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The following four species are included in the family.

Containing group: Opisthoteuthidae

Introduction

Members of this family are more muscular than is typical for cirrate octopods. The fins are extremely large and the eyes tilt dorsally. Members of the genus are restricted to high latitudes of the southern hemisphere. Cirroctopus is probably the most distinctive of the four opisthoteuthid genera.

Characteristics

1. Arms and web
   1. Suckers not enlarged in males.
   2. Cirrus length comparable to largest sucker diameter.
   3. Web nodules absent.
2. Fins
   1. Fins long (greater than body width) and very broad.
3. Mantle cavity
   image info image info
   1. Mantle septum fused posteriorly with mantle wall. (This is a unique feature within the Octopoda.)
   2. Gill (photograph above right) with half-orange appearance and with characteristic zig-zag arrangement of secondary lamellae.
4. Digestive tract

   Caecum nearly equal to or much larger than stomach. Intestine long (ca. 2.5 times esophagus length) with a variety of right-angle turns. Unilobular digestive gland.

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   The drawing on the left shows the digestive tract with the complex orientation of the intestine. The label "bend" indicates a sharp bend in the intestine toward the viewer that isn't otherwise clearly apparent.

5. Nephridial sacs
   1. Nephridial sacs extensive.
   2. Nephridial sacs with glandular lining on walls of sacs in additional to renal appendages.
1. Pigmentation
   1. Areolar spots present in young and near eyes and base of fins in adults.
2. White body, optic lobe and optic-nerve tract

   White bodies meet in dorsal midline. Numerous optic nerve bundles penetrate white body. Optic lobe kidney-shaped in cross-section.

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3. Shell

   Shell V-shaped with long wings and short saddle.

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   The shell in the photographs on the left have been stained with methylene blue.

Comments

The four species of the genus are poorly differentiated at present. Although a few potentially differentiating characters are known, identification must rely heavily on geographic location until the species are better known.

Diagnosis

Opisthoteuthids with:

Arms without enlarged sucker fields in males. Fins very large. Areolae present.

Optic lobe kidney-shaped. Numerous optic nerve bundles penetrate white body. Shell V-shaped. Sucker aperature without tooth-like structures.

Distribution

Species of Cirroctopus are known only from Antarctic and Subantarctic waters. Blue dots: C. hochbergi Red dots: C. glacialis Yellow dot: C. mawsoni Open squares: Cirrates identified as C. mawsoni by O'Shea (1999).

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References

O’Shea, Steve. 1999. The Marine Fauna of New Zealand: Octopoda (Mollusca: Cephalopoda). NIWA Biodiversity Memoir 112: 280pp.

Vecchione, M. and R. E. Young. 1997 Aspects of the functional morphology of cirrate octopods: locomotion and feeding. Vie Milieu 47(2):101-110.

Voss, G. L. and W. G. Pearcy. 1990. Deep-water octopods (Mollusca: Cephalopoda) of the Northeastern Pacific. Proc. Calif. Acad. Sci. 47: 47-94.