2. Live food aquaculture training course www.aquatrain.org Artemia Biology and Strains

3. Live food aquaculture training course www.aquatrain.org It is the ability of the Artemia to form dormant embryos or cysts that makes the Artemia nauplii the most widely used food item for the culture of fish and shellfish larvae. After harvesting and processing, cysts are packed into cans or buckets and become storable 'on demand' live feed. Artemia as live food; advantages

4. Live food aquaculture training course www.aquatrain.org Artemia as live food; advantages Resting cysts can be stored for years Live nauplii can be available within 24-36 h Security/backup at breakdown of rotifer cultures Tailor-made bioencapsulation according to the species nutritional requirements Robust upon variation in environmental parameters

5. Live food aquaculture training course www.aquatrain.org Phylum: Arthropoda Class: Crustacea Order: Anostraca Familiy: Artemidae Systematics

6. Live food aquaculture training course www.aquatrain.org Collection of cysts from the surface large amounts of cysts are produced and released when environmental conditions deteriorate the cysts float to the surface in large concentrations at this stage, they are harvested and dried for the aquaculture and aquarium industry by commercial companies

7. Live food aquaculture training course www.aquatrain.org Dry resting cysts in diapause Dry resting eggs (cysts) has an inactive metabolism and the embryo do not develop further as long as the cysts are kept dry or under anoxic conditions Main techniques for terminating diapause are dehydration, freezing and treatment with hydrogen peroxide

8. Live food aquaculture training course www.aquatrain.org Hydration and activation Upon immersion in seawater, the cysts hydrate and become spherical Embryo resumes its reversibly interrupted metabolism at a water content of 60%

9. Live food aquaculture training course www.aquatrain.org Cyst Hatching Outer membranes of the cyst burst after about 24 hours Embryo leaves the cyst shelll surrounded by the hatching membrane

10. Live food aquaculture training course www.aquatrain.org Pre-nauplius stage is developing into Instar I before hatching Emergence of hatching membrane Characheristics:  colored brownish-orange due to the presence of yolk  three pairs of appendages : antennae which have a locomotory function, sensorial antennulae rudimentary mandible  an unpaired red ocellus is situated in the head region between the antennulae. Parasol stage and hatching

11. Live food aquaculture training course www.aquatrain.org Stage: Instar II (metanauplius) Second larvae stage Instar II, functional digestive system, ingest particles of 1-50 µm Is reached about 8 hours after hatching

12. Live food aquaculture training course www.aquatrain.org Further development Undertakes about 15 molts until it reaches the 10th instar, with the following differention;  the body elongates  patricles is filtered and ingested by the setae of the antennae  paired lobular appendages which will differentiate into the thoracopods are budding in the trunk-region

13. Live food aquaculture training course www.aquatrain.org Sex differentiation at 10th Instar Male Female Adult female (1 cm)

14. Live food aquaculture training course www.aquatrain.org Uterus filled with nauplii Good conditions; ovovivipary Uterus filled with resting eggs Extreme conditions; Ovipary Copulation Reproduction

15. Live food aquaculture training course www.aquatrain.org Cyst Biology Cyst shell consist of 3 layers; Alveolar layer  Protection against UV and mechanical disruption  Can be removed by hyopoclorite (decapsulation) Outer cuticular membrane  Protects embryo from larger molecules than CO2 Embryonic cuticle  Transparent and elastic layer, develops into hatching membrane during incubation

16. Live food aquaculture training course www.aquatrain.org Different strains found all around the world

17. Live food aquaculture training course www.aquatrain.org Variability between strains of Artemia Nutritional value Size and energy content Hatching quality (hatching rate; nauplii/100 cysts; hatching efficiency; nauplii/g cysts) Number of cysts/g Growth rate of nauplii Specific cysts characteristics

18. Live food aquaculture training course www.aquatrain.org Size and energy content (I) Selection of strains with regard to mouth size Example of gape with length in cod (figure) Prey size to gape ratio varies between 0,4 to 1 in cod Puvanendran et al. 2004. Can. J. Zool. 821380-1389.

19. Live food aquaculture training course www.aquatrain.org Size and energy content (II) Size, individual dry weight and energy content of Artemia instar I nauplii from different cyst sources hatched in standard conditions (35g.l -1, 25°C)

20. Live food aquaculture training course www.aquatrain.org Growth of nauplii Growth of Artemia nauplii from different cyst sources under standard culture conditions (7 days, darkness, 10 instar I nauplii/25 ml, 35g.l -1, 25°C, fed with Dunaliella viridis)

21. Live food aquaculture training course www.aquatrain.org Specific cysts characheristics Generally three supplies of small cysts: San Fransisco Bay, Great Salt Lake and Vietnam

22. Live food aquaculture training course www.aquatrain.org Specific cysts characheristics (II) Supplies of large cysts: San Fransisco Bay, Great Salt Lake, Russia and China

23. Live food aquaculture training course www.aquatrain.org Size of nauplii after 24 h enrichment