Abraliopsis Joubin 1896

Introduction

Species of Abraliopsis are small squids that are most easily recognized by spherical "black" photophores (usually three) at the tip of each Arm IV. The black appearance is due to black chromatophores that tightly cover the photophores but when the latter luminesce, the chromatophores withdraw from the photophores. This feature is shared with Watasenia scintillans from waters around Japan.

Brief diagnosis: 

An enoploteuthid ... 

• with large, black photophores at the tips of arms IV.
• with hooks of manus in two series.
  

Characteristics

The following characters are from Young, et al., 1998.

1. Arms
   1. Suckers absent from arms IV (only hooks present).
   2. Right arm IV hectocotylized.
      
      
2. Tentacles
   1. Manus of club with two series of hooks and one series of suckers.
      
      
3. Buccal crown
   1. Buccal crown with dark epithelial pigmentation on oral surface rather than typical chromatophores.*
      

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

      

      Figure. Side view of A. pacificus. White arrow points to pigmented buccal crown. Black arrows point to large, pigmented photophores at the tips of arms IV. Photograph by R. Young.

4. 

   Figure. Ventral surface of the head and photophores of Abraliopsis pacificus. The photo on the left is an enlargement of some of the photophores.

   Fins
   1. Fins extend to posterior end of tail.
      
      
5. Photophores
   1. Two to four large photophores covered by black chromatophores on tips of each arm IV (see photograph under "Buccal crown.")*
   2. Five photophores on eyeball.*
   3. Complex organs of integument, in life, with red-colored filters.*

As in most other genera of the family, Abraliopsis has three types of integumental photophores covering the arms, head, funnel and mantle. The right-hand photo shows the ventral surface of the head and funnel. The most complex of the integumental photophores have red color filters. The other two types appear as blue photophores with white cores in the photos and can be separated only by size in these pictures. Large white ocular photophores are also easily seen through the skin.

*Characters shared with Watasenia

Classification

Species of Abraliopsis can be placed into three subgenera but these may not all be natural groups. Tsuchiya and Okutani (1988) suggested that A. felis be placed in a separate subgenus, Boreabraliopsis. The following table shows the primary taxonomic features of each group.

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

Figure. Arms IV from arms IV showing some of the group characters. Note the papillae at the base of the arms in A. falco and the smooth arms in A. felis, and the greatly expanded ventral membrane on the left arm IV of A. falco. Drawings from Young (1972).

References

Tsuchiya, K. and T. Okutani. 1988. Subgenera of Enoploteuthis, Abralia and Abraliopsis of the squid family Enoploteuthidae (Cephalopoda, Oegopsida). Bulletin of the National Science Museum, Tokyo (series A) 14: 119-136.

Young, R.E. 1972. The systematics and areal distribution of pelagic cephalopods from the sea off southern California. Smiths. Contr. Zool., 97:1-159.

Young, R. E., L. A. Burgess, C. F. E. Roper, M. J. Sweeney and S. J. Stephen. 1998. Classification of the Enoploteuthidae, Pyroteuthidae and Ancistrocheiridae. Smithson. Contr. Zool., No. 586: 239-256.