Anemone Crab Pairing

[ThRoewer]

I'm looking to confirm how to sex anemone crabs (Neopetrolisthes maculatus). It's been just too long ago that I had a pair and I don't remember anymore how male and female look on the underside.

With regular crabs like Emeralds it's easy - top male, bottom female


The folded tail on the male has been reduced to just a strip while the females covers the entire underside of the body.

But I vaguely remember that it was a less pronounced with porcelain crabs.

This is a picture I could take of the underside of my older crab. I would say it's a female but I'm not absolutely sure.


This specimen is of the small blue dot color form

The second crab I got from LA looks the same on the underside but is from another color form (uneven sized red dots)

An internet search didn't turn up anything either.

So I would be very thankful if anyone here who has or could take pictures that show the underside of his anemone crab would post them here.

[ThRoewer]

Nobody has pictures of the underside of their crabs?
What about pictures of molds?

[ThRoewer]

Got 3 new anemone crabs in from LA today, 2 large female (easy to tell because they had eggs) and one smaller male.
While in the drip-in container the male and one of the female paired up and got right on it to make more crabs

Here are the dirty pictures:









It appears they prefer the girl on top position

[Dkuhlmann]

Crab porn... Gotta love it!

Let us know when you've got babies for sale

[ThRoewer]

Female:





Male:





Right now, also due to the fact that the female carries eggs, I can't see a clear physiological difference besides the size. It is also a bit tough to examine them.
I will wait until both mold and examine the empty shells.

[Dkuhlmann]

I hate to say it but both of them appear to be female.

[ThRoewer]

No, for sure the smaller one is the male and the larger one the female.
I have a good idea what the difference is now, but it is much less pronounced than with true crabs.
I just got another one that should be a male to try it out.
As soon as I have it confirmed and better pictures I will post it here.

[ThRoewer]

OK, this is the other female I got last Thursday from LA:





Her eggs hatched during shipment so I know she is a female and right now she has no eggs.
The abdominal flap is clearly wider than the male's. Also it has a skirt of hair that is denser and longer than the males. Further it seems the abdominal flap of males is rather flat and held snug to the body while the females is held more loosely and forms a cavity for the eggs.
Finally the entire body of the female seems to be higher and more voluminous.

This is the male of the pair above:



Also I noticed that the females wouldn't fight with each other or attack other males. Males do.

This is the little guy I picked up Sunday:



I'm pretty sure it's a male.
I put him and the female above together but they wouldn't pair up and rather move away from each other. Though there was no aggression

In light of the findings above I think now that the first crab I got from LA is a male.
To see if he would pair up with the female I caught him and put him together with the female and the little male. He wouldn't pair up with the female but when getting close to the smaller male viciously attack him. I separated them quickly but the little one had already lost a leg.

All 3 have different dot pattern and I feel they may actually be different species as they do not mix and match. Even in pictures taken in the wild pairs always have the same type and color of dots.

I found this article but it only seems to compare the body size and size of the pinchers and finds that there is not much of a difference in anemone crabs.
Testing the role of male–male competition in the evolution of sexual dimorphism: a comparison between two species of porcelain crabs

[ThRoewer]

We have babies



The picture isn't great but you can see the extremely long antennae. The larva are quite big and pretty developed.
Let's see how far I can get them.

[Irishdolphin]

Reviving old thread...

@ThRoewer - how does this story end?

[ThRoewer]

Even with actual pairs I always ended up with just one crab. And that even with no anemonefish being present. I suspect that you need large anemones to keep pairs. If the anemone is too small one crab may kill off the other.

As for the larva: they are extremely difficult to raise, especially in small containers. To make matters worse the larva period of these crabs is quite long, so I would think it is unlikely these will be raised in captivity anytime soon, especially considering their rather low price point.

[ThRoewer]

I'm giving this another shot. I tossed two of the same kind together (I'm kind of sure that there are at the very least several local color forms, if not outright different species of these crabs) and hit the jackpot right away. This time I have them in a purple haddoni. I think carpet anemones are better suited for these guys.

[OrionN]

I got mine in multiple anemones and still end up with just one. These guys are aggressive toward each other. I wonder how they reproduce in the wild when they seem to kill each other the first chance they got.

[ThRoewer]

Originally Posted by OrionN

I got mine in multiple anemones and still end up with just one. These guys are aggressive toward each other. I wonder how they reproduce in the wild when they seem to kill each other the first chance they got.

In the wild they seem to get along quite okay.

And the pair I put together above is also still together, sitting peacefully side by side in the haddoni.

The key might be the size of the anemone.

[ThRoewer]

Looks like one of my haddoni ate one of my anemone crabs (the single small spot crab, not one of the large spot pair). I found it spitting out the shell and the crab is nowhere to be seen since...

The pair is still together in the purple haddoni, but the little black Darwin clown I exiled to that tank is constantly trying to chase them out.

[ThRoewer]

The pair is still together in the purple haddoni.

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[ThRoewer]

So that pair ultimately broke up - kind of literally as the smaller male ripped several legs and a claw from the larger female.

Fast forward: I got a much larger female with the same small spot pattern as the male and placed it into an uninhabited haddoni in the same tank. For a while everyone stayed in their anemones but a few weeks ago the male decided to go on a trip and hooked up with the new larger female. I don't know if size was the issue or the mismatch of spot pattern, but these two now sit almost always side by side.



Let's see if these two last...

I still have 5 more that need to be paired up...

[ThRoewer]

By now I have two pairs, one of them (the one from the previous post) spawning.


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[OrionN]

I tried several times in the past. They seem to pair, only after a time, months, one would disappeared. It is not as if I cannot keep them. I had singleton for years, 5+. seem really long for a such a small creature.
While I do have a Harlequin Tusk in the tank, Gigantea and Haddoni are petty powerful hosts that keep crab predator away. I can only think the reason they disappeared is being evicted by the resident crab, or else pick of by the other crab when they molt.


Keeping pairs or more in tank is "my mission" but I have stop trying. With your success, I think I will try again. The thing is they don't have these for sale here in Corpus. When ever I am out of town, I will try to get several.

[OrionN]

The time they kill each other is during molt, not normal every day.

[ThRoewer]

Originally Posted by OrionN

The time they kill each other is during molt, not normal every day.

I feel that the female should be larger than the male. Also the two pairs I have now are of the dense regular ordered small spot variety. So far I had not been successful with pairing the ones of the large irregular spot variety. Mixing the different pattern type individuals didn't work well either. So there might be a difference between those two general types after all.
The ones of the first pair have already molded at least once.
The second I bought at the same time but put each in a different anemone in the tank with my bicinctus. A day later they were both in the purple haddoni.

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[ThRoewer]

AC had another male and female of the dense spot variety, large ones this time. So I decided to try these in my haddoni tank where they have 4 Darwin clownfish to deal with. I hope that this will help them bond.

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[ThRoewer]

When I checked today the new pair was sitting side by side.

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[ThRoewer]

Originally Posted by OrionN

... The thing is they don't have these for sale here in Corpus. When ever I am out of town, I will try to get several.

I'm kinda out of empty anemones for these guys so if you want, next time I see a potential pair at AC I can let you know. I think that by now I got pretty good at sexing these guys as long as they are not too small. With adults like my last pair the differences are pretty clear.


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[OrionN]

Shipping from Ca to me is about 70.00. Hard to justify for a pair of crabs. A nice Gigantea, Magnifica or a pair of WC Percula. That is different.
I see if the Petco manager order me some.