Artemia Life Cycle

Over the past two decades, the brine shrimp Artemia has become a key resource in the industrial expansion of fish and crustacean larviculture. Annually, more than 2.000 metric tonnes of dry Artemia cysts are marketed worldwide to feed fish and shellfish (Sorgeloos, 2001; Dhont & Sorgeloos, 2002). The brine shrimp Artemia is a small branchiopod crustacean found almost worldwide in solar saltworks or in natural saline lakes. They are found in environments with salinities high enough that its predators cannot survive (70 g/l) and even in certain salty ponds where salinities approach the precipitation point of NaCl, 340 g/l (Clegg & Trotman, 2002). Artemia are unique organisms because they can produce dormant cysts (Léger et al., 1986) with a diameter ranging from 200-300 µm which can be stored during a long period of time (Sorgeloos, 1980). With regard to Temperature, Artemia has a good adaptation in widely fluctuating conditions ranging from 6-350 C (Van Stappen, 1996) and their pH tolerance varies from 6.5 to 8 (Dhont & Lavens, 1996).

In their natural and stable environments, can produce ovoviviparaous eggs that hatch immediately into nauplii (Lenz & Dana, 1987). However, under seasonally unstable environments, Artemia will produce cysts which are metabolically inactive and do not develop as long as they are in dry (unfavorable) conditions. When they are immersed in the seawater under appropriate conditions, the cysts will hatch after 12-16 hours of hydration (Van Stappen, 1996). The outer membranes of the cysts will burst and the embryo will appear. After a short periode of time, the hatching membrane will rupture. For the first few hours, the embryo of Artemia will hang beneath the cyst shell during what is called the umbrella stage. The newly hatched Artemia are called Instar I, measures about 400 to 500 µm in length and completely relies on yolk reserves as their digestive system is not functional yet. Instar I are easily identified as a brownish-orange animal, reflecting the yolk, and having three pairs of appendages (i.e.: antennae as locomotory apparatus, sensorial antennulae and rudimentary mandibles) and a red ocellus between the antennulae. After about 8 hours, the larvae molts into the 2nd larva stages (Instar II) and starts feeding on small exogenous food particles ranging in size from 1-50 μm. For the complete cycle, Artemia develops through 15 molts. From Instar 10 onwards, important morphological, functional changes and sexual differentiation are taking place (Van Stappen, 1996).

The adult Artemia are around ±1 cm in length and have an elongated body with two stalked complex eyes in the head region. They have a linear digestive tract, sensorial antennulae and 11 pairs of thoracic appendages. Adult male Artemia has a paired penis in the posterior part of the trunk region and adult female of Artemia can easily be recognized by the brood pouch or uterus situated just behind the 11th pair of thoracopods. Eggs develop in two tubular ovaries in the abdomen. Once ripe they become spherical and migrate via two oviducts into the unpaired broodsac or uterus (Van Stappen, 1996).

The development of fertilized eggs are largely determined by the environment. In extreme conditions: high salinities, low dissolved oxygen and food, the embryo only develops up to gastrula stage and is surrounded by a thick shell or chorion. They are released into the environment as a dormant encysted embryo. The diapause mechanism is inactivated when the cysts are hydrated in suitable seawater condition allowing the cyst to resume it’s further embryonic development. The life span of Artemia can reach up to several months and they reproduce at a rate of 300 nauplii or cysts every five days (Sorgeloos & Kujlasekarapandian, 1984).

References

Clegg, J. & C. Trotman. (2002). Physiology and biochemical aspects of Artemia ecology. In : T. Abatzopoulos, J. Beardmore, J. Clegg, P. Sorgeloos (Eds.) Artemia : basic and applied biology”. Kluwer Academic Publishers.

Dhont, J. & Sorgeloos, P. (2002). Application of Artemia. In: ARTEMIA: Basic and applied biology. Abatzopolous, T.J., Beardmore, J.A., Clegg, J.S., Sorgeloos, P. (Eds.), Kluwer Academic Publishers, Dordrecht, The Netherlands. pp. 251-286.

Dhont, J. & Lavens, P. (1996). Manual on the Production and Use of Live Food for Aquaculture. FAO Fisheries Technical Paper. pp. 295.

Lenz, P. H. & G. L. Dana, (1987). Life-cycle studies in Artemia: a comparison between a sub-tropical and a temperate population. In Sorgeloos, P., D. A. Bengtson, W. Decleir & E. Jaspers (eds), Artemia Research and its Applications, 3. Ecology, Culturing, Use in Aquaculture. Universa Press,Wetteren. Belgium: 88–100.

Sorgeloos, P. (2001). Use of brine shrimp Artemia spp. in aquaculture: A historical overview starting with the FAO conference in Tokyo, 1976. International Workshop on Artemia, 12-15 May 2001. Artemia & Aquatic Animals Research Center, Urmia University - Iran, pp. 34.

Sorgeloos, P. & Kujlasekarapandian, S. (1984). Production and use of Artemia in aquaculture. CMFRI special publication (15): 27-37.

Sorgeloos, P. (1980). The use of Artemia in aquaculture. In: Persoone, G., Sorgeloos, P., Roels, O.A., Jaspers, E. (eds) The brine shrimp Artemia, Vol.3, Ecology, culturing, use in aquaculture. Universa Press, Wetteren, Belgium, in press.

Van Stappen, G. (1996). Introduction, biology and ecology of Artemia. In: P. Lavens, P. Sorgeloos (Eds.). Manual on the production and use of live food for aquaculture. FAO Fisheries Technical paper 361. Rome.