutrients, and may provoke stress (Bernard, 1983; Cheng et al., 2002; Yang et al., 2016), which affects the settlement of the larvae (Vilanova and Chaves, 1988), and the development (Chávez-Villalba et al., 2010; Guzmán-Agüero et al., 2013) and even the reproductive cycle (Gireesh and Gopinathan, 2004; Paixão et al., 2013) of these animals. Experimental studies have also evaluated the specific effects of temperature, salinity, and nutrients on the growth, reproduction, and larviculture of C. gasar (Funo et al., 2015; Legat et al., 2017; Ramos et al., 2014). In tropical estuaries and coastal regions, however, temperatures are constant, and salinity is considered to be one of the principal factors determining the distribution, development, and reproduction of oysters (Paixão et al., 2013; Santerre et al., 2013).