Ommastrephinae Posselt 1891

Introduction

Members of the Ommastrephinae are the most oceanic members of the Ommastrephidae and are commonly attracted to surface night-lights in the open ocean. Some species are fished commercially and one species, Ommastrephes bartramii, was taken in the North Pacific in quantities over 350,000 tons per year during the 1980s (Bower and Ichii, 2005). This subfamily contains the largest species (Doscidicus gigas) reaching a size of 120 cm ML and the smallest species (Hyaloteuthis pelagica) reaching a size of about 9 cm ML (Nesis, 1982/87). A wide variety of luminous organs are present on the mantle, head, arms, viscera and eyes but vary with species.

Brief diagnosis:

Ommastrephids with ...

• photophores. 

Characteristics

1. Arms
   1. Hectocotylus (left or right Arm IV) usually with distal ventral protective membrane expanded to form a flange (not expanded in Ommastrephes where it tapers toward tip).
   2. Hectocotylus possesses pores in some genera.
   

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   Figure. Mostly oral views of hectocotylized left or right ventral arms of representatives of Ommastrephinae genera. A - Ommastrephes bartramii. B - Sthenoteuthis pteropus, right arm. C - Dosidicus gigas, right arm. D - Eucleoteuthis luminosa, left arm. E - Hyaloteuthis pelagica, distal part of left arm, simplified. F - Ornithoteuthis volatilis, distal 2/3 right arm; left - oral view; right - ventrolateral view. v - Ventral side of arm. Drawings from Roeleveld (1988).  Arrows point to pores.
   
2. Tentacles (More details of the tentacular club can be seen here.)
   
   1.  Suckers of dactylus of tentacular club in four series.
   2. Carpal locking-apparatus usually present with one to several smooth-ringed suckers and corresponding knobs (absent in Ornithoteuthis).
      
      

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      Figure. Oral view of the tentacular club of O, bartramii, 303 m ML, off Baja California. Drawing from Young (1972).

3. Head
   1. Funnel groove usually with anterior foveola and side pockets (both absent in Ornithoteuthis).
      

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      Figure. Left - Ventral view of the funnel groove comparing modifications in two of the subfamilies. Drawing modified from Roper, et al. (1985). Right - Oral-oblique view of the funnel (with funnel valve protruding) and funnel groove of Sthenoteuthis oualaniensis showing foveola and side pockets. Photograph by R. Young.
      

4. Photophores
   1. Photophores present in all species.
      
   2. Subcutaneous photophores present in all species except those of Ornithoteuthis.
      
   

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   Figure. Ventral (top) and dorsal (bottom) views of the mantle of Sthenoteuthis oualaniensis that has been cleared and the photophores (and gladius, funnel locking-apparatus) stained with alcian blue stain. The numerous small, dark dots are subcutaneous photophores embedded in the mantle muscle. The lower, left arrow points to a dense patch of several hundred photophores. Photograph modified from Kishimoto and Kohno (1992).
   

   Table. Comparison of genera of Ommastrephinae

   	Photophore patch on dorsal mantle	Visceral photophores	Enlarged, easily visible, subcutaneous photophores	Largest manus sucker	Hectocotyllus with lateral pores	Arm tips
   Ornithoteuthis	No	One or two round organs, long streak	None	Toothed, no enlarged teeth	Yes	Normal
   Dosidicus	No	Two round organs, no streaks	None	Enlarged tooth in each quadrant	Yes	Attenuate at >35 cm ML, with 200-500 small suckers
   Ommastrephes	No	None	None	Enlarged tooth in each quadrant	No	Normal
   Sthenoteuthis	Yes	Two round organs, no streaks	None	Enlarged tooth in each quadrant	Yes; No in early maturing form	Normal
   Eucleoteuthis	No	One round organ, no streaks	Circular pads and streaks	Smooth except one tooth	No	Normal
   Hyaloteuthis	No	One round organ, no streaks	Circular pads	Smooth, sometimes one/few teeth	No	Normal

   

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   Figure. Explanation of table characters: Types of largest manus suckers. Drawings from Roeleveld (1988).

References

Kishimoto, H. and H. Kohno. 1992. Development of the luminous organ in the purpleback flying squid, Sthenoteuthis oualaniensis, as shown by Alcian Blue stain techniques. Bull. Inst. Oceanic Res. & Develop., Tokai Univ, 13: 71-83.

Nesis, K. N. 1982. Abridged key to the cephalopod mollusks of the world's ocean. 385,ii pp. Light and Food Industry Publishing House, Moscow. (In Russian.). Translated into English by B. S. Levitov, ed. by L. A. Burgess (1987), Cephalopods of the world. T. F. H. Publications, Neptune City, NJ, 351pp.

Roeleveld, M. A. 1988. Generic interrelationships within the Ommastrephidae (Cephalopoda). P.277-314. In: M. R. Clarke and E. R. Trueman (eds.). The Mollusca. Vol. 12. Paleontology and Neontology of Cephalopods. Academic Press, N.Y., 355pp.

Roper, C. F. E., M. J. Sweeney, And C. E. Nauen. 1985. FAO species catalogue. Vol. 3. Cephalopods of the World. An annotated and illustrated catalogue of species of interest to fisheries. FAO Fish. Synop., (125)3:277 pp.