dimarts, 29 de juliol de 2014

Seventh and last week of incubation

Sunday morning

Curiously, when I touched one egg to take pictures, the more external layer of the shell fell off

On Monday, one of the eggs hatched. 51 days of incubation.

Today, on Tuesday, the other two are hatching. 52 days of incubation

dimarts, 22 de juliol de 2014

dijous, 10 de juliol de 2014

More about dented eggs

Casually, today I have seen a Trachemys scripta elegans with egg retention. It is kept in a place without soil and it can't lay the eggs. They have been removed using oxytocine.
There is no male, so, they are infertile.

They were nine, three were crushed once layed.

Some of the eggs are dented. Trachemys scripta lay soft shelled eggs.

The two next pictures are from the same egg. Originally the dent was on the right pole of the egg. If some pressure is applied with the finger on the left pole, the internal pressure in the right pole increases and  the dent dissappears . A new dent has appeared on the left pole,  the one that received the external pressure.

Dent on the right

If pressure is applied on the left side, the dent on the right side dissappears and a new one appears on the left side.  

When the egg is being layed, one of the poles is out but the other is still in the cloaca.  The half that is in the cloaca is under the external pressure caused by the musculature that tries to push it out. The half that is out of the body is under the internal pressure caused by the content of the egg that is being squeezed in the pole that still is in. When the egg is out, the pole that received the external pressure in the last moment, the last to come out, presents a dent.
If you apply pressure in one of the poles of the Trachemys eggs with all the fingers of a hand, trying to copy the pressure that the cloaca makes when it is pushing the egg out, the dent jumps from one pole to another depending on which pole is submited to pressure. It is quite funny.
I don't know why only one of the Clemmys eggs was dented. Is it possible that the shell of that egg was slightly thinner than the others making it more deformable? Or that for some reason this egg had less internal pressure than the others making it more responsive to pressure?

dimarts, 8 de juliol de 2014

Two days after releasing the eggs, she makes a nest

Two days ago the turtle released four eggs after more than 12 hour trying to dig a nest .
Yesterday, it rained all day and temperatures were around 14ºC. The turtles were inactive.
Today it was summer again, with a sunny day and an evening temperature of 24ºC. Today the turtle made a nest. She begun at 18:00 and it was finished at 22:00.

This time she has chosen a sandy area and she has done it very quickly,  4 hours. Sometimes, before they lay the eggs,  they make trial nests but then they don't bother to cover them. This time it was a proper nest, covered carefully.

Just in case I was mistaken when I palpated her, I opened the nest chamber. It was empty.

Two days ago the Cemmys didn't make  a proper nest. She didn't lay the eggs and carefully put them into the nest chamber, pressing them with the legs and finally covering the nest again. She just expelled the eggs and went away. It looks as though somehow in her brain she was not conscious of having layed the eggs and she still had the urge to make a nest and lay the unnexistant eggs.
Last year I injected oxytocine to a friend's Terrapene. He had them in pine cork substrate and I think it didn't let them build a proper nest. They carried the eggs for several weeks and were making trial nests day after day. So they were injected oxytocine and they layed the eggs. But then it happened something similar to today's performance: they still kept digging nests although they didn't carry eggs. The only difference is that they didn't cover those nests.

dilluns, 7 de juliol de 2014

Fourth week of incubation and second clutch

The egg seen from above

The same egg from side to side

Another egg seen from above

 The same egg from side to side

There has been a problem. I have to add water from time to time to the incubator. When I do it I switch off the heater. Last thursday I forgott to switch it on when I finished. This morning when I opened it the temperature was 20ºC instead of 30ºC but I don't think it affects the embryos. Two years ago I incubated one egg outdoors and it reached 12ºC and almost every night it reached the 20ºC.

 This summer is strange. Since the beginning of June we have afternoon thunderstoms every other day and temperatures are lower than usual, especially nocturnal ones. Today it is nearly a month since the Clemmys layed the first clutch. I palpated the eggs some weeks ago, but the female retained them until yesterday when we had a warmer day.

The female always nests in the same places, one in the west side of the pond, the other in the east side. She always changes from one to another among two consecutive clutches. It seems she somehow remembers where she layed the fisrt clutch and decides  to lay the second one in a distant place. Maybe it is a way to lower the chances of nest predation, or a way to avoid digging out the eggs of the first clucth laying the second one. It might also be a way to increase the chances of nest survival because of different microclimates in different places, which could also affect the sex of the hatchlings. 

For the second clutch she chose the west side. And there have been some problems. She began digging the nest yesterday evening (I saw her at 21:30). This morning, at 10:00, she was still digging in the same place.  12 hour making a nest and still not finished. 
According to David Carroll descriptions in his books, this turtle lays the eggs during the night to avoid the heat of the sun. A dark and small turtle can overheat easilly under the sun in land. About 10:00 the sun reached her

I doubted but finally  I picked her up to have a look. She dug a nest but there were no eggs. Could it be a dystocia? I left her in the same place again. When I came back a few minutes later I saw three eggs an no turtle. I saw her in the water section and I caught her. I palpated her and she was still carrying eggs. I put her in a bucket without water. While I was picking up the eggs my son told me the turtle was laying a fourth egg. It would have surelly been layed in the water if I had left the turtle in the pond. I palpated her again and this time I didn't feel eggs. 

Once I picked up the eggs I examined the nest chamber. It was very shallow. The earth was very hard.  When I disturbed her she just expelled the eggs and went to the water section carrying an egg that she would expell in less than two minutes.

A curious thing: the fourth egg has a shallow depression on the shell. I had seen this before

I had seen it in Terrapene carolina triunguis , in oxytocine induced clutches.

One possible explanation is pressure between the eggs in the coelomic cavity.

But if this was the explanation I think I would see it in the radiography, at least in some eggs. And it appears in all the eggs and exactly in the same place, dorsal as the eggs are layed. You can see it in the next pictures. If these were due to contact areas between the eggs, they  would show it in diferent locations, not all exactly in the same place.

I even thought if it could be some deformation of the passage of the eggs that caused it, but I discarded it when it happened with other terrapene. Always the same dent, the same size and exactly in the same place in freshly layed eggs. It dissapears during incubation.

I told about it to an expert chelonian keeper and his answer was quite logical: these are soft-shelled eggs. When they are being layed they collapse a little bit and a dent appears. Once incubation starts and the egg resorbs water the inner pressure increases and the dent dissappears.

Regarding Clemmys, also with solf-shelled eggs, I had never seen it in previous clutches. And only in one egg of today's clutch. The only difference with previous clutches is that they have been retained more than usual and that the eggs have been picked up just as they are layed.
I marked the eggs and put them in the incubator. This time I have weighted and measured them. I will repeat it by the end of incubation.



From top left to top right

1) 6g.  30,32mm x 18,31mm x 18,32mm
2) 6g.  29,30mm x 17,60mm x 18,16mm
3) 5g.  26,6mm x 18,28mm x 18,3mm
4) 5g.  26,43mm x 18,48mm x 18,28mm

Later, at 18:00, 8 hours after putting them to the incubator, the eggs start chalking, an indicator of fertility.

The fourth egg is still dented


dimarts, 1 de juliol de 2014

Third week of incubation

The egg seen from above.

The egg seen from one side (keeping it in vertical position) 

Yesterday I palpated the female to check if she was still carrying eggs. She was. I also took a picture of her back end. I do not recall that the supracaudal scutes were so brown.  Maybe I didn't notice, but it could also be that in the process of wear/growth of the keratin layer the background color became more obvious in comparison to previous years. 
In the picture the turtle is wet, which increases the constrast between colors.