<P> For brine shrimp, many functions, including swimming, digestion and reproduction are not controlled through the brain; instead, local nervous system ganglia may control some regulation or synchronisation of these functions . Autotomy, the voluntary shedding or dropping of parts of the body for defence, is also controlled locally along the nervous system . Artemia have two types of eyes . They have two widely separated compound eyes mounted on flexible stalks . These compound eyes are the main optical sense organ in adult brine shrimps . The median eye, or the naupliar eye, is situated anteriorly in the centre of the head and is the only functional optical sense organ in the nauplii, which is functional until the adult stage . </P> <P> Brine shrimp can tolerate any levels of salinity from 25 ‰ to 250 ‰ (25--250 g / L), with an optimal range of 60 ‰--100 ‰, and occupy the ecological niche that can protect them from predators . Physiologically, optimal levels of salinity are about 30--35 ‰, but due to predators at these salt levels, brine shrimp seldom occur in natural habitats at salinities of less than 60--80 ‰ . Locomotion is achieved by the rhythmic beating of the appendages acting in pairs . Respiration occurs on the surface of the legs through fibrous, feather - like plates (lamellar epipodites) </P> <P> Males differ from females by having the second antennae markedly enlarged, and modified into clasping organs used in mating . Adult female brine shrimp ovulate approximately every 140 hours . In favourable conditions, the female brine shrimp can produce eggs that almost immediately hatch . While in extreme conditions, such as low oxygen level or salinity above 150 ‰, female brine shrimp produce eggs with a chorion coating which has a brown colour . These eggs, also known as cysts, are metabolically inactive and can remain in total stasis for two years while in dry oxygen - free conditions, even at temperatures below freezing . This characteristic is called cryptobiosis, meaning "hidden life". While in cryptobiosis, brine shrimp eggs can survive temperatures of liquid air (− 190 ° C or − 310 ° F) and a small percentage can survive above boiling temperature (105 ° C or 221 ° F) for up to two hours . Once placed in briny (salt) water, the eggs hatch within a few hours . The nauplius larvae are less than 0.4 mm in length when they first hatch . Brine shrimp have a biological life cycle of one year . </P> <P> Parthenogenesis is a natural form of reproduction in which growth and development of embryos occur without fertilisation . Thelytoky is a particular form of parthenogenesis in which the development of a female individual occurs from an unfertilised egg . Automixis is a form of thelytoky, but there are different kinds of automixis . The kind of automixis relevant here is one in which two haploid products from the same meiosis combine to form a diploid zygote . </P>

When do brine shrimp produce eggs versus live birth