Buying Daphnia eggs online? Abd dry, at that?

[Bill B]

Hi all,

I was trying to figure out what to feed a salamander larva that I got from a Michigan (USA) pond, and since I have no local source of blackworms anymore, I looked into some other possibilities

I saw a link to a company that sells dry Daphnia eggs... that you supposedly culture to produce the live Daphnia. Is this for real? I have a hard time thinking that dry eggs of an aquatic invertebrate would produce anything.

https://www.etsy.com/listing/512725...bm9yGf_M2vgSK5j8lhtdsBo8yBsNATYPoLhoCjabw_wcB

Bill

 

[John]

Daphnia produce resting eggs under poor conditions and these can be dried out and hatched years later. In my experience of buying them on ebay on and off over the years, most sellers' eggs either don't hatch or hatch very few Daphnia. It's not a refined industry like Brine Shrimp eggs.

Now I haven't purchased from that seller so I can't speak to the quality of their product.

But on the topic of blackworms, I buy blackworms from Eastern Aquatics on a regular basis and I have no complaints. Yes the shipping can hurt but if you keep the worms correctly they can last for months. They even offer a discount just for Caudata.org: http://www.caudata.org/forum/f49-ad...-live-blackworm-specials-caudata-members.html

 

[kfamtvw7]

you can improve the hatch rate of daphnia eggs by putting them in the fridge for a few days before you re-hydrate them and then exposing them to a 12 hour photoperiod of bright white light when hatching. Often if they have just been dried without a cold shock the hatch rate will be poor. What you're trying to do is trick them into thinking it's spring. The colour temperature of the light is important as this changes throughout the season.

 

[caleb]

you can improve the hatch rate of daphnia eggs by putting them in the fridge for a few days before you re-hydrate them

Do you have any particular reason for doing this before, rather than after, rehydrating?

There's some evidence that a period of darkness might also improve the hatch rate (for example, this paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2202890/pdf/562.pdf ).

I've had moderate success hatching eggs/ephippia by rehydrating, putting them in a lightproof metal can in the fridge for a week or so, then moving them to a warm, light position.

 

[kfamtvw7]

Caleb you're absolutely right about the darkness but most fridges automatically shut off any lighting when the door closes as far as I know so you can kill two birds with one stone.
As you probably know the lifecycle of many cladocerans goes
hatch> grow> asexual reproduction> production of males triggered by environmental stress> sexual reproduction> ephippia> dessication as pond partially or entirely dries up towards end of summer> cold exposure over winter> re-hydration with spring rains as temperatures rise> hatching.
So for me it just made sense to cold shock them in their dried state as it seemed to follow the natural process as I understand it, however it's certainly not strictly necessary or by any means the "correct" process.
That paper you linked to is very interesting, I have never attempted to decapsulate my eggs and it seems to suggest that this might have a greater impact on actual hatch rates, or at least how many hatch at once, than the duration or intensity of exposure to light or cold

Synchronous activation could be disastrous to a temporary pond population if a second dry period happened to precede ephippial egg production by the population. By constituting a very effective and probably variable obstacle to development, the ephippial capsule acts to prevent highly synchronized activation; hence a reserve source of developmental potential is preserved.

Makes sense to me. I've only skimmed it but I'll read it properly later, thanks for the link.