Cirrina

Cirrina or Cirrata is a suborder and one of the two main divisions of octopuses. Cirrate octopuses have a small, internal shell and two fins on their head, while their sister suborder Incirrina has neither. The fins of cirrate octopods are associated with a unique cartilage-like shell in a shell sac. In cross-section, the fins have distinct proximal and distal regions, both of which are covered by a thin surface sheath of muscle.

Cirrina
Oral view of Cirrothauma murrayi showing single row of suckers and paired cirri
Scientific classification e
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Order: Octopoda
Suborder: Cirrina
Grimpe, 1916 sensu Felley et al., 2001
Families

Opisthoteuthidae
Cirroteuthidae
Stauroteuthidae
Cirroctopodidae

Synonyms
  • Cirrata
    Grimpe, 1916
  • Cirroctopoda
    Young, 1989

The suborder is named for small, cilia-like strands (cirri) on the arms of the octopus, a pair for each sucker. These are thought to play some role in feeding, perhaps by creating currents of water that help bring food closer to the beak. Cirrate octopuses are noteworthy for lacking ink sacs.

Phylogeny

A molecular phylogeny based on mitochondrial and nuclear DNA marker sequences by Sanchez et al., 2018, shows that the Cirrina is paraphyletic, i.e. it is not a single clade. Instead, a clade containing Opisthoteuthidae and Cirroctopodidae is sister to the Octopodida, while a clade containing Cirroteuthidae and Stauroteuthidae is sister to the clade that contains those other groups.[1] However subsequent studies, using a greater coverage of species and genes, have found Cirrata and Incirrata to be monophyletic clades,[2] consistent with earlier morphological and molecular studies.[3][4]

Classification

References
  1. Sanchez, Gustavo; Setiamarga, Davin H. E.; Tuanapaya, Surangkana; Tongtherm, Kittichai; Winkelmann, Inger E.; Schmidbaur, Hannah; Umino, Tetsuya; Albertin, Caroline; Allcock, Louise; Perales-Raya, Catalina; Gleadall, Ian; Strugnell, Jan M.; Simakov, Oleg; Nabhitabhata, Jaruwat (2018). "Genus-level phylogeny of cephalopods using molecular markers: current status and problematic areas". PeerJ. 6: e4331. doi:10.7717/peerj.4331. PMC 5813590. PMID 29456885.
  2. Taite, M.; Fernández-Álvarez, F. Á.; Braid, H. E.; Bush, S. L.; Bolstad, K.; Drewery, J.; Mills, S.; Strugnell, J. M.; Vecchione, M.; Villanueva, R.; Voight, J. R.; Allcock, A. L. (2023-02-10). "Genome skimming elucidates the evolutionary history of OctopodA". Molecular Phylogenetics and Evolution. 182: 107729. doi:10.1016/j.ympev.2023.107729. ISSN 1055-7903. PMID 36773750. S2CID 256804597.
  3. Piertney, Stuart B.; Hudelot, Cendrine; Hochberg, F. G.; Collins, Martin A. (2003-05-01). "Phylogenetic relationships among cirrate octopods (Mollusca: Cephalopoda) resolved using mitochondrial 16S ribosomal DNA sequences". Molecular Phylogenetics and Evolution. 27 (2): 348–353. doi:10.1016/S1055-7903(02)00420-7. ISSN 1055-7903. PMID 12695097.
  4. Lindgren, Annie R.; Pankey, Molly S.; Hochberg, Frederick G.; Oakley, Todd H. (2012-07-28). "A multi-gene phylogeny of Cephalopoda supports convergent morphological evolution in association with multiple habitat shifts in the marine environment". BMC Evolutionary Biology. 12 (1): 129. doi:10.1186/1471-2148-12-129. ISSN 1471-2148. PMC 3733422. PMID 22839506.


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