Mystery larvae caught just after dark - what will these guys become?

[DaJMasta]

Title says most of it, I was checking to see if my cleaner shrimp had released larvae and instead found these things in the water column.  I think I missed most of the spawn, but I caught a dozen or so of them in a larval trap and transferred them into a magnet-on kreisel design I've been iterating on to try and raise larvae, and even with a closer look, I have no idea what these guys are.  The clearest view is around 30 seconds in.

They're slender and sort of pointed, ad the other end they have a pair of eye spots on either side of their head, but the whole body is slender and kinked.  They seem to be able to swim reasonably and prefer staying in the flow, near the boundary between light and dark (shadow from the edge of the kreisel), and while they mostly swim continuously, they sometimes bend their back and jump somewhat like a shrimp.  I see a few little bands on the body, but no fins or legs, and they orient themselves tail upwards.

Since I'm otherwise setup to catch and try to raise similar little guys, I dropped them in, fed a bit of apocyclops, and will see what happens... but do you have any idea what they are?  There are three pairs of things in the tank and I know it's not two of them - the last pair being mandarin dragonets and they certainly don't look like images of their larvae I've seen.  I've got two firefish and two hector's gobies, but I don't think either are a pair, and one of the hector's gobies and maybe a pygmy possum wrasse are new enough that it would be feasible for them to have been carrying eggs when I got them - but I don't think there's a match for either and I think the possum wrasse is still a juvenile.

Otherwise, I've got a slew of inverts, but the few I've looked up don't seem like likely candidates.

[DaJMasta]

Well they seem to have survived their first day, and they look basically the same.  I offered live phyto, apocyclops pods, and TDO A and I can't say I've observed any feeding behavior.  They still like to orient themselves vertically and seem to be fairly strong swimmers, and hovered around the surface of the water during the day somewhat preferentially, though they were deeper in as well.

I went to check for larvae in the tank again today because I was expecting a skunk cleaner shrimp spawn, and while I did collect that (and it's maybe 200-300!), the same guys had spawned earlier in the evening and were floating around already when I setup the larval trap... since they were collected in the same trap, I just poured today's spawn into yesterday's and now I've got dozens to a hundred of these little mysterious sticks and several hundred skunk cleaner shrimp larvae all in the same vessel!

 

They are fainter, but you can see some vertical lines with little segments here and they are more visible in person because they are much better at staying stationary in the flow.

[DaJMasta]

With so many, and remembering that I have a low power microscope, I caught one with a few skunk cleaner zoeae and took a look - looks like they're pre-settled juvenile mysid (opossum) shrimp.

 

 

Where as the yellow-dot skunk cleaners (about an hour old) swim around with their paddle arms and just sort of bump into things, the opossum shrimp larva (probably not settled yet, given the swimming pattern) seems more fully formed and capable of using its legs to stand in place.  Both the forward rostrum, the small tail, and the legs (a blur in this picture as it was taking off) weren't visible by eye in the kreisel, but those little markings and appearance of a shrimp segmentation seem to be explained with the faint yellow bands and it being a shrimp!

These are likely the offspring of some unknown shrimp I found earlier which have since colonized one of the larval rearing tanks:

 

[Critteraholic]

So cool! I hope they all make it for you!

[mcarroll]

Very cool.   Keep us in the loop as things progress!

[WV Reefer]

On 1/4/2022 at 12:09 AM, DaJMasta said:

With so many, and remembering that I have a low power microscope, I caught one with a few skunk cleaner zoeae and took a look - looks like they're pre-settled juvenile mysid (opossum) shrimp.

 

 

Where as the yellow-dot skunk cleaners (about an hour old) swim around with their paddle arms and just sort of bump into things, the opossum shrimp larva (probably not settled yet, given the swimming pattern) seems more fully formed and capable of using its legs to stand in place.  Both the forward rostrum, the small tail, and the legs (a blur in this picture as it was taking off) weren't visible by eye in the kreisel, but those little markings and appearance of a shrimp segmentation seem to be explained with the faint yellow bands and it being a shrimp!

These are likely the offspring of some unknown shrimp I found earlier which have since colonized one of the larval rearing tanks:

 

So cute! I love their little eyeballs. 

[DaJMasta]

I went to collect some more skunk cleaner larvae today and apparently I misjudged them and they probably won't spawn until tomorrow.  That said, I setup the larval trap because I saw a burst of something release and collected them.  They looked like a little dot on the end of a short straight hair.

 

Under the microscope, they're a tiny shrimp, fully enclosed in a sort of bubble on their top, with a huge unicorn like projection on their head.

And I would have asked for help IDing, but I knew some invert larvae had projections like this, and with a bit of googling, I definitely found a match:

https://baynature.org/article/miniature-marvels/13-367-110418_47594/

And my tank has maybe half a dozen porcelain crabs in it - apparently they are happy!

[aclman88]

Wow this is awesome!  Any ideas to the successful spawning of so many different inverts?

[mcarroll]

Very cool!!  Porcelain crab is relative of the lobster....one of my favorite reef critters.  🙂 🙂 

[DaJMasta]

2 hours ago, aclman88 said:

Wow this is awesome!  Any ideas to the successful spawning of so many different inverts?

My guess?  Overfeeding!

In my ~45g tank I feed a cube a day of frozen plus maybe half that volume in several different particulate foods and I dose live phytoplankton daily - about 300mL, though it's basically just pouring off that much from a culture, it's not as concentrated as some commercial options.