[thedoc (OP)]

The drive to procreate is one of the most powerful forces on earth. To assure procreation, nature offers as a "bribe" a certain amount of physical pleasure. This is easy to understand for those species who actually make physical contact during copulation, but fish remain a total mystery: how does ejecting one's eggs or sperm into a stream or the ocean bring an ecstatic experience?

John Gamel
Asked by John Gamel


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[thedoc (OP)]

We answered this question on the show...



We posed this question to Mark Bretha, Marine Biologist at Plymouth University...
Mark -  The fundamental question here is whether fish are ever capable of experiencing pleasure at all, including at the spawning event when they release their gametes.  One problem that we have is that we can't exactly go up to a fish and ask, “how was it for you darling?”  And this is a general problem in understanding what feelings non-human animals might or might not experience. 
[img float=right]/forum/copies/RTEmagicC_cleaner_wrasse_and_angelfish_01.jpg.jpg[/img]One area that has been the subject of a large amount of research in fish is the experience, not of pleasure, but a pain.  In an experiment with rainbow trout, we see an injection that would’ve been painful to humans, they show behaviours like rubbing the affected area which went beyond a simple reflex response and that were also specific nerve fibres that responded to the injection.  Therefore, fish might experience something akin to pain in humans.
As far as pleasure goes, there are some anecdotal evidence that when client fish interact with cleaner wrasse, they might enjoy the touch sensations of being cleaned.
In the case of spawning, we know about the hormonal control of the events but we don't yet know whether it’s an ecstatic experience, altohugh it’s perhaps nice to think that there's the possibility that cyclids can get their kicks and brill get a thrill from spawning.
Diana -   It’s possible that there is some sort of neurological reward for fish when they reproduce, but we don't yet know if it’s pleasurable or if it makes the, er, water move.

[CliffordK]

It must be some experience...
When Salmon will travel hundreds of miles upstream.
Across Water Falls
Through Rapids
Getting hungry, battered, and bruised along the way.

Either lay eggs, or fertilize them.
THEN DIE.

[qazwart]

Not everything we do requires that we derive pleasure out of it. For example, not too many people get great pleasure out of breathing, yet we do so anyway. it can be hard to sometimes put a line between pleasure and some sort of biological instinct but we can look at some breeding practices and see that not all creatures find it "pleasurable".

• Many animals die right after mating. Reproducing takes a lot of energy, so there can be an advantage if a creature can give everything it's got to the next generation. Salmon and most octopuses fall into that class.
• Some animals allow themselves to be consumed by there mates. Spiders are an excellent example. A nitrous snack for the female can ensure that she has enough energy to lay her eggs. Plus as long as the female is munching on the male, she's not mating with someone else.
• For the title of least pleasurable mating practice, look no further than the male grouper fish.  Male grouper fish are born immature and never fully developer. They can't even eat. Their sole task is to locate a female group who is 30 to 100 times his size and bite her and hold on. Soon their jaws and mouths disappear and blend into the female. Their body organs deteriorate, and all that's left of the male is his reproductive organs hanging off The female's body.
  
  When scientists first started investigating groupers, they realized all they saw were females and never a male. And all the females had these "tumors" all over them. Only later did they understand that those tumors were the remains of various males.
  
  Scientists speculate that this mating practiced probably developed because groupers are not that common in the deep sea.  It would be highly unlikely for a male and female to meet up when the female is breeding. Therefore, a male becomes part of the female and his sperm are there whenever the female is ready to breed.

[chris]

Great points, qazwart; thanks.

[MikeS]

It's probably hard wired (instinct) and pleasure does not come into it.



edited by mod.

[Boogie]

Q : What did one male grouper say to the other?
A : Not only did she get the house and the car, but she got my testicles too!