First Record of Nudibranchs and Associated Sea Slugs Around Terengganu Islands, Malaysia via Citizen Science Observation
This study utilized citizen science observations from divers between January and May 2022 to document the first record of 71 nudibranch and sea slug species across seven localities in Terengganu, Malaysia, demonstrating the approach's effectiveness in building ecological databases to inform regional marine conservation priorities.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of a preprint that has not been peer-reviewed. It is not medical advice. Do not make health decisions based on this content. Read full disclaimer
Deep beneath the surface of the ocean, where sunlight fades and the water turns cool, live some of the most colorful and intricate creatures on Earth. These are nudibranchs, often called sea slugs. Unlike their land-dwelling cousins, these marine animals have lost their shells entirely, leaving their soft bodies exposed to the world. Instead of hiding inside a protective case, they rely on vibrant colors and strange, feathery structures on their backs to survive. These exposed gills, which give the group its name, are not just for breathing; they often serve as a dazzling display to warn predators that the animal tastes bad or is toxic. While these creatures are a favorite sight for divers and photographers, they remain a mystery to science in many parts of the world. In vast stretches of the ocean, we know very little about how many species exist, where they live, or how they are faring in a changing environment. This lack of knowledge makes it difficult to protect them, as conservation efforts require a clear picture of what is actually there.
In the waters surrounding the islands of Terengganu in Malaysia, a team of researchers decided to fill this gap, but they did not use the traditional method of sending scientists to dive and count every creature. Instead, they turned to the people who were already there: local divers and marine enthusiasts. The study, conducted over five months in 2022, asked these citizen scientists to share photographs of the sea slugs they encountered. By gathering these images from social media and online platforms, the researchers built a new record of life in the region without needing to collect physical specimens. This approach allowed them to cover a wide area quickly, capturing data from seven different locations, including the famous islands of Redang and Perhentian, as well as coastal rock formations. The goal was simple but powerful: to see how many different types of sea slugs could be found using the eyes of the community, and to compare this new list against existing records to see what had been missed.
The results were striking. From the 141 photographs submitted by just twelve contributors, the team identified 71 distinct species of sea slugs. These belonged to 35 different groups and 20 families, representing a level of diversity that had not been documented in this specific area before. The most common type found was the dorid nudibranch, a group known for its round, often brightly colored bodies, which made up nearly two-thirds of all the species found. The next most common were the aeolid nudibranchs, which are characterized by the finger-like projections on their backs. The study also recorded several other types, including sea slugs that feed on algae and those that look more like sea hares. The island of Bidong turned out to be the most diverse location, hosting 44 of the identified species, followed by Perhentian with 26. Even the smaller, less visited coastal sites contributed to the total, proving that these creatures are widespread throughout the region.
When the researchers compared their findings to the global database known as iNaturalist, they discovered that their citizen science effort had uncovered a significant amount of new information. While iNaturalist had recorded 20 species in Terengganu prior to this study, the new project added 51 species that were not previously listed for the area. This suggests that the existing records were incomplete and that many species had been overlooked simply because they were not being looked for in a systematic way. The study highlighted that some species, such as a particular type of sea slug found on the breakwater at Tok Jembal, had never been recorded on Malaysian islands in any public database before. This indicates that the local marine environment is richer in biodiversity than previously thought, and that relying solely on formal scientific surveys might leave many species undocumented.
The success of this project demonstrates that ordinary people, when equipped with cameras and a willingness to share, can play a vital role in scientific discovery. The researchers noted that the participants were well-versed in identifying sea slugs, as every photo submitted was of the correct animal, showing that the community already possessed a deep familiarity with these creatures. By combining these observations with expert verification, the team created a robust checklist that serves as a foundation for future conservation work. The study does not claim to have found every species in the region, nor does it suggest that the work is finished. Instead, it offers a clear proof of concept: that a structured, collaborative approach can rapidly expand our knowledge of marine life. It suggests that with continued effort and the involvement of local communities, it is possible to build a comprehensive understanding of these fragile ecosystems, ensuring that the vibrant, shell-less wonders of the South China Sea are not lost to ignorance.
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