Brachyrhamdia rambarrani
False Adolfoi
Classification
Order: Siluriformes Family: Heptapteridae
Distribution
Described from the Rio Unini, a tributary of the lower rio Negro basin in Amazonas state, northwestern Brazil. Much of the river lies in a protected area which may explain why this species is so poorly-known in the aquarium hobby. It’s also popular with sports anglers fishing for Cichla spp.
N.B. this species is often said to be native to the upper rio Negro but on every map we checked the rio Unini is located in the lower part of the watershed, between Manaus and Barcelos.
Habitat
The Unini is a typical black water river system, with water poor in nutrients, very soft, of low pH, and stained deeply with tannins released by decomposing organic matter. B. rambarrani occurs syntopically with, and is a mimic of, Corydoras davidsandsi, with which it shares basic colour pattern.
It remains unclear if this adaptation evolved as a means of protection from predators or to provide a competitive feeding advantage whereby items unearthed by the Corydoras school, and possibly their eggs, are consumed.
Maximum Standard Length
The largest officially-recorded specimen measured 55 mm.
Aquarium SizeTop ↑
Base dimensions of 80 ∗ 30 cm or equivalent.
Maintenance
A substrate of fine sand is ideal, and the tank can be further-decorated with driftwood roots and branches. Although aquatic plants aren’t likely to be a feature of its natural habitat species from genera such as Microsorum, Taxiphyllum, Cryptocoryne and Anubias may survive attached to items of décor. The addition of dried leaf litter (beech, oak or Ketapang almond leaves are all suitable) would further emphasise the natural feel.
It’s intolerant to the accumulation of organic wastes and requires spotless water at all times in order to thrive, therefore a stringent regime of weekly partial water changes and aquarium maintenance should be employed.
Water Conditions
Temperature: 24 – 28 °C
pH: 4.0 – 7.0
Hardness: 0 – 179 ppm
Diet
Brachyrhamdia spp. feed mostly on benthic invertebrates in nature. In the aquarium live and frozen foods such as Artemia, Daphnia and chironomid larvae (bloodworm) should be offered regularly although sinking dried foods are also accepted.
Behaviour and CompatibilityTop ↑
Generally non-aggressive although very small fishes might be eaten, and comparably-shaped catfishes with different colour pattern, e.g., spotted Corydoras spp. may be subject to harassment. It’s best-maintained alongside a group of a similarly-patterned Corydoras sp. such as C. adolfoi, C. davidsandsi, C. duplicareus, etc., and in the absence of other benthic species. Characids, gasteropelecids, or lebiasinids of sufficient size to escape predation are ideal for the upper levels.
Brachyrhamdia spp. are not especially gregarious with conspecifics but more than one can usually be maintained provided the aquarium is not too small.
Sexual Dimorphism
Mature females should be noticeably fuller in the body than males.
Reproduction
Unrecorded, but spawning of B. imitator has been observed and was apparently initiated by a group of cohabiting Corydoras melanistius which began to spawn just prior to the Brachyrhamdia.
NotesTop ↑
This species is rarely-seen in the aquarium trade and only tends to be encountered as a contaminant among shipments of other species. The vernacular name is derived from its resemblance to Corydoras adolfoi, though the two may not actually occur together in nature.
Several Brachyrhamdia species have developed colour patterns that mimic syntopically-occurring Corydoras spp. throughout the life-cycle, and the remainder may mimic Otocinclus or smaller Corydoras spp. when juvenile. They’re easily told apart from Corydoras by their significantly longer barbels and lack of scute-like plates on the body.
Among other catfishes they’re closely-related to members of the genus Pimelodella, but differ in that the posterior cranial fontanelle is closed and forms two small foramina whereas in Pimelodella it is wide open.
The family Heptapteridae was previously considered a subfamily (Rhamdiinae) of the family Pimelodidae, but molecular studies appear to have confirmed its monophyly. It’s most closely-related to the familes Pimelodidae, Pseudopimelodidae, and the genus Conorhynchos.
References
- Baensch, H. A. and R. Riehl, 1991 - Mergus, Verlag für Natur- und Heimtierkunde, Germany: 1-1104
Aquarium Atlas volume 3 - Ferraris, C. J., Jr., 2007 - Zootaxa 1418: 1-628
Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types. - Sullivan, J. P., J. G. Lundberg and M. Hardman, 2006 - Molecular Phylogenetics and Evolution 41: 636-662
A phylogenetic analysis of the major groups of catfishes (Teleostei: Siluriformes) using rag1 and rag2 nuclear gene sequences.
