Strange Copepod behaviour

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Wim van Egmond
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Strange Copepod behaviour

Post by Wim van Egmond »

I've been making some movies recently but I have to find some space to load them.

So I post some images from the archive. I have many that I think I have not posted yet. I hope I 'm not wrong.

These copepods live in brakish tide pools high on the rocky shores of Britanny. France. The first 2 images are of a male copepod, the last 2 are of a female. The image inbetween shows the rather curious behaviour called precopulatory mate guarding (pardon my french). The males grab very young females, often much smaller than this one.

Wim

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Starshade
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Post by Starshade »

Wim, the image quality is just perfect. How did you make the cyclops sit still for stacking. I just did an image of a cyclop yesterday and it was a huge challenge to get all depth at those rare moments when it wasn't moving.

And was it a proper darkfiled? I see lots of background masking (don't worry it's noticeable only for those who does it)

abpho
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Post by abpho »

Amazing work.

Wim van Egmond
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Post by Wim van Egmond »

Thank you Daniel,

Yes, it was proper darkfield but I shot them as jpegs and I made the background black instead of almost black. And there were some halos of the stacking. I removed these by darkening them. It could be done more precisely but I am sometimes a bit lazy. :)

The copepods can be motionless for some time. With a bit (or actually a lot) of patience it is possible to make a small series.

Wim

Mitch640
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Post by Mitch640 »

These are perfect. I wonder if it would be possible to make a stack from frame grabs of a video sequence when you focus down through the bug. You could pick the frames to export along the timeline.

specious_reasons
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Post by specious_reasons »

Mitch640 wrote:These are perfect. I wonder if it would be possible to make a stack from frame grabs of a video sequence when you focus down through the bug. You could pick the frames to export along the timeline.
CombineZp has the option to sample frames from a video. I've rarely used it because my video camera resolution is awful.

NikonUser
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Post by NikonUser »

Your images, as always, are superb.

But why the heading "Strange ..... behaviour"
These guys have been around forever and the males have a modified antenna for holding onto females; guess they have been doing it for a long long time.
So it seems only normal to me for a male to be attached to a female; normal not strange. If you found one attached to another male or perhaps a cladoceran then that would be strange :shock:
NU.
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No man can be truly called an entomologist,
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Wim van Egmond
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Post by Wim van Egmond »

Aha, yes, but what is a bit peculiar from a human perspective is the fact the the female is immature. And you often find very early stages 'kidnapped' by a mature male. The mature male guards the female until she is mature. He is very patient. But I think during the molding of the female he can lose her to another male.

Wim

NikonUser
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Post by NikonUser »

Could it be that males mature faster than females such that there are often more mature males than mature females? If so, some males may be 'forced' to claim immature females.
Certainly in many insects there seems to be competition for females by males early in the emergence period as there are always more males than females.
In Heliconid butterflies males will sit on a female pupa waiting for her to emerge; that's got to be close to rape.
NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.

Nikon camera, lenses and objectives
Olympus microscope and objectives

Wim van Egmond
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Post by Wim van Egmond »

I'm not sure if it has to do with the fact that the males are more numerous. This behaviour does have its advantages when there is a limited amount of fertile females.

And these copepods live in a very hostile environment. small isolated pools high up the shore, not much chance to migrate to another pool so there is a limited amount of fertile females.

I had a quick search on the web and the strategy of precopulatory mate guarding is explained as an adaptation to reduce encounter limitations. You can imagine that when you are a lonely male in a big pool (the open ocean) you have to grab every chance there is, also when you have to have some patience. In a smaller pool such as these tide pools this may also be the caase. But when there is a big population with a lot of competition I can imagine the stratagy will also work.

For copepods it is not strange, translated to human behaviour it is illegal. :-)

Wim

Mitch640
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Post by Mitch640 »

It's a wonder that they find each other at all. It's not like they can see anything with that eye.

NikonUser
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Post by NikonUser »

Sight is important for humans; probably not so for many other organisms.
Copepods have mechanoreceptors and chemoreceptors on their 1st antennae that serve for recognizing conspecifics, food, predators.
NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.

Nikon camera, lenses and objectives
Olympus microscope and objectives

Mitch640
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Post by Mitch640 »

I've often wondered if they can also hear, or more something like sonar or pressure sensors. I wonder what a waterproof pinhead mic would pick up in a drop of water. :)

dmillard
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Post by dmillard »

Wim,

These are wonderful images to see first thing in the morning!

David

phytoplankton
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Post by phytoplankton »

Mitch640 wrote:I've often wondered if they can also hear, or more something like sonar or pressure sensors. I wonder what a waterproof pinhead mic would pick up in a drop of water. :)
Well they can hear, in a way. I'm not sure if they can identify particular sounds, but they certainly can feel the pressure waves in water from movement and sounds around them. They pick up these movements with hairs on their antenna.

How sensitive copepods are to water movement depends on the species. The ones Wim pictured are possibly harpacticoid copepods. They tend to live in/on the benthos (ie. the seabed). If they do swim they often wait till after dark so they don't have a hard time avoiding sight based predators such as many fish. So they often rely more on chemoreception (essentially smell) than on "hearing", and have small antenna. Some other species of copepods, like most calanoid 'pods, are pelagic (they live in the water column). These types often have longer antenna that are extremely sensitive to the pressure waves in water. This, along with a very fast nervous system, allows them to rapidly sense and avoid approaching predators. They might all be copepods but their method of sensing the world couldn't be more different. Just like how mole rats and bats are both mammals but the senses they rely on most are vastly different.

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