Opisthoteuthis borealis: Description continued

1. Arms and web
   1. Arms subequal with length about 4 times ML; no consistent arm formula.
   2. About 80 suckers in single series on each arm; suckers embedded in semi-gelatinous tissue of arms.
   3. Web extends about 2/3 of arm length. Web formula: A=B>C=D>E.
      
      
2. Head
   1. Eyes 50% of ML.
   2. Optic lobes large, kidney shaped, with 3 bundles of nerves running to each eye.
   3. White body large, dark brown/purple in color.
      
      

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      Figure. Optic tract of O. borealis. Drawing from Collins (2006).

   4. Beak with  typical Opisthoteuthis form.
   5. Radula absent.
      
      

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      Figure. Beaks of O. borealis. Left - Upper beak. Right - Lower beak. Drawing from Collins (2006).

3. Funnel
   1. Funnel flaccid and moderately long (64% of ML) and darkly pigmented.
      
      
4. Mantle
   1. Mantle short, about 20% of total length.
   2. Mantle opening closely surrounds funnel.
      
      
5. Fins
   1. Fins moderate in size, positioned posterolaterally.
   2. Anterior and posterior fin margins thin and without proximal, anterior lobe.
   3. Each fin with internal cartilage extending from shell sac.
      
      
6. Pigmentation
   1. Skin surface smooth, reddish-brown color in preservation; Oral surface of web deeply pigmented.
   2.  Areolar spots not apparent on skin.
      
      
7. Shell
   1. Shell U-shaped with short, flaring lateral wings.
   2. Basal portion of shell with concave outer surface and convex inner surface.
   3. Lateral wings of shell with in-rolled margins, taper to acute points.
      
   

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   Figure. Three views of the shell of O. borealis. Drawing from Collins (2006).
8. Viscera
   1. Gills small, compact, spherical with 7-8 lamellae.
   2. Branchial heart rounded, half size of gill.
   3. Medial pallial adductor muscle thin, narrow.
   4. Digestive system
      1. Oesophagus, stomach and caecum with dark purple pigmentation.
      2. Digestive ducts unite prior to entering caecum.
      3. Intestine shorter than oesophagus, with S-shape.
      4. Anal flaps,ink sac absent and posterior salivary glands absent.
         
         
9. Reproductive system
   1. Male
      1. Large testis with short vas deferens; large convoluted seminal vesicle complex; three accessory glands with gland 2 largest; terminal organ short.
      2. Spermatophores oval in shape.
         
         

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         Figure. Two views of the male genital apparatus of O. borealis. Drawing from Collins (2006).

   2. Female
      1. Ovary with thin-walled proximal oviduct, oviducal glands and short distal oviduct.
         
         

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         Figure. The female genital apparatus of O. borealis. The proximal oviduct and Ovary are filled with ova. Drawing from Collins (2006).

10. Measurements and counts

    	ZMUC CEPH-3 Holotype	ZMUC CEPH-4 Paratype	ZMUC CEPH-4 Paratype	ZMUC CEPH-5 Paratype	ZMUC CEPH-6 Paratype	ZMUC CEPH-5 Paratype
    Sex	M	M	F	M	F	F
    Dorsal mantle length	60	55	65	75	68	~70
    Head width	88	105	--		*	102
    Fin span	--	130	--	150	120	135
    Fin length	32	32		48	40	37
    Fin width	16	16		32	22	20
    Eye diameter	25	31		42	42	35
    Funnel length	38	39	30	58	52	37
    Gill lamellae	8/8	7		7/7	7/8	8/8
    Web Formula	A=B>C=D>E	*	*		A=B>C=D>E	*
    Ovarial egg length	--	--	12	--	12	11
    Length, Arm I	*	260	*	280	190	*
    Arm II	*	230	*	280	205	*
    Arm III	*	250	240	255	185	*
    Arm IV	*	245	235	230	*	*
    Width, Arm I	23	*	*	31	22	*
    Max. sucker diameter, proximal field	5.8	6.3	4.5	7.2	4.2	*
    Max sucker diameter, distal field	4.8	6.0	--	7.0	--	*
    Proximal sucker field, location	4-9	5-9	--	5-10	--	*
    Distal sucker field, location	22-23	24-34	--	24-35	--	*
    Maximum cirrus length	5.0	6.0	*	6.8	6.0	*
    Sucker count	*	*	*	~81	~80	*

    *The count or measurement could not be obtained due to damage.
    Measurements in mm.

Comments

The above description is from Collins (2006). 

References

Collins, M.A. 2006. Opisthoteuthis borealis: A new species of cirrate octopod from Greenland waters. Journal of the Marine Biological Association of the United Kingdom 85: 1475-1479.