New Semi-Aquatic Spider Species Dolomedes indicus Found in Western Ghats

A research team in Kerala has identified a new species of semi-aquatic spider, Dolomedes indicus, marking the first confirmed record of a fishing spider from this genus in India. The discovery from the rainforests of Wayanad underscores the ecological richness of the Western Ghats and highlights the need for continued biodiversity research.

Discovery in the Pristine Streams of Wayanad

Researchers from the Kerala Forest Research Institute located the species in the forested areas of Lakkidi and Periya. Unlike web-building spiders, Dolomedes indicus is an active predator that hunts on water. The spider uses the surface tension of streams to detect vibrations caused by insects or small fish and darts across the water to seize its prey. Researchers also observed exceptional diving abilities, with one female remaining submerged for nearly ninety minutes by trapping a layer of air with specialised hydrophobic hairs.

Scientific Confirmation and Distinguishing Features

The team verified the species through detailed physical examination and DNA analysis. While unverified reports of fishing spiders existed, this is the first study to provide conclusive genetic and morphological evidence. Male spiders possess a distinctive snow-white stripe running from the face to the mid-back, whereas females are larger, greenish-brown and camouflaged against mossy stream banks. Specimens have been preserved in the KFRI Insect Collection for future study.

Ecology, Behaviour and Habitat Sensitivity

Dolomedes indicus thrives in cool, fast-flowing forest streams and avoids stagnant or polluted waters. Its behaviour—surface hunting, gliding, swimming and long-duration diving—reflects adaptations to a semi-aquatic lifestyle. The species appears highly sensitive to habitat quality, making it ecologically significant for monitoring freshwater health in the Western Ghats.

Exam Oriented Facts

• Dolomedes indicus is the first confirmed species of the Dolomedes genus described from India.
• Discovered in Lakkidi and Periya forest areas of Wayanad, Kerala.
• Displays semi-aquatic hunting behaviour using water surface tension.
• Confirmed through DNA analysis and morphological traits, including a snow-white stripe in males.

Conservation Significance for the Western Ghats

As freshwater-dependent predators, these spiders may serve as indicator species for ecosystem health. The discovery highlights the vulnerability of stream habitats in the Western Ghats, where climate change and land-use pressures threaten biodiversity. Researchers stress the importance of conserving pristine forest streams to protect such specialised species.