I have saved this relationship for now because it is one of
my favourites!!
Has anyone wondered how crustaceans can sometimes remain
hidden from sharks even though the sharks have the electrosensory ability to
detect the electrical pulses made by the heart when it beats?? Well I wondered,
so I did some research and found out some incredible things.
Firstly, it is due to coevolution. Secondly, it is due to
the crustaceans’ ability to induce cardiac arrest when they feel threatened!!! For
example, when a shadow passes overhead that could be a potential predator. This
absolutely blew my mind when I heard about it.
In this case it is predator-prey coevolution; the reason why it is coevolutionary is due to the sharks initially gaining an upper-hand with electrosensory detection, due to an electric signal produced each time the heart pulses; the crustaceans followed by allowing their heart to stop until a threat has past, therefore having the ability to hide from the sharks' electro-sensors (Burnovicz et al., 2009).
Neil Gribble, lecturer at JCU Cairns, did his PhD thesis on
this topic, finding that crustaceans still retained the ability to see and
catch potential prey even if their heart was “stopped”. There must have been a
way for it to retain enough blood circulating to its eyes and brain in order to respond like this. He found that there is a tiny muscle just above
the heart that contracts in a very subtle and even way so that enough blood is
circulated to the eyes and brain to remain alert, but not enough to emit an electrical
signal to other predators.
References:
2009. The cardiac
response of the crab Chasmagnathus
granulatus as an index of sensory perception. Journal of
Experimental Biology, 212, 313-324.
Image of
crab sourced 14/5/14: http://marinebio.org/gallery/indonesia/
Image of
shark sourced 14/5/14: http://www.xray-mag.com/Batoidea?page=3
Fantastic! That is really an amazing ability! Do all crabs show this ability, or is it just this particular species and does the crab stop its heart in response to any predator or is it specifically to sharks only? Is there any evidence that sharks are again gaining an upper hand by showing an ability to detect these crabs despite a lack of an electrical signal? Very cool!
ReplyDeleteThat's incredibly cool! imagine that! - stopping your heart in order to survive! Is this seen in all crustaceans or just a few special crabs? What a wicked example of predator-prey coevolution :)
ReplyDeleteHow crazy is that! Evolution, producing superpowers for c. 3.8 billion years.
ReplyDelete