Iridoteuthis iris (Berry, 1909)

Introduction

Iridoteuthis iris is a small heteroteuthin (28 mm ML in females, 24 mm in males) with very large eyes, short mantle that projects ventrally anterior to the eye lenses and unusually large fins. It is known only from Hawaiian waters.

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Figure. Iridoteuthis iris. Top - Dorsal and ventral views, male. Drawings from Harman and Seki (1990). Bottom - Ventrolateral view of live animal. © 1996 Thomas Burch.

Brief diagnosis

An Iridoteuthis ...

• without elaborate ventral protective membrane on right arm I in mature males.
  
• with size differentials in some arm suckers between dorsal and ventral series in males.
• with bare, elongate sucker stalks on tips of arms III and IV in females.
  

Characteristics

1. Arms (Harman and Seki, 1990)
   1. Males
      1. Arms I in males with dorsal series of suckers reduced in size on distal region of arms.
         
      2. Arms II in males each with slightly enlarged suckers on middle of arms.
      3. Arms III in males each with several greatly enlarged suckers in midarm of dorsal series; distal to enlarged suckers a short area without suckers and only sucker stalks (=pedicels).
      4. Arms IV ends in males each with suckers in four series.
         
      5. Enlarged dorsal keels (flags) at tips of arms I-III in males.
      

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      Figure. Oral view of the brachial crown of I. iris, male, 24 mm ML. Drawing from Harman and Seki (1990).

      

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      Figure. Oral view of the arm crown of I. iris, male. This appears to be the same specimen from which the above drawing was made. Photograph by R. Young.

      

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      Figure. Arm tips of I. iris, male, same specimen as above. Left - Oral view of arms I and II. Middle - Oral view of arm III. Right - Medial view of arm IV. Photographs by R. Young.

   2. Females
      1. Tips of arms I in females bare.
      2. Distal region of each arm III with elongate trabeculae, no suckers.
         
      3. Distal region of each arm IV with elongate trabeculae, no suckers; proximal half with relatively large suckers; next quarter with smaller suckers in somewhat irregular series.
      

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      Figure. Oral view of the brachial crown of I. iris, female, 21 mm ML. Drawing from Harman and Seki (1990).

      

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      Figure. Oral views of the arms of I. iris, female. Specimen appears to be the same as that from which the drawing above was made. Left - Left arms I-IV with arm I on the left of the photograph. Middle - Arm III tip. Right - Arm IV tip. Photographs by R. Young.
      

Comments

More details of the description of I. iris can be found here. 

Sexual dimorphism of arms apparent in animals larger than 8 mm ML (Harman and Seki, 1990).

See the Iridoteuthis page for a table comparing the most obvious differences between the species. 

Distribution

Type locality: Off the south coast of Molokai Isl, Hawaiian Archipelago, central North Pacific from over a bottom depth of 280 m. Subsequently captured at a variety of localities along the Hawaiian Archipelago from about 21°N, 157°W to about 32°N, 177°E. All captures are close to islands or seamounts and are from relatively shallow fishing depths (ca. 150-300 m). I. iris appears to be a member of the mesopelagic boundary fauna occuring over bottom depths of less than 450 m (Young, 1995).

Other Names for Iridoteuthis iris (Berry, 1909)

• Stoloteuthis japonica Kubodera, T. and T. Okutani 2011 Probable junior synonym

References

Harman, R. F. and M. P. Seki. 1990. Iridoteuthis iris (Cephalopoda: Sepiolidae): New records from the central North Pacific and first description of the adults. Pac. Sci. 44: 171-179.

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