Holotype: ZSI F313/2 38.85mm TL. The description is based on two specimens (second 42.0mm TL) and although the second is not mentioned as a paratype it should be considered as such (also at ZSI). This is the type species by original designation and monotypy of the cave‑restricted genus Horaglanis.
Type locality: A well at an undisclosed location at Kottayam, Kerala, India. Known also from a number of dug out wells in the same area (8o4'N‑10o21'N, 76o13'E‑77o38'E). The type locality of this species is also the type locality of the Synbranchid Monopterus eapeni and at this site at least the two species coexist. It is not known whether they coexist elsewhere.
The only published details are that the fish is found in dug-out wells. It may be an inhabitant of relatively small groundwater voids. Mercy (1981) suggests that they migrate from one well to another through the subsurface drainage system. Francy Kakkasery (pers. comm.) suggests that they live in the water table up to 10m below the surface and that they are only found where laterite is the predominant bed deposit.
The anatomy of H. krishnai has been relatively well studied (see references below) and it seems certain that it is rather different in several ways from other members of the family. Menon (1950, 1951a, 1951b) suggested that the differences were the result of regressive evolution and that the animal was only secondarily primitive. Chardon (1968) made a thorough study of several aspects of siluriform anatomy. He noted that the viscera are more typical of the Bagridae than the Clariidae. This and other evidence suggests that the species is a relict, close to the stem of both Bagridae and Clariidae. Although admitting that there were examples of shared derived characters, and of features associated with hypogean life, Chardon suggested that it is primarily primitive. De Pinna (1998) postulates a relationship between Phreatobius and Horaglanis based on similar skull morphology. A recent photograph of Horaglanis krishnai (Plate 6) shows that it is blood red in colour, a very rare condition for fishes (De Pinna, 1998), as is Phreatobius and this may be a synapomorphy for a group containing the two genera. Clearly there is much to be learned about the exact systematic position of this interesting animal.
The Kerala area of south-western India, principally the area of the Western Ghats, is rich in subterranean species. There are at least three unique elements within this subterranean fauna that stand out as of great evolutionary interest.
First, there are at least eight subterranean fishes: Clariidae: H. krishnai, Horaglanis alikunhii, Horaglanis abdulkalami; Kryptoglanidae: Kryptoglanis shajii, Kryptoglanis undescribed species; Synbranchidae: Monopterus eapeni, Monopterus roseni, Monopterus digressus.
Second, there is a strongly fossorial amphibian in its own family: Nasikabatrachidae: Nasikabatrachus sahyadriensis Biju and Bossuyt 2003, sister family, genus and species to Sooglossidae, an amphibian family found only in the Seychelles archipelago) (Zachariah et al. 2012).
Both the fishes and the Crustacea appear to have originated in Gondwanan times and both have close relatives in Africa. It is hypothesised that the genus Horaglanis is related to Uegitglanis zammaranoi from Somalia (Menon 1951, Silas 2010) and Eurindicus is related to three west African species (the monotypic Euryrhyncoides holthuisi, Euryrhynchina edingtonae and Eurhynchina puteola (De Grave et al. 2018).
There is considerable evidence, both from morphology and molecules, that Horaglanis is very basal within Clariidae. de Pinna (1993, 1998) and Diogo et al. (2003) considered the skull structure of specie swithin the Clariidae and concluded that Uegitglanis was sister to all other species in the family and that Horaglanis was sister to Uegitglanis plus other species making it the most basal of all studied clariids. This conclusion was supported by Pavan-Kumar (2017) who compared mitochondrial COI sequences from one (unnamed) species of Horaglanis and 13 other Clariidae and showed that it is the sister group to all other species in the family (he did not include Uegitglanis in his analysis). [Note than Pavan-Kumar (2017) is a Peerj preprint that had not been refereed so its conclusions need to be taken with caution.]
(Abraham, R. 2011. Horaglanis krishnai. The IUCN Red List of Threatened Species 2011: http://dx.doi.org/10.2305/IUCN.UK.2011-1.RLTS.T10261A3185783.en. Downloaded on 07 July 2017).
R (IUCN, 1990), R (IUCN, 1993), VU D2 (IUCN, 1996, 2000). Dahanukar, Raut and Bhat (2004) assess this species as Critically Endangered but with any explanation of how they arrive at this status.
As above plus: BMNH 1981.11.20:1‑3.
- Menon, A. G. K. (1950)
- Menon, A. G. K. (1951)
- Menon, A. G. K. (1951)
- Eapen, K. C. (1963)
- Chardon, M. (1968)
- Misra, K.S. (1976)
- Mercy, T. V. A. (1981)
- Mercy, T. V. A. (1982)
- Mercy, T. V. A., Padmanabhan, K. G. and Pillai, N. K. (1982)
- Mercy, T. V. A. (1983)
- Mercy, T. V. A., Pillai, N. K. and Balasubramonian, N. K. (1984)
- Mercy, T. V. A. and Pillai, N. K. (1984/5)
- Talwar, P. K. and Jhingran, A. G. (1992)
- de Pinna, M.C.C. (1998)
- Mercy, TVA (2000)
- Mercy, T. V. A. and Pillai, N. K. (2001)
- Mercy, T. V. A., Pillai, N. K. and Balasubramonian, N. K. (2001)
- Kurup B.M. Radhakrishnan K.V. and Manojkumar T.G. (2004)
- Dahanukar, N, Raut, R and Bhat, A (2004)
- Babu, K.K.S. and Nayar, C.K.G. (2004)
- Dahanukar, N, Raghavan, R, Ali, A, Abraham, R and Shaji, CP (2011)
- Babu, K.K.S. (2012)
- Raghavan, R., Das, K, Nameer, PO, Bijukumar, A and Dahanukar, N (2016)
- Pavan-Kumar, A. (2017)
- De Grave, S., Arjun, C.P. and Raghavan, R. (2018)
|Menon, A. G. K.||Journal Article||1950||On a remarkable blind siluroid fish of the family Clariidae from Kerala, (India)|
|Menon, A. G. K.||Journal Article||1951||Distribution of clariid fishes, and its significance in zoogeographical studies|
|Menon, A. G. K.||Journal Article||1951||On certain features in the anatomy of Horaganis Menon|
|Eapen, K. C.||Journal Article||1963||A new species of Monopterus from South India|
|Chardon, M.||Journal Article||1968||Anatomie comparee de l'appareil de Weber et des structures connexes chez les Siluriformes|
|Misra, K.S.||Book Section||1976||Horaglanis krishnai|
|Mercy, T. V. A.||Journal Article||1981||On the unique disposition of the valvula cerebelli in Horaglanis krishnai (Teleostei)|
|Mercy, T. V. A.||Journal Article||1982||On the presence of a forked barbel in the blind catfish Horaglanis krishnai Menon|
|Mercy, T. V. A., Padmanabhan, K. G. and Pillai, N. K.||Journal Article||1982||Morphological studies on the oocytes of the blind catfish Horaglanis krishnai Menon|
|Mercy, T. V. A.||Journal Article||1983||Studies on the air bladder of blind clariid Horaglanis krishnai Menon|
|Mercy, T. V. A., Pillai, N. K. and Balasubramonian, N. K.||Journal Article||1984||Studies on the oxygen consumption of the blind catfish Horaglanis krishnai|
|Mercy, T. V. A. and Pillai, N. K.||Journal Article||1984/5||The anatomy and histology of the alimentary tract of the blind cat-fish Horaglanis krishnai|
|Talwar, P. K. and Jhingran, A. G.||Book Section||1992||Genus Horaglanis and species Horaglanis krishnai|
|de Pinna, M.C.C.||Book Section||1998||Phylogenetic relationships of Neotropical Siluriformes (Teleostei: Ostariophysi): Historical overview and synthesis of hypotheses|
|Mercy, TVA||Book Section||2000||Biology of an endemic blind catfish Horaglanis krishnai Menon|
|Mercy, T. V. A. and Pillai, N. K.||Journal Article||2001||Studies on the cranial osteology of the blind catfish Horaglanis krishnai menon (Pisces, Clariidae)|
|Mercy, T. V. A., Pillai, N. K. and Balasubramonian, N. K.||Journal Article||2001||Studies on certain aspects of behaviour in the blind catfish Horaglanis krishnia Menon|
|Kurup B.M. Radhakrishnan K.V. and Manojkumar T.G.||Conference Paper||2004||Biodiversity status of fishes inhabiting rivers of Kerala (S. India) with special reference to endemism, threats and conservation measures|
|Dahanukar, N, Raut, R and Bhat, A||Journal Article||2004||Distribution, endemism and threat status of freshwater fishes of the Western Ghats of India|
|Babu, K.K.S. and Nayar, C.K.G.||Journal Article||2004||A new species of the blind fish Horaglanis Menon (Siluroidea: Clariidae) from Parappukara (Trichur District) and a new report of Horaglanis krishnai Menon from Ettumanur (Kottayam District), Kerala|
|Dahanukar, N, Raghavan, R, Ali, A, Abraham, R and Shaji, CP||Book Section||2011||Chapter 3. The status and distribution of freshwater fishes of the Western Ghats|
|Babu, K.K.S.||Journal Article||2012||Horaglanis abdulkalami, a new hypogean blind catfish (Siluriformes: Clariidae) from Kerala, India|
|Raghavan, R., Das, K, Nameer, PO, Bijukumar, A and Dahanukar, N||Journal Article||2016||Protected area and imperriled endemic freshwater biodiversity in the Westren Ghats hotspot|
|Pavan-Kumar, A.||Journal Article||2017||Molecular phylogeny of genus Horaglanis (Indian blind catfishes) within Family Clariidae|
|De Grave, S., Arjun, C.P. and Raghavan, R.||Journal Article||2018||The discovery of Euryrhynchidae (Crustacea: Decapoda) in India, with the description of a new genus and species|