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he end of the year, December 2020 brings us to the Doradidae family and what aquarists call "Mouse Catfish" due to there timid and crespecular habits. The species in question is Tenellus trimaculatus and is a very popular catfish with Dorad enthusiasts although along with most members of this genus are not too common in the hobby.

Tenellus trimaculatus

Tenellus is a new genus, described by Birindelli (2014) to include the Nemadoras genera including our factsheet of the month, Nemadoras trimaculatus, N. leporhinus, N. ternetzi and the new species N. christinae. The snout is constricted, narrowly compressed (gape very small); dorsal profile concave between tip of snout and posterior nares.

Tenellus trimaculatus - aquarium inhabitant

All of this genera are found in the Amazon, Orinoco and Essequibo River basins over sandy bottoms and are found in large shoals and behave much like Corydoras in their natural habitats. The large eyes tell us that it is a crepuscular light species coming out during the evening to look for food so maybe a good idea to feed towards the end of the day.

None

Oxydoras trimaculatus, Opsodoras trimaculatus, Leptodoras trimaculatus, Opsodoras ogilviev, Nemadoras trimaculatus

Dordinae

South America: Amazon, Orinoco and Essequibo River basins. Type Locality: Rio Jurua an affluant of the Amazons.

11.0cm. (4¼ins)

22-25°C (72-77°F)

Snout constricted, narrowly compressed (gape very small); dorsal profile concave between tip of snout and posterior nares with less than 37 mid-side plates. Large eyes without fat covering or weakly developed. Nuchal foramina present. Three pairs of barbels. Fimbriate maxillary barbels; 8 branched rays on lower lobe of caudal fin.

It has a very pale yellow body, almost white and with a black spot at the base of each lobe of the tail fin, and another at the base of the dorsal fin. The distal upper and lower lobes of caudal fin are hyaline. In an aquarium environment the colour of the body is somewhat darkened.

Best kept in groups as they will not do well singularly. Avoid boisterous or aggressive tankmates as this is a shy species that will hide out during the day and appear for food at night under darkness. Provide a dimly lit tank with floating plants and a sand substrate as they will dig into the sand for food particles. Provide a shaded area away from bright light such as driftwood/rocks and plants.

Not recorded.

Sexually mature males will exhibit dorsal fin spines prolonged by a thin flexible filament nearly as long as the spine itself, whereas mature females exhibit normal spines (Sabaj, Mark Henry et al. 2014).

In its natural habitat they will feed on insects buried in the river bottom so in the aquarium, Tubifex, Daphnia, and Cyclops. Once settled in they will take frozen foods, flake and tablet foods.

Caudal fin: Tail
Caudal peduncle: The narrow part of a fish's body to which the caudal or tail fin is attached.
Dorsal fin: The primary rayed fin(s) on top of the body.
Lateral line: A sensory line, along the sides of the body.
Maxillary barbels: Pertaining to the upper jaw (maxillary barbels).
Nuchal: Area between the skull and dorsal fin.
Pectoral: The paired fins just behind the head.

Tenellus: Comes from the Latin tener, meaning delicate, in reference to the delicate appearance of those dorads.
trimaculatus: Three spots, one at the base of each lobe of the tail fin, and another at the base of the dorsal fin.

Birindelli, J. L. O. 2014 (16 Sept.) Phylogenetic relationships of the South American Doradoidea (Ostariophysi: Siluriformes). Neotropical Ichthyology v. 12 (no. 3): 451-563 [1-102].
Conservación Internacional; seris de Guías Tropicales De Campo. Pecos del medio Amazonas Región de Leticia. 546 p.
Ferraris, Carl Jr. Dr. 1991. Catfish in the Aquarium. Tetra Press Publication.
Sabaj, M.H. and C.J. Ferraris, Jr. 2003 Doradidae (Thorny catfishes). p. 456-469. In R.E. Reis, S.O. Kullander and C.J. Ferraris, Jr. (eds.) Checklist of the Freshwater Fishes of South and Central America. Porto Alegre: EDIPUCRS, Brasil.
ScotCat Article no. 57 Mark H. Sabaj; Key to Leptodoras and Select Related Taxa.
Sleen, van der Peter and Albert, S. James; Field guide of the Amazon, Orinoco & Guianas. Princeton University Press, Princeton and Oxford. 2018.

Photo Credits

© Mark Henry Sabaj
© Haakon Haagensen @  
Map: Kmusser @ Wikipedia Commons 2020