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In argonauts, the male transfers the spermatophores to the female by putting its hectocotylus into a cavity in the mantle of the female, called the pallial cavity. This is the only contact the male and female have with each other during copulation, and it can be at a distance. During copulation, the hectocotylus breaks off from the male.
Closeup of the trunk of an Asian elephant. Muscles provide the force to move a muscular hydrostat. Since muscles are only able to produce force by contracting and becoming shorter, different groups of muscles have to work against each other, with one group relaxing and lengthening as the other group provides the force by contracting.
Opisthoteuthidae are a group of octopuses characterized by a web of skin in between their arms. They broad U-shaped shell that support muscles for a pair of small fins on the mantle, these fins are far less developed than other families in Cirrina and essentially only act as stabilizers when the animal swims (using a medusoid motion of the arms and webbing). [1]
The octopus can squeeze through tiny gaps; even the larger species can pass through an opening close to 2.5 cm (1 in) in diameter. [30] Lacking skeletal support, the arms work as muscular hydrostats and contain longitudinal, transverse and circular muscles around a central axial nerve. They can extend and contract, twist to left or right, bend ...
Cephalopod limbs bear numerous suckers along their ventral surface as in octopus, squid and cuttlefish arms and in clusters at the ends of the tentacles (if present), as in squid and cuttlefish. [9] Each sucker is usually circular and bowl-like and has two distinct parts: an outer shallow cavity called an infundibulum and a central hollow ...
Finally, the circular muscles are used as the main activators in jetting. They are muscle bands that surround the mantle and expand/contract the cavity. All three muscle types work in unison to produce a jet as a propulsion mechanism. [81] Squids do not have the longitudinal muscles that octopus do. Instead, they have a tunic. [81]
The adductor muscles have been cut, the valves are gaping. The internal anatomy is visible, including the paired siphons to the right A siphon is an anatomical structure which is part of the body of aquatic molluscs in three classes : Gastropoda , Bivalvia and Cephalopoda (members of these classes include saltwater and freshwater snails , clams ...
Cirri are the small, thread-like structures that give cirrate octopuses their name. They line the octopuses' arms. Opisthoteuthis philipii is distinguishable from other Opisthoteuthis species by its uniquely shaped beak. [5] The mantle, which contains most of the vital organs, measures up to 140 mm (5.5 in).