Reproduction of the introduced oyster Crassostrea gigas (Bivalvia: Ostreidae) cultured on rafts in Spain

Abstract

The oyster Crassostrea gigas was introduced in Spain for aquaculture purposes; however, until now, it is not known whether populations are established in the wild, being necessary to define whether this species is spawning and which environmental variables trigger this process. The influence of environmental parameters on the reproduction of C. gigas was evaluated from January 2008 to October 2009 with oysters grown on a raft in the Ría de Arousa (Galicia, NW Spain). Temperature and chlorophyll a are directly correlated to sexual maturation. Oysters can mature at temperatures below 14°C. The temperature necessary for spawning differs between the sexes, requiring a temperature above 15°C for males and 18°C for females.Females had a single massive spawn between June and September, while males had partial spawning from May to December with two peaks, one in May-September and another in October-December, with the second peak more pronounced. The first spawning peak is related to high temperatures and concentrations of chlorophyll a, and the second spawning peak is mainly related to the food availability in the water.The spawning asynchrony may be impeding establishment of wild C. gigas populations in Spain. K E Y W O R D Schlorophyll a, mollusc, reproductive biology, spawning, temperature

Reproductive cycle of a non-native oyster, Crassostrea gigas, in the Adriatic Sea

“…The Pacific oyster C. gigas is an asynchronous hermaphrodite that most commonly first mature as male (Gosling, 2003;FAO, 2019). In Lim bay, hermaphrodite individuals occurred sporadically, which is in accordance with previous studies (Steele & Mulcahy, 1999;Dridi et al, 2014;Antonio & Camacho, 2019). In our study, we observed a female-biased sex ratio.…”

“…The Pacific oyster reproductive cycle is well described along the Atlantic coast of Europe (e.g. Ruiz et al, 1992;Massapina, 1999;Steele & Mulcahy, 1999;Lango-Reynoso et al, 2000, 2006Dutertre et al, 2009;Enríquez-Díaz et al, 2009;Thomas et al, 2016;Antonio & Camacho, 2019), but in the Mediterranean region, data are generally scarce (Shpigel, 1989;Dridi et al, 2007Dridi et al, , 2014Ubertini et al, 2017), and completely lacking in the Adriatic Sea. The presence of larva and small specimens (~20 mm) in Lim Bay (Ezgeta-Balić et al, 2019;Stagličić et al, 2020) might indicate favourable environmental conditions for successful reproduction of C. gigas; however, to confirm this hypothesis, detailed research on its reproductive biology is needed.…”

Reproductive cycle of the mangrove oyster, Crassostrea rhizophorae (Bivalvia: Ostreidae) cultured in a macrotidal high-salinity zone on the Amazon mangrove coast of Brazil

“…Food quality and availability exert a strong influence on the accumulation of nutritional reserves for later release of gametes (Chávez-Villalba et al 2000). For example, phytoplankton blooms may induce spawning (Dridi et al 2014;Antonio and Camacho 2019). Chlorophyll a and particulate organic matter (POM) were significantly higher in the rainy season in our study area, indicating higher primary productivity.…”

“…Males, females and hermaphrodites were differentiated by the presence of cells of spermatogenesis or oogenesis. The gonadal development stages were determined using the scale described by Antonio and Camacho (2019), as follows: stage 0 -sexual rest; I -gonial multiplication; II -gametogenesis; IIIA -maturation; IIIB -total or partial emptying; IIICrecovery between successive releases and; IIID -end of the breeding season (spent). The spawning season was evaluated by determining the monthly distribution of the frequency of different maturation stages concerning the condition index.…”

SNP-based parentage analyses over two successive generations demonstrates the feasibility of efficient production of inbred lines in the Pacific oyster (Crassostrea gigas) by self-fertilization of simultaneous hermaphrodites despite severe inbreeding depression

“…Simultaneous hermaphrodites are scarcely observed in diploid C. gigas (Broquard et al, 2020;Guo et al, 1998) but are more frequent in triploid progenies (Normand et al, 2009). Synchronous mass spawning behaviour, in particular for females (Antonio and Camacho, 2019;Enriquez-Diaz et al, 2009), and strong inbreeding depression due to high genetic load (Launey and Hedgecock, 2001;Plough et al, 2016) are likely to explain why simultaneous hermaphrodites remain rare in C. gigas even if this reproductive characteristic might be heritable. If the occurrence of simultaneous hermaphrodites increased for the progenies of one parent showing this characteristic, this should ease the obtention of highly inbred oysters which takes, in theory, 7 generations of successive selfing to reach an inbreeding coefficient of 0.99 against more than 20 generations of crosses between full-sibs (Falconer and Mackay, 1996).…”