Iridoteuthis iris (Berry, 1909)

Introduction

I. iris is a small heteroteuthin (28 mm ML) with a broad dorsal head/mantle fusion and unusually large fins, eyes and ventral shield. It is known only from Hawaiian waters where it appears to be a member of the mesopelagic boundary fauna and occurs over bottom depths of about 350 - 450 m (Young, 1995).

Diagnosis

A heteroteuthin ...

• with mantle broadly fused to head dorsally.
• with enlarged suckers on arms I and III in males.

Characteristics

1. Arms
   1. Arms I in males not strongly modified; some enlarged suckers on arms I and III or arms II and III.
   2. Enlarged dorsal keels at tips of arms I-III.
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      Figure. Oral view of the brachial crown of I. iris, male, 24 mm ML. Left - Full brachial crown. Right - Enlargement of the tips of right arms II-IV. Drawings from Harman and Seki (1990).

   3. Tips of arms III and IV in females with elongate trabeculae.
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      Figure. Oral view of the brachial crown of I. iris, female, 21 mm ML. Left - Full brachial crown. Right - Enlargement of the tips of right arms II-IV. Drawings from Harman and Seki (1990).

2. Funnel
   1. Funnel locking-apparatus with deep, curved, anterior pit.
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   Figure. Funnel/mantle locking-apparatus of I. iris, Hancock Seamount, 29°46'30"N, 179°03'36"E, NMNH 817723, left = anterior. Top - Side-oblique view of the mantle component. Bottom - Frontal view of the funnel component. Photographs by M. Vecchione.

3. Mantle
   1. Dorsal mantle broadly fused to head (fusion nearly reaches posterior midpoints of eyes).
   2. Ventral-mantle shield large (ca. 80% of ventral mantle length); extends nearly to anterior margin of eyes; with medial anterior indentation.
   3. Mantle with middorsal arch.
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      Figure. Left - Lateral view of I. iris, male, 24 mm ML. Drawing from Harman and Seki (1990). Right - Dorsolateral view of I. iris. Arrow indicates point of head-mantle fusion. Photograph by Thomas Burch.

4. Fins
   1. Fins with pointed posterior lobes; extend to posterior margin of mantle.

Comments

These characteristics are from Harman and Seki (1990).

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.