These lecture notes are the seventh in a series from the module biodiversity: exploiters and exploited. This lecture covers everything about squids from anatomy, overfinishing and larger species from the depths. A great way to start your understanding in this module (or help you get out of the lect...
Lecture:
Classification
o Squid
Phylum = Mollusca
(molluscs)
Class = Cephalopods
Tenticles =
separated feet
Mantle cavity points forward
Shell lost/restricted (eg cuttle bone)
Species
o 650 living species
o 7500 fossil species
Subclass = Coleoidea
Order = Teuthoidea (sqiods)
Vestidule pen of shell
o Other classes
Bivalva (foot used for sticking and burrowing) with reduced radula as filter
feeders
Eg raser shells (retracted long foot), clam shells
Gastropoda
o Other subclasses in cephalopods (spiraled air filled chambers)
Subclass = Nautilodea (450 million years)
‘As far as evo can take invertebrate body plan’ – proven wrong
Subclass = Ammonoidea (same body plan as Nautiluses therefore in the
same class, proven even if extinct)
Jagged chamber walls = possibly to dive to deeper depths
Larger bottom beak (shovel) with smaller top beak
Gas filled so body at the bottom
Ideas why class were lost
o Possibly? Outcompeted in shallow waters so fell down to
deeper waters
Adapted to lose shell → protosquid
Squid reradiated back to shallow waters (w/loss of
bony fish species)
o Predation – shallower depths eaten by bony fish/reptiles so
squid could reradiate back to shallow when extinction of
some bony
o Other orders
Belemnoidea (extinct)
Sepiodea (cuttlefish)
Octopoda (octopus)
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