Yellow banded possum wrasse breeding attempts

[DaJMasta]

I've had a pair of yellow banded possum wrasses (Wetmorella nigropinnata) for a bit now, and they've shown regular courtship behaviors for more than a year. Last year (April 2023) I collected some eggs and tried to raise them, but had very little success and even less information. I had prolarvae hatch, but never start to eat, and I had thought hatching out required circulation or several days (at least according to my notes). The pair continued their normal behaviors, but I think moved to earlier in the evening, and between it being tough to notice, coinciding with evening feeding sometimes, and maybe because they actually stopped - I didn't see spawning or collect larvae for more than a year.

Until last night, when I got a couple dozen after hearing them splash at the top of the tank at about 8:30 pm and turning off the pumps to collect the larvae. 21 hours later, I have prolarvae, and even got them under the microscope. The eggs are clear and are in the ballpark of 0.5mm across (very hard to spot, even when collected), and the prolarvae are as long as about 2mm, with an elongated tadpole shape, a faint white appearance to the eye (totally clear under the microscope), and have a visible bubble (makes them buoyant as an egg, probably will go away soon.)

I don't have high expectations with what feels like a first attempt on an extremely fragile larvae, but I'll see what I can do. I have a few kinds of copepods in culture and regular artemia nauplii, and I plan on starting to feed them once I see some mouth/gut development under the microscope. If I can get a timeline for prolarvae development out of this run, it will be a success.

With the tiny amount of information, is there anyone with any experience or research available raising these animals? Whether for these wrasses or other Wetmorella genus wrasses, I'd expect they would be pretty close. I've got some experience with shrimp and invert rearing, but am basically going in blind in terms of timeline and expectation.

The eggs under a microscope

The newly hatched prolarva

 

[Dread Pirate Dave]

This is pretty cool. I hope you have some success!

Are these wrasses being aquacultured anywhere?

 

[DaJMasta]

Not as far as I know, there seems to be very little information on it, so I would assume that means they aren't, but the availability of them tends to be low, too. You can find them for sale, but not everywhere and not always in stock.

For development, last night at about 29 hours post spawn they looked like this:

Pretty similar, but a bit more contour and definition to them, and behaviorally, still right at the top of the water, but somewhat more coordinated movement (still basically random/in response to movement.)

This is 38 hours post spawn and there's less of a tadpole shape. I haven't really been able to see their eyes yet, but they are definitely responsive to light, now, and while the movement is largely random, they are better able to swim in a direction and seem to conserve their energy a bit more (long periods with little movement). They're also staying a few millimeters under the surface rather than right at it.

For both, they were more visible by eye and had the slightest red patches of color on their skin under the microscope.

 

[DaJMasta]

Whelp, aremia nauplii are not going to be an option for the early larvae:

52 hours post spawn, not sure if able to eat but the yolk sack is almost gone, so I'll be feeding sieved copepods now.

 

[DaJMasta]

This morning, I may have fewer, but I know I have some, and I know they're trying to eat. I fed 58-150um sieved copepods last night shortly after the post, and underestimated the one in the cup, so I probably fed too high a prey density, but they seem to have continued to descend in the water column, so they're just harder to see than before. I know there are at least two, I've seen them try to eat the copepods under the microscope, but also don't see a belly on the little guys.


I think I will try 45-125 or 58-125 micron sieves for later feedings because the larger copepods getting through the 150 screen definitely still appear to be too large. I think it's a copepod nauplii and little larger sort of situation.

 

[DaJMasta]

Unfortunately, this run is over. I had a couple yesterday evening, but by the time midnight rolled around, I haven't seen any since. Under the microscope at around 73 hours, they are further along in development but are alarmingly slender - there could be something in its belly (a little less than 2 head lengths in), but its only one and all the strikes I watched weren't successful. At this point, the eyes are pretty well defined and have the red color they will have as an adult - I think I can see them move slightly, but for the most part they are just looking sideways (adults can pivot both to look forward), and they still have those couple of dark marks they got as a prolarva.

To get a sense of scale, the red specks in this image are phytoplankton swimming around - the microscope being used is just a couple millimeters above the tiny 5mL beaker they are in, and it's close to as far in as it can focus.

So where to go from here? First, collect more eggs. I think they spawned last night but I got home too late to see it (there was a splash of water on the net lid.) Then I will do similar microscope checks, aiming to feed a little later (an hour or two) if possible, because bumping into things also makes them react (waste energy) and I don't think they could eat when I first fed them last time. I'll aim for hour 53-54 after spawn, though I may try at hour 50 or so to give one under the microscope some and see if it tries to strike. The feeding will be smaller - no artemia (a few were still swimming around from the single drop I tried early on for size) initially, and probably 45-120 micron sieved, though maybe I'll just go down to 100 micron maximum size. Like this batch, they'll stay in the collection basket (about a 100mm cube) so I can monitor them, catch them, and keep prey density pretty high. I think the smaller mesh size will mean the density looks a lot less even when there are more swimming around, and they seem to be happy enough to strike a few times a minute.

 

[Paul B]

This is extremly cool and I am interested. I think mine have been spawning for a couple of years but my reef is way to old and big to try to collect any fry but I would like to hear how you make out.
Very nice.
Good Luck
I think one of mine is over 8 years old, maybe 10. I don't remember exactly when I got him.

 

[DaJMasta]

Wow I didn't realize they lived so long, I've only had the two of them for maybe two years. My favorite pic of them by far was their introduction - they did not start off on the right fin....

 

[F i s h y]

Ill be following along to watch your progress. I just recently raised my first batch of Percula clowns successfully. It had been nearly 2 decades since I had raised any fish, before that it was maroon clowns. I have a breeding pair of Fridmani Psuedochromis and a pair of Springeri Damsels that breed consistently for me that i want to try to raise.

One question I have up front for you, where do you get the material for your sieves and how to do you make them. I have a pvc one that i got from an online retailer when i bought my starter cultures and its simply to small for me to use. It takes forever to portion out what i need.

 

[DaJMasta]

For my sieves, I buy inexpensive measuring cups, cut a window in the side with a dremel tool, sand around the edge of the hole (for better glue adhesion), cut a piece of mesh to cover the window, glue in place with aquarium silicone, and then come back for another small bead on the inside when the first is dry. They've been pretty durable and I've amassed a good variety. Don't forget to inscribe the mesh size on the handle to keep track.

As for sourcing the mesh, it's been mostly ebay for me. You can get nylon or polyester screen from some fabric suppliers but also by just cutting up filter socks of appropriate size. You don't get every choice of size without paying a premium, but you can cover a pretty broad range with what's otherwise random scraps.

 

[F i s h y]

For my sieves, I buy inexpensive measuring cups, cut a window in the side with a dremel tool, sand around the edge of the hole (for better glue adhesion), cut a piece of mesh to cover the window, glue in place with aquarium silicone, and then come back for another small bead on the inside when the first is dry. They've been pretty durable and I've amassed a good variety. Don't forget to inscribe the mesh size on the handle to keep track.

As for sourcing the mesh, it's been mostly ebay for me. You can get nylon or polyester screen from some fabric suppliers but also by just cutting up filter socks of appropriate size. You don't get every choice of size without paying a premium, but you can cover a pretty broad range with what's otherwise random scraps.

Perfect thank you!

 

[Paul B]

Wow I didn't realize they lived so long, I've only had the two of them for maybe two years.

I know I have one of them from my last house and I lived here for 6 years. I think I had him a few years in my last house.

This is one of mine when he was young.



And this is one of them now.

 

[DaJMasta]

I got some more eggs! Seems like the spawning cadence is basically every other day. Since there's so little documentation of the whole process, I'll document a bit of it from my observations.

Spawning happens around when other wrasses are most active, in the evening but with some "sun" still shining and before shrimp/mandarins spawn. The pair will leave the rockwork and swim around, and if the pumps are off, they'll go to the far corners and all the way to the top regularly, while they would rarely do so at other times. I am presuming the sex of my fish, but I believe the larger of my pair is the male. Assuming that, courtship is the male chasing the female, periodically swimming up to her and showing her his side (sort of turns 30-45 degrees and slows down a little). I see her flashing her pectoral fins sometimes, but I know they communicate this way for other things too, I don't know if it's part of it. The male is usually slightly lighter than his normal color, specifically between the two yellow bands.

This behavior usually goes on for a bit - 15 to 20 minutes - and a good portion of it includes brief, fast swims horizontally or to the top of the tank. One of these fast swims eventually ends with a swish of the fins, they spawn in the moment, and then immediately swim back to the rockwork.

After this, sometimes they are seen out again, but usually it's only the male, who will prowl around the tank for half an hour or more in some cases - this may suggest they are harem spawners rather than monogamous, though I don't know whether they'd get along in a larger group than a pair.

Now I want to emphasize how small the eggs are. I can write about the spawn in detail because I watched it happen tonight, with the pumps off, and within a minute collected the water where they spawned in a strainer to set up my egg collector. I could not see any eggs in that first strainer full of water at the time, though as it ran and the lights got darker, I was able to spot some. They are completely transparent, can only be seen against a dark background with side lighting which refracts off the shape of it. Can you see the one here?

There's actually two in the picture, but the only way I could get a decent picture was to add enough water to make a meniscus over the top of the spoon, and then side light it. The egg in the picture is on the right, about half way up, and pretty close to the edge. This is a quarter tablespoon measure.

Under the digital microscope, I got a decent image of it as it floated by, but also then got a ruler in frame, and I can say the egg is right about 0.6mm across.

I know I have several eggs, but I got enough other gunk from the top of the water (it collects a bit when the overflow isn't running) that I really can't say if it's a dozen or several dozen. I think I'm going to bust out the real microscope this time for looking at the larvae - should give me a better idea if they've been eating and they seem to sit still long enough that it should be something I can focus on. I'll also see if I can feed one under it and see if I can see a strike too.

 

[DaJMasta]

It'll be a few days before anything substantial, and it is quite tricky getting one in focus on the big-boy microscope when also trying to let them stay alive and free swimming (even a few drops of water in a well is difficult to find focus, and the tall well slides I have are interfering with other objectives...), but I have a little to report:

Incubation time for the eggs is shorter than I expected, from an 8:30 pm spawn, they were already hatched by 3 pm the next day - so may be 18 hours or less. I've got maybe 3-4 dozen from the last collection, and they look like this in person:

And the parents spawned again this evening, I think I collected another few dozen eggs.

 

[F i s h y]

It'll be a few days before anything substantial, and it is quite tricky getting one in focus on the big-boy microscope when also trying to let them stay alive and free swimming (even a few drops of water in a well is difficult to find focus, and the tall well slides I have are interfering with other objectives...), but I have a little to report:

Incubation time for the eggs is shorter than I expected, from an 8:30 pm spawn, they were already hatched by 3 pm the next day - so may be 18 hours or less. I've got maybe 3-4 dozen from the last collection, and they look like this in person:

And the parents spawned again this evening, I think I collected another few dozen eggs.

Love this! Please keep up with the updates.

 

[Tamberav]

Following! Very cool!

 

[Paul B]

I am also following this although my breeding days are over. My copperband laid an egg but it's bigger.

 

[strich]

Another great project! It's a shame there isn't much literature on this breed. Makes it more rewarding to make progress though!

Unlike the inverts that spawn larvae that are attracted to light it would seem almost impossible to automate rearing these invisible eggs in a home aquarium right?

 

[DaJMasta]

Another great project! It's a shame there isn't much literature on this breed. Makes it more rewarding to make progress though!

Unlike the inverts that spawn larvae that are attracted to light it would seem almost impossible to automate rearing these invisible eggs in a home aquarium right?

I've thought for a while now that the next tank I make would have an overflow with a big overflow box, so that I could set in a mesh basket (solid bottom with small lip to retain some water). The basket may even need to be pleated to maximize surface area (and minimize crushing suction force against the mesh), but a lower return pump setting in the evening would probably help. The eggs are still slightly buoyant, so if they don't get eaten, something like that could automate spawn collection.

Of course, that still means you need to move them to other vessels to raise them, but that was sort of a given.


After the possum wrasse spawn last night, my mandarins spawned too. Here's the egg size difference:

 

[jkcoral]

This is really, really cool. And as a longtime lover of the possum wrasses, I am excited to see someone make as much progress as you have.

I bet some of the labs working on captive breeding efforts would be interested in seeing your work so far.