AT A GLANCE
- Common Name: Tire Track Eel
- Scientific Name: Mastacembelus armatus
- Category: Fish
- Subcategory: Spiny Eels
- Range: South and Southeast Asia, from Pakistan, India, Sri Lanka, and Nepal east through Myanmar, Thailand, Malaysia, Cambodia, and Vietnam to southern China
- Habitat Type: Lowland rivers, canals, streams with sandy or gravelly substrates, flooded wetlands, swamps, and reservoirs with abundant submerged driftwood and roots
- IUCN Red List Status: Least Concern
- Lifespan: 8 to 15 years
- Diet: Carnivorous/Predatory (nocturnal hunting for earthworms, aquatic insect larvae, freshwater shrimps, crabs, and small benthic fishes)
- Average Size/Weight: Total length 50 to 90 cm (rarely up to 100 cm in large rivers); weight 500 to 1,500 g
- Key Defining Feature: Slender, eel-like freshwater fish with a row of sharp, erectile dorsal spines, an elongated mobile snout, and a bold, reticulated dark brown pattern resembling zig-zag tire tracks
Overview
The Tire Track Eel (Mastacembelus armatus), also widely known as the Zig-zag Eel or Leopard Spiny Eel, is an imposing, nocturnal benthic predator in the spiny eel family Mastacembelidae. Native to the freshwater river systems of South and Southeast Asia, this long, serpentine fish is not a true anguillid eel, but rather an advanced spiny-rayed teleost. Named for the intricate, reticulated dark brown markings along its flanks that resemble the tread of an off-road automobile tire, it spends daylight hours buried deep in river silt with only its mobile, whiskered snout exposed.
Biology and Physical Characteristics
Mastacembelus armatus has an elongated, laterally compressed, ribbon-like body covered in tiny, smooth cycloid scales and a thick protective slime layer. The dorsal fin is uniquely modified: its anterior portion consists of a row of 33 to 40 sharp, isolated, erectile spines that lie flat in a dorsal groove and lock upright when the fish is attacked by predatory birds or otters. Its snout terminates in an elongated, trilobed, fleshy rostral appendage that is highly sensitive and mobile, packed with chemoreceptors used to sniff out subterranean prey. The body coloration is a rich sandy-tan to olive-brown, covered in a bold, zig-zagging network of dark chocolate-brown loops, blotches, and interconnected bars that mimic tire tracks.
Behavior and Ecology
Exclusively nocturnal, the Tire Track Eel is a master burrower. Using its pointed snout and undulating body, it effortlessly burrows tail-first into soft sand, mud, or gravel, concealing its entire meter-long body so that only its periscope-like snout and eyes poke out into the water. When night falls, it emerges to prowl the riverbed, probing its flexible rostral appendage into leaf litter and stone crevices to detect earthworms, river prawns, and sleeping minnows, which it engulfs with a swift strike of its toothy jaws.
Conservation and Human Impact
The Tire Track Eel is evaluated as Least Concern by the IUCN Red List. It is widely distributed and common across major Asian river basins including the Ganges, Mekong, and Chao Phraya. Highly prized as a delicious, tender food fish in Asian gastronomy, it is heavily harvested in inland freshwater fisheries and occasionally exported for the freshwater aquarium trade.
Interesting Factoid
The Tire Track Eel can bury its entire three-foot-long body completely under the river sand in just five seconds, leaving only its flexible nose sticking up like a tiny submarine snorkel.