Cirroctopus Naef, 1923

Introduction

Members of Cirroctopus 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.

Diagnosis

An opisthoteuthid ...

• with very large fins.
• with V-shaped shell. 

Characteristics

1. Arms and web
   1. Suckers not enlarged in males.
   2. Sucker aperature without tooth-like structures.
   3. Cirrus length comparable to largest sucker diameter.
   4. Web nodules absent.
      
      
2. Fins
   1. Fins long (greater than body width) and very broad.
      
      
3. Mantle cavity
   

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   Figure. Left - Diagram of G. glacialis with the ventral wall of the mantle cavity removed to show fusion of the mantle septum with the posterior mantle wall. Drawing from Vecchione and Young, 1997. Right - Ventral view of preserved gill of G. glacialis. Photograph by R. Young.

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

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   Figure. Side view of the digestive tract of C. glacialis 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. Drawing from Vecchione and Young, 1997.

5. Nephridial sacs
   1. Nephridial sacs extensive.
   2. Nephridial sacs with glandular lining on walls of sacs in additional to renal appendages.
      
      
6. Pigmentation
   1. Areolar spots present in young and near eyes and base of fins in adults.
      
      
7. White body, optic lobe and optic-nerve tract
   1. White bodies meet in dorsal midline.
   2. Numerous optic nerve bundles penetrate white body.
   3. Optic lobe kidney-shaped in cross-section.
   

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   Figure. Optic lobe with optic nerve bundles penetrating white body of G. hochbergi. Drawing from O'Shea, 1999.

8. Shell
   Shell V-shaped with long wings and short saddle.
   

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   Figure. Dorsal and ventral views of the shell of G. glacialis, stained, preserved. Photograph  by R. Young.

Comments

The four species of Cirroctopus 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.

Distribution

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Figure. Distribution chart of Cirroctopus spp. Blue dots: C. hochbergi. Red dots: C. glacialis. Yellow dot: C. mawsoni. Open squares: Cirrates identified as C. mawsoni by O'Shea (1999). Chart modified slightly from O'Shea (1999).

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.