Brachyrhamdia marthae
Sands & Black, 1985 |
he third month of the new decade (2010)
brings us to another indepth look from the catfish world from
regular contributor, aquarist and author, Steve Grant. His subject
is a member of the Heptapteridae family and
a very pretty catfish at that. I now hand you over to Steve.
This species is closely related to the
subject of the January 2006 Factsheet, Brachyrhamdia
meesi Sands & Black, 1985. In fact they were both
described by the same authors, in the same publication. However,
this does not appear in shops as often as B. meesi.
As discussed in the B. meesi factsheet,
the genus Brachyrhamdia Myers, 1927 has been accepted
as being different to Pimelodella Eigenmann & Eigenmann,
1888 since Lundberg & McDade (1986) showed differences in
the posterior (the one nearer the dorsal fin spine) fontanel (gap)
in the upper cranium. The B. meesi factsheet quotes Lundberg
& McDade page 4, which states that “Brachyrhamdia
and Pimelodella differ in the former having the posterior
cranial fontanelle wide open from the frontals to the supraoccipital
whereas it closes to two small foramina in the latter.”
This seems to state that in Brachyrhamdia the posterior
fontanel is wide open (in an elongated gap) whereas in Pimelodella
it closes to two foramina (small openings). However, if one looks
at fig. 6 in Lundberg & McDade it appears that it is Brachyrhamdia
that has two small foramina, not an elongated posterior fontanel.
This is also backed by the text on page 9. Therefore the differences
are that it is Pimelodella that has the posterior fontanel
as an extended gap, whereas in Brachyrhamdia it is reduced
to two small foramina. Therefore it should be corrected to ‘Pimelodella
and Brachyrhamdia differ in the former having the posterior
cranial fontanelle wide open from the frontals to the supraoccipital
whereas it closes to two small foramina in the latter.’
For aquarists the easiest method to use is the much shorter body
form in Brachyrhamdia compared to the more elongated
body of Pimelodella. B. marthae has been placed
in Rhamdia and Pimelodella but is certainly
a Brachyrhamdia.
As well as the 5 described species of Brachyrhamdia there
are at least 2 undescribed species. 4 of the 7 appear to mimic
Corydoras, but what about the other 3? B. heteropleura
(Eigenmann, 1912), B. meesi, and B. marthae don’t
easily match up with the patterns of other Corydoras.
The answer may lie in how I found my two specimens of B. marthae.
The two specimens were very small (approx. 2cm) and came in with
a wild shipment of a similarly Otocinclus sp; probably
O. vestitus Cope, 1872. At this size the two were not
easily distinguishable at a cursory glance at the shoal. It may
well be that the young of B. marthae and the similar
B. meesi mimic Otocinclus rather than Corydoras,
and if this is the case they may only do so whilst juvenile, due
to the difference in sizes of the respective genera’s adults.
They are very greedy eaters, accepting
dried and live food but seem to prefer bloodworm. They have grown
quite quickly in a short space of time. They can be a little aggressive
with other Brachyrhamdia’s and it is important
to have a few hiding places such as plants, caves, and pipes to
keep aggression down.
It differs from the similar B. meesi
by the lack of an eye band and there is a slight violet hue to
the body.
Deep but squat pim-like body. Three pairs
of barbels. Posterior cranial fontanelle reduced to two small foramina.
Differs from the similar B. meesi by the lack of an eye
band and there is a slight violet hue to the body.
Greyish violet body colour with a violet-black
line from the end of dorsal insertion to the caudal peduncle,
ending in a small blotch. Similarly coloured markings in the dorsal
fin and anal fin.
Not to be trusted with smaller inmates such
as smaller tetras and fry but will do fine with larger Barbs etc.
May nip Corydoras and other Brachyrhamdia species
when feeding, so you will need to keep an eye out for this behaviour.
As yet unknown.
| Sexual
differences |
There are no known
external sexual differences, but females are probably more
robust in the body.
|
| Feeding |
Readily accepts all manner of prepared
foods. Catfish pellets and tablets and are particularly fond of
frozen bloodworm and other "wormlike" foods.
| Etymology |
Brachyrhamdia:
Brachy = short; rhamdia = from the vernucular name 'Nhamdiá
or 'Jamdiá.
marthae : In honour of Martha
Elizabeth Sands.
|
| Glossary |
Fontanel:
The space(s) between the bones on
top of the skull covered by skin.
Supraoccipital:
Unpaired bone at the back at the back
of the skull, usually with a crest.
|
| References |
Lundberg,
J. G. and L. A. McDade,
1986. On the South American catfish Brachyrhamdia imitator
Myers (Siluriformes, Pimelodidae), with phylogenetic evidence
for a large intrafamilial lineage. Notulae Naturae (Philadelphia)
No. 463: 1-24.
Myers, G. S., 1927.
Descriptions of new South American fresh-water fishes collected
by Dr. Carl Ternetz. Bulletin of the Museum of Comparative
Zoology v. 68 (no. 3): 107-135.
Sands, D. D. and B. K. Black, 1985. Two
new species of Brachyrhamdia, Myers, 1927, from Brazil and
Peru, together with a redefinition of the genus. In: D.
Sands, Catfishes of the World. v. 3, Suppl (first set):
58(1)-58(8).
|
Top image: Steven
Grant.
Bottom Image: Chris Ralph.
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