This article is for species of the Caridina genus that reproduce and mature entirely in freshwater and have fully suppressed larval stages (direct development).
Caridina shrimp are ovoviviparous; fertilisation occurs internally and the eggs are retained until hatching.
Moulting of the female:
The moulting of the female that initiates reproduction is known as the parturial moult. When a mature female shrimp undergoes her first parturial moult (either the first of the reproductive season or in general), she undergoes an anatomical transformation. Her abdomen deepens and widens to allow space for the eggs, and there is also enlarging of the pleopods to assist in carrying them. These physical changes are collectively known as the female ‘breeding dress’.
It is advantageous for moulting to stimulate breeding, as the newly formed cuticle is free of bacteria and other microbes that would otherwise colonise on and harm the eggs.
Attracting a mate:
In many cases the female releases pheromones during apolysis to attract the males in anticipation of ecdysis. Once the female undergoes ecdysis, she releases more pheromones that induce restless searching in the males (and in some cases the females too).
Mating takes place once a male finds the receptive female. The male mates with the female, fertilising the oocytes of the female internally to form zygotes. The female can mate with a single male or many, depending on the species.
Formation of eggs:
Soon after fertilisation, the embryos of the female’s mature ovaries are transported down between the cephalothorax and the abdomen and are secreted into the underbelly of the shrimp, forming spherical eggs on the pleopods. These are cemented in place by gland secretions.
The eggs are carried within the abdomen of the female until they hatch, which usually takes between 2-4 weeks. If the embryos become victims of particulate and microbial fouling, vital gas exchange and excretion of toxins are reduced, and the microbes can damage the eggs by release of noxious chemicals and colonisation. To counter this the female ensures water flow over the eggs by rhythmic fanning of the pleopods and also grooms them using her chelipeds.
If the female becomes diseased or stressed, or if the brood is unsuccessful, she is capable of abortion by ‘dropping’ the embyros.
When the eggs begin to hatch, the female vigorously fans the pleopods periodically to assist the juveniles. In many species the female hides when the eggs are ready to hatch as this reduces the risk of predation.
The juveniles immediately assume a benthic lifestyle. As long as the correct conditions are provided and there is a plentiful supply of natural food (algae, biofilm) within the aquarium, the juveniles should mature without problems.