RSS 2.0 Feed

» Welcome Guest Log In :: Register

    
  Topic: Then Why Do We Still Have Land Mammals?, Extra fins proof of former legs< Next Oldest | Next Newest >  
Arden Chatfield



Posts: 6657
Joined: Jan. 2006

(Permalink) Posted: Nov. 05 2006,07:09   

Dolphin May Have 'Remains' of Legs
By HIROKO TABUCHI, Associated Press Writer
Saturday, November 4, 2006

Printable Version
Email This Article
(11-04) 23:30 PST TOKYO, Japan (AP) --

Japanese researchers said Sunday that a bottlenose dolphin captured last month has an extra set of fins that could be the remains of hind legs, a discovery that may provide further evidence that ocean-dwelling mammals once lived on land.

Fishermen captured the four-finned dolphin alive off the coast of Wakayama prefecture (state) in western Japan on Oct. 28, and alerted the nearby Taiji Whaling Museum, according to museum director Katsuki Hayashi.

Fossil remains show dolphins and whales were four-footed land animals about 50 million years ago and share the same common ancestor as hippos and deer. Scientists believe they later transitioned to an aquatic lifestyle and their hind limbs disappeared.

Whale and dolphin fetuses also show signs of hind protrusions but these generally disappear before birth.

Though odd-shaped protrusions have been found near the tails of dolphins and whales captured in the past, researchers say this was the first time one had been found with well-developed, symmetrical fins, Hayashi said.

"I believe the fins may be remains from the time when dolphins' ancient ancestors lived on land ... this is an unprecedented discovery," Seiji Osumi, an adviser at Tokyo's Institute of Cetacean Research, said at a news conference televised Sunday.

The second set of fins — much smaller than the dolphin's front fins — are about the size of human hands and protrude from near the tail on the dolphin's underside. The dolphin measures 8.92 feet and is about five years old, according to the museum.

Hayashi said he could not tell from watching the dolphin swim in a musuem tank whether it used its back fins to maneuver.

A freak mutation may have caused the ancient trait to reassert itself, Osumi said. The dolphin will be kept at the Taiji museum to undergo X-ray and DNA tests, according to Hayashi.

(see here)

--------------
"Rich is just mad because he thought all titties had fur on them until last week when a shorn transvestite ruined his childhood dreams by jumping out of a spider man cake and man boobing him in the face lips." - Erasmus

  
skeptic



Posts: 1163
Joined: May 2006

(Permalink) Posted: Nov. 05 2006,07:52   

I would think that it is more likely that this is just a rare expression of a normal gene rather than the reassertion of a latent ancient gene or...

we could be witnessing evolution in action and dolphins will be moving onshore and will once again develop into land mammals which, of course, means that due to the superior intelligence of dolphins they will soon take over the world and the end of human civilization is finally at hand!

  
someotherguy



Posts: 398
Joined: Aug. 2006

(Permalink) Posted: Nov. 05 2006,08:30   

I, for one, welcome our new Dolphin Overlords.

. . .


Somebody had to say it!

--------------
Evolander in training

  
Arden Chatfield



Posts: 6657
Joined: Jan. 2006

(Permalink) Posted: Nov. 05 2006,09:00   

Quote (someotherguy @ Nov. 05 2006,14:30)
I, for one, welcome our new Dolphin Overlords.

. . .


Somebody had to say it!



--------------
"Rich is just mad because he thought all titties had fur on them until last week when a shorn transvestite ruined his childhood dreams by jumping out of a spider man cake and man boobing him in the face lips." - Erasmus

  
Ichthyic



Posts: 3325
Joined: May 2006

(Permalink) Posted: Nov. 05 2006,23:40   

Quote
I would think that it is more likely that this is just a rare expression of a normal gene rather than the reassertion of a latent ancient gene or...


It could be just a mutation, but what do you base your "likelihood" on?

do you have estimates of mutation rates in Delphinus spp. based on sampling data?  

have you studied the same thing in animals like snakes (a good thing to do if you want to understand what might be happening here, btw, and a great introduction to Hox-type gene regulation)?

does the expression of legs rarely in snakes follow a homologous pattern to that seen here, you think?

Hint:

anybody interested in this topic might want to read the Hox gene regulation system and implications for evolution and development in Scott Gilbert's text, Developmental Biology:

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=dbio.section.5413

have you read that book?

--------------
"And the sea will grant each man new hope..."

-CC

  
BWE



Posts: 1898
Joined: Jan. 2006

(Permalink) Posted: Nov. 06 2006,00:04   

So long and thanks for all the fish :)

--------------
Who said that ev'ry wish would be heard and answered
When wished on the morning star
Somebody thought of that, and someone believed it
Look what it's done so far

The Daily Wingnut

   
Ichthyic



Posts: 3325
Joined: May 2006

(Permalink) Posted: Nov. 06 2006,01:14   

I'd be guessing that if they could, they would.

bail, that is.

I was involved in studies of organochlorine/phosphate contamination in bottlenose dolphins along the pacific coast of CA about 20 years ago.  

the levels were the highest of any mammal ever recorded.

10 years later, similar studies near Monterey Bay were showing the same thing, and physiological studies were showing signs of stress from the contamination levels (not just in dolphins, but in several different species of marine mammals).

as a tangent, a preliminary study I was involved with on elasmobranchs in the same areas was also indicating high levels of similar contaminants.

It would be interesting to see if these kinds of toxics affect the expression of these specific traits.  Hard to get enough numbers to study in dolphins though; maybe have to test a homologue and do some inference.

--------------
"And the sea will grant each man new hope..."

-CC

  
BWE



Posts: 1898
Joined: Jan. 2006

(Permalink) Posted: Nov. 06 2006,09:28   

Do you know anything about the study (Can't remember who's sponsoring- it uses NOAA ships) off the west coast of Panama? They've been tagging and taking blood samples from a particularly far ranging population for a long time. I see notes about it now and then but I can't remember the project.

On a related note. The Washington State F&W guys working on the saltwater side are developing models of offshore bottom currents and they are using zinc,PCB, mercury and a few other specific poisoning in various flatfish to check their results. The reason it worked out is they got all these great data overlays for arcview after doing a study on Puget sound fish (including salmon- Gasp!;) and found that PCB levels were unsafe. THe dat shows huge variablity though and when you use the overlays with the limited current info, they matched quite closely! Wow. It's like not knowing that only your well is downhill from the drainfield.

--------------
Who said that ev'ry wish would be heard and answered
When wished on the morning star
Somebody thought of that, and someone believed it
Look what it's done so far

The Daily Wingnut

   
jeannot



Posts: 1200
Joined: Jan. 2006

(Permalink) Posted: Nov. 06 2006,10:12   

What's particularly interresting in this discovery is that it gives us a glimpse of the loss of fins in the past.
If the pelvic fins had been lost gradually until their complete disparition, through hundreds of mutations and alleles (at different loci or not), should we expect them to re-appear this way, in a single individual? It seems probable that the mutation which occurred in that individual is the reverse of the mutation that happened in its lineage.
Even a recombination of two or more "ancestral" alleles could not easily explain that. Those alleles must have been lost a long time ago.
This dolphin show us what the pelvic fins looked like just before they were completely lost. Of course, it was in a different species and the fins were not exactly the same.

Not to mention that I may be completely wrong. What do you guys think?  :)

  
Ichthyic



Posts: 3325
Joined: May 2006

(Permalink) Posted: Nov. 06 2006,14:10   

Quote
Do you know anything about the study (Can't remember who's sponsoring- it uses NOAA ships) off the west coast of Panama? They've been tagging and taking blood samples from a particularly far ranging population for a long time. I see notes about it now and then but I can't remember the project


yes, it's part of a much larger project that has been ongoing for quite some time now.

I haven't looked at anything but the pacific data in years though, so I haven't a clue how it is proceeding at this point.

probably should search the NOAA site, or contact my buddies in the sanctuary dept. to see what's new at some point.

I kinda don't want to really know, if you catch my meaning, even if I am curious.

Quote
...and found that PCB levels were unsafe


these things bioconcentrate, so you can imagine the levels in the marine mammals that feed on them.

*shudder*

--------------
"And the sea will grant each man new hope..."

-CC

  
Ichthyic



Posts: 3325
Joined: May 2006

(Permalink) Posted: Nov. 06 2006,14:15   

Quote
Not to mention that I may be completely wrong. What do you guys think?


since it's only a single data point, it's hard to make any conclusions, but I am curious to see if delphinids share homologous developmental pathways to those of other limbless vertebrates (like the hox system in snakes).

I did run across this:

http://www.blackwell-synergy.com/doi....ode=ede

hard to get samples for experiment though...

--------------
"And the sea will grant each man new hope..."

-CC

  
  10 replies since Nov. 05 2006,07:09 < Next Oldest | Next Newest >  

    


Track this topic Email this topic Print this topic

[ Read the Board Rules ] | [Useful Links] | [Evolving Designs]