The larger-growing and more active species such as Gymnogeophagus labiatus require an aquarium
of 50 gallons or more, with a good amount of lateral area for swimming.
alternative an is Mouthbrooding
procedure that enhances the survival
rate of the fry, and some gymnos are
mouthbrooders. Here the female takes the
eggs into her mouth as soon as they are
fertilized, or sometimes just before the
eggs hatch. This breeding mode allows
the male to mate with several females and
leave the female to provide parental care
alone. The male is thus free to breed with
other females and guard his territory.
It is not clear whether all mouthbrooding
gymnos take up the eggs immediately
after fertilization. It is thought that
the most advanced technique is when,
upon fertilization, the eggs are taken
immediately into the female’s mouth. The
introduction of the eggs into the mouth
just before hatching can be considered an
intermediate step in the evolution from
substrate spawning to mouthbrooding.
In all gymno species, the young fry
take shelter in their parents’ mouths when
threatened. The “threatened” signal for the
fry to take refuge in the parent’s mouth
seems to be a dark visual circle, as in the
parents’ open mouth.
Gymnogeophagus sp. “Cuaró.”
Aquarium Dazzlers
At the present time, 10 described species
of Gymnogeophagus exist, six of which
are present in Uruguayan territory (G.
meridionalis, G. rhabdotus, G. balzanii, G.
australis, G. labiatus, and G. gymnogenys),
and at least four species which have
not been described to date. Uruguay
is the most diverse region in terms of
Gymnogeophagus species.
Reproduction
Gymnogeophagus exhibit the same vigilant
parental care provided by cichlids in general.
The ancestral parental care in these fish
involves substrate spawning, which is one
of the most common breeding habits in
South American cichlids and involves a
monogamous mating in which, after
choosing and cleaning a substrate surface,
the eggs are laid and guarded by both
parents. Once the eggs hatch, both parents
keenly guard the fry—although in general,
the females guard them more intensively.
well. Feeding is quite easy, as these fish are
undemanding when it comes to diet. They
will all accept the standard smorgasbord of
dry, frozen, or living foods.
Another Gymnogeophagus sp. “Cuaró,” this one showing more orange than blue on its flanks.
Natural Range
These cichlids are from the Río de la
Plata Basin (Ríos Paraná, Paraguay, and
Uruguay) and small coastal basins of
southern Brazil, with the exception of
one species—Gymnogeophagus balzanii—
which is also present in the Río Guaporé
(Amazonas Basin).
The Substrate-
Spawning Species
GYMNOGEOPHAGUS
MERIDIONALIS
Frequently called G. sp. “high dorsal,”
Gymnogeophagus meridionalis has been
thoroughly confused by scientists and
aquarists alike. It has been misidentified
with another more common species that
is similar in dorsal and caudal fin designs.
Following the original description and
type locality of G. meridionalis, the “high
dorsal” species is, without a doubt, the true
Gymnogeophagus meridionalis.
This gymno is distributed around the Río
Uruguay Basin and is also abundant in the
basin of the Río Negro (the largest tributary
of the Río Uruguay). They possess a tall
body and high dorsal fins that are spangled
with blue or green dots. The caudal fin is
