Raising squid in aquaculture has been challenging for decades due to their sensitivity to water flow, disease vulnerability, complex life cycles, picky diets, and aggressive behavior. Wild squid populations are also declining due to overfishing and climate change, with Japan’s population now only 10% of what it was in the 1980s. In 2022, researchers at the Okinawa Institute of Science and Technology (OIST) created a highly efficient cephalopod aquaculture system, successfully rearing ten generations of squid. Recently, they discovered and treated a new parasitic copepod that was killing many squid eggs.
This eco-friendly treatment and its findings were published in Scientific Reports. Dr. Zdenek Lajbner, co-author and a key figure in OIST’s squid aquaculture program, emphasized the importance of disease management in aquaculture and was pleased to have eliminated this threat to squid health.
Despite improvements to a new aquaculture system, a persistent problem remained: only about 70% of squid eggs hatched, and many young squids died within 1-3 days. Dr. Mehmet Arif Zoral identified the cause: parasitic copepods infested the squid egg clutches, feeding on and damaging the eggs.
Copepods are crustaceans that can live freely, form symbiotic relationships, or act as parasites. The newly discovered species, named Ikanecator primus, lives on squid eggs, breaking them down with enzymes and causing death or premature hatching. The parasites also latch onto hatchlings, causing further damage and making them prone to bacterial infections.
“Copepods reproduce rapidly,” explains Dr. Zoral. “Each female carries 50-60 eggs that hatch in three weeks, while squid eggs take a month to hatch. This results in hundreds of copepods per squid egg clutch.” Aquaculture squid eggs are especially vulnerable due to their proximity, but copepods were also found on wild squid eggs.
Researchers described the copepods’ appearance and behavior and found a solution to protect the hatchlings. They used peracetic acid (PAA) in industries like aquaculture and veterinary medicine.
“We tested PAA solutions and found one that kills 100% of the parasites in under two minutes, with no harm to the squids or their future generations,” explains Dr. Zoral. Dr. Lajbner adds that PAA is biodegradable, unlike many current treatments in Japan that harm the environment.
The discovery and eco-friendly treatment were a joint effort between OIST researchers and local fisheries, combining aquaculture, veterinary science, and molecular biology. They used the latest sequencing technologies to identify the enzymes copepods use to destroy squid eggs.
The OIST Core Facilities and local fisheries provided essential support and resources. The team has filed a patent for the PAA solution. It aims to prove its effectiveness across different cephalopod species and parasite infections.
Dr. Lajbner said, “Aquaculture will always face new challenges, but advances like these improve squid health in aquaculture.”
The eco-friendly treatment developed by researchers at OIST successfully saves squid eggs from a newly discovered parasite. Using biodegradable peracetic acid (PAA), they eliminated 100% of the parasites without harming the squid.
This breakthrough, supported by collaboration between different fields and local fisheries, improves the health of squids in aquaculture and has the potential to benefit cephalopod aquaculture worldwide.
Journal reference:
- Zoral, M.A., Lajbner, Z., Zifcakova, L. et al. Peracetic acid treatment of squid eggs infected with parasitic copepod (Ikanecator primus gen. et sp. nov.). Scientific Reports. DOI: 10.1038/s41598-024-65290-z.