Hynobius retardatus (Ezo Salamander)

[Tim Johnson]

Engaged in Hynobiid swap the other day and brought home this single H.retardus larvae, which hails from Japan's northernmost main island of Hokkaido:



Adult, juvie, larvae, egg and habitat pics can be seen at the following site:

http://www.rieo.net/amph/saramand/sansyouo/ezosan.htm

Hai Tim,
I have just counted my H. retardatus larvae and it seems I was able to raise 105 large larvae. most of them look a bit darker then yours, more black mottling... Will try to make some images monday on this.
Also one of the larvae is extremally white with a very very dark black tail. I know they can be lighter sometimes (especially at night during stratification) but this one is just snowwhite ... and that's odd.

[Tim Johnson]

Hi Henk, congrats on your success. That's a lot of larvae! I'm looking forward to seeing the pics. Maybe you can start a snow-white strain!

As for retardatus, I wish I had some basis for comparison but I have only that one larvae. There were a couple more in the shop, but they were all similar. I'll try to post a pic that's a bit clearer/brighter than those above.

Also on the Hynobius front, I just sent away 20+ Hynobius nebulosus morphs to a local enthusiast by special refrigerated (not frozen!) delivery service. That's lightened my load a bit, but nobody here seems to want my H.tokyoensis morphs (too common?). I wouldn't mind keeping 6 or so but not 30+! Also managed to unload around 10 of my 20 or so H.dunni larvae, the interesting thing about them being that they are still haven't morphed since hatching over 6 weeks ago and are twice as large as my nebulosus and tokoyoensis morphs.

On the downside, I lost one of my precious 3 new Onychodactylus japonicus larvae to a power-failure-related temperature rise last week. I've decided to move them into the vegetable compartment of my fridge (IF my girlfriend consents...) rather than maintaining my current setup, which involves cooling the living room (i.e. newt room) to around 20C and then lowering the tank temp to 18C using a fan directed at the water surface. I've been using an overflow filter with them as I'd heard they require a current, but I now hear that's not necessarily the case if the temp is cool enough. Same goes for kimurae and other such Hynobiids that don't inhabit still water, or so I hear.

Do you use any filtration or apply any kind of water current with your fridge-cooled sal larvae?

Cheers!

Well Tim this might come as a shock but I do not cool off anything. What I do have are stones that ar partially placed in the water and as such suck up the water and evaporate it. On top of those stones you will find moss and plants, in fact those plants are sucking up the water through the stones and with the evaporation this
helps to cool off.

Offcourse this is not enough for Onychodacvtylus and I did loose two of them I had (unfortunatelly because they are sooo beautifull). But for all my other Hynobius I only use this tric and this works out well. This year I 'm busy trying out something new as well.

Well for H. tokyoensis I have about 34 large larvae now. I hope they do well since this is, so far, the most difficult Hynobius to keep. they are quite fragile compared to the others. Streamside Hynobius are on the other hand not always that difficult to keep. My H. okiensis do prefectly in such a setup. The H. chinensis go in the water about every night searcihng for food. They are georgeous....
Still need to shoot the larvae, since yesterday we went out on a family trip. Haven't counted the dunni larvae... would be too much of work.

I hope one day to find some extra strains of H. species. As to today I have not been able to succesfully breed H. leechenatus (got only 3 of them, among which certainly 1 male). But so far this is the sole 'resisting species'.... and breeding the Hynobius chinensis would be ok.

Do I understand you well, can you actually buy larvae or eggs on the pet trade shops ??

[Tim Johnson]

Henk, yes, quite a few pet shops here sell eggs and larvae during the spring, along with adults. When I purchase something, I often ask them to throw in a few larvae and/or eggs of other species for free. Today I brought home another 2 retardus larvae for comparison, though one seems a bit weak and might not make it.

As promised, here are a couple clearer pics of the same one larvae shown above, taken today.

[Tim Johnson]

Indeed, the two new ones are both darker than the one above, though at an earlier stage of development and they may become lighter as time goes on.

[Tim Johnson]

And finally, here are a couple of comparative pics (the originally acquired one is on the left and one of the newly acquired ones is on the right in both)




By the way, these are probably the last Hynobius larvae to appear in the shops this season (considering that Hokkaido is in the far north where it's still cool).

As for breeding them, well, I'll leave that to you! So far I've only ever raised larvae. Hopefully, some years in the future, I'll be at that level...with ample doses of effort, advice and luck!

I had never heard before that H. tokyoensis are the most difficult Hynobius to keep. Uh oh...
But what you said about streamside Hynobius being not always that difficult is new to me and comforting. I'd supposed the opposite. Good news!

[Tim Johnson]

Here's a new pic of the original larvae (I've since the last pics parted ways with the other 2):

Hai Tim,
it'(s about time to make up a balance of a breeding season and for what concern H. retardatus I have done good. Lots of juveniles are raised and doing well for now, despiute very hot weather out here.

Among my larvae I had seen an odd one and set it aisde : the larvae has a normal eye, white body and entirely black tail fins (untransparant), the mid of the tail is white. I first though it would turn normal, but now that all the other animals are on land, this larvae remains larvae and it starts to look as a neotenic form (with tailfins and very red large gills). I know there are some neotenic strains in H. retardatus (in lake Kuttarush I thought) but these are not white so I think this form remains neotenic due ot partial flavism (like I had the case with an adult S. terrestris). Anyway the larvae currently is about 8-9 cm.... and looking wellfed.

[Tim Johnson]

What's become of this odd larvae Henk? Has it morphed yet? I'll have to try and get around to posting a pic soon of my single H.retardatus juvenile, which long since morphed and is being kept together with my H.dunni considering its relatively large size.


(Message edited by TJ on September 26, 2003)

Well it has a golden color for now and tends to grow as a neotenic animal, with black tail and red gills... about 9 to 10 cm by now.

[Tim Johnson]

Wow...look forward to seeing a pic of that! Anyway, as promised, here is my retardatus:

[Tim Johnson]

Got a few more larvae the other day. They're slightly darker than the ones I've raised before.

[Tim Johnson]

[Tim Johnson]

This one has particularly attractive coloration:

[Tim Johnson]

Here's an interesting graph from a Japanese book showing how the Ezo salamander breeds/mates. The light-colored one is the female and all the rest are males, which scramble to fertilize the egg sac as she deposits it on a branch. The last one remaining in the pic is the most successful male, which monopolizes the sac for 8-10 minutes before parting.



Source: The Encyclopaedia of Animals in Japan
Heibonsha Ltd., 1997

today I discovered both 2 males and one female in the water. Since I didn't have enough branches/twigs I had not yet entered some in this setup, but hurried now toi install some. After an extra hour I discovered 2 males close to eachother on the twig like mentioned on image 1.
I have also setout my second H.retardatus breeding group. This form colors up quite heavyly in breeding and develop that brassy coloration again they have when they were juveniles... Beautifull animals...

[Tim Johnson]

Good luck with them Henk! It'll be a while before mine are of breeding age...

Well Tim I really should be taking precise records, but I think that it takes about 3 years for H; retardatus and H. dunni to breed. now it is evening and I discovered 2 males around the twig (at the bottom) and 1 heavylyl loaded female on the branch... so big suspense ... The female is really very very heavy...

WEll I should better play on the lotery. The animals effectively reproduced tonight. Watertemperature in the neighbouring tank was 6°C. The eggs were deposited on the spot where I saw the female crawling and as always, just underneath the water