Question

why are the spatial relations in squid so confusing? when the animal swim one end goes forward first. why not call that the anterior end (instead of the dorsal)? alternatively, the eyes, mouth and tentacles are found at one end. why not call that the anterior end?

Answer 1

• Squids belongs to phylum named cephalopoda in which the body mass is extended along the dorsoventral axis above the foot which results in head and foot closer together on the ventral side. The name Cephalopoda suggests this same fact where (Cephalo= head and pod= foot) head and foot are closer together
• Let us see the different positions and the organs present on the squid surface:
• Dorsal surface is the surface with the pointed end (apex) of the head. Ventral surface is the ends with tentacles and arms. The side with the siphon is called as posterior end while side opposite to the siphon is called anterior end
• The position of head and foot is now actually on the dorsal surface. Usually the direction in which the organism is moving is termed as anterior surface. The squids move in the direction of their anterior surface which is making anterior side functionally a dorsal side and posterior side functionally ventral side
• Squid presses its arms and tentacles(present on ventral surface) together to form acute, thick horizontal plate which is used as rudder and to cut its way across water while swimming. This gives the explanation why squids are said to swim backwards.
• Thus in a nut shell, due to the presence of organs and dorsoventral stretching (fusion) there is ambiguitous naming of the squid spatial relations, but the terms are so named according to the functional nature