Please note that all images of preserved specimens are copyright of the institution to which the specimen belongs / the photographer; for photographs of live specimens and the drawing of M. pelusius the copyright is that of the photographer or the institution mentioned.
Tympanic semi-ocellus / spot
The spot overlays the ‘tympanum’, which is a membranous covering of the swim bladder. The tympanic semi-ocellus / spot is usually posteriorly further along the body in comparison with the humeral semi-ocellus / spot, and is usually bigger.
But for some species the only definite differences are that of measurements and proportions (morphometrics) and also counts of gill rakers, vertebrae etc (meristics). Obviously I have not mentioned these differences as they are useless for most users of this article.
I hope this article will go some short way in assisting anyone interested in the identification of this ‘group’ of catfish.
Mystus albolineatus Roberts, 1994 (Please see image of live specimen)
See holotype CAS 79030 which originated from Prachinburi Market, Bangpakong basin, Thailand, but the species is also present in the lower Mekong basin, Cambodia. Largest type specimen is 13.5 cm SL. See also a paratype (ANSP 16453), and a live specimen by Kamphol.
This species has a white or pale stripe running along the lateral line. The stripe is bordered above and below by dark patterning. Some specimens have a dark spot at the dorsal fin base; some a small dark triangular spot at the middle of the body near the base of the caudal fin (midpeduncular spot); some with a humeral semi-ocellus.
Can be visually distinguished from other species by combination of a very long adipose fin which originates more or less directly after the dorsal fin, very long maxillary barbels which extend at least to the posterior point of the body, the white lateral streak, and the caudal fin lobes curling inwards.
Mystus ankutta Pethiyagoda, Silva, & Maduwage, 2008
See image of one of the type specimens. This species is only present in south-western Sri Lanka, from the Kelani, Kalu, Bentara, and Nilwada Rivers. The largest type specimen is 7.92 cm SL.
This species has a thin black stripe running along the lateral line of the body, a diffuse grey humeral blotch and a distinct black sub-triangular blotch on the hypural (near the caudal peduncle) base.
Can be distinguished from M. canarensis by the supra-occipital process being longer (extending further towards the nuchal plate). It also appears to be less elongated than M. canarensis. It is very similar to the true M. malabaricus; I haven’t used the detailed information in Pethiyagoda et al, 2008 because I respectfully do not agree on the identity of M. malabaricus or M. armatus used therein (see further discussion under M. canarensis, M. malabaricus, and M. oculatus). In my opinion the specimens used in Pethiyagoda et al as M. armatus (apart from the photograph of the syntype of M. armatus) are probably closer to M. malabaricus, although they slightly differ to AMS B.7573 and NMW 45165 which I use here as representing M. malabaricus. Using the aforementioned specimens, M. ankutta can be distinguished from M. malabaricus by the narrower anterior portion of the anterior fontanel.
It differs from M. keletius by the fontanel being split (vs not split) by an epiphyseal bar. It differs from M. oculatus (and its proable junior synonym M. armatus) by the posterior portion of the fontanel not extending near the base of the supra-occipital process (versus extending).
See holotype ANSP 67907 (which
originates from Pitsanulok, Thailand) and paratype ANSP
67908, and live specimen by Kamphol. Largest type specimen
is 8.62 cm SL but is believed to grow to at least 11
Colouration as per original description: “Back and upper surface of head brown. Dark to blackish grey median lateral band, wide as vertical eye diameter and including lateral line, bounded above by whitish parallel longitudinal narrower band its whole extent, and below by whitish colour of under surfaces of body. Pale brownish streak, narrowing behind, back from pectoral axil until over front of anal. Iris grey. Lips pale or whitish. All barbels pale, with brown margins and nasal and maxillary pairs darker. Fins all more or less dull brownish.”
Colour from original description:
“Brownish grey, with two longitudinal bands, one
above the other below the lateral line, some specimens
have a dark shoulder spot and a dark band along the
middle of the anal fin. The fins are mostly darkest
at their edges.” The “dark shoulder spot”
is a tympanic spot.
Said to attain 12.5 to 13.5 cm
Similar to Mystus atrifasciatus but M. bleekeri has shorter maxillary barbels (in M. atrifasciatus they extend to or past the caudal peduncle), the posterior edge of the adipose fin is angled off (versus rounded in M. atrifasciatus), and has the fontanel indented (versus not). Also similar to M. vittatus (Bloch, 1794) and often mistaken for it; see under that species for information. Could at first glance be confused with M. montanus but that species has a smaller adipose fin and the fontanel is shorter, only extending to midway between eye and base of supra-occipital process.
Mystus bocourti (Bleeker,
see image of live specimen)
M. bocourti was originally
described from the Mé-Nam River at Bangkok, Thailand;
it is also present in Laos and Cambodia. It reaches
up to 24 cm (SL). See holotype (MNHN 1553).
It is sometimes still listed
in the genus Heterobagrus Bleeker, 1864, although
this is currently considered to be a synonym of Mystus.
This species is usually uniform
silver, bronze or platinum in colour but I have seen
at least one specimen that has two light bands above
and below the dark lateral line (Burgess, 1989, Plate
As per Roberts (1994) it also
sometimes has a humeral semi-ocellus and / or a dark
spot on the body near the base of the dorsal fin spine.
It is easily differentiated from the other species by the extraordinary long dorsal fin.
This name was described by me
as a replacement name for Hara malabarica Day,
1865(b) as that species belongs in Mystus and
in my opinion it is not a junior synonym of Mystus
malabaricus (Jerdon, 1849) (see further discussion
under Mystus oculatus).
The type specimen (see discussion below) of M. canarensis (AMS B.7624) measures 11.1 cm SL and originates from the district of Canara (or Kanara), Karnataka State, India and is probably from Mangalore (see Ferraris et al, 2000 for information on another AMS Day specimen listed as Macrones armatus - but not representing that species in my opinion - also listed as being from ‘Canara’). The coordinates given in my description were taken from the specimen label but must be in error as the coordinates given are much further north and away from the Canara region. Although Mangalore is in Day’s view of what is meant by Malabar, in the description of Hara malabarica he mentions receiving some specimens from Travancore. Travancore is still in the Malabar region but is further south than Mangalore. However, it is not clear if all the syntypes were from Travancore, and in any case Jayaram & Sanyal (2003:71) found M. canarensis specimens in Travancore (under the account of M. malabaricus), and AMS B.7624 was labelled as Hara malabarica by Day himself.
It is probable that AMS B.7624
is the specimen figured by Day (1877, Plate CI fig.
2) as “Macrones Malabaricus” (but it is
important to note that Day captioned it as his species,
not Jerdon’s Bagrus malabaricus), showing
a fish with a tympanic semi-ocellus, a dark stripe along
the lateral line, and spots on the fins making the upper
portion of the dorsal fin and lower third of the anal
fin appear blackish. The original drawing of Hara
malabarica is not a good one. In fact in the copy
that I was originally provided with the adipose fin
wasn’t even showing. However, it does show in
the reprint that I now have. In my opinion Fig. 12 in
Jayaram & Sanyal (2003), and Fig. 119 in Easa &
Shaji (2003) show M. canarensis, captioned
as M. malabaricus.
There are no known preserved type specimens of this species which was described from the ponds of northern Bengal.
In Hamilton (1822) there is no
reference to any drawing but as per Hora & Law (1941),
Plate 23, Figs. 60 of Hamilton (1822) are erroneously
captioned as Pimelodus batasio (which is now
Batasio batasio), and should have been captioned
as Pimelodus carcio. It is quite obvious when
one reads the description of B. batasio and
M. carcio that Hamilton made a mistake with
designating which fish figs 60 represented. Thus we
can quite clearly see what M. carcio looks
like. The specimen in my image matches exactly the written
description and figures in Hamilton (1822).
It can be differentiated from all others by its small adult size, very small adipose fin, a dark horizontal mark across the tympanum, greenish yellow colouration, large laterally placed eyes, and relatively long and wide fontanel which is distinctly split by a thick epiphyseal bar. Usually confused as representing M. vittatus or M. tengara.
This species was originally described
as Macrones montanus var. dibrugarensis.
Contrary to Jayaram (1954) and subsequent authors it
is not a junior synonym of Mystus montanus
(Jerdon, 1849). M. montanus was described by
Jerdon from the Kabini River of the Kaveri (or Cauvery)
system in south western India as: “greenish above
and on the fins; yellow on the cheeks and beneath.”
There is no mention of any stripe(s) on the body, or
semi-ocellus. Jayaram & Sanyal (2003) give information
on M. montanus from further south than the
type locality and show that whilst in life it is silvery
grey with light yellowish bands along the sides, it
can exhibit greenish bands along the sides with a dark
spot at the base of the caudal fin, and a dark mark
near the tympanum. In M. montanus the caudal
lobes are shaped differently, the adipose fin appears
to have a longer base, and the body and fin patterns
differ. In my opinion the different zoogeography should
be taken into account, M. dibrugarensis being
from the upper Brahmaputra River in north eastern India.
M. dibrugarensis differs from M. canarensis by having the supraoccipital process raised, long, and touching the basal bones of the dorsal fin (versus not raised, very short, and not touching); body not elongated; caudal fin lobes being equal (versus upper lobe being longer than lower lobe). Also see notes on M. malabaricus, M. pulcher and M. rufescens.
Originally described from “Higher
parts of Gangetic estuaries”, this species lives
in fresh and brackish waters. Sometimes when young it
can exhibit pale stripes along the body.
It is easily differentiated from
the other species by the combination of its greyish
silver colour and small adipose fin.
Can reach approx. 40cm SL.
See discussion under M. oculatus regarding the identity and zoogeography of the true M. gulio.
Mystus horai Jayaram, 1954
Bagrus albilabris (Specimens
from Pondicherry, and possibly Sri Lanka) Valenciennes,
M. keletius was originally described from Java, and Pondicherry. Ng (2002) examined the type specimens and concluded that the one from Java represents Mystus nigriceps (Valenciennes, 1840); and after a lectotype designation restricting the type locality for M. keletius to Pondicherry [Puducherry], India.
See image of the lectotype (MNHN A.9011) from Pondicherry, India; the specimen measures approx. 9cm SL. In earlier versions of this article I said that Valenciennes stated that the colour and pattern was very similar to Mystus tengara (Hamilton, 1822) in its colouration and pattern, but differed due to the supraoccipital and humeral (cleithral) processes being more granulated, the supraoccipital process being longer, the dorsal fin appearing rounder and the maxillary barbels being shorter. This is an error. Valenciennes actually stated that (translated from French) “is a species very close to the preceding, and which is confused at Pondicherry under the same name”. The preceding species was Mystus cavasius (Hamilton, 1822) (although the ‘M. cavasius’ at Pondicherry is actually M. seengtee (Sykes, 1839) – see Chakrabarty & Ng (2005)), and at the end of that account Valenciennes refers to M. tengara of Bengal and that is why my error was made. Ferraris (2007) classed it as a junior synonym of M. vittatus; Pethiyagoda et al, 2008 tentatively agreeing with him. In the earlier versions of this article I said it was different to M. vittatus based on the more rugose bony plates, slightly different fontanel, and shorter barbels. Also, Baensch & Evers (2002) show a picture captioned as M. keletius and state that it has a yellow/silvery colouring, with a “dark shoulder mark”, two silvery to golden strips bordering the lateral line, and black marks near the dorsal and caudal fin. Jayaram & Sanyal (2003) state it is "Brownish turning dull white beneath. A dark shoulder spot and a light band along lateral line present. Dorsal and caudal fin tips tinged black, anterior portions of anal fin black". If this colour and pattern is correct for specimens from the type locality and they are conspecific with the lectotype then M. keletius is valid in my opinion. Jayaram & Sanyal also show a drawing of a specimen which is clearly different in its morphology to that of M. vittatus.
Interestingly Easa & Shaji (2003: Fig. 118) picture a specimen that they caption as M. gulio (Hamilton, 1822). The true M. gulio appears (in my opinion) to be restricted to north, and north eastern India, Nepal, and Bangladesh (and possibly Pakistan). The identity of the species distributed in Myanmar, Thailand, Vietnam, Malaysia, and Indonesia has not yet been proved (and there are several names already available if these do prove to be distinct). It is possible that the species captioned as M. gulio and present in south western India, and Sri Lanka is actually M. keletius. If this is the case the syntypes of M. albilabris from Pondicherry (and possibly Sri Lanka – if the type information in Eschmeyer, 2008 is correct – the original description does not mention Sri Lanka) may be synonymous with M. keletius; certainly they have similarly originally described colour patterns, overall shape and proportions, relatively short adipose fins, and similar cranial morphology (see images of some of the MNHN syntypes of M. albilabris on http://www.fishbase.org/Photos/ThumbnailsSummary.php?ID=5139). M. keletius and M. albilabris were described in the same work. Because M. albilabris is based on syntypes that may not be conspecific with each other due to their differing localities, it may be an idea in the future to designate one of the specimens from “Ganges” as the lectotype. If it came down to being the first reviser I consider that M. keletius should take precedence over M. albilabris.
Based on Valenciennes showing that M. keletius is similar to M. seengtee; the information and drawing in Jayaram & Sanyal; the possibility of it being what has been incorrectly captioned as M. gulio in south western India; and the lectotype of M. keletius being different to the holotype of M. vittatus, M. keletius should remain as a valid species until further specimens can be studied and compared to M. vittatus.
Although the pattern is more like M. seengtee it clearly differs from that species in morphology, the obvious difference being in the length of the adipose fin (longer in M. seengtee) and the much longer fontanel of M. seengtee (see images above of a non type specimen, and the possible holotype of M. seengtee). Although there are zoogeographical differences to M. gulio, morphological differences need further work. It differs from the similarly patterned M. oculatus (and therefore M. armatus) by the shape and structure of the fontanel (longer and broader, and split in M. oculatus).
See under M. ankutta
for differences to that species.
? Mystus armatus nec
Day, Day 1877
Described from “Mountain
streams in Malabar, India”. There are no known
preserved type specimens therefore the original description
of the colour and pattern is important: “blueish
leaden above, silvery beneath; fins yellowish.”
No semi-ocellus, or stripe(s) on the body are mentioned.
I wondered if based on the locality
and that colour and pattern if it was possible that
Jerdon’s species is a synonym of M. armatus
and/or M. oculatus, the latter being the senior
synonym. However, Jayaram & Sanyal (under the account
of M. armatus) state that although it is brownish
on top, and becoming lighter beneath, freshly collected
specimens have a dark band on the sides along the lateral
line ending in a dark blotch at the base of the caudal
fin. Also a dark band along the anal fin and upper half
of the dorsal fin. This would make it very close to
M. dibrugarensis in terms of colour and pattern,
although that species has a definite tympanum spot,
more vivid black markings (with some in caudal fin),
and different zoogeography. I doubt that the specimen
from Kenchong River, Myanmar listed in Jayaram &
Sanyal (2003) is M. malabaricus, I think it
will possibly be M. dibrugarensis or even M.
castaneus Ng, 2002 in view of the zoogeography.
I am aware of at least 2 new species from Myanmar so
it is unlikely that the Myanmar specimen is M. malabaricus.
discussion under Mystus pelusius (Solander,
The original description states “Colour greenish above and on the fins; yellow on the cheeks and beneath” and this was the colour and pattern at about 6 inches. See further discussion under M. dibrugarensis about the colour and pattern in live/fresh specimens from different localities as found by Jayaram & Sanyal (2003). Jerdon stated that he “only found it in the river at Manantoddy in Wynaad” which I think is now called Mananthavady, and the river the Kabini (or Kabbani), but Jayaram & Sanyal found it in other localities in Kerala and Tamil Nadu.
At first glance it is also similar
to M. pulcher but that species has a much more
distinctly round tympanic spot, as well as morphometric
differences and zoogeography.
The laterally placed eyes (visible when viewed from above or below), and the combination of small adipose fin, humeral semi-ocellus, and dark tympanum differentiate this from all other species.
See holotype (MNHN 1195) of M.
oculatus. According to the original description
by Valenciennes, and Day (1877) there is no stripe present
on the body in M. oculatus. The colour/pattern
is said to be grey at the top, silvery on the sides,
lighter beneath. The reason I have included it here
is that Jayaram & Sanyal (2003) state it is dark
brown above, yellowish beneath with a dark shoulder
spot, a dark spot at the base of the dorsal fin (spine),
a dark band along the middle of the dorsal fin, and
a dark broad band along the lateral line. I’m
not sure if this is from observations of the specimens
they used, or from the figure in Day (1877), which in
my opinion is just trying to illustrate the lateral
line itself, not any band of colour or pattern along
it. However, they did have four recently preserved specimens
so this may be from them and if so it is possible that
the body spot and bar quickly fade in older or less
well preserved specimens? However, in Easa & Shaji
(2003) and Mercy et al (2007) no stripe is present along
the lateral line.
In the 2004 and 2006 versions
of this article I included M. armatus (Day,
1865) as a valid species. However, I raised the point
that M. armatus needed checking against M.
oculatus as they might be conspecific. Day described
M. armatus as new in 1865a from “rivers
and backwaters of Cochin, India”, but did not
include any details regarding its colour or pattern,
but did thankfully say (amongst other morphological
details) that the base of the adipose fin equalled that
of the anal fin, the supra-occipital reached the basal
bones of the dorsal fin, and the fontanel almost reached
the origin of the supra-occipital process (which he
showed in a drawing).
In 1865b he used the same morphological
information but went on to say that the colour and pattern
was “Bright leaden silvery, lightest along the
sides and with a purplish gloss over the cheeks. A black
spot just anterior to the root of the dorsal spine.
Fins finely dotted with minute black points.”
He then stated that the adipose fin commenced a short
distance anterior to that of the anal fin.
Unfortunately no figure was published
of the whole fish and as yet the type specimens have
not been definitely identified. However, in my opinion
BMNH 18188.8.131.52 does constitute one of the syntypes
(one of a number of type specimens originally used by
Day), alternatively it may be a specimen used by Day
in 1865b (although they were probably one and the same,
even taking into account the slightly different statements
about the adipose fin). According to the BMNH website
the locality for the specimen is “Malabar”.
Looking at the descriptions by Day in 1865, the BMNH
specimen certainly seems to match. In particular the
bony plates on the head (cranium); the size, shape and
placement of the fontanel; the size and length of the
supra-occipital process; the dorsal and pectoral fin
spine morphology; and the darkish mark near the dorsal
fin spine base (which on the BMNH specimen looks like
it is on the anterior and median nuchal plates) all
match. I have compared the BMNH specimen with the holotype
of M. oculatus. Although the MNHN specimen
is not as well preserved the two specimens appear to
closely match in all these factors. In particular the
morphology of the bony plates of the head and nuchal
plates are virtually identical. The size, shape, and
placement of the fontanel match, and the supra-occipital
process matches. Although one could be mislead by Day
(1877) into thinking that the maxillary barbels of M.
armatus are shorter than that of M. oculatus,
in 1865a and b it is clear that the maxillary barbels
reach the anal fin (in fact in the original description
it states that they reach the caudal fin), as they do
in M. oculatus. The main possible difference
is the size of the eyes. In M. oculatus at
first glance they appear larger, however (using images)
in the holotype of M. oculatus the eye goes
into the head length 3.4 times, and in the syntype of
M. armatus it goes in 3.57 times. This is very
close. It is my tentative opinion that based on the
locality details and the colour, pattern, and morphology
that M. armatus is a junior synonym of M.
oculatus. Hopefully an ichthyologist will resolve
this problem once they have definitely defined the true
M. armatus, although unfortunately even in
2008 this still doesn’t appear to be happening.
Thanks to Mark Sabaj Peréz and Kyle Luckenbill
I have also been able to compare the BMNH syntype with
NMW 45165 (see images above) which has previously been
highlighted as a possible syntype of M. armatus.
The NMW specimen does not match the original description
of M. armatus or of the BMNH syntype. Notable
differences are in the fontanel. In the BMNH (syntype)
the fontanel is very long and narrow, commencing anterior
to the eyes and ending near the base of the supra-occipital
process, whereas in the NMW specimen it stops well short
of the base of the supra-occipital process and its anterior
portion is wider than the posterior portion. In the
BMNH syntype it is partially split by an epiphyseal
bar near the anterior rim of the eye, whereas in the
NMW specimen it is not split at all (although there
is a slight indentation in the shape). For these reasons
I do not consider NMW 45165 as a syntype of M. armatus.
There is no mention of stripes in the original description of M. armatus, but in Day (1877, Plate CI fig. 3.) a drawing is shown of a fish with a mid-lateral stripe terminating in a blotch on the body near the base of the caudal fin, and the adipose fin being much longer than the anal fin base. In my opinion this is probably AMS B.7573, which Ferraris et al. (2000) have correctly stated is not a type specimen of M. armatus. AMS B.7573 is from Canara district and as such could represent M. canarensis or M. malabaricus, thus accounting for the differences in pattern and morphology. Thanks to Shobnom Ferdous I have been sent images of AMS B.7573 (see above). It matches exactly with the drawing and account in Day (1877). In the text in Day (1877) he states that M. armatus doesn’t always show the dark lateral line or dark shoulder mark. Unfortunately AMS B.7573 is not conspecific with M. armatus as originally described by Day in 1865. Bearing in mind that BMNH 18184.108.40.206 does match M. armatus as originally described, if one compares AMS B.7573 with that BMNH syntype one can see that not only is the general shape of the head and body different, but that the fontanels are a completely different shape, but more importantly a different length (bearing in mind the drawing and information about this in the original description of M. armatus). The differences between the BMNH specimen and the NMW specimen are mirrored here; the AMS specimen appearing conspecific with the NMW specimen. In my opinion this misidentification in Day (1877) (using a non type and non conspecific specimen) has led to Jayaram (1954) and subsequently (Ng 2002), Jayaram & Sanyal (2003), Eas & Shaji (2003), Jayaram (2006), and Pethiyagoda et al (2008) considering M. armatus as having a dark stripe along the body. Day’s 1877 account of M. armatus (and therefore Jayaram’s et al) shows the maxillary barbels as only reaching around the ventral (pelvic) fins, whereas as stated above it is clear from the 1865 accounts that they are longer. Also, it is clear that as originally described M. armatus has the dark mark around the base of the dorsal fin spine (also present in M. oculatus), and this is missing in the Day (1877) account and therefore in the subsequent accounts by Jayaram et al. My theory is that the M. armatus as originally described is a synonym of M. oculatus, and that Day’s 1877 account (and therefore all accounts since) of M. armatus are actually M. malabaricus of Jerdon. As an example, compare the cranium of the specimen figured in Pethiyagoda et al (2008: fig. 6a) as representing M. armatus with that of the syntype of M. armatus (BMNH 1865. 7.17.21) and you will see that the fontanels are of a completely different shape, placement, and length.
See image of a live specimen
under M. malabaricus that appears conspecific
with the NMW and AMS specimens, but not the BMNH one.
As mentioned previously, a final and definite determination
and then examination of a syntype of M. armatus
and then a comparison with that of the holotype of M.
oculatus, with then a comparison with the specimens
identified as M. armatus by Jayaram et al,
then in turn a comparison with the type of M. canarensis
will resolve this issue one way or another. Until then
I consider M. armatus a tentative junior synonym
of M. oculatus.
M. pelusius is currently considered
to be the type species of Mystus but the earliest designation
has not yet been fully resolved. Solander described
the species in 1794, from Kowick (Coic?) River, Aleppo,
Syria based on earlier invalid names proposed by Russell
in 1756 and Gronow in 1763.
Roberts (1994) tentatively considered M. colvillii (from the Tigris River at Baghdad, Iraq) and M. misrai (from Lake Antioche, Syria) to be junior synonyms of M. pelusius, although he did note that in the future M. colvillii may prove to be distinct. Thanks to Anthony Troncale of the American Museum of Natural History I have now managed to see the original drawing of M. pelusius from Solander (1794), and the text of the description, which is very basic in terms of colour and pattern information, just saying it was predominantly dark silver. The colour pattern of the alleged junior synonym M. misrai (see image of a type specimen) is (in alcohol): pale yellowish brown with head slightly lighter. No spots or stripes present.
The drawing of M. pelusius
looks more similar to M. colvillii than it
does to M. misrai, although the profile of
the dorsal fin is different in M. colvillii
than the drawing of M. pelusius. The image
here of BMNH BMNH 19220.127.116.11 (a syntype of B. halepensis,
and possibly of M. pelusius also) looks very
different to M. colvillii.
M. colvillii is said to be olivaceous in colour, with three narrow, white, parallel, longitudinal stripes, one along, one above, and one below the lateral line. The type specimens are “9 inches long”. According to Ferraris (2007) BMNH 1918.104.22.168 is a syntype of M. halepensis (a junior synonym of M. pelusius). If you compare the M. halepensis specimen with the syntypes of M. colvillii you will see that the whole body, head, and fin shape is different. In addition the fontanel in M. colvillii appears to extend much further forward anteriorly. Based on these points and the different locality data, I consider that M. colvillii is probably valid. M. misrai appears to be a junior synonym of M. pelusius.
Described as “Dorsal and
upper part of the body dark brown, with lighter or paler
whitish brown stripes: one median, from the tip of the
snout to the base of the dorsal spine, and two lateral
longitudinal on each side, one above and the other below
the middle line, which is distinguished by being dotted
black for the openings of the lateral organs.”
“…nasal and maxillary barbells blackish
brown, adipose fin dark brown, dorsal, anal and caudal
fins are brownish with black spots on the membranes
between the rays.”
It has an intensely black tympanic
spot/semi-ocellus, and also a spot near the caudal peduncle,
followed by a thin white band. Its supraoccipital process
meets the basal bones of the dorsal fin.
The difference in length of the supra-occipital process differentiates it from M. canarensis. The light body stripes differentiate it from M. dibrugarensis. Differs from M. rufescens by the fact that its fontanel is not split by an epiphyseal bar, and it has a shorter adipose fin.
As per original description:
“Very light or pale brown, lower or under surfaces
more or less whitish. Upper surface of head and back
sprinkled with dark grey dots. Band of dark dots along
lateral line and broader one along lower side of trunk
and tail parallel. Iris greyish, also maxillary barbell,
other barbells whitish. Outer edge of adipose fin dusted
with dark grey dots. Caudal dark grey. Other fins pale
This is a small and graceful
looking species, which reminds me of species of the
South American pimelodid genus Pimelodella Eigenmann
& Eigenmann, 1888.
The lack of any semi-ocellus, the thin dark band across the lateral line, and large gap between the small supraoccipital process and basal bone of the dorsal fin spine differentiate this species from all the others.
Differs from the similar M.
canarensis, M. dibrugarensis and M.
pulcher by having its fontanel split by an epiphyseal
Bloch described the colour and pattern as head, ‘back’ fins, and caudal chestnut brown. Other fins steel coloured. Stripes light blue, with yellow interspaces. The plate of the holotype shows the general shape of the body and fins but the accuracy of its pattern is doubtful. See images of the holotype of M. vittatus: ZMB 2939 that originates from Tranquebar, Tamil Nadu, India.
Since its description in 1822 from “Ponds of India”, M. tengara has been discussed as being very similar to or perhaps a junior synonym of M. vittatus. Jayaram & Sanyal (2003) have classed them both as valid but they did not have access to the holotype of M. vittatus and as such they may have been using non type specimens and information from years of wrongly identified specimens which has just added to the confusion. They may have used misidentified specimens of M. carcio as representing M. tengara, and therefore incorrectly distinguishing M. vittatus as distinct from M. tengara.
If one looks at the original drawings of M. tengara (see images) and compares them with the images of the holotype of M. vittatus, you will see that the structure of the fontanel and supraoccipital process are very similar, the only difference being that in the drawing of M. tengara the front portion of the fontanel is thin, the second is wider, whereas this is the opposite in the holotype of M. vittatus. This could be a mistake in the drawing. Everything else from the description of M. tengara appears to fit M. vittatus. If one looks at the images of ANSP 85780 from Bombay [Mumbai], India (which definitely represent M. vittatus in view of the exact same fontanel and supra-occipital morphology when compared to the holotype) you will see that the pattern, and shape of the body, especially relating to the high back and adipose fin matches that of the drawing of M. tengara. The adipose fin on the holotype of M. vittatus has shrunk in size due to its age.
The only possible evidence I have seen so far for classing M. tengara as possibly valid is that of specimen CAS-SU 34858 from Calcutta [Kolkata], India (see images). If you look at the lateral image of this specimen it appears visually very similar to that of ANSP 85780. But if you compare the fontanels of each specimen you will see that the fontanel of the CAS specimen is long and evenly portioned, unlike that of the holotype of M. vittatus and of the ANSP specimen. I feel that for the validity of M. tengara to be properly determined, future ichthyologists need to bear in mind that validity and identity of M. carcio when comparing lots of specimens from different localities. Until then, I feel that M. tengara should be classed as a questionable synonym of M. vittatus. I say questionable because of the possible aforementioned differences, and because M. vittatus comes from southern India, M. tengara possibly representing the Ganges population (but with M. carcio distinct from both).
M. vittatus differs from most species (except M. carcio) by the higher number of dark body bands, but can also be differentiated from the most similar species by:
M. atrifasciatus differs due to M. atrifasciatus having less dark lines on the body and having a thinner, non indented fontanel.
M. bleekeri differs due to M. bleekeri’s more elongated body, adipose fin and fontanel.
M. carcio differs due to M. carcio’s distinctly separated fontanel, much smaller adipose fin, and laterally placed eyes.
M. montanus by the distinct shape of the fontanel in M. vittatus
M. multiradiatus differs due to M. multiradiatus having a humeral semi-ocellus and having the fontanel not as visible.
M. mysticetus differs due to M. mysticetus’s large laterally placed eyes.
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