Effect of the alveolate parasite Perkinsus olseni infection on sexual maturation and spawning efficiency of the clam Ruditapes decussatus

The effect of Perkinsus olseni infection on the reproduction ability of clams has been underestimated so far. Although some studies found evidence of reduction of egg production and delay in gonad maturation after infection, the total effect of the infection is still unclear. In this study, Ruditapes decussatus clams from a naïve population were injected with two different doses of P. olseni parasites, a low dose leading to a light infection and a high dose leading to a heavy infection. Clams were maintained during 2 months for maturation, and at the end of the experiment, the spawning was induced, the number of larvae release and mortality were evaluated. During the maturation period, infection level, gonadal stage, condition index, gross biochemical composition and oxidative status of progenitors were evaluated at days 0, 30 and 60 post-injection. The effects of P. olseni infection on clams showed alterations on biochemical parameters, namely lipid peroxidation, a significant mortality and a delayed gonad maturation, with a greater effect in the highly infected individuals. The reproductive capacity of the clams was impaired in both infected groups showing a lower production and a higher mortality rate of larvae. Finally, this study indicates that the production of natural beds with a high prevalence of P. olseni could be compromised by a deregulation of the natural reproduction cycle and a decrease in larvae production by infected animals, probably due to a combination of lower egg production and lower lipid reserves in larvae from infected clams.

This article is a result of the project ‘INOVAmêijoa: Da maternidade ao viveiro: Inovação no cultivo integral de amêijoa-boa (R. decussatus) e amêijoamacha (V. corrugata)’ ref: CENTRO-01-0247-FEDER-047018/ ALG-01-0247-FEDER-047018, supported by Centro Regional Operational Programme (Centro 2020) and Algarve Regional Operational Programme (CRESC Algarve 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERDF). This work was also supported by the project Tools4Breed with reference FA_05_2017_025, co-financed by Fundo Azul and Minister of the Sea of the Portuguese Republic, by the project ‘EUROCLAM – Unlocking the potential of Euro-native bivalves’ (CENTRO-01-0247-FEDER-113950) co-financed by CENTRO 2020, PT2020 and ERDF and also by the project BISPECIAl: BIvalveS under Polluted Environment and ClImate chAnge (PTDC/CTA-AMB/28425/2017) funded by FEDER, through COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI), and by national funds (OE), through FCT/MCTES. This research was also supported by national funds ‘through FCT – Foundation for Science and Technology’ within the scope of UIDB/0443/2020 and UIDP/04423/2020. Sergio Fernández-Boo was financed by the FCT Scientific Employment Stimulus programme with reference CEECINST/00027/2021. Thanks are also due to FCT/MCTES for the financial support to CESAM (UIDP/50017/2020; UIDB/50017/2020; LA/P/0094/2020) through national funds.

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