In News:

Researchers have discovered a new spider species, Dolomedes indicus, in the evergreen rainforests of the Western Ghats, specifically in Wayanad district, Kerala.

What is Dolomedes indicus?

• Dolomedes indicus is a newly identified species of spider belonging to the genus Dolomedes, commonly known as raft spiders or fishing spiders.
• This discovery marks the first recorded member of the Dolomedes genus in India.

Genus Dolomedes (Raft/Fishing Spiders)

• Members of this genus are known for their semi-aquatic lifestyle.
• Unlike web-building spiders, they are active hunters.
• They are typically found near freshwater streams, ponds, and wetlands.

Habitat

• Found in evergreen forest streams of the Western Ghats, a global biodiversity hotspot.
• Prefers cool, clean, shaded freshwater habitats under dense forest canopies.
• Its presence indicates pristine stream ecosystems with minimal disturbance.

Behaviour and Hunting Strategy

Dolomedes indicus is a semi-aquatic predator that:

• Uses surface tension of water to stand and move on water surfaces
• Detects vibrations caused by insects or small aquatic animals struggling in water
• Swiftly lunges across the water to capture prey
• Is capable of swimming and diving to escape predators or catch prey

This makes it ecologically different from typical web-dependent house spiders.

Physical Characteristics

• Males: Identified by a distinctive snow-white marking extending from the face to the middle of the back
• Females: Larger in size and greenish-brown, helping them camouflage against mossy rocks and streamside vegetation

Sexual dimorphism (difference in appearance between males and females) is clearly visible.

Ecological Importance

• Being highly sensitive to environmental changes, Dolomedes indicus may serve as an indicator species
• Its survival depends on:
  • Clean freshwater
  • Stable forest canopy cover
  • Undisturbed stream ecosystems

Thus, its presence can help scientists monitor freshwater ecosystem health and assess the impact of habitat degradation.

Significance of Discovery

• Highlights the rich but understudied biodiversity of the Western Ghats
• Expands the known geographical range of the Dolomedes genus
• Emphasizes the importance of conserving freshwater habitats within forest ecosystems