Comments on this page refer to living Octopoda. for comments on extinct Octopoda see: Teudopseina and Incirrata.

Octopods have rather short, compact bodies and only eight arms; no trace of the missing second arm pair remains even during embryonic development. Many species are benthic (bottom-living) and crawl over the ocean floor with the mouth facing the substratum. Others alternate between a benthic and a pelagic (free-swimming) habitat and some species are completely pelagic. The two suborders of Octopoda are very different in appearance but there is little doubt that it is a natural group as the monophyly of the Octopoda is supported by a large variety of characters. The Cirrata is a group of deep-sea octopods commonly known as the "finned octopods" due to their large, wing-like fins. The Incirrata contain the common (benthic), shallow-water octopods as well as many deep-sea benthic and pelagic species.

Brief diagnosis:

An octopodiform ...

• with one arm pair, presumaably true arms II, absent.
  
• with suckers on proximal halves of arms.
  

1. Arms
   1. Suckers with cuticular lining.
      
   2. Sucker stalks are broad, muscular cylinders.
      
      
2. Head
   1. Nuchal cartilage absent.
      
   2. Inferior frontal lobe system present; superior buccal and posterior buccal lobes fused; suprabrachial commissure separate from brain (absent in Japetella).
      
      
3. Funnel
   1. Funnel valve absent.
      
      
4. Viscera
   1. Visceropericardial coelom reduced.
   2. Oviducal glands act, in part, as spermathecae.
   3. Oviducts with oviducal glands subterminally located on oviducts.
   4. Photosensitive vesicles located on stellate ganglia.
      
   5. Dorsal mantle cavity present.

Octopoda (octopuses) is prey of:
Homo sapiens

Based on studies in:
USA: Alaska, Aleutian Islands (Coastal)

This list may not be complete but is based on published studies.

Octopoda (octopuses) preys on:
Decapoda

Based on studies in:
USA: Alaska, Aleutian Islands (Coastal)

This list may not be complete but is based on published studies.

• Octopoda
  • Cirrata
  • Incirrata
  • Teudopseina †

The monophyly of both suborders is well established. Young and Vecchione (1996) found two apomorphic character states that defined the monophyly of the Incirrata:

• Presence of a cornea.
• Hectocotylization of one of the third arms.

Another character can probably be added to the list of apomorphies although it hasn't been included in a cladistic study:

• Chorion of egg drawn out into a stalk (Young, et al., 1999).

Young and Vecchione (1996) found three character states that defined the monophyly of the Cirrata:

• Spermatophores as sperm packets without ejaculatory apparatus.
• Presence of horizontal arm septa.
• Buccal position of posterior salivary glands.

Voight (1997) also found morphological, cladistic support for the Cirrata and Incirrata but her study is controversial. Carlini (1998) found molecular analyses supported the monophyly of both groups.

Ink cloud distracts predators: octopus
 

The ink cloud emitted by an octopus when threatened aids escape because it resembles the shape of the octopus.

   
  "When their speed alone is not enough for safety, [cuttlefish] squirt a cloud of dense, dark coloured ink that is synthesised in their bodies. This ink surprises their predators for a few seconds, which is usually enough for them to escape." (Yahya 2002:104)

"Sometimes the ink cloud itself resembles the blobby shape of an octopus and acts as a decoy, allowing the octopus to escape while the predator eyes the blob." (Crump 2005:109)
  Learn more about this functional adaptation.

Siphon directs underwater movement: octopus
 

Siphons of octopi, squid, and cuttlefish jet through the water with directional control via jet propulsion.

     
  "Octopuses, squid, and cuttlefish have a more sophisticated version of jet propulsion. They expel water through a moveable tube called a siphon, which combines power with directional control." (Downer 2002:17)
  Learn more about this functional adaptation.

Barcode of Life Data Systems (BOLD) Stats
                                        

Specimen Records:	2,207	Public Records:	1,224
Specimens with Sequences:	2,031	Public Species:	87
Specimens with Barcodes:	1,985	Public BINs:	114
Species:	175
Species With Barcodes:	158

Access Published & Released Data: Download FASTA File

Collection Sites: world map showing specimen collection locations for Octopoda