Lysmata wurdemanni

Peppermint shrimp with eggs

After several failed attempts, I’ve just now succeeded in raising my first peppermint shrimp from egg to post-larva. I took a bunch of photos and videos, and they’re all terrible.

This species has a reputation for being fairly easy to raise, although googling turns up more tales of failure than success. The process I’m using now is dead simple, and I’ve met with success on my first try with these particular parents, so I suspect that the variation in success with captive rearing is a result of a bunch of different species being imported with the same ‘peppermint shrimp’ label. Are my shrimp really L. wurdemanni? I’ll probably never know.

I started out with a paltry number of larva — around a dozen. I have an air-powered plankton collector in the tank with the adults, but also a protein skimmer which I’m sure is snagging most of the hatchlings. I moved half the larva into a 1-liter box with blacked out sides (as per googled suggestions). Those didn’t last long. The other half went into an extremely low-tech, improvised kreisel:

planktonbowl - 1

That’s a 2-gallon drum bowl with a bit of bubbling airline in the corner. This worked surprisingly well — shrimp larvae and their brine shrimp food remained suspended in the water column at all times, unlike the larvae in the smaller box who tended to bump around on the bottom.

Here are close-ups of newly-hatched Lysmata, along with a high-speed video of their weird bendy pleopods:

L_wurdmanni_larva - 2

L_wurdmanni_larva - 1

After five days, not much had changed.

A week later, they had changed shape completely. I mistook the longer legs for pincers, but closer inspection shows that they’re back legs rather than forelegs — it seems like they’re used for stability when floating rather than for hunting.

larva_11_days - 1

At day 25, the larvae are much bigger, but the body form remains much the same. It’s hard to tell scale from the photos, but they’re in the neighborhood of 10-15mm at this point. They have the same constantly-waving pleopods that they had on day one; the front four pairs of legs look like legs, and the back pair are still those crazy, giant oar-like shapes.

larva_21_days - 1

Finally on day 30, one of the larvae changed in a flash into a shrimp. The crazy oars are gone, the pleopods are tucked under the body, and it’s almost entirely adult-shaped. Rather than drifting aimlessly in the bowl, it’s sitting on the back or the sides, occasionally zooming with purpose to a new roost.

For scale, this photo includes a US quarter dollar. The video is completely boring, since now the shrimp is capable of resting.

L_wurdmanni_postlarva - 1

I still have six more late-stage larvae floating in the bowl. Their sizes vary quite a bit; I’ve no idea how they decide when to metamorphose and settle.

Care is pretty simple. I feed the larvae newly-hatched artemia onec per day, and leave the brine shrimp to swim amongst the Lysmata for as long as it takes to be eaten. Every three days or so I also feed 3-day-old SELCO-enriched artemia. I’ve no idea if the SELCO is essential or not — it’s certainly a lot more trouble. At no point did I attempt to feed larger or different foods.

Every few days I scooped 1/4 of the water out of the bowl and exchanged it with water in the 40-gallon tank that houses the adults. I didn’t attempt to vaccuum the bottom of the bowl — some debris accumulated but it doesn’t seem to do any harm. A light shining on the bottom of the bowl keeps the larvae down low to reduce the chances of them getting scooped out during water changes.

There’s no direct light over the bowl. Other reports complain of larva getting trapped in biofilm along the edges of the container; I didn’t see anything like this, possibly because there wasn’t enough light for biofilm or possibly because the circular current prevented larvae from resting on the glass.

None of the regimen was very compulsive. I missed days of feeding here and there, and two or three times a breaker tripped and the bowl was without aeration for half a day at a time.

The one post-larva is now inhabiting a much-too-big net breeder in the parent’s tank. I’m hoping to keep the young adults separate from one another to avoid cannibalism during molting… we will see how many more I get, and if raising them after metamorphosis is harder than rearing them before.

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UPDATE, 2015-09-05: Now six of the seven larvae have settled. All the tiny shrimp are in a long row of tiny net breeders, and all are still alive.

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