Most commonly, females hatch from eggs in the spring; produce females asexually
throughout the summer; in the autumn they start producing males, they mate and lay
resting eggs. This breeding system is called Cyclic Parthenogenesis
When attempting to culture Daphnia at home it is important to supply your colony's
with the correct conditions in-order not to stress the entire culture which will lead to
a crash and possible loss. The culture can become stressed if the population density
is too high, poor water quality, food shortages and extreme water temperatures. During these times of stress the female will produce more male embryos (which is not
what we want) they will begin to re-produce sexually rather than asexually. The female upon mating with a male will expel the resultant eggs which will fall to the
substrate and will only hatch (into females) when conditions in the body of water
improve and a non stressful environment persists.
Daphnia - Biological Make-Up
Lifecycle
Daphnia has long been celebrated for possessing the power of re-production without the intervention of the male and for laying two different sorts of eggs....
CHARLES DARWIN 1857
Under favourable conditions, a female will produce a clutch of eggs after every adult
moult, these eggs are placed in a brood chamber which is located dorsally beneath
its carapace. The development of these eggs starts immediately. After around 24
hours at a temperature of approximately 20?C the eggs will hatch but remain inside
the brood chamber for a further three days, after which time they are released by the
mother. The young daphnia resemble their adult counterparts except that the brood
chamber will not yet be fully developed. In most species young Daphnia will pass
through 4-6 juvenile instars (developmental stages such as moults) before being able
to produce eggs for the first time this may take anywhere between 5-10 days at 20?C
and can take considerably longer if food is scarce. An adult Daphnia may produce a
brood of eggs every 3 to 4 days until she dies. Life expectancy of a female is around
8 weeks and a little longer if food availability is poor. Brood sizes vary considerably
and are dependent on the species you are dealing with, they can range from a couple
of eggs to over one hundred for the larger species.