Study to develop farming methods for native sea snails in Singapore finds successful start

SINGAPORE – The larva development of two cowrie species native to Singapore waters has been successfully recorded by marine biologists from the Tropical Marine Science Institute (TMSI) at the National University of Singapore in a study published in April. 

Offspring of the cowries from one of the two sea snail species – the Arabian cowrie (Mauritia arabica) – even survived into the second life stage of the animal and remain alive to this day.

Ms Teresa Tay, the TMSI research assistant on this study, said: “Previous reproduction studies have managed to collect egg masses from the wild and rear their larvae, but none of them reported success in getting the larvae to develop and settle into juveniles.”

Both the Tiger and Arabian cowrie species are endangered in Singapore because of habitat loss and over-collection, and this study seeks to develop farming methods so that the production of cowries can be scaled up for research, conservation and the aquarium trade.

Cowries, especially the rare species, are popular among shell collectors and aquarium hobbyists because of their polished ornate shells and striking appearance when their mantle is fully extended.

Cowries are often harvested from the wild and are not protected under any international agreement like the Convention on International Trade in Endangered Species of Wild Fauna and Flora (Cites), which makes them vulnerable to overexploitation, said Dr Neo Mei Lin, senior research fellow at TMSI and principal investigator of the study.

Cites regulates the international trade in over 36,000 species of plants and animals.

“Previous reproductive studies on cowries have also not reported success in breeding juvenile cowries, which meant that the trade in cowries would continue to rely on wild harvesting that may become unsustainable in the near future,” she added. 

The life phases of cowries can be divided into three stages – the larva stage, where the hatched larvae are in their swimming forms as their shell volume increases, before settling on the seabed as juveniles. Their shell continues to thicken even as they mature into adulthood and reach sexual maturity.

Dr Neo said: “Our study found that growing cowrie larvae require clean seawater and suitable microalgae diets to thrive. In addition, being able to identify the behavioural cues of larvae was critical for the metamorphosis from larvae to juvenile, and settlement.”

Researchers had to wait eight months before their study subjects of 14 Tiger cowries (Cypraea tigris) and seven Arabian cowries produced egg masses. 

The study began in July 2021 and took over a year to complete. The strongest larva of the tiger cowrie species survived for 37 days.

More than 80 per cent of the tiger larvae survived the first four days after hatching.

But the surviving larvae kept dying from day five to day 14, and the study concluded that a few batches of the Tiger larvae were ravaged by severe algal growth on their shells, which can impede shell growth. At the same time, they were also attacked by parasites.

Dr Neo concluded that the results can be incorporated into how to culture the larvae “to increase the success of cowrie reproduction in captivity”.