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CHAPTER – I
Introduction
Freshwater biodiversity constitutes a vitally important component of the
planet, with a species richness that is relatively higher compared to both
terrestrial and marine ecosystems (Gleick, 1996). The freshwater ecosystem
supports various orders of animals, plants and fungi contributing to a quarter
of vertebrate diversity and almost as much of invertebrate diversity described
to date.
Fish forms the most important wetland product on a global scale, and
is certainly the most utilized wetland resource. Asia accounts for 63% of total
fish production (Briones et al., 2004) and fish accounts for 30% of the typical
diet across Asia as a whole (World fish, 2010). It has great cultural and
psychological value to human beings. Freshwater fishes are defined as those
that spend all or a critical part of their life cycle in freshwaters. There are an
estimated 13,000 freshwater fish species in the world (Leveque et al., 2008).
IUCN Red list assessment of freshwater fishes of the Eastern Himalaya shows
that about 2% of fishes of the region are at high risk of extinction.
Northeast India which forms a part of the Eastern Himalaya extends
from Sikkim eastwards embracing the Darjeeling hills of West Bengal to
Arunachal Pradesh and to Mizoram in the south-east. It is a land of Blue
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Mountains, Green Valleys and Red River. It lies between 21°57´ and 29°23´ N
and between 87°58´ and 97°09´ E. The region extends over an area of about
2,62,230 sq. km. It comprises of the eight sister states, viz., Arunachal Pradesh,
Assam, Manipur, Meghalaya, Mizoram, Nagaland and Tripura and Sikkim.
Drainages of Northeast India
The fish faunal resources of northeast India may be subdivided into four
drainage based systems, viz., the Brahmaputra, the Barak-Meghna-Surma, the
Kaladan and the Chindwin.
The Brahmaputra drainage system. The Brahmaputra also called
Tsangpo-Brahmaputra, is a trans-boundary river and one of the major rivers of
Asia. From its origin in the southwestern Tibet as the Yarlung Tsangpo River,
it flows across the southern Tibet to break through the Himalayas in great
gorges and into Arunachal Pradesh where it is known as Dihang. It flows
southwest through the Assam Valley as the Brahmaputra and to the south
through Bangladesh as the Jamuna (not to be mistaken with Yamuna of India).
In the vast Ganges Delta it merges with the Padma, the main distributary of
the Ganges, then the Meghna, before emptying into the Bay of Bengal. The
river drains the Himalaya east of the Indo-Nepal border, southern-central
portion of the Tibetan plateau above the Ganges basin, the south-eastern
portion of Tibet, the Patkai-Bum hills, the northern slopes of the Meghalaya
hills, the Assam plains and the northern portion of Bangladesh.
Portions of the Brahmaputra drainage located in Arunachal Pradesh,
Meghalaya, and northern Bengal, together with parts of Assam and the
Himalayan foothills between Nepal and Bihar exhibit the most diverse fish
fauna. Species richness is highest in the Tista, Kameng, Dikrong, Subansiri and
Siang basins. The richness in those areas is due to the diversity of habitats and
environments existing between the plains of the Brahmaputra at a low altitude
(120-200 m) to the upland coldwater regions (1, 500-3, 500 m) in the hill ranges
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in Arunachal Pradesh and also in Meghalaya and Assam within a short aerial
distance of 200-500 km. Similar levels of richness are expected in other basins
i.e., the Lohit and Dibang basins and those in Bhutan flowing to the
Brahmaputra drainage and headwaters of the Barak and Chindwin basins and
Kaladan drainage.
Fig. 1.1. Drainage map of Northeast India
The Barak-Meghna drainage system. The Barak River rises in the
Manipur hills and enters the plains near Lakhipur. The river flows southwards
on the eastern side of the Vangai range and then makes a U-turn at Tipaimukh
where it is joined by the Tuivai River, flowing westward between Manipur
and Myanmar. The Barak then flows northward on the western side of the
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Vangai range and then enters the Cachar district of Assam to finally enter
Bangladesh and join the Surma-Meghna basin.
The Kaladan drainage system. The Kaladan River is a drainage that
flows between the Ganga-Brahmaputra and Chindwin-Irrawaddy drainage.
This drainage is separated from the Barak-Brahmaputra basin in India by the
Chittagong hill tract and from the Chindwin- Irrawaddy basin in Myanmar by
the north-south extension of Arakan Yoma hill range.
The Chindwin drainage system. The Chindwin originates in the broad
Hukawng Valley of Kachin State of Burma, roughly 26°26′ N, 96°33′ E, where
the Tanai, the Tabye, the Tawan, and the Taron (also known as Turong or
Towang) rivers meet. It enters the Irrawaddy River at about 21°30′N, 95°15′E.
The extreme outlets into the Irrawaddy are about 35 km apart, the interval
forming a succession of long, low, partially populated islands. Chindwin -
Irrawaddy almost drains the heart of Myanmar. It consist of the Imphal River
and its tributaries, the lakes and marshes lying in the valley and the hill
streams of Ukhrul and Chandel districts which drain into the Chindwin in
Myanmar. Some part of it also reaches Nagaland as Tizu River. In the
meantime some part of Arunachal Pradesh is also drained by the Chindwin
drainage.
According to Abell et al. (2008) the region encompasses middle
Brahmaputra and parts of the Upper Brahmaputra, Himalayan foothills,
Ganga delta and plain, Chin-Arakan coast and the Sittaung-Irrawaddy
ecoregions.
Fish Diversity in Northeast India
Northeast India has rich freshwater fish diversity. Kottelat & Whitten’s (1996)
map of freshwater fish diversity hotspots in Asia included major parts of
Northeast India and Myanmar. The diversity is attributed to several factors,
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viz., habitat diversity, existence of different drainage basins, recent geological
history (the collision of Indian, Chinese and Burmese plates and the
Himalayan orogeny) which played an important role in the speciation and
evolution of groups inhabiting mountain streams (Kottelat, 1989). The
evolution of the river drainages in Northeast India and adjoining areas has
been the subject of several studies that utilize geological evidence to
reconstruct the palaeodrainage patterns (Clark et al., 2004). Phylogenetic
studies of fishes of the region have indicated vicariance events which may
have played important role in shaping the current distribution pattern of the
freshwater fishes of the region (He et al., 2001, Peng et al., 2006, Guo et al., 2005,
Ruber et al., 2004).
Fig. 1.2. Freshwater threatened fish species map of Eastern Himalaya © IUCN
After the breakup of the supercontinent Gondwanaland, about 140
million years ago, Indian plate attained a very high speed compared to other
continents probably because of its thin lithosphere. The lithosphere roots in
South Africa, Australia and Antarctica are between 180 and 300 km deep,
whereas the Indian lithosphere extends only about 100 km deep (Kumar et al.,
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2007). The vigorous collision with the Asian plate resulted in the Himalayan
orogeny and the consequent changes in drainage patterns, aquatic life, etc.
According to IUCN assessment, 2010, on eastern Himalayan region, majority
of threatened fishes are in Chindwin basin in Manipur, particularly the Imphal
River and its tributaries draining the surrounding hills and the central plain of
Manipur and the adjoining areas in Myanmar, i.e., the eastern part of the Chin
Hills and the Kabaw valley.
The diversity in north east India was thought to be due to the presence of
a ‘centre of origin’ of ostariophysan fauna in Southeast Asia, somewhere in the
Yunnan China, from where they distributed centrifugally to the east, west and
southeast; the distribution in the west via the northeast India corridor. The
dispersal theory considers that most advanced species would be found at the
centre of origin with more conservative or primitive species, the farthest from it.
This concept of Southeast Asia as the ‘centre of origin’ of freshwater
fish fauna by Darlington (1957), Menon (1973), Banarescu & Nalbant (1982)
and Briggs (1979) has been rejected as there is no evidence to support it
(Kottelat, 1989). The Satpura hypothesis has been reviewed by many authors
and found to be untenable for different reasons (Dilger, 1952; Mani, 1974;
Kottelat, 1989; Daniel, 2001 and Praveen, 2003) and hence the concept of fish
evolution, affinity of Indian and Southeast Asian freshwater faunae has
changed.
With the new concept of fish evolution and distribution in this part of
the world, there are three distinct adjacent faunae corresponding to the three
plates and drainages as follows:
1. Indian, constituted by the species of India, the Irrawaddy and the
Salween,
2. Southeast Asian, by the Chao Phraya, Mekong and Sunda Islands, and
3. Chinese, by those of China and the Red River.
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Out of the 34 biodiversity hotspots listed by Conservation International
(Roach, 2005), two, viz., the Himalaya and Indo-Burma lie in north east India.
The Himalaya is the home of the world’s highest mountains and deepest
gorges. The mountains rise abruptly, resulting in a diversity of ecosystems.
The Indo-Burma, also called Indochina bioregion covers the area from eastern
India to Vietnam. The whole of Arunachal Pradesh and Assam, north of
Brahmaputra, and Sikkim belong to the Himalaya while Mizoram, Assam,
south of the Brahmaputra, Meghalaya, Nagaland and Manipur belong to the
Indo-Burma. Kottelat & Whitten’s (1996) map of freshwater biodiversity
hotspot also covers areas of north east India.
Catfishes
Catfishes are characterized by having naked body, barbels usually four pairs:
one each of nasal, maxillary and two pairs mandibular; adipose fin usually
present. Body often covers with bony plates. The order also characterized by
the absence of parietal, symplectic, suboperculum, and intermuscular bones.
The second third and fourth vertebrae were fused to a single ossification called
a “complex vertebrae”. Principal rays of the caudal fin fewer than 10+9, with
upper principal rays equal to, or fewer than, the lower rays.
Catfishes (order Siluriformes) are a wonderfully diverse clade with
over 3000 valid living species (Ferraris, 2007; Eschmeyer et al., 2004). In the
first six years of the 21st century 332 new catfish species were described, and
among these are the first representative of nine new genera and one new
family (Ferraris, 2007; Eschmeyer et al., 2004). This high rate of discovery
shows no sign of diminishing. Ferraris (2007) also recognized 3,093 species of
catfishes as valid, and are found to be distributed among the 478 genera and
36 families. He recognized major changes in the membership of some of the
higher level taxa and also stated that the current emphasis given to catfish
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taxonomy at present is likely to result in a dramatic increase in the total
number of valid taxa.
Freshwater Fish Inventory
Ichthyological research in the northeast region started with the pioneering
works of Hamilton (1822), followed by Day (1878). S. L. Hora made
tremendous contribution to the ichthyology of the region till the middle of 20th
century. However, works on the Burmese forms became almost standstill after
Hora’s (1941) report on the Vernay-Hopwood Upper Chindwin expedition. In
the later part of the 20th century and in the beginning of the 21st century,
scientists from all over the world have focused their research on the
ichthyofaunal exploration in south-east Asia. Many new species have been
discovered and many taxa have been reviewed. More than 75 research papers
have been published and as many as 139 species of fishes have been described
new from the region. J. E. Gray, J. McClelland, J. Muller & F. H. Troschel, R.L.
Playfair, B. L. Chaudhuri, S.L. Hora, D.D. Mukherji, E. Ahl, A.G.K. Menon, K.
C. Jayaram, P. Banarescu, T. Nalbant, G.M. Yazdani, R.P. Barman, W.
Vishwanath and co-workers, P. Nath & S. C. Dey, R. Tilak, A. Hussain, J.
Vierke, T. K. Sen, N. Sen, S. P. Biswas, L. Arunkumar, P. Musikasinthorn, S.
Kullander & R. Britz, H. H. Ng, D. R. Edds, K. Nebeshwar et al., contributed to
the descriptions (Vishwanath, 2009).
Vishwanath et al. (2007) listed 90 species of catfishes under 38 genera
and 11 families from northeast India. Among the catfishes, maximum diversity
is found among the superfamily Sisoroidea and in the family Bagridae.
Linnaeus (1758) reported 1 species of catfish from northeast India. Several
workers have added more to the list: Bloch (1794) [4 species], Schneider (1801)
[1], Hamilton (1822) [28], Burchell (1822) [1], Sykes (1839, 1841) [3], McClelland
(1842) [4], Muller & Troschel (1849) [1], Blyth (1860) [1], Day (1870, 1877) [3],
Vinciguerra (1890) [1], Boulenger (1894) [1], Regan (1905) [1], Chaudhuri (1911,
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1912, 1913) [3], Prashad & Mukerji (1929) [1], Hora (1923, 1936, 1937) [5],
Menon (1954) [1], Jayaram (1966a) [1], Datta et al.. (1987) [1], Nath & Dey
(1989) [2], Sen & Biswas (1994) [1], Roberts & Ferraris (1998) [1], Ferraris &
Runge (1999)[1], Vishwanath & Kosygin (1999, 2000c) [2], Arunkumar (200d)
[1], Ng & Lahkar (2003b) [1], Chakrabarty & Ng (2005) [1], Ng (2005c, 2005d,
2006a, 2006b) [6], Vishwanath & Joyshree (2006) [1], Vishwanath & Nebeshwar
(2006) [1], Vishwanath & Darshan (2005, 2006, 2007) [4] and Vishwanath &
Linthoingambi (2007a) [3].
Hora (1921a) reported 10 species of catfishes from Manipur, viz., Ompok
bimaculatus, Mystus bleekeri, Clarias batrachus, Wallago attu, Batasio affinis,
Glyptothorax dorsalis, G. minutus, Gagata cenia, Erethistes hara and Erethistoides
elongata. Menon (1954) described Glyptothorax manipurensis from Barak
drainage of the state. Vishwanath & Tombi (1986) recorded Hemibagrus
microphthalmus (Day) and Selim & Vishwanath (1999) recorded Mystus pulcher
(Chaudhuri) from Manipur. Vishwanath & Kosygin (1999) newly described
Myersglanis jayarami; Vishwanath & Kosygin (2000), Hara serratus; Vishwanath
& Darshan (2005 & 2006), Sisor barakensis and Batasio niger; Vishwanath &
Linthoingambi (2005), Glyptothorax ventrolineatus; Vishwanath & Nebeshwar
(2006), Pterocryptis barakensis; Vishwanath & Linthoingambi (2007a);
Glyptothorax chindwinica, G. granula, G. ngapang and Vishwanath & Darshan
(2007), Pseudecheneis ukhrulensis. They also described P. sirenica from
Arunachal Pradesh.
Many new forms of catfishes have been newly described from Nepal,
North East India, Bangladesh and Myanmar. Those from Myanmar are: Gagata
dolichonema (He, 1996); Batasio elongatus (Ng, 2004); Glyptothorax panda from
Myanmar (Ferraris & Britz, 2005); Psudolaguvia tenebricosa (Britz & Ferraris,
2003) and Mystus falcarius (Chakraborty & Ng, 2005). Species described from
Brahmaputra basin in Assam are: Sisor chennuah (Ng, 2003); Pseudolaguvia
foveolata (Ng 2005a); Erethistoides sicula (Ng, 2005b); Pseudolaguvia ferula (Ng,
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2006b) and Conta pectinata (Ng, 2005c). Batasio spilurus and B. fasciolotus have
been described respectively from Assam and North Bengal (Ng, 2006b).
Pseudolaguvia inornata and P. muricata (Ng, 2005d) and Gogangra laevis (Ng,
2005e) are also described from Bangladesh. Erethistoides infuscatus is also
described from the Brahmaputra and Meghna basins in north East India and
Bangladesh (Ng, 2006c).
From Kosi drainage of Nepal and North Bengal, Batasio macronotus (Ng
& Edds, 2004), Erethistoides ascita and E. cavatura (Ng & Edds, 2005a);
Pseudecheneis crassicauda and P. serracula (Ng & Edds, 2005b), and Pseudecheneis
eddsi (Ng, 2006d) are described.
National Science Foundation of United States of America launched “All
Catfish Species Inventory Project” in 2003 with its headquarters at Florida
Museum of Natural History, Florida. It is a mission to facilitate the discovery,
description and dissemination of knowledge of all catfish species by a global
consortium of taxonomists and systematists. Dr. Lawrence M. Page was the
principal investigator of the project. Nearly three hundred scientists all over
the world were engaged in the project. The objective was to find out the
approximate global distribution of catfishes, repositories of siluriform types
field and museum projects, phylogenetic studies on catfishes and catfish
oddities. The project on its completion expected discovery of about 1,750 new
species of catfishes, 2,300 to 4,600 new species of freshwater fishes (Annon,
2006). However, the study did not cover Northeast India which has diverse
catfish fauna. During the project, 37 families of catfishes were recognized from
the world of which 12 are found in India. Out of the 12 families, 10 families are
recognized from northeast India.
The works of Hamilton (1822), Gray (1832), and McClelland (1842)
covered certain areas of W. Bengal and western parts of Assam, Arunachal
Pradesh and Meghalaya only. Surveys and description of Dr. S. L. Hora were
mostly from Nagaland, Manipur till 1940’s. These precious pieces of works
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were mostly based on small collections because of inaccessibility. It is difficult
to arrive at a phylogenetic relationship of the siluroid fishes based on these
data. Interrelationships of the fishes of the order Siluriformes are poorly
known. Despite numerous recent papers on the morphology of catfishes, no
satisfactory arrangement of families, generic status is at present possible due
to lack of data of many fishes.
Anatomical Study and Phylogeny
Phylogenetic study is based on the morphology, anatomy especially the
osteological features and the molecular data, now-a-days. Several workers
consider that the only phyletically significant characters in distinguishing
higher taxa of vertebrates are the osteological ones (Banarescu & Nalbant,
1995; Chen & Lundberg, 1995; de Pinna, 1996). Actually all characters
including external morphology, rays, scales etc. have phyletical significance.
Knowledge on the osteological structures of all the available catfishes
are necessary for comparison with the fossil and to make an attempt at
understanding the evolutionary history of catfishes. The external morphology,
especially the skeleton is the only complete organ system available for detailed
comparison with fossils (Greenwood et al., 1966). But till date, there is no true
phylogenetic classification for any group of animals, except (to some extent)
that of horses. This is due to incomplete fossil records and also because the
comparative data collected through other approaches fail to possibly give a
clear picture by itself (Kapoor, 2001). In the history of systematics, more
published materials on fish phylogenies have been found over the last decade.
Worldwide projects tackling the relationships of enormous taxonomic groups
such as the siluriformes and cypriniformes, along with more general surveys
employing DNA barcoding have directed substantial resources into data
collection and phylogeny reconstruction. However fish systematics is found to
be in crisis. Over the last decade or two, molecular approaches have come to
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dominate phylogenetics. This, of course, is not bad in and of itself; the more
data, the better. But processing this volume of data has moved workers away
from an intimate understanding of character distribution, homology and
meaning of evidences. Phylogenetic relationships have been studied based on
molecular data by several workers (Rüber et al., 2004, 2007; Jiang et al.., 2011;
Liao et al., 2011). However, the results based on molecular and morphological
and anatomical data are often found to contradict each other, mainly
regarding proper identification of species. Mooi & Gill (2010) also could find
many contrasting characters during the comparison of molecular and
morphological results.
The fundamental trends of cladistics are that common ancestry can
only be inferred from derived character states. Two methods of distinguishing
primitive and derived character states have been promoted vigorously in the
literature, the ontogenetic method and the out-group comparison (Farris, 1982;
Maddison et al., 1984). Of these, the latter is more widely used because it is
often difficult to obtain adequate ontogenetic series for most taxa and
characters.
Maddison et al. (1984) have shown that if two or more of the in-group
character states occur among the out-groups, and the relationships among the
out-group taxa are unresolved; the primitive in-group character state cannot
be determined by parsimony. They have also shown that if the relationships
among the out-group are known, polarization may be possible, even in the
face of such out-group variability. Out-group comparison is thus most
effective when out-group relationships are as broad and resolved as possible.
Osteological character provides valuable data as it does not fluctuate
physiologically, rhythmically or seasonally throughout the post-embryonic life
of the fish (Jayaram & Anuradha, 2003).
McClelland (1842) was a pioneer worker who made use of osteological
studies in separating the tribes and group of fishes in family Cyprinidae.
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Sagemehl (1885) observed the cranium and Weberian apparatus of several
Characids for phylogenetic study. Sorenson (1890) examined the Weberian
apparatus of Siluroid, Cyprinoid, Characids and Gymnotid eels. Bridge &
Haddon (1894) described in detail the Weberian apparatus of Siluriformes.
Boulenger (1904) studied teleostean skeletons in the British Museum and gave
a classification of the suborders and families of the bony fishes reflecting their
phylogenetic lines. His observations on the osteological parts included
Weberian ossicles, anterior vertebra, osteocranial feature regarding the
articulation of the posttemporal bones with the skull, parietals with
supraoccipital etc. Regan (1909, 1911) laid down for the first time a firm basis
for the classification of catfishes based on osteological characters. His work
raised the sub-family Bagrinae to the rank of a family Bagridae. Gibian (1912)
studied hyobranchial skeleton of the cartilaginous fishes.
Hubbs (1920) enumerated many of the important evolutionary changes
in the branchiostegal of living fishes. He also noted the tendency for decrease
in branchiostegals during evolution and the differences in shape and
arrangement of the branchiostegals of Malacopterygeans and
Acanthopterygeans. Woskoboinikoff (1932) commented on the branchiostegal
series and hyoid arch in a general study of the respiratory apparatus of fishes.
Corsy (1933) studied the evolution of the hyoid arch of vertebrates which
included the structure found in teleosts.
Bimachar (1934) was the first Indian who showed the utility of
osteocranial studies in portraying interrelationships and affinities of various
families and genera of Indian freshwater catfishes. Allis (1935), while studying
some teleostean skulls, had mentioned various modifications found in the
sensory canal system in snout.
Eaton (1945) gave a detailed account of the skeleton supports of the
median fins in fishes. He reported that as a general rule, the skeletal supports
of median and paired fins are of the same nature. The two primary functions
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of the series of their pterygiophores are: support of the dermal fin rays by
articulation distally and provision of an area for attachment of the radial
muscles which erect and depress those rays.
Harry (1953) described the osteology of Amphilius longirostris
(Boulenger). He pointed that this African catfish have many common
characters with Sisoridae and Amblycipitidae and Bagridae. He also
hypothesized that Amphiliidae might be an intermediate form between
Bagridae and the two Asiatic families: Sisoridae and Amblycipitidae.
Khanna (1960) described the hypobranchial skeleton of some fishes,
viz., Pangassius pangassius, Rita rita, Sperata seenghala and Wallago attu. He
showed variability in the number and shape of pharyngo-branchials among
siluroid fishes.
Alexander (1962) analyzed the structure of Weberian apparatus in
Bagridae, Malapteruridae, Siluridae, Clariidae, Callichthydae and Loricariidae.
Tilak (1963) studied osteocranium and the Weberian apparatuses of Ailia coila,
Clupisoma garua, Neotropius navalchor, Pangasius pangasius, Pseudeutropius
atherinoides and Silonia silondia and compared with those of Eutropiichthys and
the members of the family Bagridae. He mentioned that Neotropius navalchor
and Pseudeutropius atherinoides closely resemble bagrid fishes and suggested to
put them in the family. He showed their great difference from schilbeids.
Saxena et al. (1963) observed osteocranium and vertebral column of
Mystus seenghala in detail and reported that the specialization in the skull
structure went far greater in Siluriformes than that of Cypriniformes. Jarvik
(1963) reviewed the intermandibular bones of some early teleosts.
Alexander (1965) felt that catfishes might have evolved from an
ancestor resembling primitive Characinoidei. He also verified Diplomystes to
be more primitive than other known catfish based on the forms of its maxilla,
pectoral girdle and position of dorsal fin.
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Tilak (1966) observed the osteocranium and the Weberian apparatus of
Amblycep mangois and compared with those of Bagridae and Schilbeidae.
Gauba (1966) also gave a detailed osteological structure of the skull of
Glyptothorax cavia.
Jayaram & Bimachar (1967) observed osteological structures of Mystus
bleekeri, M. cavasius, M. lecucophasis M. gulio, M. vittatus, M. tengara. Sperata aor
and S. seenghala. They made attempts to analyse the basic osteological patterns
that reflected phylogeny. They also mentioned that osteological characters
have immense value in clarifying the systematic status and affinities among
the species.
Rosen & Patterson (1969) described various osteological features of the
upper jaw, hyoid arch, and occipital region of the neurocranium, median fin
and caudal skeleton of Myctophids in their discussion of familial and ordinal
relationships. Rosen & Greenwood (1970) studied the origin of the Weberian
apparatus and the relationships of the Ostariophysean and Gonorynchiform
fishes. Sorescu (1972) compared the Weberian apparatus in the sub-families
Danioninae and Cultrinae.
Gosline (1971) discussed the relationships of a number of lower teleost
families including Myctophids, in the light of osteological features. Characters
of the skull, pelvic girdle and caudal skeleton were discussed.
Roberts (1973) observed the interrelationship of Ostariophysan by
studying their morphology including osteology. He proposed subfamilies
Siluroidei, Cyprinoidei and Characoidei respectively for catfishes, carps and
characins.
Lundburg (1975) reviewed the problem of the homologies of the two
bony elements between cleithrum and roof of skull in Siluriformes. He
concluded these bones to be hightly modified supracleithrum and post-
temporal. Lundberg (1982) described the skeleton and soft anatomy of the
toothless blind catfish Trogloglanis pattersoni and discussed relationships with
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Amiurus, Noturus, Prietella, Pylodictis and Satan. He concluded subgenus
Ictalurus to be a sister group of all other living Ictalurids and considered to be
monophylectic.
Kobayakawa (1989) studied osteology of seventeen species of the genus
Silurus in his revision of this genus. From the phylogenetic analysis, he
divided the species of the Silurus into cochinchinensis group and glanis group.
Bornbusch (1991) hypothesized the monophyletic nature of family
Siluridae by observing many derived character states in the osteological
structure. He commented the absence of distal radials in the dorsal fin support
has not observed in other siluriforms and interpreted as a synapomorphy of
the Siluridae.
Mo (1991) discussed on the anatomy and the phylogeny of the Bagrid
fishes. He used eighty-six morphological characters in the analysis using
cladistic methodology. He removed Horabagrus from Bagridae and placed
within Schilbeidae and Neotropius to Bagridae. His studies suggested the
monophyletic nature of Bagridae.
Kobayakawa (1992) also studied the shape and development of bony
elements of neurocranium and suspensorium in Silurus asotus, S. biwaensis and
S. lithophilus. Srinivasachar (1958) observed the development of skull in
Heteropneustes fossilis.
de Pinna (1993) examined bagrid phylogeny using 239 morphological
characters from 27 species. His studies suggested that monophyly of Bagridae
was not strong enough. Further, de Pinna (1996) used 112 characters to study
the relationship among the Sisoridae, Akysidae, and Amblycipitidae.
de Pinna & Ng (2004) reported the existence of second ural centrum in
the caudal skeleton of certain catfish families, viz., Akysidae, Amblycipidae,
Amphilidae, Aspredinidae, Auchenipteridae, Cetopsidae, Erethistidae,
Mochokidae, Pimelodidae and Sisoridae. They suggested that the inclusion of
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N. Anganthoibi : Inventory and Systematic Studies of Catfishes of Northeast India
17
neotropical Aspredinidae into Asian clade was supported by the presence of
second ural centrum.
Literature shows that very little work has been done on the inventory
and systematic study of catfishes of northeast India. Most of the publications
are based on preliminary surveys. Identification and studies on the
relationships between species, genera and families based on anatomical
examinations have not been done. When the world has become very keen in
the inventory and conservation of freshwater habitat and biodiversity and
scientists from other countries have taken pains to visit remote and
inaccessible water bodies, many of our workers are unaware of the facts.
So, a detail survey of the catfishes was carried out and studied in
respect to taxonomic status, species diversity and phylogenetic relationships
among them were taken up. Thus, the present work has the following
objectives:
1. To carry out detailed inventory of catfish fauna of the major
river drainages of northeast India and to establish correct
identity of species.
2. To describe new taxa (many new species and genera) are
expected.
3. To carry out phylogenetic analysis of some groups of
catfishes based on morphometric and anatomical studies.