Cirrina

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. However, subsequent studies, using a greater coverage of species and genes, have found Cirrata and Incirrata to be monophyletic clades, consistent with earlier morphological and molecular studies.

Locomotion and feeding

Cirrina octopods swim by a combination of fin action and medusoid propulsion. This mode of locomotion differs from other octopods that primarily rely on jet propulsion, which is less effective in cirrates. In cross-section, the fins have distinct proximal and distal regions, both covered by a thin muscle sheath. The distal region has dorsal and ventral muscle layers similar to those in decapod fins. In the proximal region, the fin cartilage forms a flat central core, providing skeletal support for muscle attachment. Limited data on the stomach contents of cirrate octopods indicate a diet primarily consisting of Crustacea and Polychaeta.

The cirri, relatively long in Cirroteuthis with reduced musculature, may be used to scan seafloor for prey during feeding and to capture prey. Reports on Stauroteuthis syrtensis suggest it consumes copepods and employs a hunting strategy that involves trapping prey in a muccous web produced by buccal secretory glands.

Reproduction

It is currently unknown how long female cirrate octopus are able to retain sperm. It is believed that female cirrina octopods produce eggs for the majority of their lifespan. Based on captured samples, scientists have been able to determine that female cirrina store a large amount of eggs, which vary in size and developmental stages. They release mature eggs one or two at a time, with the pre-mature eggs remaining attached to the ovary by a follicular sheath.

Cirrate octopods produce eggs which are different from Incirrates. For example, dumbo octopuses (Grimpoteuthis) lay their eggs one at a time. According to Ziegler, there are not enough egg specimens to draw conclusions about cirrate octopod development. Currently, microscopical data gathered from egg specimens are only enough to support inferences. It is believed that the eggs of species found in the mesopelagic and bathypelagic zones are substantially different from eggs of species found in the epipelagic and bathypelagic zones.

Classification

The family level clades recognized within Cirrina has changed over time. Currently five families are recognized by the World Register of Marine Species allocated to two superfamily level clades, Superfamily Cirroteuthoidea (Cirroteuthidae, Stauroteuthidae) and Superfamily Opisthoteuthoidea (Opisthoteuthidae, Grimpoteuthidae, and Cirroctopodidae), with these groups also recognized in recent molecular work.

The family Opisthoteuthidae are primarily found in benthic regions of the sea, whereas Grimpoteuthidae and Cirroctopodidae reside in the benthopelagic regions. Lastly, the Cirroteuthidae family can be found in the pelagic region near the seafloor.

The families Cirroteuthidae and Stauroteuthidae have been problematic, while they are distinct morphologically, molecular studies using mitochondrial genes revealed a single family (Stauroteuthidae being synonymized under Cirroteuthidae), but more recent analysis using nuclear genes does show separation. The family Grimpoteuthidae has also at times been synonymized under Opisthoteuthidae but is currently well supported.

• Class Cephalopoda
  • Subclass Nautiloidea: nautilus
  • Subclass †Ammonoidea: ammonites
  • Subclass Coleoidea
    • Superorder Decapodiformes: squid, cuttlefish
    • Superorder Octopodiformes
      • Family †Trachyteuthididae (incertae sedis)
      • Order Vampyromorphida: vampire squid
      • Order Octopoda
        • Genus †Keuppia (incertae sedis)
        • Genus †Palaeoctopus (incertae sedis)
        • Genus †Proteroctopus (incertae sedis)
        • Genus †Styletoctopus (incertae sedis)
        • Suborder Cirrina: finned deep-sea octopus
          • Superfamily Opisthoteuthoidea
            • Family Opisthoteuthidae (containing Opisthoteuthis, Exsuperoteuthis & Insigniteuthis)
            • Family Grimpoteuthidae (containing Grimpoteuthis, Cryptoteuthis, & Luteuthis)
            • Family Cirroctopodidae (containing Cirroctopus)
          • Superfamily Cirroteuthoidea
            • Family Cirroteuthidae (containing Cirroteuthis, Cirrothauma, & Inopinoteuthis)
            • Family Stauroteuthidae (containing Stauroteuthis)
          • Family & Superfamily uncertain: †Paleocirroteuthis
        • Suborder Incirrina: octopus without mantle fins or cirri.

References

References

1. (2006-06-13). "Oceanography and Marine Biology: An annual review. Volume 44". CRC Press.
2. (2008). "Late Cretaceous octobrachiate coleoid lower jaws from the north Pacific regions". Journal of Paleontology.
3. (2018). "Genus-level phylogeny of cephalopods using molecular markers: current status and problematic areas". PeerJ.
4. (2023-02-10). "Genome skimming elucidates the evolutionary history of OctopodA". Molecular Phylogenetics and Evolution.
5. (2003-05-01). "Phylogenetic relationships among cirrate octopods (Mollusca: Cephalopoda) resolved using mitochondrial 16S ribosomal DNA sequences". Molecular Phylogenetics and Evolution.
6. (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.
7. Vecchione, Michael. (1997). "Aspects of the functional morphology cirrate octopods: locomotion and feeding.". Vie et Milieu / Life & Environment.
8. (2008-04-15). "Cephalopods: Ecology and Fisheries". John Wiley & Sons.
9. (2006-06-13). "Oceanography and Marine Biology: An annual review. Volume 44". CRC Press.
10. (2006-06-13). "Oceanography and Marine Biology: An annual review. Volume 44". CRC Press.
11. (2021-12-20). "Novel insights into early life stages of finned octopods (Octopoda: Cirrata)". Swiss Journal of Palaeontology.
12. (2021-12-20). "Novel insights into early life stages of finned octopods (Octopoda: Cirrata)". Swiss Journal of Palaeontology.
13. "WoRMS - World Register of Marine Species - Cirrata".
14. Verhoeff, Tristan Joseph. (2023-11-24). "The molecular phylogeny of cirrate octopods (Cephalopoda: Octopoda: Cirrata) using COI and 16S sequences". Folia Malacologica.
15. (2006-06-13). "Oceanography and Marine Biology: An annual review. Volume 44". CRC Press.
16. (2006-06-13). "Oceanography and Marine Biology: An Annual Review, Volume 44". CRC Press.
17. (2022-01-02). "New records and two new species of Grimpoteuthis (Octopoda: Cirrata: Grimpoteuthididae) from southern Australia and New Zealand". Molluscan Research.
18. (2021-04-23). "Holistic description of new deep sea megafauna (Cephalopoda: Cirrata) using a minimally invasive approach". BMC Biology.
19. (March 2008). "Late Cretaceous octobrachiate coleoid lower jaws from the north Pacific regions". Journal of Paleontology.