Lecture notes Biodiversity: Exploiters and Exploited Cephalopods (Squids) (BI2EEE4)

19.11.19


L7 – Cephalopods (squid)
Keywords:


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)