variation (meaning that individuals from
one part of a river do not look identical
to individuals from another part, the
differences becoming greater the further
apart we go), making the designation of
species tricky and possibly subjective.
The other dominant group of cichlids in
Costa Rica include the “Astatheros” group,
with such species as Amphilophus (Astatheros)
alfari, A. bussingi, and A. rostratus.
Nicaragua and northern Costa Rica have
a few intriguing cichlids that do not
clearly relate to other groups, such as
Hypsophrys nicaraguensis and Neetroplus
nematopus (now possibly combined in the
same genus, Hypsophrys).
There is also a small group that has
intrigued us for many years, which includes
Tomocichla tuba, T. sieboldii, and the more
recently discovered T. asfraci. T. tuba extends
up to eastern Nicaragua into the “mosquito
coast,” where it has received very little study
(the name of the region tells you why).
It occurs throughout eastern Costa Rica
down to the northeastern tip of Panama. It
is replaced by T. asfraci, a beautiful orange
and black fish in northeastern Panama.
T. tuba does not occur to the west of the
spine of mountains running roughly north-south, which divide Costa Rica into east
and west. To the west of those mountains,
and specifically in the southwest, we find T.
sieboldii, an enigmatic fish that superficially
resembles a small tuba, complete with a
distinct breeding mask—but it lacks the
specialized breeding style that distinguishes
the tuba species. T. tuba spawns in the open,
laying extraordinarily large eggs, which
hatch into large wrigglers that transform
into large, bumblebee-colored fry capable
of swimming in the fast-moving waters of
eastern Costa Rica, unmatched by any other
cichlid. These fish have been the focus
of our investigations for many years. T.
sieboldii do not lay large eggs. Instead they
lay moderately sized eggs in caves, like so
many other Central American cichlids, and
the fry, though wonderful as all cichlid fry
are, are not capable of the world-champion
swimming status attained by tuba fry, nor
do they sport the distinctive vertical bands
of the tuba fry (though the fry of T. asfraci
do have this distinctive coloration).
The banded tetra Astyanax aeneus is found all over Costa Rica. In the south, they can occur in
schools of hundreds and even thousands. (Specimen from Río Kilometro 20.)
The predatory cichlids are also puzzling.
In much of Central America, the top
of the fish food chain is held by the
genus Parachromis. Fish like the wolf
cichlid Parachromis dovii, at around 28
inches total length and with a toothy
mouth that can swallow other fish in
one gulp, hold top position in northern
Costa Rica and Nicaragua. The jaguar
cichlid (P. managuensis) and its relatives,
like P. motaguensis, play similar roles as
one moves north. Southwestern Costa
Rica is a bit of a puzzle. There are no
Parachromis species in this area. This is
not because there are no fish to eat—
in fact, the abundance of fish in these
rivers seems much higher than any rivers
we have encountered in the north and
east. We have seen schools of literally
hundreds and possibly thousands of tetras
Gobiomorus maculatus, a guavina or sleeper goby, dives into leaves on the substrate from which it
attacks passing fish. Despite being a large fish of up to a foot or more in length, they are superbly
camouflaged and difficult to spot. (Specimen from the Río Coloradito).
in tiny rivers and creeks in the southwest.
In fact, we had great difficulty taking
photographs of fishes not because the
water was murky (like in the north), but
because almost inevitably a tetra would
dart through the frame just as we were
shooting a photograph. We must have
taken hundreds of photos of blurry tetra
tails (thank goodness for digital cameras
and the ability to erase unwanted images).
Worse yet, the tetras seemed to delight
in wedging themselves between my mask
and the viewfinder of the camera! Who or
what eats all of these fishes?
And so, we have been drawn from our
typical study sites in the northeast of Costa
Rica, centered around La Selva Biological
Station near Puerto Viejo de Sarapiquí, to