Quali pesci sono cefalopodi?

Quali pesci sono cefalopodi?

I cefalopodi (Cephalopoda, dal greco kephale, testa e pous, podos, piede) sono molluschi esclusivamente marini, tra i più evoluti, con conchiglia ridotta internamente o del tutto assente, prettamente nectonici (come le seppie e i calamari) o bentonici (come il polpo e il moscardino).

Come si riproducono i molluschi cefalopodi?

I Molluschi si riproducono tutti soltanto per mezzo di gameti. Le specie che dimorano nel mare hanno sessi separati (ma i Gasteropodi pelagici sono ermafroditi). Uova e spermatozoi di regola vengono emessi nell'acqua circostante, ma i Cefalopodi si accoppiano ed hanno fecondazione interna.

What is the anatomy of a cephalopod?

• Anatomy, Diversity, and Evolution. Anatomy. Cephalopod literally means “head foot” in Greek, a reference to the way the cephalopod’s head connects to its many arms. The basic cephalopod body plan includes two eyes, a mantle, a funnel (also called a siphon), and at least eight arms.

What is the smallest cephalopod in the world?

• The smallest cephalopod is the squid Idiosepius, rarely an inch in length. The average octopus usually has arms no longer than 30 centimetres (12 inches) and rarely longer than a metre (39 inches). But arm spans of up to nine metres (30 feet) have been reported in Octopus dofleini.

What are cephalopods and nautiloids?

• Cephalopods are the most complex and motile of the nonvertebrate metazoans and show numerous modifications of the general molluscan body plan. The nautiloids first appear in the late Cambrian and undergo a rapid diversification in the Ordovician.

Are there cephalopods in the Lower Ordovician?

• Deep-water cephalopods, whilst rare, have been found in the Lower Ordovician – but only in high-latitude waters. The mid-Ordovician saw the first cephalopods with septa strong enough to cope with the pressures associated with deeper water, and could inhabit depths greater than 100–200 m. [119]