The controversial use of eyestalk ablation in black tiger shrimp to trigger ovarian maturation may soon give way to a more humane and sustainable practice if a new technique developed by a molecular biologist at Mahidol University proves to be a viable alternative.
Dr. Supattra Treerattrakool, a researcher at Institute of Molecular Biosciences, has come up with a strategy to induce reproductive maturation in female adults of black tiger shrimp (Penaeus monodon) by working at molecular level to block the activity of the so-called gonad-inhibiting hormone (GIH) that regulates maturation.
The technique, she hopes, would replace the removal of eyestalk, where the gland that produces the hormone is located.
While eyestalk ablation is a commonly used technique to induce ovarian maturation in crustacean in aquaculture, especially black tiger shrimp production, it exhausts female broodstock quickly, increases production costs, and draws criticism for the cruelty of the method.
Yet, due to the lack of alternatives, the practice seems unavoidable considering the huge economic benefits of the black tiger shrimp industry—incomes for shrimp farmers and employment for farm workers. The shrimp has become one of the country’s top ten export products, bringing in more than 50 billion baht in annual revenue.
In her Ph.D. dissertation that won a research award in agriculture and biology from National Research Council of Thailand 2011, Dr. Supattra cloned and characterized the DNA of the GIH of P. monodon.
The genetic information was then used to develop molecular substances—GIH-dsRNA and anti-GIH antibody—that were injected into female broodstock of black tiger shrimp.
The introduction of the substances was found to deplete GIH and neutralize its activity, and in the case of GIH-dsRNA, led to ovarian maturation and successful spawning in both domesticated and wild black tiger shrimp when compared to eye-ablated shrimp.
Further development of multiple induction of ovarian maturation and spawning with this technique would make it a viable substitute for eyestalk ablation in the future, the researcher said.
This possibility offers several benefits for shrimp farmers. The technique would reduce the use of female broodstock from wild catch as well as domesticated ones and thus cut production costs for breeding.
Another indirect but significant benefit is that female broodstock could be maintained for much longer periods which allow time for breed selection of brooders with healthy and rapid growth to supply high-quality seed for the industry.
“(The strategy) would benefit the long-term
sustainability of the country’s black tiger
shrimp industry and increase its competitiveness
in the global market,” she said.
Date : August 1, 2012