Aquazoa wrote:Hello Denebanger,
Have you noticed any 5th parapodia on your zoeae yet?
It has just been my experience that when using simple nursery tanks with airstones that many late stage zoeae have these delicate appendages twisted, torn off, missing one or even both and that their poor swimming abilities they expend more energy and that tends to result in longer larval marking times.
With a sophisticated planktonkreisel (with slotted inflow apertures close to the bottom of the tank) not only are larvae suspended more effortlessly in the center of the tank, so is their food items (and groups of peppermint larvae can share a floating suspended cube of squid...a sight to behold). There are no dead corner zones and all the water is moving in a gentle uniform ferris wheel gyre.
Presence of both parapodia on larvae in a well designed kreisel attests to the more gentle upwelling flow patterns and, most importantly, settlement was achieved
by day 20 as opposed to six weeks in an airstone driven rectangular nursery.
Of course there are many factors and permutations of technique (Wittenrich used black tubs with airstone in center, Riley and Palmtag used cylindrical screened tanks in larger tanks, earlier researchers used beakers, but Rhyne, Calado, and others at Florida Tech seemed to have had some of the most remarkable results with cylindricoconical upwellers). Actually I still think a rounded black tub shaped like one of those big restaurant dough mixing bowls with a gentle air release 2/3 of the way down in the center might be just fine. Nevertheless my best results have been achieved with my perfected Greve/Helgoland planktonkreisel...for what it's worth.
Porter Betts
Thanks for your input Porter, I haven't got far enough along yet with the zoeae....the first batch died off between Z2 and Z3 but I think that they were just a batch of low quality larvae. I am familiar with the methods that you are describing; however, I'm going to keep working with this system design because of its very low daily maintenance, ease of use and ability to provide optimum water quality. In this system I don't use any air and have a gentle circulation, my past observations with adding air stones or using air are fluctuations in pH.
Quick update....still no larvae! Both PS are STILL holding and the eggs on both are now a distinct silver and plenty of eye spots are visible to the naked eye...perhaps I'll have a nursery full of larvae tonight.
Now a note about the snails that I've added to the nursery, I added them too soon! On several occassions I've caught the adult PS killing them for a little escargot even though they are very well fed....so not a good idea to add the snails until after the larvae have arrived and the adults have been moved back to the broodstock tank. With this new diet that the adults are on I've observed significant growth and of course this prolonged period of carrying the eggs. We are now at day 22, I was of the understanding that it only takes 10-14 days for the larvae to hatch as was my experience with the first batch. Now, I'm starting to think that this prolonged period is far better and should produce higher quality larvae (time will tell) and that the previous 14 day cycle may well be a premature cycle as a result of poor nutrition (this is only an idea based on what I'm currently observing).
Now as far as the system goes, I am running a set of NO flourescents across the broodstock and the nursery; however, because the nursery has very little flow through I am starting to see the development of cyano , so the plan is to move the lights to a position several feet above to create more of an ambient lighting effect. If this doesn't help with the cyano then I'll switch to a light source for the broodstock only tank and leave the nursery with no direct lights. (The photoperiod is important to get the PS to keep spawning).
....my next entry should be the announcment of the larvae (I hope).