11 replies to this topic

[Mermaid Lady]

Heard this disturbing bit of news today:

http://news.bbc.co.u...ech/6681793.stm

If they lose their ability to reproduce sexually, genetic diversity drops to a minimum. Such species often end up on an evolutionary dead end, unable to adapt and often end up extinct.

Hope that this does not happen to these wonderful creatures.

[shadragon]

If they lose their ability to reproduce sexually, genetic diversity drops to a minimum. Such species often end up on an evolutionary dead end, unable to adapt and often end up extinct.

Hope that this does not happen to these wonderful creatures.

...or Moose...

Seriously though, a Genus that has lasted hundreds of millions of years is threatened. Makes you think... I am still waiting for Sharkwater to come to my local theater. I think I will have to find it elsewhere...

[DandyDon]

I guess it's natures way of saying parthenogenic birth is better than no birth. It happened in a couple of cases with the Komodo lizard, and while never a good approach - there is one small lizard specie that has no males at all, just females reproducing without any sex. It is unknown if they have any other fun in life?

Unfortunately, many shark populations are under stress, and a critical minimum breeding number is important to any population. The smaller & stressed populations of large mammals wiped out by the first Amerindians at the end of the last ice age were probly finished off in part from such. It's not a biggie to have a remote Andean tribe with 12 fingers each and a number system based on 12 - until they have to deal with a new challenge like smallpox.

Edited by DandyDon, 23 May 2007 - 12:20 PM.

[drbill]

I tried to tell my ex-girlfriend that she must have reproduced parthenogenetically, but she wouldn't buy it.

[DandyDon]

I tried to tell my ex-girlfriend that she must have reproduced parthenogenetically, but she wouldn't buy it.

Had a GF like that once. She only had one kid.

[Hipshot]

I didn't see anything in the article that said that this shark was exclusively parthenogenic. If it's facultatively parthenogenic, then they can still reproduce sexually, in which case the parthenogenesis just ensures that the female's genetic material will be passed on to reproduce sexually at a later time. Also, the shark was in captivity, and there was no evidence cited of parthenogenesis occurring in the wild. That said, it was an interesting article--thanks for posting it.

Rick

[ScubaDrew]

I woudln't worry to much about this particular problem until more data is in. Parthenogenesis has been observed in localised populations with in-sufficient breeding opportunities before (like captivity), while larger more robust populations of the same species continue on normally. It is kind of like a safety net.

Nature is a facinating place, and stuff like this just keeps the minds going.

[casematic]

I had a thought.... (doesn't happen often, but sometimes).... Dr Bill may have some to add to this line of thinking....

Aren't there several species of fish and amphibian who when faced with a single sex environment can spontaneously 'change' sex.... I believe that the anemone fish (NEMO) is this way... but I think they start out as males.... but in an all male environment, one can change to female... maybe someone with a marine biology background could clarify this.

[Hipshot]

I had a thought.... (doesn't happen often, but sometimes).... Dr Bill may have some to add to this line of thinking....

Aren't there several species of fish and amphibian who when faced with a single sex environment can spontaneously 'change' sex.... I believe that the anemone fish (NEMO) is this way... but I think they start out as males.... but in an all male environment, one can change to female... maybe someone with a marine biology background could clarify this.

Quite correct. It's called hermaphrodism. We see it in snappers, and in temperate waters, striped bass, just to name a couple of instances.

Rick

Edited by Hipshot, 14 June 2007 - 02:27 PM.

[drbill]

The really smart ones are synchronous (or simultaneous) hermaphrodites, having both sex organs functioning at once. That way they can mate with whatever gender (of their species) they encounter. Some sea basses (including hamlets) fall into this category.

Others (especially wrasses and parrotfish) change sex as they age, depending on the gender structure of the population. If there aren't enough males (or females), they simply transition from one to the other. They are called sequential hermaphrodites. If they begin life as males and change to females, they are protandrous. If they begin as females, protogynous.

[TraceMalin]

Dr Paulo Prodohl, a co-author on the Biology Letters paper from Queen's School of Biological Sciences, said: "Vertebrates in general have evolved away from parthenogenesis to boost genetic diversity and enhance evolutionary potential... The concern for sharks is that not only could we be reducing their numbers but we could be making them less fit as well."

Yeah, um... isn't this sort of like the movie "The Hills Have Eyes 2"? "The Sea Has Hammers"... just when you thought it was safe to go back in the water... if you thought inbred mutant people were bad news... just wait until you see parthenogenic born mutant hammerhead sharks!

~ Trace

[Hipshot]

When it comes to hermaphrodism, the slipper shell or American limpet is quite a piece of work. They are protandrous, so the older, larger ones are females. They stack up on top of each other, sometimes piled several shells high, with the larger females on the bottom and the smaller males on top, sometimes with transitional genders in the middle. (Does this mean it's natural for guys to be on top? I won't go there!!!)

So, that's how they can reproduce. The funniest thing, however, is their scientific name...Crepidula fornicata...you can't make this stuff up.

Rick