Question

Siphonophora is the order name of
(a) Pelecypoda
(b) Cephalopoda
(c) Scaphopoda
(d) Gastropoda

Answer 1

Hint: The order name of a class which is referred to as the head foot is Siphonophora. It is a reference to the relation of their head to its many arms. For example, cuttlefish, squids, octopuses, etc come under this group. They come from the lower Cambrian. They're often referred to as ink fish. Nautiloidea, Ammonoidea, and Coleoidea are the 3 subclasses of this class.

Complete answer:
Siphonophora is the order name of Cephalopods. They are completely aquatic, discovered from the surface to the depths of 5000 m. In the seas or the open oceans, they are known as epibenthic and pelagic.

Cephalopods have muscular appendages that reach from their heads and cover their mouths, as the name suggests. In eating, mobility, and even reproduction, these are used. They number eight or ten in coleoids. They occur as decapods as in the case of cuttlefish and have five pairs in the case of squid.
So, the correct answer is, ‘Cephalopoda’.

Additional information: The characteristics of Cephalopods include:
- Their body is bilaterally symmetrical with a well- developed head that carries around the mouth a crown of mobile muscle appendages.
- Oral appendages are formed by modification in the foot.
- Appendages other than Nautilus bear suckers or hooks.
- External shell, usually either reduced or absent (example: Idiosepius and some octopuses) and enveloped in most species by the mantle. Only in Nautilus, an external shell exists.
- They possess mouth like jaws with horny or calcareous beaks.
- Jet propulsion occurs with the help of an existing funnel or siphon that expels water from the mantle cavity.

Note: Siphonophora is a member of the Cnidarians that are very polymorphic. They belong to the Hydrozoa superclass. As a colony, composed of highly modified medusae and polyps, the fully evolved siphonophore is organized. In this class, polymorphism is much more carried out than in other hydrozoan classes, and the colony is a true superorganism.