Daphnia culture

[Moontanman]

I noticed my Daphnia magna cultures are beginning to proliferate, the days are getting longer and unicellular algae is starting to replace the strings of hair algae. I've noticed as the Daphnia magna start hatching out of resting eggs the daphnia are quite large, some as much as 6mm or more across. My 6500 gallon vat has the biggest daphnia, i was wondering if anyone else has noticed their daphnia cultures coming back and if the Daphnia are bigger than they are when the weather is warm? All these daphnia are females giving live birth, the males are absent and will not appear until September or October. I am thinking that the evolution of the population of large daphnia at the beginning of the season gives way due to environmental influences or do different species of daphnia replace the big ones as the season progresses. Summer daphnia are maybe half the size, at best, of winter daphnia, also behavior changes as the seasons progress as well with late summer daphnia clinging to the sides of vats instead of swimming freely. Any thoughts?

 

Oh yeah, the bigger daphnia seem to grow when the cyclops are dormant and give way to smaller daphnia as the cyclops become active...

[Blahah]

This is interesting, why do you keep Daphnia cultures? Toxicology? Or just curiosity? Or with a vat that large are you using them as a feedstock?

 

Sorry that I don't know the answer to your question.

[Moontanman]

This is interesting, why do you keep Daphnia cultures? Toxicology? Or just curiosity? Or with a vat that large are you using them as a feedstock?

 

I use them as feed stock for unusual fishes I collect with or are given to me by the State Fisheries people from time to time. Wild caught fish will often starve before they will eat commercial fish food, I have a friend who writes books about North American Native Fishes, his scientific collecting permit allows him to collect almost anything, i go with him and I get to have specimens of some of the animals we catch, he has identified several new species (I am cited as source in one of his papers on a new species makes me feel special even if it isn't that big a deal) Daphnia magna are greedily eaten by any fish and or aquatic animal. Breeding fish and other unusual aquatic animals is a hobby... that ate my life

 

Sorry that I don't know the answer to your question.

 

Actually this question generated quite a bit of interest on another more appropriate science forum directed more toward fish biology, the predatory nature of the Cyclops drive the smaller size due to the large daphnia not being as able to get away from the Cyclops seems to the general consensus so far.

 

Oh yeah IMHO the large size of the newly hatches females when the weather begins to warm is because they have live young and a bigger females can give birth to more babies faster than a smaller daphnia, that's why the cyclops usually win by late summer and the daphnia disapear...

Edited February 15, 2011 by Moontanman