The Main Characteristics Of Cephalopods

The body is somewhat streamlined. The mouth has a parrot-like palate and tooth tongue. The digestive system also includes the esophagus, salivary glands, stomach, caecum, liver and intestines. Except for the Nautilus and certain deep-sea Octopus species, there is an intestinal pouch (or ink sac) near the anus, which secretes dark liquid (ink duct).

The circulatory system is mostly closed tube, while Nautilus is partially lacunar, and the respiratory pigment hemocyanin is dissolved in the plasma. In addition to the heart, there are 2 gill hearts. The gills are feather-like and suspended in the mantle cavity. The mantle shrinks rhythmically, allowing water to flow through the gills. The excretory organ is the kidney, with 2 to 4 in number. The senses are eyes, olfactory horns, balancers and tentacles.

Nautilus's eyes have no crystals and are an open nest. The eyes of the subclass Coleoptera are complex, and their structure and function are close to those of vertebrates. The central nervous system is highly developed, and the main ganglion centers are concentrated in the head, forming a real brain, encased in the cartilaginous brain (except Nautilus). The brain center of some squids is divided into different centers. The foot ganglion sends out nerves, and then expands into the carpal ganglion and foot ganglion, which innervate the wrist and funnel respectively. The mantle of some calamari is innervated by pairs of giant axons (the largest known nerve fibers) on the back.