Marine Biotechnology Lab The brine shrimp Artemia salina

Taxonomy PHYLUM: Arthropoda CLASS: Crustacea ORDER: Anostraca FAMILY: Artemidae GENUS: Artemia

Brine shrimp (Artemia salina) The brine shrimp is a small crustacean living in salt lakes and man-made brine ponds throughout the world. Tolerance water salinity values over 200 ppt. body permeability to salts is very low

Morphology and natural history Each spring as Salt Lake warms, masses of brine shrimp cysts begin to hatch. The first larval stage of Artemia measures is( nauplii)about 500 μm in length and has three pairs of appendages. Under optimal conditions brine shrimp reach the 10-mm long adult stage in eight days and can live for several months.

The adults are characterized by an elongated body with two stalked complex eyes, sensorial antennule and 11 pairs of legs Males are easily recognizable for their pair of large muscular claspers (the 2nd pair of antennae) in the head region. Females bear the brood pouch or uterus behind the 11th pair of legs.

Reproduction of Artemia Two modes of reproduction exist in Artemia: Parthenogenetic. Bisexual. Where ovoviviparous and oviparous reproduction alternates.

Ovoviviparous In ovoviviparous reproduction fertilized eggs are retained inside the uterus until embryonic development is fully completed (4- 5 days) and free swimming nauplii are then released. Oviparous In Oviparous reproduction embryos surrounded by a thick shell , enter a state of metabolic standstill or dormancy and are then released by the female.

Uterus of oviparous Artemia filled with cysts. Uterus of ovoviviparous Artemia filled with nauplii (first larvae are being released).

Artemia use in aquaculture Artemia salina represents an excellent prey for marine fish larvae. Having a larger size than rotifers, the brine shrimp Artemia salina are used as the second (after rotifers), and last live food fed to fish larvae before their weaning on artificial feed. Later on in the rearing process, and before weaning, larger Artemia metanauplii stages replace nauplii for larger fry. Some fish fry however, due to the large size of their mouth at first feeding, they can accept Artemia as a first prey, making rotifer supply not compulsory.

The advantages of Artemia are multiple: The widespread commercial availability as dormant cysts. They are easy to produce. Its short production cycle. They are visible as prey and are highly palatable to fish larvae. Its nutritional value and mobility in water makes it a perfect prey for young fish.

Nutritional value of Artemia The nauplii are rich in yolk. Larger metanauplius, whose nutritional value has to be improved by feeding them special enrichment diets e.g. adding essential fatty acids (HUFA’s)12 to 24 hours before being offered to fish to upgrade their nutritional value for fish larvae.

Hatching Disinfect the cysts by hypochlorite solution (NaOCl). Add not more than 5 g of cyst for 1 liter of clean natural seawater (33 ppt). The hatching containers should be cylindrical tanks with conical bottom, aerated from the bottom. The hatching containers should be illuminated at least during the first hour of hatching. NaHCO3 is added to adjust the pH to 8–9 whenever necessary. Complete hatching takes 24–36 hrs at 25–30°C.

Various Artemia stages Various Artemia stages. A spherical hydrated cyst, breaking stage (Nauplii emerging from eggs), embryo in ‘umbrella’ stage, hatching instar I nauplius

Harvesting Once hatching is completed, switch off aeration and start harvesting of Artemia nauplii after 5 to 10 minutes. Empty cyst shells float to the surface, while the nauplii concentrate in the lower part of the tank and the unhatched cysts accumulate underneath the nauplii.

Since most nauplii are positively phototactic, their concentration can be hastened and increased by shading the upper part of the hatching container with a black plastic sheet so that light reaches the lower part of the container only. Remove the unhatched cysts, after which the nauplii can be collected and used as live food organisms.

Assessing hatching process It is important to assess the hatching results To feed the larval rearing tanks at the established densities Artemia nauplii. To select a suitable brand of Artemia cyst.

DETERMINATION OF HATCHING EFFICIENCY (HE) The two main criteria to evaluate hatching results are: hatching efficiency: the number of hatched nauplii obtained from 1 g of cyst; top quality cysts yield about 300 000 nauplii/g. hatching percentage: the number of nauplii hatched per 100 cysts; good batches have a hatching percentage around 90-95%.