The Lord Geekington: Cirrate Octopodes
and the two other fossil octopodes, they certainly are not "living fossils" or "prehistoric survivors". I'll let
Darren Naish explain to you
why I also dislike those terms. A 2006 paper by Collins and Villanueva appears to be one of the most definitive work on this group to date and demonstrates many remarkable characteristics. Cirrate octopodes are adapted to living in deep and cold waters and display adaptations such as a gelatinous composition, reduced gills, lost ink sac, and lost/reduced radula. The cirri of this group's namesake have not been investigated but are believed to be sensory in function. This group also appears to have lost (or never evolved) the ability to change coloration but possesses photophores capable of generating light. Males do not have the sperm transfer arm (hectocotylus) of cirrates but they do posses enlarged dorsal arms for no clear reason. The internal cartilaginous shell is variable in shape and is associated with the muscles used to drive the fins. I'd like to suggest the possibility that the internal shell re-evolved when the animals abandoned jet propulsion for fin propulsion - it would be an interesting theory to test.
The "Dumbo Octopus" Grimpoteuthis sp. taken from Wikipedia
As far as behavior is concerned the paper mention that jet propulsion was lost due to being high energy concerns although it could possibly still be present during burst swimming. The trait of high speed is not selected for and these species get around by benthic crawling with the arms, umbrella-style drifting, swimming with fins, and medusoid contractions i.e. jellyfish-like movements. Predation is little documented but these species are known to "balloon", invert their web (also in
|
