Abraliopsis pacificus Tsuchiya and Okutani 1991

Introduction

A. pacificus is distributed from the Northwest Pacific along the southern border of Kuroshio Current and its extension waters.  Females reach at least 36 mm ML and males 26 mm ML.

Click on an image to view larger version & data in a new window

Figure. Ventral view of a paratype of A. pacificus, female, 26 mm ML. Photograph by R. Young.

Brief diagnosis

An Abraliopsis (Abraliopsis) ...

• with dorsal flap (very small) on hectocotylus.
• with 16-30 (x̅ = 21) hooks on arm IV.
• with distribution in subtropical Northwestern Pacific.
  

Characteristics

1. Tentacle clubs
   1. Two rows of Different-sized hooks on manus.
   2. Carpal flap and aboral keel, large.
      
   

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   Figure. Oral view of the tentaclular club of A. pacificus, northwest Pacific, male. Drawing from Tsuchiya and Okutani (1989).
   

2. Head
   
   1. Occipital folds 2-4 not clearly connected by posterior crescent ridges.
      
   2. Head width index - Males: 30.7-39.9 (x̅ = 35.4, n = 5); Females: 30.9-33.8 (x̅ = 32.9, n = 5).
      
      
3. Arms
   1. Arms IV of moderate length; ALI IV = 62-76 (x̅ = 68.2, n = 16).
   2. Arms with 16-30 hooks (mainly 16-23, x̅ = 21, n = 15) and 10-25 distal suckers.
      
      
4. Hectocotylus
   1. Hectocotylus (right arm IV) with two different-sized flaps: long, narrow, proximal flap on ventral margin and short (about 1/4 length of ventral flap), distal flap on dorsal margin.
   

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   Figure. Aboral (top) and oral (bottom) views of the hectocotylus of A. pacificus, male, Northwest Pacific. Drawing from Tsuchiya and Okutani (1989).

5. Fin width index - 88-95 (x̅ = 91.5, n = 10).
   
   
6. Photophores
   1. Ocular photophores: 5 photophores on each eye.
      
   2. Integumental photophores: Ventral mantle and head with scattered arrangement of photophores.
      
      

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      Figure. Ventral views of the head  and anterior mantle regions of an A. pacificus paratype, female 28 mm ML. Photograph showing integumental photophores. Right - Outline drawing from previous photograph with all integumental photophores represented by colored dots. Red dots - Complex photophores. Blue dots - Non-complex photophores. Images by R. Young.

      More details of the integumental photophores can be found here.

7. Reproductive structures
   1. Spermatangia receptacles located dorsal-collar pocket on either side of nuchal cartilage.

8. Measurements and counts
   

   	Holotype	Paratype 2	Paratype 4	Paratype 8	Paratype 1	Paratype 3	Paratype 5	Paratype 7
   Sex	Male	Male	Male	Male	Female	Female	Female	Female
   Mantle length	26	26	25	23	36	35	34	32
   Head width index	30.7	33.9	34.9	39.9	33.4	32.9	30.9	33.8
   Fin Length index	76.6	81.2	78.3	77.7	76.9	75.6	74.7	76.2
   Fin width index	90.8	87.9	95.2	92.3	91.2	90.2	90.3	92.9
   Arm length index: I	36.4/33.0	35.8/36.6	37.4/45.4	42.5/44.4	46.3/44.9	40.4/41.8	45.0/47.7	49.9/45.8
   II	43.3/48.7	32.3/44.8	51.4/53.0	49.4/59.2	52.9/50.7	45.2/43.2	54.1/55.6	52.9/57.6
   III	46.7/42.2	41.3/38.9	44.2/49.4	53.2/53.7	47.7/52.1	43.5/43.2	49.1/48.8	54.8/51.1
   IV	65.1/69.4	64.2/63.8	62.3/61.9	74.7/75.8	74.9/76.3	63.1/64.0	67.4/71.8	72.1/65.0
   No. hooks, I	20	21	28	18	20	19	19	18
   II	23	19	25	21	21	23	22	22
   III	21	21	22	20	25	17	19	20
   IV	17/17	16/20	16/16	16/16	20/23	-/18	19/19	18/17
   Club length index	19.9/18.8	22.2/21.0	20.1/24.1	- /-	24.2/23.1	19.3/21.0	21.8/20.9	21.7/23.5

Comments

This Abraliopsis pacificus is sometimes confused with Abraliopsis sp. B (e.g., Young, 1978. 1995).  A. pacificus, however, has ...

• a dorsal flap on the hectocotylus (flap absent in A. sp. B).
• a greater number hooks on arms IV than in A. sp. B.
• a narrower head then in A. sp. B.
  

See Abraliopsis (Abraliopsis) page for comparisons of all species of the subgenus.

Distribution

Geographical Distribution

This species is found in the Northwest Pacific between about 30° and 35° N. (Tsuchiya and Okutani, 1990).

References

Tsuchiya, K. 1993. Distribution and zoogeography of the family Enoploteuthidae in the Northwest Pacific. In: Okutani, T., O’Dor, R. K. and Kubodera, T. (eds.) 1993. Recent advances in fisheries biology (Tokai University Press. Tokyo). pp. 571-585.

Young, R. E. 1978. The vertical distribution and photosensitive vesicles of pelagic ceph- alopods from Hawaiian waters. Fish. Bull. 7 6 : 583-615.

Young, R.E. 1995. Aspects of the natural history of pelagic cephalopods of the Hawaiian mesopelagic-boundary region. Pacific Science, 49:143-155.