Red Light Treatment Could Be a Sustainable Way to Breed Cleaner Shrimps

Red light irradiation of Cleaner shrimp offers an efficient, animal-friendly maturation strategy in shrimp farming, scientists show

Owing to the high demand of Cleaner shrimp, an ornamental marine animal, artificial breeding involves speeding up the sexual reproduction. Conventionally, to induce sexual maturity, eyestalk of the shrimp is removed. But, this process is not animal-friendly and reduces the economic value of the shrimp. To this end, researchers from Korea have shown an alternative method to promote sexual reproduction in shrimps, that is, red light illumination, making this process feasible and more humane.

Cleaner shrimp, a marine animal, is widely farmed and traded for its ornamental value. Owing to its high demand, breeders often induce sexual maturity artificially to speed up the reproductive process in the shrimps.

One popular technique to induce sexual maturity is the removal of the eyestalk of these shrimps. This method works by inhibiting the “vitellogenesis-inhibiting hormone” (VIH), which is found in the eyestalk. Blocking VIH induces sexual maturation in shrimps. However, it also suppresses other important hormones such as crustacean-hyperglycemic hormone (CHH) and molt-inhibiting hormone (MIH). This severely impairs the quality of eggs and increases the chances of bacterial contamination, thus reducing the economic value of the shrimps. Therefore, there is a need to develop alternative efficient, animal-friendly methods to induce sexual maturity in Cleaner shrimp.

Previously, environmental factors, such as light of different wavelengths, have been shown to influence sexual maturity in shrimps. Moreover, injection of sex steroids like “17β-estradiol” (E2) may also yield similar results. Prof Choi explains, “In general, the eyestalk ablation method commonly used for the promotion and reproduction of crustaceans increases the likelihood of pathogen exposure and low-quality egg production and decreases the commercial value. Our study aimed to overcome the shortcomings of this method by finding an effective alternative.”

To begin with, the researchers divided the shrimps into two test groups: one received two doses of E2 injection and the other, red-light treatment. Then, they measured the ex-pression of the eyestalk hormones VIH, CHH, and MIH are produced in all groups. They also measured the levels of hormone receptors like the “Vitellogenin receptor” (VTG-R) and “Estrogen receptor” (ER), which are known to play a role in egg development.

The findings showed that CHH, VTG-R, and ER levels increased in the group treated with red light, meaning that they effectively promoted sexual maturity in these animals. On the other hand, in the E2 injection group, there was no change in the CHH and VIH levels but an increase in ER. This means that the E2 injection aided the egg maturation process but not the promotion of eyestalk hormones. Thus, the scientists concluded that red-light treatment could be a potentially effective method to induce sexual maturity and artificially breed cleaner shrimps.

Prof Choi and his team are confident that these findings can lead to an improved breeding environment in shrimp farming. He concludes, “Our study can contribute to stress reduction and sexual maturation induction of marine organisms in a sustainable manner. Red light irradiation is cost-effective, animal-friendly, and can also be economical to fishermen.”

Not just this, these findings can be applied to other marine animals too. This study, indeed, paves the way for sustainable shrimp farming.

DOI: 10.1093/jcbiol/ruz080

*Corresponding author’s email: choic@kmou.ac.kr

About the author

Dr. Cheol young Choi is a Professor at the Division of Marine Bioscience at Korea Maritime and Ocean University. His group is currently working on endocrine regulatory mechanisms of Cleaner shrimp using the LED light wavelength, endocrine regulatory mechanisms of the gonadotropin-inhibitory hormone in protandrous cinnamon clownfish, and biomarker development for marine environmental risk assessment by ex-pression analysis of oxidative stress-related genes. Before joining the Korea Maritime and Ocean University, he completed his postdoctoral training at Calgary University and National Institutes of Health (NIH). Dr. Choi completed his PhD from Tokyo University of Marine Science and Technology.