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Re: Coelacanth article in current NatGeo



Excellent points on both counts.  One brief note, however, in that the 
Mauthnerian system does not generate a particularly large advantage without the 
proper fast-start skeletomuscular morphology and body plan to go with it.  
Having a very rapid reflex for avoidance won't translate into much of a 
superfast start unless a massive drag-based push can be initiated in response; 
so there's a number of different (and likely co-evolving) systems involved in 
the teleost avoidance response system.  

Cheers,

--Mike


On Feb 25, 2011, at 3:51 AM, Choo, Brian wrote:

> The real question is why clade Teleostei is so successful (as they form the 
> vast bulk of living actinopts) - other extant ray-fin lineages are relictual 
> and haven't produced new genera since the early Paleogene. Teleosts seem to 
> have two utterly unfair adaptive advantages over other fishies:
> 
> 1) Mauthnerian system (greatly enlarged nerve cells in the medulla connected 
> to elongated axons running down the spine) = superfast avoidance reactions 
> when threatened.
> 
> 2) Teleost jaw suspension (mobile maxilla & premaxilla) allowing the lips to 
> protrude far in advance of the rest of the skull. A highly efficient means of 
> feeding (greater reach/ suction draws food items into the mouth) but, more 
> importantly, it is very easily reconfigured to tackle any sort of food item 
> anywhere in the water column. Put a single species of teleost in an isolated 
> lake, come back in a couple of 100k years and chances are it will have 
> exploded into numerous novel forms, with the jaw modified into all sorts of 
> odd configurations (as happened with cichlids the African rift lakes). Put a 
> single species of lungfish in an isolated lake, wait around for the same 
> amount of time and chances are you'll essentially have the same lungfish.
> 
> Cheers
> Brian
> 
> 
> ________________________________________
> From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu] On Behalf Of Augusto 
> Haro [augustoharo@gmail.com]
> Sent: Friday, 25 February 2011 5:00 AM
> To: erikboehm07@yahoo.com
> Cc: DML; david.marjanovic@gmx.at
> Subject: Re: Coelacanth article in current NatGeo
> 
> I think Choo is right. Chondrichthyans also have fleshy fins, thus
> suggesting fleshy fins came first. Thus, the reason by which fleshy
> fins were good may reduce to the reason by which fins are good. Now,
> it may be asked why ray fins are more adaptive, if they persisted
> because of intrinsic adaptive superiority and not because of luck at
> the mass extinction (or because of other improvement in
> actinopterygians).
> 
> 
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Michael Habib
Assistant Professor of Biology
Chatham University
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mhabib@chatham.edu
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