Halitosis in pike & perch make crucian carp grow taller!

[Chris Plumb]

Clever fish - them crucians.

 

I'm currently devouring Crock of Gold - Seeking the Crucian Carp by Peter Rolfe. Having got it for Chrimbo - and dipped into it since then - I'm now giving it the cover to cover treatment - and I'll no doubt get around to doing a full review for Elton once the 15th of March rolls around!

 

The book is packed with lots of fascinating snippets about the fish but this one knocked my socks off!

 

Crucians come in many shapes and sizes - even when they're not hybridising like mad, true crucians come in a variety of shapes. Some with very high 'shoulders' come from waters with a lot of predators - this response - by growing deeper is called the 'gape defence' - deeper fish are harder to grab and swallow. Below are a couple of picture of crucian's I've caught to illustrate. Both fish are very similar in size (low 3's). The first is a fish from a lake with a lot of pike - and perch. This crucian is very deep as a consequence. The second is a Marsh Farm fish - a lake I'm pretty sure is pike free.

 

What I didn't realise is that crucians have the ability to morph from one shape to the other - and quite quickly too - a mere matter of months. Quite unbelievable.

 

Lab experiments have been conducted to establish what stimulus triggers this. One might expect it would be the repeated sightings of predators but here the clue is in the title of this post (which I've nicked from the book) - they are responding to the smell or 'alarm substances' from digested prey emanating from the mouths of pike and perch!!!

 

As I said - clever fish them crucians!!!

 

 

C.

[Ken L]

clever fish them crucians!!!

Yep and when clever doesn't work, they can out survive other fish in frozen ponds by having world beating tolerance for oxygen depletion.

[arbocop]

That is interesting. A number of animals can adapt their body shape like that in reposne to to stimuli, but I never suspected that crucians did it - and certainly wouldn't have expected the stimuli to be that!

 

I'm doing a similar thing to you Chris, I'm reading the book Chevin by the chub study group. I've found out some things about chub I had no idea about. I'll report all when I've been through it for a second time.

 

There's a couple of articles by a Steve Plumb - any relation?

[Tigger]

Interesting stuff Chris and I have no doubt they do vary in shape from water to water but i'm not convinced they can change shape, especially so quickly.

[arbocop]

Interesting stuff Chris and I have no doubt they do vary in shape from water to water but i'm not convinced they can change shape, especially so quickly.

 

 

Why not, Salmon do? Different response obviously and very different species.

[Tigger]

Why not, Salmon do? Different response obviously and very different species.

 

 

Like you say, a very different species and they change appearance for a differant reason after moving from salt to fresh water. I just can't see predators causing crucians to change their body shape so dramatically and especially in such a short period of time. I would say the differing shapes of crucians from water to water is due to the genetics of the fish, habitat, food etc. I'm no crucian expert mind !

[arbocop]

Like you say, a very different species and they change appearance for a differant reason after moving from salt to fresh water. I just can't see predators causing crucians to change their body shape so dramatically and especially in such a short period of time. I would say the differing shapes of crucians from water to water is due to the genetics of the fish, habitat, food etc. I'm no crucian expert mind !

 

 

Yes, there would certainly be localised genotypic differences - I think it's called phenotypic when it's only body shape or colour difference - and this could be confused. I suppose the halitosis effect would be triggered by enzymes.

[Vagabond]

It certainly stretches belief as well as crucian height!

 

Is there any documented evidence of (say) a pond initially containing only crucians, into which pike and/or perch were then introduced, and subsequent change of crucian shape observed?

 

Like Tigger, I had assumed different shapes arose via a genetical route.

 

BTW I have caught fish that changed shape in seconds!

Puffer fish - different species, different physiological mechanism, but the same objective - to make life more difficult for would-be predators.

[Steve Walker]

Yep and when clever doesn't work, they can out survive other fish in frozen ponds by having world beating tolerance for oxygen depletion.

 

Indeed - by means of an unusual metabolic pathway so that instead of respiration in the absence of oxygen leading to lactic acid production, it leads to ethanol. Not a bad way to spend the winter!

[Bowsa]

I wish my change in shape was more scientific than because of the number of pies I eat!!!