Agamyxis pectinifrons (COPE, 1870)

Spotted Talking Catfish

Classification

Order: Siluriformes Family: Doradidae

Distribution

The type locality is given as ‘Pebas, Equador’ by Cope (1870) but this apparently refers to the settlement of the same name located east of the city of Iquitos in Loreto Region, northern Peru, an area once disputably claimed by Ecuador. The precise extent of its natural range is a little unclear, though it appears restricted to parts of the Amazon basin in Bolivia, Brazil, Colombia and Peru.

Habitat

This species is found in various habitat-types but shows a preference for slow-moving or still waters with an abundance of submerged or floating structures, among which it conceals itself during daylight hours. The whitewater Caño Yarina, a tributary of the Río Pacaya located close to the confluence of the ríos Marañon and Ucayali represents a typical biotope. The main channel is around 100 m wide although the surrounding terrain is inundated for the majority of the year with a short period of low water between July and September with flooded forest comprising 85% of the area. Where there is open water, around 40% of it is covered by ‘floating meadows’ consisting of rafts of macrophytes which tend to form most thickly around lake and stream margins.

The conditions in Caño Yarina are typical of Amazonian whitewaters with dissolved sediment reducing visibility and the water stained darker during the high water period due to decomposing organic materials. Plant species involved in the formation of floating meadows mostly include Polygonium sp., Pistia stratiotes, Eichhornia crassipes, Paspalum sp. and an unidentified leguminous species, with others including unidentified members of the genera Azolla, Neptunia, Ludwigia, Salvinia, Utricularia and Echinochloeta.

During an expedition conducted by the Swedish Museum of Natural History in 1981 this species was collected from a ‘floating meadow‘ near Pebas alongside numerous other species including Bunocephalus coracoideus, Trachelyopterus galeatus, Lepthoplosternum altamazonicum, Anadoras grypus, Oxydoras niger, Pterodoras granulosus, Leiarius marmoratus, Sorubim elongatus, Pseudorinelepis genibarbis, Apistogramma agassizii, A. eunotus, Apistogrammoides pucallpaensis, Cichlasoma amazonarum, Heros efasciatus, Hypselecara temporalis, Mesonauta mirificus, Prochilodus nigricans and Rivulus ornatus plus unidentified species of Farlowella, Pimelodus, Pyrrhulina, Mylossoma and Gymnotus.

Maximum Standard Length

120 – 150 mm.

Aquarium SizeTop ↑

Base dimensions of at least 120 cm x 30 cm are recommended.

Maintenance

Best maintained in a dimly-lit set-up with a soft, sandy substrate and plenty of cover in the form of aquatic vegetation, tangles of driftwood or artificial caves of some kind. Bright lighting isn’t really appreciated since this species is largely nocturnal by nature.

Water Conditions

Temperature: 22 – 26 °C

pH: 5.5 – 7.5

Hardness: 18 – 357 ppm

Diet

This species is an omnivorous generalist and will accept most commonly-encountered prepared and frozen foods. A varied diet comprising good quality, dried, sinking pellets or tablets supplemented by regular meals of live or frozen bloodworm, Tubifex, mosquito larvae, etc. is ideal, and the occasional whole or chopped earthworm will provide valuable additional protein.

Behaviour and CompatibilityTop ↑

Non-aggressive though adult individuals may consume very small fishes. It makes an excellent addition to a medium-to-large-sized community of Amazonian species alongside peaceful characins, cichlids and other catfishes, for example. It’s gregarious by nature so will display more natural behaviour when kept in a group of 4 or more specimens, though can be maintained individually if you wish, and it will also group together with similarly-looking relatives such as Platydoras armatulus, Acanthodoras spinosissimus, and Amblydoras hancockii.

Sexual Dimorphism

Mature females tend to be noticeably fuller-bodied than males.

Reproduction

No reports of breeding in the hobby other than via the use of hormones to artificially induce the process.

NotesTop ↑

This species, which may also be referred to by the alternative vernacular names ‘spotted raphael’, ‘white-spotted’ or ‘white-barred’ catfish, is very common in the trade and despite its adult size is recommended to beginners and experienced aquarists alike since it is hardy, attractive and relatively-long-lived. The light body markings are highly variable in terms of exact placement and may be either white or pale to darkish yellow in colour.

It is very similar in appearance to the congener A. albomaculatus with the most useful distinguishing character seemingly represented by collection locality since the latter is known only from the Río Orinoco drainage in Venezuela. Both species are probably sold under the same trade names.

Members of the family Doradidae can be distinguished from all other Siluriformes by possession of a unique infranuchal scute, a dermal bone consisting of an elongate plate formed by expansion of a ligament located between the posterior nuchal plate and the rib on the sixth vertebra. This feature is associated with the lateral line canal and represents the first in a series of prominent midlateral scutes exhibited by most doradids. There are two major lineages recognised within the family, one with simple barbels and a comparatively flattened head, the other with fimbriate barbels and a relatively deep head.

Within the order Siluriformes doradids are most closely related to the family Auchenipteridae, most commonly referred to as ‘driftwood’ catfishes by aquarists, and these two were grouped together in the superfamily Doradoidea by Sullivan et al. (2006). In their molecular phylogenetic analysis Doradoidea appeared to form a sister group pairing with the family Aspredinidae (banjo catfishes) with this constituting a significant departure from earlier hypotheses in which the African family Mochokidae and Asian Sisoridae were assumed to be most closely-associated with doradids and aspredinids, respectively. The authors stopped short of naming this putative Aspredinidae-Doradoidea clade, for the time being at least, ostensibly because certain prominent theories of fish biogeography would require substantial re-assessment if it were accepted.

Doradids are often referred to collectively as ‘talking catfishes’ in reference to the fact that many of them are able to produce audible sounds. In some genera (e.g. Acanthodoras, Agamyxis) these are produced via stridulation of the pectoral spines within their sockets, with the pelvic girdle possibly involved in projection of the resultant noise. The ‘elastic-spring apparatus’ is also used to produce sound, this comprising a highly-specialised arrangement of the parapophyses of the fourth vertebrae, the swim bladder plus associated muscles and ligaments.

Take care when netting doradids for any reason since the pectoral fin spines and body scutes easily become entangled in the mesh of standard aquarium nets and can break human skin in many cases.

References

1. Cope, E. D. 1870 - Proceedings of the American Philosophical Society 11: 559-570
   Contribution to the ichthyology of the Marañon.
2. Correa, S. B., W. G. R. Crampton, L. J. Chapman and J. S. Albert. 2008 - Journal of Fish Biology 72: 629–644
   A comparison of flooded forest and floatingmeadow fish assemblages in an upper Amazon floodplain.
3. Ferraris, C. J., Jr. 2007 - Zootaxa 1418: 1-628
   Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types.
4. Ortega, H. and R. P. Vari. 1986 - Smithsonian Contributions to Zoology 437
   Annotated checklist of the freshwater fishes of Peru.
5. Reis, R. E., S. O. Kullander and C. J. Ferraris, Jr. 2003 - In: Checklist of the Freshwater Fishes of South and Central America
   Doradidae (Thorny catfishes).
6. Swedish Museum of Natural History. 1999 - Ichthyology Section, Department of Vertebrate Zoology, Swedish Museum of Natural History, Stockholm, Sweden.
   NRM Ichthyology collection database.