Overview
Nature of squid, cuttlefish
and octopus
Squid, cuttlefish and octopus are cephalopods, a group of invertebrates
consisting of bilaterally symmetrical mollusks. These wonderful
creatures first appeared about 500 million years ago in the
Upper Cambrian Period, and weathered evolutional trials through
the ages with their unique organs. These cephalopods have become
highly developed creatures with three-dimensional vision, memory
and high swimming speed. Their body colors change with their
environment to provide camouflage for catching prey or evading
attacks. They can squirt ink in times of danger. This inky fluid
is delicious and can be used for cooking. For all cephalopods,
the smaller the size is, the tenderer the flesh is.
They are closely related to the mollusk phylum, characterized
by the absence of backbone, and thus have no relation to fish.
The bulbous head houses a two-jawed mouth surrounded by tentacles
dotted with suckers, which are used for crawling and seizing
prey. The sack-shaped body contains a mantle cavity occupied
by stomach, gills and sex organs. Squid, cuttlefish and octopus,
the three major cephalopods, have typical nature and traits
as follows:
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