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Walking shark on sea floor

by thorium1010
Tags: floor, shark, walking
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thorium1010
#1
Aug31-13, 09:42 PM
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A new species of shark that "walks" along the seabed using its fins as tiny legs has been discovered in eastern Indonesia, an environmental group said Friday.
http://phys.org/news/2013-08-shark-indonesia.html

‘Walking’ sharks, also known as bamboo sharks or longtail carpet sharks, belong to the family Hemiscylliidae in the shark order Orectolobiformes.Rather than swim, these slender-bodied sharks ‘walk’ by wriggling their bodies and pushing with their pectoral and pelvic fins.
They are relatively small, with the largest species measuring about 48 inches (1.22 m). The newly discovered species, called Hemiscyllium halmahera, reaches 28 inches (70 cm) in length.
http://www.sci-news.com/biology/scie...sia-01335.html

There's a video included in the second link.
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Borek
#2
Sep1-13, 03:01 AM
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Strange, looks pretty clumsy.
thorium1010
#3
Sep1-13, 01:15 PM
P: 201
It is clumpsy , atleast it does not use limbs rather fins to acheive the goal. Its quiet interesting to see fins used the same way (movement) certain lizards use their legs.

Pythagorean
#4
Sep1-13, 01:37 PM
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Walking shark on sea floor

I find this interesting because the evolution of limbs would require a neural control system that knew how to use them appropriately, and here we see an example of a neural control system ready and waiting for the morphology. As thorium says, the motion does look similar to some species of amphibian/reptilian gait.
Borek
#5
Sep1-13, 02:27 PM
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I see your point, and I agree it is interesting.

Still, it looks clumsy and I don't see in what way it is beneficial (obviously somehow it is).
Pythagorean
#6
Sep1-13, 02:33 PM
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Me either, but it doesn't need to be beneficial; it could just be a spandrel. Or is there evidence that it was selected for?
thorium1010
#7
Sep1-13, 08:41 PM
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Question is why would it need to be beneficial? Too long it has been drilled into our heads that many traits have to be beneficial to survive in our environment. Maybe this trait was just an accident or has little benefit to the organism or it rarely uses this trait, we do not know. There are many areas in the field of biology, that does not make sense. It is our ingrained sense to see usefulness in a particular thing, probably biases our understanding of traits and survival of organism.
Borek
#8
Sep2-13, 02:24 AM
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Perhaps you are right - it doesn't have to be beneficial.

My line of thinking was that there are at least several species of sharks living and feeding on the bottom, and I have never heard about any of them behaving this way - as far as I know, they all swim (compare http://www.youtube.com/watch?v=iYRfcPkeFV4 - there is both a walking bamboo shark and a swimming houndshark). For me that suggests bamboo sharks behave this way for a reason. It is not clear to me how close to the surface they live - would they feed in the intertidal zone (breakers, strong currents), these fins would make a great sucker to keep the fish safe on the bottom, and then the motion could be a spandrel as Pythagorean suggested. But I am under impression they live slightly deeper, where swimming is enough. Another explanation could be that they do use fins as sucker as part of their feeding strategy - say to create a stable base for pulling food from between the rocks.

But now I am speculating and I should ban myself.
Curious3141
#9
Sep2-13, 05:24 AM
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It is really cute!

Sorry if that wasn't a scientific comment.


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