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Immature fish reproduced using biotechnology

Experts from the research institution IRTA and the biotechnology company RARA AVIS BIOTEC, S. L., have for the first time in a fish species, induced the entire development of eggs and sperm to produce fertilised eggs using species-specific synthetically produced hormones. These techniques are similar to the Assisted Reproductive Technologies that are used routinely in human medicine to address infertility.

The ability to control reproduction from immature stages to the production of viable eggs and sperm gives the potential for the aquaculture industry and conservation agencies to reproduce any species at any stage of development during any season of the year.

The scientists, Sandra Ramos, Neil Duncan (from IRTA) and Ignacio Giménez (RARA AVIS), working in IRTA Sant Carles de la Rapita, treated captive flathead grey mullet (Mugil cephalus) males and females that were in immature stages of maturation with the species specific recombinant gonadotropins produced by RARA AVIS. Initial stages of the reproduction process were controlled with mullet recombinant follicle stimulating hormone and the later stages were controlled with mullet recombinant luteinizing hormone. Using protocols with these hormones, both sperm and eggs were produced and mixed in vitro to provide fertilised eggs that hatched to produce viable larvae. Although the number of fertilised eggs was low, the protocol worked with three different females and offers great promise for the future of fish reproductive control. Control fish did not mature and remained in the immature stages of reproductive development. The study has partly built on the initial work of Hanna Rosenfeld (IOLR, Israel) in the joint project with IRTA (DIVERISFY, GA 603121) where recombinant follicle stimulating hormone was used to advanced development of fish already undergoing gametogenesis.

The biotechnology company RARA AVIS used recombinant biotechnologies to produce the synthetic gonadotropins, which are a very close copy of the hormones that circulate naturally to control reproduction in wild flathead grey mullet. The structure of the hormones was based on the cDNA sequences that the scientists François Chauvigné and Joan Cerda from IRTA isolated and sequenced from wild flathead grey mullet.

The director of RARA AVIS, Ignacio Giménez, said “These advances demonstrate for the first time that we can control reproductive development to provide fertilised eggs when needed and in the species selected, on-demand.”

The senior researcher from IRTA, Neil Duncan added “This is a very promising development that shows the potential of these biotechnologies, but we have lots of work to do to improve the protocols and produce large numbers of fertile eggs, which are necessary for commercial aquaculture”.

Altogether, the research team consisted of Ignacio Giménez in RARA AVIS and Sandra Ramos, Neil Duncan, François Chauvigné and Joan Cerda in IRTA. The team also included Josep Lluis Celades and IRTA technicians, who ensured that the fish were provided with optimal rearing conditions and welfare. The work was funded by the Spanish Government (Instituto Nacional de Investigación y Tecnología Agraria y Alimentación (INIA) and Ministerio de Ciencia, Innovación y Universidades (MICINN)), RARA AVIS BIOTEC, S. L. and the European Union Project DIVERSIFY GA-603121. A proposal to build on these exciting and promising results has been submitted recently as a project proposal to the Spanish State program of R+D orientated to the challenges of society (Programa Estatal de I+D+i Orientada a los Retos de la Sociedad, MICINN).