Monday, September 25, 2006

Development in the duckweed

Litoria peronii, Perons Treefrogs, amplexus
A few nights ago the Perons Treefrogs (Litoria peronii) in my garden spawned for the first time this season. Two years ago when they spawned I took a few photos of the developing eggs in their early stages, and a few minutes ago I took a few more shots of a later developmental stage. What the early shots in particular show is to me quite amazing.

So it all begins one warm night when a female decides on the man she wants and they embrace in amplexus. She deposits the eggs singly or in small clumps and he immediately fertilises them.
I check the pond at 7:45 in the morning and find this. The eggs are only at the 4-cell stage labelled Stage 4 (modified Gosner stage from Anstis 2002). That means there have only been two cell divisions. Now that is cool.

An hour later, 8:35, and another cell division has occurred. The eggs are now at stage 5 and consist of eight cells. You can clearly see the division between the animal (top) and vegetal (bottom) poles.

It's 9:20 now, and stage 6 (16 cell)

10:30 and the cells are getting smaller and smaller (stage 7-8ish)

The cells are scarcely distinguishable from each other at midday

The surface is now almost entirely smooth at 4:45 in the afternoon, after stage 9. Next stop, gastrulation! But I don't have photos of it. So there's a big gap between now and the next photo.

So this is the stage of the little guys in the tubs outside now as I type (stage 19ish). They're already capable of doing a bit of wriggling within the egg, and will hatch over the next few days. Interestingly, there's often what appears to be a bit of staggered development. So some of the embryos are more advanced than these ones, and will probably hatch sooner. Some stay in the capsules for ages.
Litoria peronii, Perons Treefrog eggs with developing embryos

Reference: Anstis, M. 2002. Tadpoles of South-eastern Australia: A guide with keys. Reed New Holland (Australia).


tapperboy said...

Astounding stuff David :)

Anonymous said...

Hmmm. You didn't give the time interval between the last two shots!

David Nelson said...

As I said, different set of years (the early photos are just under two years old, so that's the interval there (-:)

Can't really say how long the gap takes. My guess is about 24-48 hours.

Snail said...

Bonza! I'm looking forward to the next sequence.

Vandalhooch said...

David, would it be OK if I used your photos in lesson for my biology classes (high school)? I'm a public school teacher.

I think the photos are amazing and the kids would really get a kick out of seeing them.

David Nelson said...

No worries Vandalhooch, hope the kids are as amazed to see the process as I was.

sarala said...

Wow. Great photos. A classic.