Cephalopods
Cephalopoda is a class under the phylum Mollusca. It includes octopus, squid, cuttlefish and nautilus. These organisms are referred to as cephalopods. They have a distinct head, muscular hydrostats, and a bilateral body. There are approximately 800 surviving species of cephalopods. Cephalopods occupy the deep sea and cannot tolerate freshwater (except Atlantic brief squid).
They have developed brains and senses. The brain is well protected inside a cartilaginous cranium. Their nervous system is complex compared to most invertebrates. They have a unique sensory receptor called the statocyst that detects gravity.
Gastropods
Gastropoda is another class of invertebrates under the phylum Mollusca. It includes slugs and snails from freshwater, saltwater as well as terrestrial habitats. There are currently around 476 surviving gastropod families that comprise 65000-80000 slug and snail species.
The gastropods can produce torsion, and thus change their body plan into asymmetric. Terrestrial gastropods respire through lungs, and the aquatic ones respire through gills. They have an open circulatory system. Marine gastropods have a chemoreceptor called rhinophores. It helps them to detect the pheromones and the trails of their prey.
Explore: Snail-Skeletal System
Difference between Cephalopods and Gastropods
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Cephalopods |
Gastropods |
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They are invertebrate animals under the class Cephalopoda and phylum Mollusca. |
They are invertebrates under the class Gastropoda and phylum Mollusca. |
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It includes squid, cuttlefish and octopus. |
It includes slugs and snails. |
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They are less in number compared to gastropods. |
They include numerous living species compared to cephalopods. |
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They are strictly marine (except Atlantic brief squid). |
They can be seen in freshwater, saltwater and terrestrial habitats. |
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They have a bilaterally symmetrical body. |
Their body changes asymmetrical due to torsion. |
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They have a complex and developed nervous system compared to most invertebrates. |
They have a less complex nervous system compared to cephalopods. |
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They have a closed circulatory system. |
They have an open circulatory system. |
Frequently Asked Questions on Difference between Cephalopods and Gastropods
What is teuthology?
The study of cephalopods is called teuthology, and a person who studies this is called a teuthologist. It is a branch of study under malacology (study of molluscs).
What are bivalves?
It is a class of molluscs that has laterally compressed bodies that are enclosed inside a shell. Typically the shell has two hinged parts. Examples – mussels, oysters, clams, scallops, etc.
Extended Reading: Phylum Mollusca
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