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from the RioUatuma. From this it canbe
assumed that
S. cf.altispinis
is a solitary-li-
vingpiranha that feedsmainlyonpiecesof
the finsofother fishes in thewild.However
feedingwithsmall feeder fisheshasproved
unproblematic.
S. cf. altispinis
probably
grows toover30cm long,although the lar-
gest specimenonwhich thescientificdes-
criptionof
S.altispinis
measuresonlyama-
ximumof 18.2 cm long (not including the
caudal fin).Likeall
Serrasalmus
species,
S.
cf.
altispinis
is a fish for specialists who can
learn a lot form such a fish.Unfortunately
S
. cf.
altispinis
seems tooccur only excep-
tionally in the RioXinguwhere fishes for
export for theaquariumareusuallycollec-
ted.Asalthoughahighpremiumhasbeen
offered for thecaptureofadditional speci-
mens,so far thespecimenpicturedhere re-
mains theonly theoneknown.
Acnodonnormani
Metynnis fasciatus
Acnodonnormani
Acnodonnormani
likewisecomes from the
RioXingu,and is sometimes knownas the
SheepPacu. It is closely related to thepir-
anhas discussed above,but is aherbivore.
Piranhas,pacus,andsilverdollarsbelong to
the so-called saw characins (
Serrasalmi-
dae
).Thisnamedoesn't,asonemight think,
refer to thesharp,saw-like teethof thepir-
anhas, but to a saw-like row of scales on
theventral keel.Anumber of serrasalmids
have specialized inbiting chunks of flesh
from their prey (piranhas of thegenus
Py-
gocentrus
);others feedon the finsofother
fishes (piranhasof thegenus
Serrasalmus
);
yetothers feedon thescalesofother fishes
(piranhas of the genus
Catoprion
); some
consume small organisms, others crack
nuts, and yet others eat plants. Acnodon
probably mainly grazes aufwuchs in the
wild.
This attractive and comparatively small
pacu (maximum length13.5cm) is impor-
ted only rarely. This is because
Acnodon
normani is anopen-water species,as indi-
cated by its pattern of vertical lines on a
lightbluebackground,whichprovidesout-
standing camouflage in natural waters
with sunlight entering from above. Their
habitatmeans they relyon flight,and they
arenotonlyexceptionallydifficult tocatch,
but inadditionacclimatizationby the col-
lector requiresgreatcareanda lotof "feel".
As is evident from what has been said
above,these fishes requireacomparatively
large tank in captivity.
Acnodon
are not
highly specialized herbivores like many
otherPacus,andshouldbe fedavarieddiet
containing a certain amount of vegetable
fare - for example in the form of special
flake foods designed for herbivorous fis-
hes. Sheep Pacus are relatively peaceful
among themselves and towards other
types of fishes.They requirewarm (26-30
°C), clean, andoxygen-richwater and ap-
preciatea strongcurrent in theaquarium.
Metynnis fasciatus
This fish, again a serrasalmid, is currently
still somethingofapuzzle toscientists.The
species
Metynnis fasciatus
was described
from a juvenile from Brazil (Rio Capiuru).
The type specimen is thought to be lost.
On thebasisof counts the species is iden-
tical with
M.hypsauchen
, but differs in ju-
venilecolorationby the regular stripepat-
ternof the species.Todatenoadult speci-
mens with regular striping have been
known to science, for which reason it has
beenassumed that
M.fasciatus
is just a ju-
venilecolorphaseof
M.hypsauchen
.Aqua-
