Horaglanis krishnai

Menon 1950

Horaglanis krishnai
Redrawn by Rhian Kendall from Menon (1950)






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.

Jarayam (2006:309) proposed the subfamily Horaglanidinae for the, then, two species in the genus but this has not received support since.

Diogo et al. (2003), also de Pinna (1993) and de Pinna (1998), have suggested, on morphological grounds, that the most basal member of the Family Clariidae is Horaglanis, and that the next most basal is Uegitglanis.

Biological Notes

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 eleven subterranean fishes: Cobitidae: Pangio bhujia; Clariidae: H. krishnai, Horaglanis alikunhii, Horaglanis abdulkalami; Kryptoglanidae: Kryptoglanis shajii, Kryptoglanis undescribed species; Synbranchidae: Monopterus eapeni, Monopterus roseni, Monopterus digressus; Aenigmochannidae: Aenigmachanna gollum, Aenigmachanna mahabali. What is most remarkable about these fishes is that the Families Kryptoglanidae and Aenigmochannidae were both erected recently (2014 and 2020 respectively) and contain only these species. The erection of new families within teleost fishes is very uncommon and this greatly emphasises the importance of this area.

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).

Third, there are two aberant Crustacea: Euryrhynchidae: Eurindicus bhugarbha De Grave, Arjun and Raghavan 2018 and Palaemonidae: Troglindicus phreaticus Sankolli and Shenoy 1979.

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.]

Conservation Status

MuG [DD:3.1:2011]

(Abraham, R. 2011. Horaglanis krishnai. The IUCN Red List of Threatened Species 2011: 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.

Museum Holdings

As above plus: BMNH 1981.11.20:1‑3.

Internet Resources


Only genus defined, species not known

Genbank HE819391.1     mt COI                  specimen voucher M-CCI-HL1

Genbank HE819392.1     mt COI                  specimen voucher M-CCI-HKA

Genbank HE819393.1     mt COI                  specimen voucher M-CCI-HKB

Genbank HE819394.1     mt COI                  specimen voucher M-CCI-HKC

Genbank HG937614.1    mt cytB                 specimen voucher M-CCI-HL

Genbank HG937613.1    mt cytB                 specimen voucher M-CCI-HKB

Key References

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. Thesis 1981 Monographic study of the fish Horaglanis krishnai Menon
Mercy, T.V.A. Journal Article 1981 On the unique disposition of the valvula cerebelli in Horaglanis krishnai (Teleostei)
Mercy, T.V.A. Thesis 1981 Biology of the blind catfish of Kerala, Horaglanis krishnai Menon
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. Thesis 1993 Higher-levelphylogeny of Siluriformes,with a new classication of the order (Teleostei, Ostariophysi).
de Pinna, M.C.C. Book Section 1998 Phylogenetic relationships of Neotropical Siluriformes (Teleostei: Ostariophysi): Historical overview and synthesis of hypotheses
Mercy, T.V.A. Book Section 2000 Biology of an endemic blind catfish Horaglanis krishnai Menon
Ponniah, A.G. and Gopalakrishnan, A. Book 2000 Endemic fish diversity of Western Ghats
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
Ranjit Daniels, R.J. Journal Article 2001 Endemic fishes of the Western Ghats and the Satpura hypothesis
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)
Arratia, G., Kapoor, B.G., Chardon, M. and Diogo, R. Book 2003 Catfishes
Diogo, R., Chardon, M. and Vandewalle, P. Journal Article 2003 On the osteology and myology of the cephalic region and pectoral girdle of Heteropneustes fossilis (Siluriformes: Heteropneustidae), with comments on the phylogenetic relationships between Heteropneustes and clariid fishes
Biju, S.D. and Bossuyt, F. Journal Article 2003 New frog family from India reveals an ancient biogeographical link with the Seychelles
Teugels, G.G. and Adriaens, D. Book Section 2003 Taxonomy and phylogeny of Clariidae - an overview
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
Bossuyt, F., Meegaskumbura, M., Beenaerts, N., Gower, D.J., Pethiyagoda, R., Roelants, K., Mannaert, A., Wilkinson, M., Bahir, M.M., Manamendra-Arachchi, K., Ng, P.K.L., Schneider, C.K., Oommen, O.V. and Milinkovitch, M.C. Journal Article 2004 Local endemism within the Western Ghats-Sri Lanka biodiversity hotspot
Roelants, K., Jiang, J. and Bossuyt, F. Journal Article 2004 Endemic ranid (Amphibia: Anura) genera in southern mountain ranges of the Indian subcontinent represent ancient frog lineages: evidence from molecular data
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
Diogo, R. Book 2005 Morphological evolution, aptations, homoplasies, constraints and evolutionary trends. Catfishes as a case study on general phylogeny and macroevolution
Jayaram, K.C. Book 2006 Catfishes of India
Gunawardene, N.R. et al. Journal Article 2007 A brief overview of the Western Ghats-Sri Lanka biodiversity hotspot
Subhash Babu, K.K. and Sivasankaran, B.N. Conference Paper 2010 The hypogean fauna of selected ecosystems of Kerala, India, with two new records
Dahanukar, N., Raghavan, R., Ali, A., Abraham, R. and Shaji, C.P. 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, P.O., 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
Varma, A. Book 2017 Groundwater resource and governance in Kerala: status issues and prospects
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
Britz, R., Anoop, V.K., Dahanukar, H. and Raghavan, R. Journal Article 2019 The subterranean Aenigmachanna gollum, a new genus and species of snakehead (Teleostei: Channidae) from Kerala, India
Anoop, V.K., Britz, R., Arjun, C.P., Dahanukar, N. and Raghavan, R. Journal Article 2019 Pangio bhujia, a new, peculiar species of miniature subterranean eel loach lacking dorsal and pelvic fins from India (Teleostei: Cobitidae)
Sidharthan, A., Raghavan, R., Anoop, V.K., Philip. S. and Dahanukar, N. Journal Article 2020 Riddle on the riffle: Miocene diversification and biogeography of endemic mountain loaches in the Western Ghats biodiversity hotspot
Britz, R., Dahanukar, N., Anoop, V.K., Philip, S., Clark, B., Raghavan, R. and Rüber, L. Journal Article 2020 Aenigmachannidae, a new family of snakehead fishes (Teleostei: Channoidei) from subterranean waters of South India
Mohan, M., Bijoy Nandan, S. and Harikrishnan, M. Book Section 2020 Taxonomic notes on subterranean fish collected from Kerala, India
Raghavan, R., Britz, R. and Dahanukar, N. Journal Article 2021 Poor groundwater governance threatens ancient subterranean fishes
Raghavan, R., Sundar, R.L., Arjun, C.P., Britz, R. and Dahanukar, N. Journal Article 2023 Evolution in the dark: Unexpected genetic diversity and morphological stasis in the blind, aquifer-dwelling catfish Horaglanis