Oita Salamander (<i>Hynobius dunni</i>)

[TJ]

I didn't raise any H. dunni last year but will do so this year after having received this nice egg sac from a friend who recently visited an area of Kyushu Island where this species is locally abundant.

(Message edited by TJ on March 13, 2005)

 

[TJ]

The size and shape of this particular sac:

(same as in pic above)

(Message edited by TJ on March 13, 2005)

 

[TJ]

My other H. dunni are now about 2 years old and around 8 cm in length, but still too young to breed:

 

[TJ]

Some embryos have died so it's a race against time for the others to develop before the egg sac becomes nonviable:

(Message edited by TJ on March 15, 2005)

 

[TJ]

Two hatchlings so far. Three-quarters of the embryos have developed without incident.

(notice the balancer below the head

)

(Message edited by TJ on March 27, 2005)

 

[jennifer]

Beautiful and amazing eggs. Tim, can you describe the hatching process? At a certain point, are the larvae moving freely within the egg sac? Do they swim out one end, or both?

 

[TJ]

Yeah, aren't they fantastic

The hatching process involves the egg sac, which is very firm at first, softening and disintegrating to the extent that an opening emerges (usually) on each end:

In the middle of the egg sacs, the membranes around each embryo also disintegrate so that the larvae are able to move more or less freely inside the sac (though there are obstacles, namely other larvae and dud eggs). They eventually find themselves at one of the ends of the sac and liberate themselves!

About 30 viable larvae hatched from this sac.

What are Taricha egg sacs like? Similar to this?

 

[TJ]

Here's one just seconds away from "hatching":

 

[jennifer]

It almost seems like you need two separate words to describe this process. First, they "hatch" to become free from the individual membrane, and then they "de-sac" to make their way out of the egg sac. Thanks for the pics, Tim!

 

[TJ]

Pleasure's all mine

 

[TJ]

It sure would be nice if they turn out like this particularly colorful one kept by a friend

(Message edited by TJ on March 23, 2005)

 

[TJ]

They're starting to look real nice -- plump too

(Message edited by TJ on March 26, 2005)

 

[TJ]

(Message edited by TJ on March 27, 2005)

 

[TJ]

(Message edited by TJ on May 15, 2005)

 

[TJ]

Balancer apparently absorbed, front legs formed:

 

[jeff]

What an interesting egg sac. I've honestly never seen anything like it. It looks about 12-13 cm long, is that correct? I don't know much about Hynobius species, guess I'll read up on them now. Thanks, Tim!

 

[TJ]

Hi Jeff,

Glad to see somebody show an interest in Hynobius

That egg sac (long since disintegrated) was a bit over 7 cm from side to side in its curled form, though I suppose if it were straightened out it might be 12-13 cm from end to end.

Yes, the egg sacs really are fascinating. It's especially interesting how each species has a unique type of egg sac. They differ in size, texture, consistency, shape and color.

There are two types of Hynobiids -- lotic, which generally lay their eggs under rocks in streams, and lentic, which favor ponds or slow-moving water for breeding and oviposition, and mostly lay their eggs on branches.

Hynobius dunni is a lentic-breeding species.

I'll post this again for your perusal:

(source: A Monograph of the Tailed Batrachians of Japan, by Ikio Sato, 1943)

B is H. tokyoensis
D is H. kimurae
E is H. lichenatus
F is H. nigrescens

I'll identify the others later{smile6}

(Message edited by TJ on March 29, 2005)

 

[jeff]

I'm guessing "A" is H. Dunni. Is that correct? Also, is "G" H. peasinapodus? Only kidding

!

 

[TJ]

Hahaha, nice try

Nah, A is H. nebulosus and G is Onychodactylus japonicus.

As for the others, C is H. tsuensis and H is H. sadoensis (which is no longer considered a separate species in its own right but rather synonymous with H. nigrescens.

I'm about to post pics of H. tsuensis egg sacs and larvae on another thread.

(Message edited by TJ on March 29, 2005)

 

[henk]

Well Tim, mine just laid this night... which is very late. I have at least 16 males active climbing on everything that goes up and aparently only 2 females... which is very odd. I think I will raise and keep most of the offpsring this year in order to compensate and fill the gaps with extra females later...