ID Crab, Geosersarma nemesis

[joydiv]

Hi

Anyone can confirm id?

This is a really hardy crab, good for beginner.

[hwchoy]

they are selling this in LFS? its endangered I believe.

[Frogfrog]

Don't look like nemesis to me. Where are they from?

[BEASTIEPENDENT]

Hmmm, would need more detailed pics to identify.

For a first view You can take a look here: http://johorasingaporensis.blogspot....arch?q=nemesis – there are most pictures of G. nemesis You will find on the internet.

I think I have an ID key for this species but as I said I would need more detailed photos…

ATTENTION: IF it is G. nemesis – they can drown! So do supply just a very shallow water dish!

[hwchoy]

yes this is what G. nemesis should look like:

[joydiv]

From the picture I dont think its geosersarma nemesis then, perhaps another species. It also gives birth to live babies as I have seen the babies in the Supplier's tank.

Any other geosesarma species that appear brownish? This crab is found on Java island.

[hwchoy]

do note my G. nemesis come from an official collection. they are protected throughout Singapore (as are most wild animals) so do not go out and catch them.

[BEASTIEPENDENT]

Any other geosesarma species that appear brownish? This crab is found on Java island.

I'll take a look, but Friday ('til then I have to work )… But brownish-reddish species exist, sure. For example G. perracae, but there are more.

[joydiv]

Ok thanks beastie. will wait for your reply.

This crab is really hardy. Good for beginner althought the colour might not be as attractive.

[BEASTIEPENDENT]

Hi there

Since I was lucky and work was done much faster than usual I' home earlier than expcted and can give at least a short answer.

First: All Geosesarma are more or less terrestrial crabs. That means You keep 'em in a terrarium with a small (water dish) or bigger real water part.

Second: There are some species from which a similar coloration is known as Yours, for example G. foxi, perracae, penangense, cataracta, nemesis or malayanum. Coloration for many species is unknown. In general there are many of the now accepted 50 Geosesarma (plus at least two yet undescribed) species where there isn't known anything (!) more than their original description.

Third: On Java the species G. noduliferum and rouxi are known – so if You are sure they really are from Java without doubt it would help a lot by IDing Your species.

@kwchoi: Do You know who ID'd the G. nemesis on Your photos? Was it eventually P. K. L. Ng himself or is it just a wild guess from a pet keeper like us? Would be really interesting for me.

G. nemesis and perracae are at least in Singapore endangered species – so You're probably right that collecting and exporting them without a special permittance form the conservation authority of Singapore isn't allowed.

[hwchoy]

@kwchoi: Do You know who ID'd the G. nemesis on Your photos? Was it eventually P. K. L. Ng himself or is it just a wild guess from a pet keeper like us? Would be really interesting for me.

G. nemesis and perracae are at least in Singapore endangered species – so You're probably right that collecting and exporting them without a special permittance form the conservation authority of Singapore isn't allowed.

specimen passed to me by RMBR themselves (Raffles Museum of Biodiversity Research) so yes the ID is confirmed, as good as Prof PKL himself

in fact the curator himself visits this forum so if you have anything to discuss I can make sure they look at it

[BEASTIEPENDENT]

Hi hwchoy,

specimen passed to me by RMBR themselves (Raffles Museum of Biodiversity Research) so yes the ID is confirmed, as good as Prof PKL himself

Thx a lot, so the pictures are useable for ID'ing – photos sometimes give a better (or at least an additional) impression than just the scientifical description, especially for laymen. Yes, RMBR is well known of course

[hwchoy]

yes the photo is useful to show live coloration. in recent years some description papers have start to include colour photos of specimens and type locality.

[joydiv]

The specimen is from Java, Bogor Region, around 2 hours drive from jakarta. Is G nemesis found on the island of Java as well or endemic to Singapore?

The crabs I got was rejected by supplier for export to overseas market due to its drab colouration.

By the way, which part of the crab will be best for iding the species?

Thanks alot Beastie, really helpful. There are so many species here, hopefully I can know what they all are, trade names are fanciful and useless.

[hwchoy]

from what I understand G. nemesis ranges in Singapore and southern Malay peninsula.

[Frogfrog]

So far, G. nemesis is only found in the Singapore and Southern Peninsular Malaysia. So the ones that you have are unlikely to be them.

The gonopods of the male crabs are used to Id them. However, this also means you have to kill them before you can Id them properly.

I don't know anything about the freshwater crabs in Java. So cannot Id for you. They could be G. noduliferum and rouxi as BEASTIEPENDENT mentioned.
Though unlikely, it is also possible that this is a new species of Geosersarma

[BEASTIEPENDENT]

Hi there

The specimen is from Java, Bogor Region, around 2 hours drive from jakarta. Is G nemesis found on the island of Java as well or endemic to Singapore?

Okay, so up to 1995 there were just two known Geosesarma species on Java: G. noduliferum and rouxi. Then Ng and Davie found another one: G. bicolor but that does not fit: "In the holotype male and larger female, the anterior one-third of the carapace is bright purple, the posterior two-thirds being bluish-grey. In the smaller paratypes, the anterior one-third is also clearly defined, but the purple color is paler. The corneas of all four specimens are bright yellow." So we can exclude this species).

G. noduliferum was found 1930 in Colocasia leaf axils.

That is everything (!) I can find about these species – so I can't help further by identification. You only could send specimen or exuviae to Prof. Ng and ask him to identify them.