VISAKHAPATNAM: A biodiversity documentation exercise during the City Nature Challenge in April this year, has led to what could be the rediscovery of a sea slug species not recorded for over 160 years.
Marine biologist Sri Chakra Pranav, who is also the founder of the East Coast Conservation Team (ECCT), came across a translucent, ethereal-looking nudibranch while surveying the coastal waters of Visakhapatnam.
Speaking about the discovery with TNIE, Pranav said the sea slug did not match any of the photo records or species previously documented by the ECCT. “After verifying our data and not finding any match, we referred to historical records, and found an exact match in a British journal published in 1864 by zoologists Joshua Alder and Albany Hancock. The species they had documented, Phidiana unilineata, appeared identical to what we observed,” he said.
The nudibranch was reportedly first recorded in Visakhapatnam itself by Alder and Hancock during their study of marine slugs along the South Indian and Sri Lankan coastlines. Since then, there have been no recorded observation or documentation of this species, making the recent sighting potentially significant.
Pranav was supported on the field by Dr Deepu Visweswar and Chandra Sekhar, members of the ECCT, while Vishal Bhave, a nudibranch expert, helped in identification. He noted that more research is needed to confirm the rediscovery scientifically. “This species may be endemic to the Visakhapatnam coast. The region between Visakhapatnam and Srikakulam has rare rocky shorelines that support the growth of hydroids, which are a food source for these sea slugs,” Pranav explained.
‘Sea slugs are indicators of healthy marine system’
He said each slug species typically feeds on specific hydroids and corals, underlining the ecological significance of such biodiversity. Historical records indicate that around 20 different sea slug species were documented from Visakhapatnam alone in Alder and Hancock’s work, highlighting the area’s unique marine habitat. “Sea slugs are indicators of a healthy marine ecosystem. Their presence points to the diversity of corals and hydroids in the region,” he said.
Pranav is currently working on a research paper detailing the list of sea slug species identified along the Visakhapatnam coast, which will include both new discoveries and possible rediscoveries. He emphasised that citizen science efforts, such as the City Nature Challenge, play a crucial role in such documentation, and in fostering public awareness of local biodiversity.
“This discovery underlines the importance of community participation in biodiversity surveys and the need to document and preserve our coastal ecosystems,” he added. Marine researchers are consistently recording both rediscoveries and new findings of sea slugs, flatworms, and other lesser-known marine species. These sightings highlight the growing importance of continued documentation and research.