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Mastiglanis asopos Bockmann, 1994

his month (June 2019) we concentrate on a species from the Heptapteridae family that was described not that long ago in ichthyological terms in 1994 with a new genus by Flávio Alicino Bockmann.


Mastiglanis asopos
Mastiglanis asopos


Mastiglanis asopos - in the aquarium

Mastiglanis asopos - in the aquarium


M. asopos is a strictly sand-dwelling species. It spends the daytime buried in the top layer of sand and it forages mostly at night and sometimes in the morning. As an ambush predator, when foraging, it poises in the streamlet channel where water is flowing, supported by a tripod formed by its pelvic and anal fins, spreading both its very long barbels and the filamentous dorsal and pectoral-fin rays, thus forming a kind of "drift-trap". When the fish intercepts food, it will lunge at these food particles; after lunging for a short distance, it will return to its previous hunting spot.


This behavior is similar to that seen in the tripod fish. Small trichopteran larvae (ingested with the sand cases) and ephemeropterans constituted a considerable portion of the gut contents in a study of Mastiglanis asopos, but their foraging behavior allows a varied diet which includes large chironomid larvae and small adult beetles that would not be consumed by other sand-dwelling animals. This fish has long barbels and long first pectoral fin rays which are used for feeding. It also has an acuminate (tapered to a point) snout.




Mastiglanis asopos - View of upward facing eyes - Loreto, Peru, September 2017


Mastiglanis asopos - View of upward facing eyes - Loreto, Peru, September 2017



The sandy banks of the Amazon River and sandy spits and islands have their own unique aquatic fauna. - A psammophile is an organism that loves and lives in sand. The sand inhabiting catfish Mastiglanis asopos spends its daytime hours buried in the sand - sometimes with the eyes exposed. They forage for food at night by propping themselves up on their long fins (like a tripod) and waiting for small invertebrates to pass by - at which they lunge. They are only found living in sandy aquatic habitats. The upward facing eyes and the shape of the pupils keep the eyes above the sand when buried. (Danté Fenolio 2017)



one of the Type localities: tributary of RioTrombetas, near Porto Trombetas

One of the Type localities: tributary of RioTrombetas, near Porto Trombetas


The generic name “Mastiglanis” means “Whip-Catfish” due to the long first fin rays of the dorsal and pectoral fins and the specific name is derived from the greek river god "Asopos", given in reference to the widespread distribution of this fish throughout Amazonian drainages.



Dorsal profile slightly ascendent toward dorsal fin origin, nearly straight to adipose fin origin and from there slightly concave caudally. Ventral profile straight to anal fin origin, gently concave to caudal peduncle. Body relatively elongated, elliptical in cross-section at dorsal fin origin, gradually more compressed toward caudal peduncle. A conspicuous axillary organ present on each side of trunk, immediatly above pectoral fins, composed of globular corpuscles covered by translucent skin. Lateral line complete. In preserved specimens, myomeres conspicuous along body, totaling around 32. Head depressed, dorsally covered by a thin skin, cheek filled with muscular mass of aductor mandibulae. Snout long and pointed. Large eyes placed high on head and with slit shaped pupils.

Overall body colour pale transparent (yellowish when in alcohol). Dorsal portion of body with seven conspicuous areas of concentrated dark chromatophores: one between head and dorsal fin (just behind nape). one in front of dorsal fin origin, one at the level of last three branched dorsal fin rays, one between dorsal and adipose fin, one just behind the adipose fin origin, one on the posterior point of adipose fin base and one on the caudal peduncle. There are also some scattered melanophores on top of head region.

Aquarium Care

I keep them in a 4 ft. by 2 ft.by 18 ins. deep tank (120 x 600 x 457mm) with a sandy base with a mix of Corys, Synos, Tatia, eel tailed banjos and whiptails plus a few other cats. There is plenty of plant and wood cover in there, anubias and java moss and a few caves. They seem to hang around under the sponge fillter and don't see them in the sand very much. (M.Kirkham pers. comm.)



No problem to keep in a community tank as stated above.

Not recorded

Sexual differences
Not recorded but would sufice that the females would be fuller in the breeding season.


Seem to be no problems with feeding with the usual aquarium fare of live and dried foods.

Glossary of Terms

Psammophile: An organism that loves and lives in sand

Caudal fin: The 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
Pectoral fins: The paired fins just behind the head.

Ventral fins: The paired fins, between the pectorals and the anal fins.
Adipose fin: Fleshy finlike projection without rays, behind the rayed dorsal fin.
: The skeletal muscle tissue found commonly in chordates. They are commonly zig-zag, "W" or "V"-shaped muscle fibers. The myomeres are separated from adjacent myomere by connective tissues and most easily seen in larval fishes or in the olm.
Aductor mandibulae
: Adductor mandibulae muscles (english) Paired head muscles originating on the lateral faces of the quadrate process of the palatoquadrates and inserting on the lateral surface of the Meckel's cartilages; the primary jaw-closing muscles of the sharks.
Melanophores: The pigment cells that permit colour change, and the concentration of pigment granules within these cells determine the type of colour that is produced.


Mastiglanis: Greek, mastax, meaning whip in allusion to the filamentous elements of pectoral and and dorsal fins; and glanis the name of the greek catfish of Arisotle, a common denomination for fishes of the order Siluriformes.
Derived from the greek river god "Asopos", given in reference to the widespread distribution of this fish throughout Amazonian drainages.



Bockmann, F.A. and G.M. Guazzelli, 2003. Heptapteridae (Heptapterids). p. 406-431. 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.
Bockmann, F. A. "Description of Mastiglanis-asopos, A New Pimelodid catfish from northern BrazilL, with comments on Phylogenetic-Relationships inside the subfamily Rhamdiinae (Siluriformes, Pimelodidae)." Proceedings of the Biological Society of Washington 107.4 (1994): 760-777.
Ferraris, C.J. Jr., 2007. Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types. Zootaxa 1418:1-628.
Zuanon, Jansen; Bockmann, Flávio A.; Sazima, Ivan (2006). "A remarkable sand-dwelling fish assemblage from central Amazonia, with comments on the evolution of psammophily in South American freshwater fishes". Neotropical Ichthyology 4 (1): 107–118.
Kirkham, Michael: pers. comm. 2019
Fenolio, Dante: internet pers. comm. 2017.


Photo Credits
© Steven Grant
© Michael Kirkham

© Danté Fenolio @ anotheca
Factsheet 276

Common Name:


South America: Amazon, Capim and Orinoco River basins. Type locality: Brazil, Pará, Igarapé Saracazinho, tributary of rio
Trombetas, near Porto Trombetas.
6.5cm. (2¾ins)
25-28°c (77-83°f.)
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