Sunday, December 29, 2013

Pelagic Threshers - epic Video!

All tail - source.

What a beautiful, elegant animal!

This is really, really nice stuff!
It not only shows them hunting but even feeding!
Remember the paper?



jsd said...

'During three of the successful events, bubbles were observed to form where the tip of the tail reached its maximum speed and height (Figure 4, Movie S1). The fastest tail-slap, which had a mean speed of 21.82 ms−1, resulted in prey capture and the formation of a plume of bubbles.'

If I have understood the use of the term 'stun' in the paper, it does not appear the shark's tail must contact the sardine: one can well imagine the swim bladder of the teleost being shattered at close proximity to the tail slap because of the pressure wave.

Cousteau Crony said...

JSD people have been pressure wave fishing for decades. The Thresher just perfected it eons ago.

DaShark said...

Posted here ages ago... :)

jsd said...

It does, however, make you wonder how the elongated tail evolved as a revolutionary feeding mechanism. If the modern threshers' ancestors were shoal-feeders and dashed around with slightly elongated tales that occasionally zapped fishes (most likely in schools) via the pressure wave hypothesis, one has the beginning of a Darwinian process that could yield the incredible refinement we now have.

DaShark said...

Methinks the pressure wave technique may have evolved as a "bonus".

The Sharks may have started out by first accidentally and later on, intentionally hitting/stunning prey via direct impact.

Quite possibly, those with the longer tails were more successful = had a competitive advantage = were fitter = had a higher chance of procreating - with evolution thusly selecting for ever longer tails until they were long enough to generate the adequate speed at the apex?

jsd said...

Yes -- that would be the mainstream view. It's getting the system going that I struggle with because the downside of elongating that tail has to be set against how many lucky strikes there are. And all those requiem sharks that feed on bait balls never evolved the same.

A further question is whether the power generated by the tail that is sufficient accidentally to injure a fish (via impact) is simultaneously generating a damaging pressure wave. Perhaps it's the fluke combination that allowed the mutation to be selected for and then refined.

DaShark said...

Getting the system going is ALWAYS the crux ain't it...

It may be safer to revert back to square one, invoke the Creator's omnipotent and omniscient wisdom and design skills, and be done with it! :)