unspecified

I’d given up on all the test tanks other than the one with sg 1.008.  Today, though, I found post-larvae living and growing in two other tanks — 1.016, and the one between (presumably about 1.012.)

This suggests that this species doesn’t migrate at all — it may be that they can happily live and reproduce in brackish water, start to finish.  I’ll try to maintain a population in a brackish tank at length and see if they are able to mature and lay eggs.

Maybe these are dyed (or otherwise altered) C. propinqua.  The behavior fits, and all the importers give ‘Indonesia’ as their place of origin.

For a couple of months I’ve been hoping that the offspring of the orange shrimp would color in as they reached maturity.  They’re about half-grown now, and they’re all still shades of brown and clear.

For comparison, here’s a photo taken of a parent under the same lighting conditions:

Possibilities I can think of are

1)  The orange color is a recessive trait, and even though the mother was orange, she coincidentally (and repeatedly) mated with a homozygous clear male.  That seems pretty unlikely.

2) The young need to grow up more before they’ll display the orange color.  Possible, but the largest of the new generation are approaching the smallest orange members of the older generation.

3) Color is the result of parasitic infection (a parasite that really, really wants to be eaten.)

4) Color is dietary.

5) Color is the result of some dying process done by the importers.

#4 and #5 (or a combination) seem the most likely, but that raises questions as well.  How could a bright coloration like that persist for months through repeated molting?

#3 I can try to test by raising the new generation in close quarters with the parents.  However, a “wants to be eaten” parasite surely requires one or more predators as part of its lifecycle, and that’s going to be pretty hard to simulate.

#2 Would be obvious in another few months.

#1 Is fairly easy to test, but will take a long long time,

A couple of days ago I collected a few hundred zoes from this ‘Christmas shrimp’:

I’m pretty sure that this is the same kind that was sold in Singapore as ‘ninja.’ It definitely does the ninja color-changing thing… the pictured shrimp has always been shades of grey and white until I moved it to take its picture, at which point it opted for shades of yellow. It’s anybody’s guess why the importers chose to call it ‘Christmas’ — I thought briefly they might be from Christmas Island, but apparently they were actually caught in Sulawesi.

Anyway, I’m just making a note here so I’ll remember when I collected the larvae on the offhand chance that they grow up. They’re extremely tiny.

Here is the high-tech equipment that I’m using to photograph my plankton. The center of attention is two microscope slides sealed together with a 3mm gap betwixt.

You wouldn’t think that depth of field would be an issue with a 3mm photo studio, but my auto-focus camera keeps grabbing the front slide, or the paper behind the slide, as areas of interest and yanking the subjects out of focus. Today I crammed some bits of moss in between the slides thinking that my newly-benthic photo model would want to perch on the moss. It didn’t, but the presence of the moss gave the camera something non-transparent to focus on in the right field of view… so, look for tiny green sprigs in my future shots. (That might also give some sense of scale which I’ve been missing heretofore.)

Thinking about teeny tiny photo shoots inspired me to run a google image search for “Flea Circus,” revealing the fact that there is a thriving flea-circus-equipment business in the UK which sells tiny stages, chariots, trapezes, etc. Look it up if you don’t believe me.

Yesterday the ‘Borneo orange’ zoes started metamorphosing into post-larvae. The visual change isn’t very dramatic, but their behavior is totally different. Rather than hovering in the water column occasionally puttering backwards, now they perch in one place and occasionally zoom forwards to a new perch.

Most likely this means that they’re ready to start a marathon swim upstream into fresh water. I moved the above photo subject into a cup of fresh water to see how it likes the change. With larvae that live in pure sea water (Yamato shrimp and others) I’ve been very careful to move them gradually through several stages of brackish before transferring them into pure fresh water. Since these guys live in water that’s already only barely salty, I’m hopeful that I can skip that tedious phase.

24-hour lighting may work after all.  The ‘borneo orange’ zoes in the tank second-from-the-left, specific gravity 1.008, are thriving.  That’s well below what I would have guessed, but a bit of googling suggests that that’s right in the middle of the salinity range for a river mouth, and a bit on the low end for a mangrove swamp.