Eels and snakes, with their elongated bodies, often prompt questions about their biological relationship. Despite similar appearances and shared aquatic habitats, these animals belong to very different branches of the tree of life. This article clarifies their distinct classifications and the reasons for common confusion.
Are Eels and Snakes Related?
Eels and snakes are not closely related, despite their superficial resemblance. Eels are a diverse group of fish, classified under the order Anguilliformes. They are aquatic vertebrates with gills and fins, living their entire lives in water. In contrast, snakes are reptiles, belonging to the suborder Serpentes.
Their evolutionary paths diverged hundreds of millions of years ago, long before modern fish and reptiles emerged. Eels evolved from ancient fish ancestors, while snakes descended from lizard-like terrestrial reptiles. This fundamental difference in their lineage means they are as biologically distinct as a fish is from a bird or a mammal.
Why the Confusion?
The common confusion between eels and snakes stems from their similar body shapes and movement patterns. Both evolved elongated, limbless bodies, allowing efficient movement through narrow spaces, whether in water or on land. This similar body plan results from convergent evolution, where unrelated species develop similar traits due to adapting to similar environmental pressures or lifestyles.
Eels and some snake species, particularly sea snakes, inhabit aquatic environments, further contributing to the visual mix-up. Their undulating, slithering movements in water appear strikingly alike, reinforcing the misconception. However, these shared characteristics are merely adaptations to their environments, not indicators of a close genetic link.
Key Differences Between Eels and Snakes
Beyond their shared elongated forms, eels and snakes exhibit profound biological differences. Their respiratory systems are distinct: eels possess gills, allowing them to extract oxygen directly from water. Snakes, as reptiles, breathe air using lungs and and must periodically surface. Some aquatic snake species can absorb oxygen through their skin, but still rely on lungs for primary respiration.
Their skin coverings also differ significantly. Eels typically have smooth, slimy skin, often scaleless or with tiny embedded scales, covered in mucus. Snakes, conversely, are covered in dry, overlapping scales made of keratin, which aid in protection and locomotion.
Eels possess fins, including continuous dorsal, anal, and caudal (tail) fins, for propulsion and maneuvering in water. Snakes lack fins, though some aquatic species have flattened, paddle-shaped tails for swimming. Skeletal differences are apparent; snakes feature highly flexible jaws that can dislocate to swallow large prey, a specialized adaptation for their carnivorous diet. Eels have different jaw structures suited for their feeding habits, which typically involve grasping prey.
Eels are exclusively aquatic, living in both freshwater and marine environments throughout their lives. While many snakes are terrestrial, some adapted to aquatic life still need to return to the surface to breathe. Their reproductive strategies vary: eels release eggs into the water for external fertilization, often involving complex migratory life cycles to specific spawning grounds. Most snakes lay eggs on land, though some give birth to live young, with reproduction occurring terrestrially or, in some cases, in water for live-bearing aquatic snakes.