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Kryptoglanis shajii is a species of small catfish (order Siluriformes) first found in 2003 in shallow (30-70 cm or 1-1.6 feet deep) freshwater underground springs and artificial wells, as well as hiding in vegetation on the banks of narrow, slow-flow paddy fields channels in the extreme western Ghats of the Thrissur district of Kerala, India. This catfish is referred to as the “extreme or enigmatic" catfish; it is rarely seen and its features (reduced eyes, diminished body pigmentation, small body size and exaggerated appearance of chemo- and mechano-receptors) clearly indicate that this is because it primarily lives underground. The generic epithet Kryptoglanis refers to its subterranean habitat (crypta is Latin for vault/tunnel). Researchers propose that individuals occasionally emerge into surface waters through underground crevices formed in the dense laterite soil they inhabit, especially when spring waters build up after monsoons (Binoy et al. 2012).
Kryptoglanis shajii have a dark reddish-brown translucent body that is well camouflaged with the iron-rich banks on which they were found. They are catfishy-looking and small - the largest measured is about 5.8 cm (3 inches). In captivity they readily eat small pieces of earthworm, mosquito larvae and boiled egg, suggesting these fish are probably carnivores that naturally feed on small aquatic invertebrates and larvae (Binoy et al. 2012; Britz et al. 2014).
In addition to its enigmatic habitat, Kryptoglanis shajii also presents a taxonomic puzzle. It is very different morphologically from the other two subterranean catfish in India (Horaglanis krishnai and H. alikunhi, family Claridae). Furthermore, use of radiography and high definition CAT scans as well as clearing and staining techniques to examine the fish’s skeletal anatomy (Vincent and Thomas 2011; Lundberg et al. 2014; Britz et al. 2014) show that K. shajii has a unique combination of highly modified and complex morphological traits, especially in the head and the jaw. These huge differences from other catfish have confounded the placement of K. shajii with respect to other catfish. As it cannot be appropriately included in any of the 13 known Indian catfish families, or for that matter any of the world’s 36 siluriform families at all (Jayaram 2006 and Nelson 2006, as cited in Lundberg et al. 2014), scientists place Kryptoglanis in its own family, Kryptoglanidae, perhaps as a sister taxon to the family Siluridae (Britz et al 2014). These conclusions, however, are based upon very few informative characters because these fish are so unusual. Further morphological study as well as analysis of molecular data is in progress to corroborate these findings (Lundberg et al. 2014), although, as troglomorphic taxa often do, this species also appears to have DNA sequences highly divergent from those of other catfish, so its evolutionary history may remain a puzzle (Ewing 2014).
Some of the characters that make this catfish different from any other include (Lundberg et al. 2014; Binov et al 2012; Vincent and Thomas 2011):
•absence of a dorsal fin
•the presence of relatively small and subcutaneous eyes
•four pairs of barbels including one pair of nasal barbels
•a long-based anal fin connected by membrane to the caudal fin
•a projecting lower jaw that projects out “like a bull dog” (Winter 2014; Palermo 2014)
•posteriorly reduced lateral line
Binoy et al. (2012) remark on the urgency of investigating the habitat that this fish, and possibly a complex ecosystem inhabited by so-far unknown troglomorphic vertebrates and invertebrates, as expansion of human activity and urbanization seriously threaten these unstudied environments.