Day 14, Attempt #2
Two weeks in, and can I just say that they are so freaking adorable? I can really see a lot more about the individuals when I have ten or so in a jar. Not that I'm happy about that low number, but it's better than zero.
Ironically, the container that I put the most zoeae in for my 48 hours away did the worst. And not because of the numbers, but because of the water flow. In my last attempt I lost the most in one day when I put them into the fish bowl and tried to let it cycle with sand and shells in the bottom. I assumed it was the substrate (and that was a big part of it), but that wasn't all it was because this time the fishbowl was completely clean at the bottom except for some fresh food added just before I left. I keep stubbornly thinking that the best container for water flow MUST be a sphere, right? What circulates better than a circular container? Well, a mason jar does. Twice now, I've taken that hard lesson, but this time I do believe it will stick, having finally gotten through my thick skull.
I had three airstones in the fish bowl, even, and the zoeae appeared to be circulating before I left. But there is apparently a "dead zone" at the bottom where the 1/4-inch foot of the jar is. Over time,I believe that one or two got caught there, suffocated, and then created a sort of "log jam" that then kept trapping others. There was a semicircle of dead bodies in the little rim of that ring (which is a HUGE rim to a larval hermit crab). My thinking made sense--three times the volume of water would stay fresher longer with only half the zoeae for the volume. But it didn't bear out. I think there was maybe one survivor in there out of two jars worth. Fortunately, at the last minute I had decided to leave about ten in a mason jar just as an experiment. Most of those survived, so if I had just left them all in the jars I would have had a much higher survival rate.
But it does appear as if I may have up to twenty survivors. There were a lot of motionless ones that really looked dead but I decided to do the same "crabby CPR" trick that I did with the eggs that were left on the sand. I sucked them up with the eyedropper, but then lifted it above the water line while it was still filling and that sucked a bunch of air into the eye dropper and that tosses the zoeae around with lots of air. It also gets off any gunk that might be sticking to them (which sometimes happens if they've gotten completely still at the bottom). They didn't all revive, but many did. So crazy! As you say, renroc, they are tougher than I think and they just keep on proving it.
The strange areas at the center of their bodies I am no longer worried about. I've figured out that it's the "feathery" ends of their legs and they hold them out wide to catch floating food, then clamp the food toward their bodies and eat it while swirling through the water. This is the origin of the "freaking adorable" comment. They really are smart and super visual. In fact, I've been thinking a lot about their eyes. With baby animals, you can usually tell what is the most important skill for them to have based on what is largest on them at birth. Human babies have giant heads for their big brains. Ungulates are born with long, sturdy legs and stand shortly after birth, etc. It's the idea that reproduction puts the most energy into what will be most important for that particular animal and hermit crabs are definitely all eyes from day one. Shoot--prior to day one! You see their eyes when they are still in the eggs. And when a zoea carcass starts to decompose, the last things to go are the eyes. It can be really hard to find them in detritus, but two little black specks close together are the first thing to look for. Sometimes it's only a head left, but most of the time it leads me to survivors. I gave myself a headache yesterday staring so hard trying to locate any survivors among the gunk.
Anyway, I'll keep them in two jars even though with only twenty I could easily use one, but it's a matter of spreading out the risk at this point--and I also enjoy being able to track individual swimmers a little better.
I also think there are sheds in the water today so we may be entering stage 4, although I hate to be too certain in my assessment since I was so off on my count last time around.
YAY BABIES!