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or our factsheet for April 2023 we take a first look into the Hypoptopoma genera from the Loricariidae family and a group of catfishes that are notoriously difficult to identify unless you know the precise location that they have been collected from. We are pretty certain that we have the correct identity for Hypoptopoma inexspectatum as this species is unusual for this genus as it does not posses an adipose fin, and it emanates from the South American country of Paraguay.

Hypoptopoma inexspectatum

The holotype was collected in Argentina in the Rió Paraguay, near Formosa city by Solari in March 1885. The distribution is in the Rió Paraguay and Rió Paraná drainage basins and there are no records for the upper Paraná upstream of Salto das Sete Quedas (Mato Grosso do Sul, Brazil).

Hypoptopoma inexspectatum - collected by the image contributor Haraldo Bishop in 2003 in the Paraná river, about 25 miles near to the town of Valle María.

Hypoptopoma inexspectatum is distinguished from all congeners by having the odontodes on the snout margin, the rostral plate, and first and second infraorbitals arranged in regular series (note the image above). Along the rostral margin, the dorsal and ventral series are separated by an odontode-free discontinuity approximately as wide as the base of individual odontodes. Along the first and second infraorbitals, the discontinuity becomes narrower, but forms a dividing line between ventral and dorsal odontode series. The odontode arrangement becomes more irregular posterolateral to the second infraorbital, and individual odontodes become roughly oriented with the trunk axis. In contrast, in all other species of Hypoptopoma, the ventral and dorsal odontodes on the rostrum are variably separated and/or covered by soft tissue, and odontodes are typically not clearly aligned in series (Aquino, A.E. and S.A. Schaefer).

None

Aristommata inexpectata, Hypoptopoma guentheri

Hypoptopomatinae

South America: Argentina, Paraná/Paraguay River basin. Type Locality: Río Paraguay, Formosa Prov., Argentina.

10.0cm. (4ins)

18-26°c (63-79°f.)

Flat head and large eyes that are set latterly on the head and their heavy body armour. The ventral region is also armored and you can sometimes identify a species by the pattern on the underbelly. In saying that the species in this genus are notoriously difficult to identify and most of the time you would need the location of the catchment area or even down to the river itself to pinpoint a certain species. Vertebrae: 25. This species is distinguished from its congeners by having the odontodes on the snout margin, the rostral plate, and first and second infraorbitals arranged in regular series; along the rostral margin, the dorsal and ventral series are separated by an odontode-free discontinuity approximately as wide as the base of individual odontodes; along the first and second infraorbitals, the discontinuity becomes narrower, but forms a dividing line between ventral and dorsal odontode series; odontode arrangement becomes more irregular posterolateral to the second infraorbital, and individual odontodes become roughly oriented with the trunk axis; in all other congeners, the ventral and dorsal odontodes on the rostrum are variably separated and/or covered by soft tissue, and odontodes are typically not clearly aligned in series (Aquino, A.E. and S.A. Schaefer).

Will not bother other fish in the aquarium. They like to hang on to thin stalks of plants so they can see around it with their laterally located eyes. Provide shaded hiding areas in the tank with rocks or cave-like structures. It has to be maintained at cooler temperatures at times as in their natural habitat it can fall below 20°c (67°f) in winter.

Not recorded

Male urogenital papilla present. Males with patch of tightly arranged small odontodes oriented as a swirl covering second, third, and fourth plates of ventral series, lateral to urogenital papilla. Female anus tubular, without separate urogenital papilla. In females, size and arrangement of odontodes on plates lateral to anus similar to adjacent plates, without distinct patch of differentially arranged odontodes (Aquino, A.E. and S.A. Schaefer).

Feed an all round diet but prefers a vegetable diet such as algae, spirulina tablets and cucumber/courgette.

Adipose fin: Fleshy finlike projection without rays, behind the rayed dorsal fin.
Caudal fin: The tail.
Dorsal fin: The primary rayed fin(s) on top of the body.
Hyaline: Transparent or clear without pigment.
Medial: Middle or inner.
Odontodes: Hair - like stuctures on the body.
Papilla: A small fleshy projection, plural papillae.
Rostrum: Snout (usually applied to long snouts).
Vertebrae: The bones of the axial skeleton; divided into two sections, precaudal and caudal vertebrae.

Hypoptopoma: Hypo = underneath; opter = pertaining to site.

Photo Credits

© Gert Blank
© Haraldo Bishop
Map:© By TUBS - This vector image includes elements that have been taken or adapted from this file:, CC BY-SA 3.0.