Congo Killies - PageSuite

Right: Typical habitat of Triops in Australia. The top
picture was taken in June when the depression was filled
with water. The bottom picture shows the same biotope
in April of the following year, during the dry season.
on the 11th pair of legs, which is adapted for
this purpose. Up to 70 pairs of legs and 44 body
segments are seen in tadpole shrimp. On the
first 12 body segments there are only one pair of
legs each, while further back there can be up to
10 pairs per segment, and the last few segments
usually have no legs.
Crustaceans have mandibles as mouthparts
to chew food and two pairs of antennae. These
two characteristics are sufficient to differentiate
the tadpole shrimp from the Xiphosura or horseshoe
crabs, which have a similar appearance.
However, the four surviving species of the
family Limulidae belong to the Chelicerata (spiders,
scorpions, and sea spiders) and have chelicerae
as mouthparts and no antennae.
The genus name Triops stems from the three
eyes found at the front of the carapace, or shield.
The two larger ones are complex eyes; the middle
one is a so-called nauplia eye. Interestingly, the
eye design may permit the animal to detect light
coming from below. Also worth mentioning
is the oxygen-transporting hemoglobin that is
dissolved in the hemolymph (blood analog of arthropods)
of Triops. The intense red color often
observed in Triops longicaudatus in the aquarium
is due to this protein.
Heterosexuals, hermaphrodites,
and virgins
The main survival advantage of Triops is their
efficient reproduction. Many populations consist entirely
of hermaphrodites (organisms that have both male and
female reproductive organs in the same individual) or
females that reproduce by parthenogenesis (development
of an embryo from an unfertilized egg cell). In Triops
longicaudatus it was observed that 594 cysts were deposited
within 72 hours (Gruner 1993). I have to assume
similarly high numbers in other Triops strains that reproduce
by parthenogenesis or through self-fertilization.
For example, two to three days after adding water to an
aquarium of about 32 gallons (115 L), myriad nauplius
larvae and molded instar stages of Triops cancriformis cancriformis
were observed. In Triops cf. newberryi from Australia,
within 24 hours after adding water to a dry tank
with resting cysts, masses of larvae hatched. It is possible
to raise 40 of these up to a size of 2 inches (5 cm) in a
15-gallon (55-L) aquarium within a week’s time.
Reproduction in captivity is usually less productive
in available Triops species and strains, which propagate
conventionally via two sexes and copulation. With Triops
B. TIMMS
australiensis australiensis and T. granarius, I have never
encountered as many hatching larvae in the first three
filial generations as with the species above. However,
they seem to reproduce at a high rate in nature as well,
given the larger expanses of available habitat. In the wild,
there are lots of developing animals present and therefore
always plenty of sexual partners, which might represent a
bottleneck in captivity.
In summary, Triops possess all the possible reproductive
strategies known to science: sexual (gonochoric, or
one sex per individual), self-fertilization in hermaphrodites,
and parthenogenesis of females. Moreover, all three
strategies may be observed within one species in biotopes
found in the same region (Garcia-Velazco 2009).
Glass or Plexiglas
Glass aquariums are the most convenient way to house
Triops. I used to buy 12-gallon (45-L) tank sets that measured
20 inches (50 cm) long, 12 inches (30 cm) wide,
and 12 inches (30 cm) high. For some years now, the
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