Opisthoteuthis pluto: Description Continued

1. Eyes
   1. "Moderately large."
      
      
2. Funnel
   1. Long and narrow; funnel organ with a pair of well-separated oblique oval pads.
   

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   Figure. Funnel of O. pluto laid open to show funnel organ.  Drawing from Berry (1918).

3. Fins
   1. "...large, flabby, oblong, about twice as broad as long."
4. Gills
   1. Gills with 8 primary lamellae.
      
      
5. Optic lobes and nerves
   1. Unknown
      
      
6. Digestive system
   1. Digestive gland bilobed (O'Shea, 1999).
      
      
7. Beaks
   1. Beaks illustrated but not described.
   

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   Figure. Lateral view of lower (left) and upper (right) beaks of O. pluto. Drawings from Berry (1918).

8. Shell
   1. Broadly U-shaped.
   2. Saddle with groove along posterior surface.
   3. Wings with a vertical thickening, then rapidly tapering, outer surface slightly excavated at point of expansion.
   

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   Figure. Dorsal (bottom) view of the shell and oblique view of the shell wing (top) of O. pluto.  Drawings from Berry (1918).

9. Pigmentation
   1. Upper surfaces with chocolate and dark slate gray.
   2. Oral surface of web dark chocolate brown, paler toward mouth and periphery.
   3. Suckers and cirri light brown.
   4. Oral surface of arms same color as web.
   5. Areolar spots present (drawings on right): generally appear with small, sharply defined nucleus surrounded by a narrow zone of dark chocolate then a wider paler region which is succeeded by a poorly defined zone of bluish slate.
   6. Arrangement of areolae uncertain: absent from body; a series beginning between eyes extends along each arm I; similar but less numerous series extend along other arms.
   

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   Figure. Areolae of O. pluto. Left - areola in contracted state from a medium-sized octopod. Right - areola in expanded state, same animal. Scale bar is 5 mm. Drawings from Berry (1918).

10. Measurements and counts

    Sex	? Holotype	?	? Paratype	?
    Spread (arm tip to arm tip)	540	350	275	195
    Fin span, mm	210	115	115	70
    Fin length	60	30	20	10
    Fin width	30	15	10	5
    Head width	100	70	75	30
    Arm I, length (right/left)	260/260	160/160	145/145	85/85
    Arm II, length	250/250	155/155	150/140	85/85
    Arm III, length	270/245	170/145	140/145	90/90
    Arm IV, length	245/250	160/160	115+/130	85/90
    Diam. sucker no. 5, arm I	7	4	3.5	2
    Depth web sector A	170	105	95	60
    Depth web sector C	145	95	100	55
    Depth web sector E	140	100	80	55

    These measurements and counts are from Berry, 1918.

Comments

The above description is taken from Berry (1918) except where otherwise noted.

References

Berry, S.S. 1918. Report on the Cephalopoda Obtained by the F.I.S. "Endeavour" in the Great Australian Bight and Other Southern Australian Localities. Biological Results of the Fishing Experiments carried on by the F.I.S. "Endeavour", 1909-1914, 4(5):201-298.

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