At a glance
Essentials
- Size
- Reaches a total length of up to 2.8 cm. The range may vary with age, sex and population.
- Distribution
- Endemic to Thailand, recorded in the Pang Mapha karst system in Mae Hong Son province.
- Habitat
- Lives in fast-flowing underground waters in karst caves.
- Activity
- Observed climbing steep rocky surfaces in fast-flowing waterfalls.
- Diet
- Depends on microorganisms and organic matter from the caves.
- Conservation
- Classified as Vulnerable by the IUCN.
Observation guide
What to look for
- 01
Absence of visible eyes and bodily depigmentation.
- 02
Ability to climb rocky surfaces in fast currents using its fins.
- 03
Morphology of the pelvic girdle robust and fused with the vertebral column.
Lighting, age and viewing angle can hide features. If identification affects consumption, handling or conservation, consult specialist sources.
Ecology
Description and characteristics
Cryptotora thamicola is a freshwater fish of the family Balitoridae, endemic to Thailand. It is a troglobitic species, meaning it lives permanently in underground environments. Unlike other fish, it lacks pigmentation and does not have visible eyes, adaptations characteristic of life in the darkness of caves.
This species is known for its ability to climb rocky surfaces in fast currents. Studies have documented that Cryptotora thamicola walks using a diagonal-couplets lateral sequence gait, a movement pattern similar to that of salamanders and other tetrapods. This locomotion is achieved through the rotation of the pectoral and pelvic girdles, creating a standing wave in the axial body, instead of the body undulation typical of other fish that move out of the water.
Anatomically, the fish presents a robust pelvic girdle that joins directly to the vertebral column through fusion with a hypertrophied sacral rib. This structure is unusual in fish, where pelvic bones are usually suspended in a muscular band or loosely joined to the pectoral girdle. The morphology of the vertebral column in the sacral region also shows traits associated with terrestrial organisms, such as large spinous processes and transverse processes. These convergent adaptations with tetrapods allow the fish to hold firm and move on wet surfaces and in fast-flowing waterfalls.