Parental care with gastrotrichs

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Michael Müller
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Parental care with gastrotrichs

#1 Post by Michael Müller » Fri Jul 03, 2020 10:41 am

Hi,

eggs of gastrotrichs are quite frequent in pond samples. Most of them are laid openly without regard to the exact position, while other species choose the spot for the deposition with care. You may often find "nest" full of eggs within the empty shells of water fleas. But besides this careful deposition of eggs, no further parental care is known with gastrotrichs.
But every now and then I found eggs of two gastrotrich species, which have a shell carefully covered with debris:

Image

This is a egg of the freshwater gastrotrich Chaetonotus cordiformis:

Image

I wanted to know, how this decorated shell is formed and filmed the deposition of the egg in real time and the decoration of the egg with a time laps factor of 12.5:



After the deposition of the egg, the mother brings particles of detritus and decorates the shell of the egg. This is an incredibly complex behavioral pattern for a about 200µm small animal with perhaps 50 nerve cells. The reason for this behavior is probably to camouflage the egg chemically. Amoeba often feed on eggs of gastrotrichs. Maybe they do not recognize the camouflaged egg as food. Some time ago I was lucky to film the attack of an amoeba on a developing egg of a different gastrotrich species:



But the egg of Chaetonotus cordiformis survived and a juvenil gastrotrich hatched after about 48h development:

Image

Best regards,

Michael
Leitz Ortholux II

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Re: Parental care with gastrotrichs

#2 Post by janvangastel » Fri Jul 03, 2020 11:07 am

Very interesting information Michael. And beautifull photographs.

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75RR
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Re: Parental care with gastrotrichs

#3 Post by 75RR » Fri Jul 03, 2020 4:50 pm

Two great videos that complement each other nicely. Amoeba proofing (if that is what it was) does make sense after seeing the second video.

Did you manage to see the gastrotritch collecting algae? I imagine it rubbed against the alga rather as it did with the egg.
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Michael Müller
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Re: Parental care with gastrotrichs

#4 Post by Michael Müller » Sun Jul 05, 2020 7:55 am

Thank you for your nice an encouraging words!
75RR wrote:
Fri Jul 03, 2020 4:50 pm
Did you manage to see the gastrotritch collecting algae? I imagine it rubbed against the alga rather as it did with the egg.
Most gastrotrichs, including this species, do not feed on algae - the mouth is to small for them. They feed on bacteria, which are scrape off some substrate and sucked in.
For the decoration of the egg, the mother brings particles of detritus (rest of dead organisms, which make up most of the mud) within its pharynx. This particles are not transferred into the intestine but are spit on the egg and carefully spread on the sticky surface of the egg.

Best regards

Michael
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75RR
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Re: Parental care with gastrotrichs

#5 Post by 75RR » Sun Jul 05, 2020 9:26 am

Michael Müller wrote:
Sun Jul 05, 2020 7:55 am
For the decoration of the egg, the mother brings particles of detritus (rest of dead organisms, which make up most of the mud) within its pharynx.
This particles are not transferred into the intestine but are spit on the egg and carefully spread on the sticky surface of the egg.
Thanks for the explanation. Had a closer look, and think I almost saw it.

A slow motion video of this would be very interesting to see.
.
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Re: Parental care with gastrotrichs

#6 Post by Michael Müller » Sun Jul 05, 2020 2:30 pm

75RR wrote:
Sun Jul 05, 2020 9:26 am
A slow motion video of this would be very interesting to see.
Sorry, no slow motion. The video is a time laps picture; only 2 frames per second.
As far as I remember, there was a second observation same years ago, where I took a "normal" video. I'll see, if I can find the video tomorrow and cut it to a reasonable length for youtube.

Have a good weekend,

Michael
Leitz Ortholux II

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Re: Parental care with gastrotrichs

#7 Post by Michael Müller » Mon Jul 06, 2020 3:09 pm

Hi 75RR,

as promised, a little "real time" video which shows the transport of the particles for the decoration of the egg:



Please remember, that this animals are smaller then many ciliates (about 200µm). To me it's incredible, how complex the behavior is!

Best regards.

Michael
Leitz Ortholux II

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Re: Parental care with gastrotrichs

#8 Post by hkv » Mon Jul 06, 2020 7:20 pm

Wow, amazing video of the amoeba eating the egg. Great work!

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Re: Parental care with gastrotrichs

#9 Post by 75RR » Mon Jul 06, 2020 7:53 pm

Many thanks for taking the trouble to look up the old video. Such behavior is very interesting.

I have come across them before but never laying an egg nor camouflaging it after either!


This was one I was lucky to be able to video, they are usually so fast that I don't even try to capture them unless they happen to remain in a small area for some reason.

https://www.youtube.com/watch?v=kFkwgdXZN-U
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Re: Parental care with gastrotrichs

#10 Post by Michael Müller » Tue Jul 07, 2020 10:32 am

Hi 75RR,

your video is great! You may not be aware, that you show some very rare details. Freshwater gastrotrichs hatch as parthenogenetic animals. They lay unfertilized eggs and no male gastrotrichs are known. This mechanism produces a rapid increase of the gastrotrich population. It's not uncommon, that the population doubles every two or three days. Most of the animals die after this exhausting period in their lives, but some (perhaps one of twenty) survive and develop slowly into a hermaphrodite, which produces eggs and sperm simultaneously. Your video shows one of this hermaphroditic gastrotrichs.This can be seen by the conspicuous bi-lobed x-body near the hind gut of the animal in your film. The function of this x-body is still unknown; it may produce some secretion, which is necessary for the mating. Additionally it is often possible to see packets of sperm, which is astonishingly not motile. I couldn't see the sperm in your video - it may not be developed yet.
Even more, your video shows a gastrotrich species (which I unfortunately cannot identify without a good view to the scales), which has a conspicuous round structure between the x-bodies and beneath the ventral skin. I only saw a similar structure once with Chaetonotus brevisetosus where it develops simultaneously with the x-body and which I interpret as an opening for the x-bodies. This structure is not described in the literature.

Image
x-bodies, sperm and x-opening with Chaetonotus brevisetosus; ventral view

Image
x-bodies, sperm and x-opening with Chaetonotus brevisetosus; lateral view

Well done and very interesting,

Michael
Leitz Ortholux II

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Re: Parental care with gastrotrichs

#11 Post by 75RR » Wed Jul 08, 2020 3:19 pm

Many thanks for the detailed info, I was not aware of those details.

I am afraid I have read very little on gastrotrichs so far. Something I will have to amend!
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