Tropical Fish Hobbyist

have cleaned off a suitable spawning site (usually a flat stone). After 24 to 36 hours, just before the eggs hatch, the female will take the eggs in her mouth (known as delayed mouthbrooding). At this time, the male abandons the female, leaving her to guard the fry by herself.

G. balzanii make superb aquarium
residents. They are majestically shaped,
very peaceful, and will not uproot plants in
their enclosure.

GYMNOGEOPHAGUS AUSTRALIS

The distribution of this species within Uruguay remains somewhat murky. G. australis seems to share its distribution range with G. balzanii. They coexist in the artificial lake formed by the Salto Grande Dam on the Río Uruguay. More field explorations need to be implemented to ascertain whether G. australis occurs in other areas within the country.

These are perhaps the least studied of the described Gymnogeophagus species. The reason for this is that their distribution range remains unclear—the scarce presence of these individuals in the fish collections and museums of the region also hamper information regarding this species.

Appearing similar to G. gymnogenys, albeit with taller bodies, these eartheaters seem adapted to lacustrine environments in which they have been found. Males in the reproductive season gain a strong yellow coloration in their nuchal hump and red dorsal and caudal fins.

Gymnogeophagus gymnogenys “Paso de la Lana.”

amazing red fins make them a standout among cichlids of the world. The Río Uruguay (and also the Río Negro) variety of G. gymnogenys shows a more yellowish coloration, especially in the adipose hump at breeding time. Sparkling dots and dashes ornately decorate their operculum. The blazing yellow colors of these varieties make them brilliantly colored aquarium subjects.

The Merín Basin G. gymnogenys possess a more roundish nuchal hump (as opposed to tall and pointed) which is orange in color. The amount of variations can be so high that even in small basins, different forms can be found. Differences in the populations from the lower, medium, to upper reaches of the same river system may be drastically different. An example of this would be the race of G. gymnogenys from the Río Santa Lucía. In the south, the specimens from the middle reaches are pale and large, with a yellowish hump. The populations of the Santa Lucía gymnogenys from the upper reaches have an orange coloration in their hump and more intense colors on the

GYMNOGEOPHAGUS

GYMNOGENYS

This species probably has the largest distribution for any mouthbrooding species in the entire region. Because of their large range, these are by far the most variable of the gymnos in color and shape.

There remains much debate as to whether all of these different shapes, colors, and design differences are just phenotypic variations within the G. gymnogenys species, or if they are actually different undescribed species. For now we will consider all of them as variations of G. gymnogenys.

Brilliant colors make all members of this complex stunning and desirable aquarium inhabitants. Perhaps the most colorful G. gymnogenys are the ones from the east. The individuals from Rocha are spectacularly garbed with a blazing orange crown at breeding time. The fiery head combined with a beautifully pearled blue body and

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Gymnogeophagus cf. gymnogenys “Caraguata.”

body; they also appear to be smaller. Such differences may be due in part to variations in feeding, substrates, or other ecological factors of each particular site.

In the wild, G. gymnogenys is found mostly on sandy or rocky bottoms with clear, flowing water, in small streams to large rivers. Being a typical mouthbrooding species, the male guards the territory while the female takes care of the fry.

Although territorial, this is a fairly peaceful species for the home aquarium, and freshly captured individuals will accept any type of food offered to them. Breedings in captivity have been somewhat sporadic. It will be interesting to see if these different forms also have different breeding behaviors. These factors may help determine whether all of the varying forms are of the same or different species.