TerralogNEWS101
29
Sexualdimorphism
Leaving aside size – as already mentioned, females are larger than
males–thesexescanbereadilydistinguishedbythesizeofthedorsal
andanal fins.Both finsareconsiderablymoredeveloped inmales.The
dorsal finofmales inparticular isvery impressiveandextendsalmost
to theendof thecaudal fin,butneverdoesso in females.
Reproduction
The Pike Characin is once again an exception among the characins
when it comes to its reproductivebehavior.Thispredator is theonly
characin to construct a bubblenest, not dissimilar to those familiar
from the labyrinthfishes.In thewild reproduction isdependentnotso
much on the season of the year as on the water temperature.
Spawning takes place at low water and comparatively high
temperatures.Thismeansthatsomepopulations,forexamplethose in
the Okavango Delta, spawn mainly between August and January,
othersfromAugusttoMay,dependingonwhentheannualOkavango
flood reaches thehabitat inquestion. It appears that both sexes are
involved in the construction and defense of the bubblenest. It is
thought that the strange flaps of skin on the jaws are employed in
bubblenest construction.However, the fishes alsodeploy these flaps
ofskinwhenwaterconditionsdeteriorate.It isprobablethatwhenthe
fishes swim close to the surface these flaps help to improve the
oxygensupply.
Thebubblenest isdome-shaped (around17x16cmandabout9cm
deep) and is constructed among reed stems near the bank. As the
eggs,whichnumber 2,600onaverage–develop they ascend to the
surface of the nest, which is also where the larvae hatch. They are
better protected from predators there, and the oxygen supply is
optimal.The ascent of the eggs is causedby the parents producing
moreairbubblesbeneath thenest after spawning.The larvae sink to
thebottomofthenestandattachthemselvesto itviaadhesiveglands
on their heads.Thenest nowbecomes significantly shallowerwitha
depth of only around 2 cm, and broader (around 40 x 30 cm). The
parentsguard thenest,but there isno indicationof anydirectbrood
care,forexamplecollectingup theyoungsters.
PikeCharacins in theaquarium
Hepsetus odoe
are wonderful and interesting study objects in the
aquarium. They are peaceful among themselves and towards other
fishes that don’t represent potential food.Only if theyhave too little
space are Pike Characins likely to indulge in quarrelsome disputes
among themselves. All in all,
Hepsetus
can be classified as fairly shy,
and are liable to be intimidated by cichlids half their size. Ideal
tankmates include peaceful bushfishes (
Ctenopoma
), bichirs
(
Polypterus
),and/or lungfishes (
Protopterus
).
Fortunately feeding iseasy,asthese fisheswillacceptdeep-frozen fish
as foodwithoutproblem.Whole,deep-frozenStintarethe ideal staple
food for Pike Characins of upwards of 12 cm in length. If necessary
these fisheswillalsotakestripsof fish fillet,butthis foodshouldbethe
exception rather than the rule.
