Open Access PDF - Sven Kullander

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been available of that species, the smallest specimen
examined 88 mm SL, at which size bars and
horizontal band are well developed (Fig. 90).
Juvenile and subadult individuals of Cichla
are fairly uniform in colour within samples and
largely within species, and effects of preservation
differences may account for most variation in
museum specimens. There is variation in life
colours of adults which has been related to habitat
(Winemiller, 2001) and which also includes
intensification of particularly red pigment in
breeding individuals (Winemiller, 2001). Large
adults in breeding colour, however, show considerable
individual variation not only in intensity
of markings but notably in the shape and
distribution of ocellated components, and in the
presence of various additional markings, observable
in preserved specimens. The two sides of an
individual may be quite differently patterned.
We consider this variability to be highly unusual
for adult cichlid fishes. In other South American
cichlids, there may be variation particularly in
intensity of markings, e.g., in Symphysodon (Bleher,
2006), but large conspicuous markings tend to be
similar in expression between all individuals. We
have three possible explanations for the variability
of ocellated markings in adult Cichla, which
we interpret as reduced or absent selection for a
uniform colour pattern. Actually, variation in
expression of colour markings among cichlids is
usually considered as species markers.
a) Scale. Cichla species are among the largest
cichlid species and the concerned markings
are proportionally large. In a small cichlid,
variation in expression of markings is likely
to be less conspicuous than in a very large
cichlid. In contrast, the other large cichlids,
including species of Crenicichla, Boulengerochromis
microlepis, Caquetaia umbrifera, Oreochromis
andersonii, and Parachromis dovii, do
not display the same variability. None of these
species, however, possesses an elaborate pattern
of conspicuous large markings on the
body.
b) Individual recognition markings. In Cichla
parental care and pair-formation during breeding
may be facilitated by markings permitting
individual recognition. Because of the large
size, adult Cichla may have very few predators.
There are almost no predatory fishes in South
America that can attack and kill Cichla of
sizes between 20 and 60 cm SL. Exceptions
may be even larger Cichla, Arapai ma gigas,
large Hoplias and Hoplerythrinus and some
large catfish species. The cost of a conspicuous
breeding colour for breeders may thus be very
low in relation to visibility to predators. The
conspicuous colouration may also have a
function in deterring smaller predators from
approaching the brood, but could also signal
presence of brood to brood predators. Biparental
care is common among cichlid fishes,
and usually involves some degree of sexual
dichromatism, which facilitates sex recognition
but not necessarily individual recognition.
It remains to test why it would be more important
in Cichla species to have individual
recognition.
c) Relative growth. Colour pattern is related to
surface dimensions such that growth patterns
determine the development of colour markings.
Under a steady growth to fixed adult
size, genetically determined colour markings
may be expected to produce identical patterns,
as seems to be the case in small, early-maturing
fishes. In large, late-maturing species
which suffer several seasonal fluctuations in
food availability, growth may be more irregular
and development of pigment patches
relative to body proportions may yield significant
differences. This hypothesis requires
further testing for correlation between pigment
patch size and body proportions.
The caudal ocellus of Cichla and other large South
American cichlid species has been interpreted as
an anti-cannibalism marking (Zaret, 1977) or as
an eye mimic deterring fin-eating piranhas (Winemiller,
1990). Those studies were based on species
in which additional ocellar markings are absent
from the body or other fins (C. monoculus, and
Astronotus cf. rubroocellatus), and should be extended
to more prominently ocellated species. In
Crenicichla species the caudal ocellus is fully
formed at very small sizes (about 20-25 mm SL),
at which size fin nipping by piranhas does not
seem to be a major predatory threat, and the
presence of the ocellus must have some other
explanation. Nevertheless, we can confirm that
piranha bites on the caudal fin are very rare in
Cichla, although we are unable to judge if the low
proportion is less than in sympatric species which
lack a caudal ocellus. Figures 45 and 48 (lower
specimen) demonstrate bites in the anal fin, presumably
by piranhas; Figure 69 shows a bite in
the lower part of the caudal fin. In large Cichla
Kullander & Ferreira: Review of Cichla