Reproduction and Development

The reproduction of the Triops is completely different as most of the populations they live are either female or male dominated. In the Northern Hemisphere you will find pools that are mostly female dominant and we move towards the southern hemisphere where we will find the pools that are male dominant. Hence, the most common strategy of the reproduction is through the unfertilized egg which is called Parthenogenesis. However, there are many strategies each population of the Triops display according to the availability of male and female species.

The eleventh pair of the legs in the females is converted into a sack to hold the eggs where they are carried for several hours. The two sacs will be able to hold equal number of eggs. The eggs are not released in clusters but are laid randomly though all the eggs in the sacs are released simultaneously. The fecundity of the Triops is very high and they can lay more than 1000 eggs. The shell of the eggs is very thick and can withstand drought as well as a freezing condition so that they survive from one season to the next. The eggs should become completely dried before they get submerged into the water for hatching. The eggs also have the capability to stay in the state of diapauses for almost 20 years. Some eggs would be hatched within days however; some remain unhatched in the soil for many years. This is an effective way for the tadpole shrimps to maintain their population and their breed. May be the characteristics of the eggs might have enabled the population to survive during the natural disasters that have killed even dinosaurs 65 million years ago.

The paired gonads extend the entire length of the trunk on either side in the female tadpole shrimps. These gonads are filled with cysts occupy the cavity of the body along with the gut. Every gonad consists of a germanium at the tip of many follicles. These follicles have ducts that join the longitudinal oviduct and this longitudinal oviduct will lead to the ovary sac.

The ovarian follicles in the female tadpole shrimps consist of an oocyte and three nurse cells. These ovarian follicles are in turn surrounded by a thin layer of the follicle cells. The size of the oocyte cells was smaller to the nurse cells in the initial stages. The cytoplasm of these oocytes is filled differently with the yolk globules which are in turn surrounded by the membranes of the endoplasmic reticulum. Apart from the oocytes even the nurse cells consists of yolk globules that are characterized by a slightly darker cytoplasm.

The follicle duct wall is a single layer and it is very closely packed with the cells on the basal lamina. In the beginning the oocyte do not have any coating, however it pushes the shell material towards the end of the tubules into the oviduct. The covering of the egg begins here, as the egg passes through this material before entering the longitudinal oviduct also called as uterus. After the vacuolization is completed, the coating on the egg becomes uniform and also it becomes a definitive egg shell. When the eggs are completely deposited in the ovigerous pockets then completely display the characteristic of the shell structure.

Larval Development »