What came first the isopod or the egg?

At risk of turning this article into a biology lesson, the lifecycle of an isopod begins with a male and female isopod in a synchronised courtship. Typically, the isopod breeding season begins in the spring, however, isopod breeding depends less on the time of year and more upon the right habitat. 

If the habitat is right, the female enters a receptive period where she will form a pair and mate with a male. During this receptive period, the female releases aggregate pheromones to attract male suitors. 

Adult isopods can reproduce for several seasons. On average, they live for approximately a year and a half. However, some individuals can live for two years or more. Mortality rates are higher in animals that have been isolated from other isopods, suggesting that social behaviour is important for their survival.

Both males and females’ mate with multiple partners, and females can store sperm from several different males for later use. She can store sperm for an entire year to use in the next breeding cycle.

And so the cycle begins…

After mating, the female produces eggs. Unlike their aquatic pod relatives, land isopods utilize a unique structure known as a marsupium. 

The marsupium is a fluid-filled pouch on the female's underside which she uses to brood her eggs.

During the brooding phase the mother seeks out a burrow. The female broods the eggs within her marsupium for a period of two or three months. Once the eggs hatch, the young can remain inside the marsupium for an additional three or four days. The young offspring are known as mancas and they have 6 pairs of legs during this phase of their life.

Typically, the mother remains hidden in the burrow until her young emerge from the marsupium with up to 200 babies. The young isopods remain hidden within the burrow until they have molted several times, growing into juveniles and growing 7 pairs of legs. Once they have completed enough molts, their armour stiffens to protect them from harm and they are ready to leave the burrow.

Once they reach between two and three months of age they are ready to reproduce themselves.