confused?

[zoe4eva]

i bought some rotifers in a vial from you. On the back it says...
"Just 20ml of sterile Saltwater (10-15ppm) is sufficient to hatch 1000 to 5000 eggs. Use clean aged saltwater."
Now when is the point i change the 'sterile water' for normal 35ppm salt water? it actually doesnt say? I have water going for other cultures and just have those at 1.025 (35ppm) and the rotifers are doing great in there. But i havent used the vial ones before, just fresh. i want to use these rotifers for rotifer only cultures, because in my others i have copepods too. Im really confused about the water needed and the water used to culture all 20,000 eggs? Because its quite unclear.
Can you perhaps give me a few small instructions, so i can start my bigger cultures.
Thanks

[FUGU]

Hi Zoe

I'm away from work this week so I haven't got one of those instruction cards in front of me.

Sterile water: is used in the first instance when the cysts are rehydrating before hatching; this period is sometimes 24hrs but the current stock takes 2-3 days. If the water isn't sterile there's the opportunity for bacteria to attack the cysts during the rehydration stage.

Salinity: I will have to check that further when I'm back in. I've always used 20-22 ppt salinity for the culture work as rotifers are reported to be more productive at this level and this has the bonus of saving on salt. The rotifers will live a wide salinity range and if yours are happy at 35ppt keep going with it. I'm not certain why 10-15ppt is recommended on the card unless it's similar to the conditions of where dessicated cysts end up naturally ie brackish shores...?

Initial Guideline: Use a shallow dish like a petri dish. Start with 15ppt salinity for rehydration and add the cysts using a pipette as per instructions. Add a small amount of live phyto after 24-48hrs to tint the water lightly green. Once you have seen many rotifers moving around and actively feeding transfer the culture to a larger 500ml volume. Following this stage I see no reason why you cannot raise the salinity by 2.5-3.0ppt each time you double/triple the culture volume each week until you reach your desired salinity.

Access to a microscope is highly recommended for this rotifer work so you can observe the cysts rehydrating and see when the rotifers start swimming/feeding.

Hope that helps.

Cheers

FUGU

[zoe4eva]

thanks for that, the instructions are quite confusing:D I will do the rehydrating as soon as i have time. Thankyou.
OOOh do they really need 24 hours light when they re-hydrate?:confused:

[FUGU]

Hi Zoe - if you go for the shorter light cycle the rehydration period will just take longer. Let me know if you have any other questions. Cheers, FUGU