his is a discussion on the identities
of the species of the genus Chaca Gray, 1831. After a
brief run down of each species, and images of them, there
is a section on how to try and visually differentiate
Chaca hamiltonii Gray,
1831 - Unneeded replacement name for Platystacus chaca
Chaca lophioides Cuvier & Valenciennes, 1832
- Unneeded replacement name for Platystacus chaca
Chaca buchanani Günther, 1864 - Unneeded
replacement name for Platystacus chaca
Originally described using material
(not deposited in an institution) from ‘rivers and
ponds of the northern parts of Bengal’, the current
accepted range is India, Bangladesh, and possibly Nepal.
There are reports from Myanmar, Malay, and Indonesia but
these probably represent the other two species. According
to Roberts (1982) the name chaca is transliterated
from a Bengali name for the fish, and that this in turn
derives from the sound the fish makes when it is out of
water. This species reportedly reaches 19 cm SL, but I
have never seen true C. chaca that size.
Roberts rightly points out that the three species listed
above were not intended to be new species, but were unneeded
replacement names for Platystacus chaca, which
was the name originally used by Hamilton. It was customary
in practice that if a species was placed in a genus with
the same name i.e. chaca into the genus Chaca,
that the species name would be altered to avoid tautonomy
(‘the use of the same word for the name of a genus
and one of its included species‘). This was unnecessary
(as per the International Code of Zoological Nomenclature)
and therefore the combination Chaca chaca is
valid and doesn’t need any replacement names.
Hamilton described the colour and
pattern as “above clouded with green and black,
and below with the latter colour: but all its colours
are dirty and ill defined. The fins are spotted with black.”.
See the original drawing from Hamilton (1822). Some aquarists
consider that you can easily tell C. chaca from
the other species by the light tan colouration that we
tend to see in most specimens (but which doesn’t
match the colour given by Hamilton!), but also mainly
the pattern. This is because (as you can see from the
drawing from Hamilton) C. chaca usually has some
spots or blotches on the body (see images). However, I
recently came across a specimen of C. bankanensis
which also has pale colouration, but also the spotting/blotching
of C. chaca. Therefore it is important that aquarists
use the other methods of identifying them discussed later,
and not just rely on colour or pattern.
The specimens pictured by me were
imported direct from India. The bizarre specimen pictured
by Anne Waal (which I have only tentatively identified
as chaca) has numerous cirri on the head and
body, some of them being very thick. Even though these
appear to be (currently) technically the same species
they differ greatly in: colour, the extent of the cirri
or papillae on the head and body, and also the fact that
Anne’s specimen has much more conspicuous cirri
around the eye, than in my specimen and the one pictured
by Ingo Seidel. However, its colour and pattern does match
that given by Hamilton. The specimen was purchased as
a C. burmensis by Anne from an aquarium shop,
and at first glance its colouration appears reminiscent
of C. burmensis. However, based on the great
extent of the cirri on the head, and the fewer cirri along
the inside fringe of the lower lip, I have tentatively
identified it as a C. chaca.
Chaca bankae Giebel,
1857 (emendation or mistake for C. bankanensis?)
described this species based on one small (68 mm) specimen
from the island of Bangka (which he misspelled Banka),
in Indonesia, and this is where the species takes
its name (so it could have actually been called bangkanensis!).
See exclusive images of the holotype (RMNH 5405), and
the drawings from Bleeker (1862). The current distribution
for the species is Peninsular Malaysia, the extreme southeastern
tip of peninsular Thailand (Udomritthiruj, pers. comm.,
and Vidthayanon, 2004), Sarawak, Indonesia (Kalimantan,
Sumatra, Bangka, Belitung, and possibly Java - Tandjong),
and possibly Singapore (Bukit Merah). This species will
reach at least 20 cm SL.
colour of this species can vary from reddish brown specimens,
which are usually the ones from Singapore, Thai or peninsular
Malaysia (see images by Ingo and Kamphol) which I will
call the Peninsular Form; or some specimens from the remaining
localities (which I will call the Archipelagic Form) can
be brown in varying lighter or darker shades; some specimens
having greenish patches, and very few having blackish
blotches (similar to C. chaca).
It is possible that the peninsular Malaysian, Thai, and
Singapore specimens represent a
new species or sub species in their own right. I have
noticed that some Archipelagic Form specimens have much
broader heads when compared to others (and also when compared
to all Peninsular Form specimens), and this is due to
much longer maxillary bones. I thought that this may be
a clue to differences that may
warrant a different species or subspecies for the Peninsular
Form, as this is one of the differences given by Brown
& Ferraris (1988) to differentiate their (then) new
species. This was because I had seen adult (19 cm SL)
specimens from different imports, of equal sizes of bankanensis
of both forms, which had much different sized head-shapes
due to the relative size of the maxillary bones.
I have since found this difference in small specimens
of equal size from the same import of the Archipelagic
Form (see images). However, none of the Peninsular Form
that I have seen have the broad head. My views are then
that these differences are not just related to age / ontogeny
/ size, or in their own right differences in species or
sub species, but are probably differences in the gender
of the fish where the Archpelagic Form is concerned. Again,
however, it does not rule out the possibility that the
Peninsular Form is different to the Archipelagic Form,
especially when none of the Peninsular ones I have seen
have the broad heads, as do some of the Archipelagic Form.
As well as this difference, and the difference in colour,
the Peninsular Form seems to have much smaller nasal barbels,
than the Archipelagic form.
In some specimens Peninsular Form (particularly from Toh
Daeng Peatswamp, Narathiwat Province, Thailand), there
doesn’t even appear to be a barbel, just a small
flap of skin. This of course needs more work on it than
I can give, but don’t be surprised if we get a fourth
species of Chaca, or a new sub species described
for the Peninsular Form.
As reported in Ferraris (1991),
some specimens have white eyes, (see image). The white
appears to be confined to upper part of the cornea, and/or
sclera, and not to the iris, therefore I do not think
that this makes them blind. One of Kamphol’s photographs
appears to show an albino or a xanthic (yellow) specimen.
bankanensis Peninsular Form from Narathiwat
Young female?, exhibiting
green colouration on upper surface of body
Compare lateral line and
number of cirri to that of Chaca chaca
Archipelagic & Peninsular Form
Archipelagic form: approx.
20 cm SL, showing wide head and long maxillary
Peninsular Form: approx.
20 cm SL, showing comparatively narrower head
and shorter maxillary bones
Archipelagic Form, showing
white eye, and the nasal barbel on the posterior
burmensis Brown & Ferraris,
This species was described on the
basis of four specimens in the Natural History Museum,
London (see image of holotype). The largest type specimen
is 20.35 cm, and they originate from the Sittang River,
Burma (Myanmar). Obviously the species takes it’s
name from Burma.
The shape, and outward appearance
of this species are more similar to chaca than
to bankanensis. It tends to be a dark / black
base colour, mottled with light brown to tan colour, which
can be the case for some C. chaca.
I have found that a small (approx. 7 cm TL) specimen from
Pegu, Myanmar, killed two Hypostomus and almost
killed two Bunocephalus species within a week
of being put in their tank (which was approx. 12 inch
by 10 inch). The Hypostomus died first, and at
the same time the Bunocephalus started to develop
open sores/burns in their skin and were hanging in upper
water, but within a day of removing the burmensis
and doing a 25% water change, they quite obviously started
to pull round and return to normal. I considered whether
it was the water parameters crashing, but the burmensis
was absolutely fine, so I consider that it was releasing
a poison into the water. Roberts (1982) states that there
is an axillary (pertaining to the axilla-
literally the ‘armpit’, so in fishes, near
the junction of the pectoral fin and the pectoral girdle,
more specifically the cleithrum - Diogo et al 2004) pore
in all Chaca’s but there was no evidence to show
that it secreted a poison. Based on my observations I
would guess that it does. He does state that earlier authors
had written that the “natives” consider its
flesh poisonous, although this report probably relates
to bankanensis. Ferraris (1991) reports that
certain feeder fish tend to die if not eaten, and in the
early 1990’s in the Catfish Association of Great
Britain magazine, I also reported this in a tank of chaca
and bankanensis that I had.
Kamphol Udomritthiruj (who exported the burmensis
specimens pictured), has seen many specimens from Pegu,
Myanmar. He informed me that he has witnessed burmensis
curling the maxillary barbels to lure prey.
from Pegu, Myanmar
burmensis from Pegu, Myanmar
Specimen is approx 7 cm
TL and is coated in sand
Specimen is approx 7 cm
TL and is coated in sand
Specimen is approx 7 cm
TL and is coated in sand
As mentioned earlier, colour and/or
pattern alone is not a reliable indicator. Ferraris &
Brown give some characters, but some of them can only
be accurately used by utilising dead specimens and having
knowledge of their anatomy (for which Diogo et al 2004
visually differentiated C. chaca from C.
bankanensis by the fact that C. chaca has
5 soft pectoral fin rays, versus 4. This can quite easily
be seen if you look at the fish from above (see images),
even without counting the rays you can see the different
shape and relative size of the fin. Unfortunately burmensis
can also sometimes have 4 rays, so the number of rays
themselves are not indicative. The first indicator to
use then, is to look for the tiny barbel on the rim of
the posterior nostril (see image). C. chaca and
burmensis do not have this, but unfortunately
some Peninsular Form bankanensis don’t
either, so if the fish has no posterior barbel, also then
look at the shape of the pectoral fin when viewed from
above. If it has a posterior nostril barbel, or the shape
of the fin is that in the image above, you have a bankanensis.
There are some other minor visual differences that are
sometimes quoted, but I find it more reliable to use the
ones I have given.
Chaca chaca showing
Archipelagic Form, showing pectoral fin
showing pectoral fin
from burmensis using the naked eye is not as
easy. Most of the differences listed in Brown & Ferraris
use information inaccessible for aquarists using live
fish. The number and extent of cirri is very variable
in chaca, so although burmensis appear
generally to have less, some chaca do also. C.
burmensis tend to have a blacker base colour, but
again this can be seen in chaca also. Brown &
Ferraris state that “On the head, flattened flaps
of skin, usually branched at the tip, occur laterally
in the region of the cheek and opercle. None is found
along the dorsal surface of the head or immediately posterior
to the eye, as in C. chaca”. However, in
some C. chaca, there aren’t any flattened
flaps of skin on the head, or associated with the eye
either (although there are cirri, but there are also some
cirri in burmensis). The easiest way I have found
to differentiate them using live specimens, is to look
at the number and relative size of the cirri along the
inner edge of the lower lip. In the C. burmensis
I have seen, they usually number around 10 or 11 small
cirri, and they don’t tend to have them near the
corners of the mouth. In the C. chaca that I
have seen, they tend to number at 14+ and tend to be relatively
longer and/or thicker.
Ingo Seidel, and Anne Waal for the kind permission to
use their images. Roy Blackburn for permission to photograph
his fish, and Mr & Mrs Pygott for permission to photograph
their fish. Martien van Oijen of the Nationaal Natuurhistorisch
Museum, Leiden for the images of the holotype of Chaca
bankanensis. Mark Allen, for permission to use his
image of the Holotype of Chaca burmensis. To
Dr Carl Ferraris for his advice
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