DNA and chromosomal damage in Senegalese sole (Solea senegalensis) as side effects of ozone-based water treatment - contribution to optimization of fish-farming practices

The progressive growth of aquaculture implicates a dependence on large water amounts, which are submitted to disinfection processes, namely ozonation. Considering the importance of genomic integrity, it is critical to improve the knowledge on ozone-related genotoxic hazard to organisms reared in recirculating aquaculture systems (RAS) applying ozonation. Therefore, genetic damage induced by ozone exposure in the Senegalese sole (Solea senegalensis) was assessed, combining the comet and the erythrocytic nuclear abnormalities (ENA) assays, reflecting different damage levels, i.e. DNA and chromosomal damage, respectively. Fish were subjected to a daily 6-h ozone (0.15 mg L-1) exposure, repeated for 3 consecutive days, simulating a short-term event of overozonation. To assess the temporal impact of the previous event, the progression of damage was evaluated 7 days later, following transference to ozone-free water or to 0.07 mg L-1 ozone, a routinely adopted level in RAS. Both endpoints pointed to the ozone genotoxic potential, displaying DNA oxidation as a possible mechanism of damage. Overall, the present findings pointed out the genotoxic hazard of ozone to fish, highlighting the importance of these types of studies and contributing to improve aquaculture practices, namely in RAS systems. These early genotoxic signals may be a prelude to negative repercussions on fish health, which may affect the aquaculture productivity. The present findings recommend precautions in relation to accidental or intentional overozonation in fish-farming, even when short-term events are considered. The strategies to mitigate the impact of ozonation in S. senegalensis may include a dietary extra supplementation of antioxidants (regularly, or punctually in cases of overozonation).publishe

Ozonated seawater induces genotoxicity and hematological alterations in turbot (Scophthalmus maximus): implications for management of recirculation aquaculture systems

Ozonation has proven useful in recirculating aquaculture systems promoting the stabilization of water quality and disease control. Nevertheless, its cytogenetic and physiological effects on fish are still largely unknown. Hence, this research investigated the effects of ozone exposure in juvenile turbot (Scophthalmus maximus) by assessing its genotoxic potential (erythrocytic nuclear abnormalities — ENA — assay) and alterations on hematological parameters (hemoglobin concentration — Hb, red blood cell — RBC — count, mean cell hemoglobin — MCH). Fish were subjected to a daily 6-h ozone (0.15 mg L− 1) exposure, repeated for 3 consecutive days. In order to assess the potential recovery after ozone treatment, fish were also analyzed on 1-day (R1) and 7-day (R7) post-treatment. An ENA induction was recurrently detected along the exposure period, suggesting genetic damage. Moreover, this clastogenic effect was prolonged beyond the exposure period up to day R7. The Hb concentration increased on days 1, 3 and R1. Similarly, RBC count increased on days 2 and 3, showing a prolonged effect on day R1. No alterations were observed on MCH levels. Since the previous hematological alterations are regarded as physiologic adjustments rather than as an expression of toxicity, the cytogenetic damage emerged as the most serious outcome of ozone treatment. This ozone-induced genotoxicity can later lead to detrimental effects at the organism level, with negative repercussions on fish health and aquaculture productivity. Therefore, overdose of ozonation, even as short-term events, should be avoided in aquaculture operations.publishe

Effect of hormonal treatments on senegalese sole sperm quality

Trabajo presentado en el 5th International Workshop on the Biology of Fish Gametes, celebrado en Ancona (Italia), del 7 al 11 de septiembre de 2015Senegalese sole (Solea senegalensis) F1 reproduction still presents some constraints that difficult the use of these individuals to guarantee further production. F1 breeders do not reproduce naturally in the tank, and therefore, gamete collection and artificial fertilization is a procedure that has been developed (Rasines et al., 2012) and is being adapted to fish farms. One of the principal problems is the difficulty in obtaining sperm due to their low volume and concentration, a characteristic specific in this species (wild males) but more pronounced in F1 males. Some hormonal treatments already proved to be efficient in slightly increasing sperm volume (Guzmán et al., 2011), but there are still some gaps on the evaluation of this contribution. No reports on the quality of sperm has been delivered so far that guarantee a safety use of this material, especially if some management techniques such as cryopreservation will be applied. The main objective of this work is to perform an exhaustive evaluation of sperm quality from Senegalese sole F1 males exposed to different hormonal treatments.Peer reviewe