Handsfree
Australian Fast Bowler
Posts: 27
(20/12/05 13:31)
Reply
|
hatching brine shrimp
Within the first few hours of hydration, the Artemia cyst swells into a spherical shape and its diameter does not subsequently increase further. At full hydration, active metabolism will begin provided illumination of approximately 2000 Lux at the water surface is present as a trigger. This metabolism converts embryo food reserves into glygogen, (for energy), and glycerol which accumulates in the outer cuticle membrane.
Glycerol itself is very hydroscopic and more water from the surrounding hatching solution is absorbed. At a critical point, the outer cuticle membrane ruptures, (“breaking”), and the glycerol is released into the hatching solution. Up to breaking, salt is not necessary in the hatching solution. Indeed, as the salinity increases, a higher concentration of glycerol must be built-up over a longer period of time to rupture the membrane, resulting in increased depletion of food reserves.
At breaking, the Artemia embryo is in indirect contact with the hatching solution which must now be of similar ionic strength to seawater with a pH 8 – 9. Natural seawater has a salinity of about 35 parts per thousand. However, at 5ppt, less glycerol is needed for breaking to occur; hatching efficiency is greater and nauplii have a higher energy content. Therefore, it is recommended that the hatching solution is prepared by diluting one part seawater with seven parts freshwater and the addition of 2g/L sodium bicarbonate.
There are some other critical factors that effect hatching:
·Temperature should be maintained constant between 25 and 30 degrees.
·A minimum dissolved oxygen of 2mg/L is essential for hatching. This can be easily achieved with coarse air bubbling into the hatch container. Fine airstones are not recommended because of foaming which will trap the cysts and nauplii.
·Cyst density should not exceed 5g/L
This concept of dilute a hatch solution seems rather radical and many people question its validity. However, it has been well tested by the original author, (and myself). I suggest you give it a try, either out of curiosity or just for the savings in seawater use.
Reference
Sorgeloos P. 1986. Manual for the culture and use of brine shrimp artemia in aquaculture. The Belgian Administration for Development Cooperation. The FAO of UN
|
Email This To a Friend
Topic Commands
Click to receive email notification of replies 
Click to stop receiving email notification of replies