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Fwd: Volvox as fry food



Mark is not a member of the list as of this submission, so he will not see
any responses to the list.  Please direct any correspondence to him as well
if you want him to see it.

BTW, I found this post very interesting.

Forwarded message follows:
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From: "Mark O'Connor" <marko at Canberra_teknet.net.au>
Subject: Volvox as fry food

The following is a message I have just put on the AUNZZA (Southern
Hemisphere killifish) network, and may also be of interest to your members.

 As I'm very short of time, I'm not sure if I can extend the offer made in
it to distribute my local strain of volvox to all who might want to
experiment with it, and there may be problems with mailing it abroad from
Australia.  But there are strains of volvox everywhere, and  the ideas in
this piece should be of great interest to livefood enthusiasts.

*****************
 
 
 
     VOLVOX SPECIES 
      
     --A NOTE ON A MOST PROMISING LIVE FOOD. 
      
     Volvox  is  a giant infusorian. It is  a  slow-swimming  colonial  
     algae,  but  vastly larger than those mobile algae  species  like  
     Euglena that are found in ordinary "green water".  Adult individ- 
     uals  or colonies are visible to the naked eye (against a  fairly  
     good  light)  as green or pale green globules,  almost  perfectly  
     round.  Adults of the species I am offering to spread around  are  
     about  the size of brine shrimp, but a culture will also  contain  
     juveniles  of a size suitable to feed very small  egg-layer  fry.    
     Their  lack of projections and the fact that they do  not  thrash  
     around like microworms or vinegar eels are added advantages.  The  
     fact  that they move slowly to the light enables them to be  bred  
     in a vat and concentrated for use. 
      
     The Encyclopaedia of Live Foods says they are found in  iron-rich  
     waters,  usually under a layer of duckweed (i.e. not in  in  full  
     sunlight)  and that they can co-exist with daphnia.  It  comments  
     that  during  the  season when they swarm "fish  fry  grow  fat".  
     Presumably this refers to European or North American species.  
      
     My  culture,  which thins out or disappears in  summer,  has  re- 
     appeared for the last three winters as a dense culture in a broad  
     1-gallon  (5 litre) glass sweets-jar left out against  the  North  
     wall of my house. (There is a half teaspoon of salt in the  water  
     to  make it less likely to freeze and crack the jar,  though  the  
     top  does freeze fairly often). I added some chelated iron  after  
     identifying  the  culture,  and the odd drop  of  aquarium  plant  
     fertiliser  since. There is a thick layer of azolla and  duckweed  
     on  top,  and the jar is heavily shaded from  overhead  sun,  but  
     takes  in  quite a lot of direct but slanting light  through  its  
     sides especially in winter. Perhaps less crucial than the shading  
     is  the fact that as the azolla and duckweed multiply there is  a  
     slow but steady suppy of drowned plants which can no longer  find  
     room  at  the surface.  Their decay also feeds  a  population  of  
     tubifex  at the bottom of the jar, and no doubt  releases  nutri- 
     ents.  Last summer daphnia and cyclops re-appeared and seemed  to  
     eliminate  the  volvox, but it re-appeared recently as  a  fairly  
     pure culture. 
      
     Not much is known about this Australian (?) species of volvox.  I  
     would urge fish breeders to experiment with pipetting off a  pure  
     culture  and  experimenting  to find the  temperature  and  light  
     intensity  in which it can best be cultivated.  (Windowsill  cul- 
     tures,  which  get steadier temperatures, don't seem to  work  so  
     well,  though this may be simply because cyclops etc are able  to  
     predominate). 
      
     I believe volvox has great potential as a trouble-free  permanent  
     fry food.  If cultivated in bulk, it might also be ideal food for  
     young  live-bearers. If it can be cultivated  alongside  ordinary  
     "green  water"  the  result might be a "one-stop"  fry  food  for  
     egglayers of all ages. I also wonder whether it might not  enable  
     discus  fry  to be artificially reared without  troublesome  egg- 
     pastes, etc. 
      
     I can supply a small vial of this strain of Volvox to any  aquar- 
     ist  genuinely interested in cultivating them (for  $5  including  
     mail).  
      
     I  would  also encourage people to experiment  with  their  local  
     strains of volvox. (There are some much larger species around  in  
     SE Australia, but to date I have been unable to cultivate them). 
      
     Mark O'Connor 
 


Mark O'Connor
8 Banjine St O'Connor ACT 2602  Australia
ph. 61 6 247 3341
Fax 06 249 0102 c/- Mrs Jan O'Connor





David W. Webb           Texas Instruments
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