How are aquatic caecilians adapted differently from burrowing caecilians?

While most caecilians are specialized for a subterranean existence, aquatic caecilians—specifically those in the family Typhlonectidae—exhibit distinct secondary adaptations for life in the water.12

The primary differences between these groups include:

• Feeding Habits: Terrestrial, burrowing caecilians primarily consume earthworms and other soft-bodied prey found in soil. In contrast, aquatic typhlonectids are predators that feed on fishes, eels, and various aquatic invertebrates.3
• Reproductive Strategy: While many caecilians lay eggs in terrestrial burrows, aquatic typhlonectids are viviparous, meaning they give birth to live young.4
• Morphology and Locomotion: Burrowing caecilians possess a compact, spadelike cranium and a specialized axial musculoskeletal system designed for concertina locomotion through soil. Their bodies are encased in a tough muscular sheath anchored to the skin to facilitate tunneling. Aquatic species have evolved secondary adaptations to transition away from this strictly subterranean morphology, allowing them to thrive in aquatic environments.12

It is important to note that despite these environmental differences, all caecilians share fundamental traits such as a limbless, cylindrical body and internal fertilization via a male copulatory organ called the phallodeum.24