Iridoteuthis Naef, 1912

Introduction

Iridoteuthis is similar in appearance to Stoloteuthis and Amphorateuthis. The genus contains two species, one of which is unnamed. The discovery of the second species has allowed us to better define the genus. Like all heteroteuthins, members of the genus are small and colorful. The best known and most distinctive species is I. iris known from Hawaiian waters. 

Brief diagnosis:

A heteroteuthin with ...

• mantle broadly fused to head dorsally.
• funnel locking-apparatus having a curved groove with deep, angular pit.

Characteristics

1. Arms
   1. Oral surfaces of arm bases, proximal to suckers, in females, covered with small papillae.
   2. Aboral surfaces of arms in both sexes with distal, expanded, tough, membranous keels (= flags).
   3. Arms III in males without enlarged sucker(s).
      
   

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   Figure. Left - Oral view of the papillate areas at the bases of the arms (upper arrow - arm III, lower arrow - arm I) in female Iridoteuthis sp. A.  Middle - Oral-lateral view of arm III tip, I. iris, male, showing keel. Right - Ventral view of arms III, I. iris, female, showing keel flags (arrows). Photographs by R. Young. 

2. Tentacles
   1. Tentacular club with a tentacular organ that extends well along the sucker-bearing portion of the club.
      
   

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   Figure. Oral view of the tentacular club of I. iris. Note the tentacular organ (arrow) extends along the proximal half or more of the sucker-bearing region of the club.

3. Funnel
   1. Funnel locking-apparatus with deep, angular, 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 in photographs is anterior. Top - Side-oblique view of the mantle component. Bottom - Frontal view of the funnel component. Photographs by M. Vecchione.

4. Mantle
   1. Dorsal mantle broadly fused to head (fusion approximately reaches posterior midpoints of eyes).
   2. Ventral-mantle shield large (ca. 80% of ventral mantle length); extends nearly to anterior margin of eyes; with strong anterior-medial indentation.
   3. Mantle with middorsal arch.
      

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      Figure. Lateral view of I. iris, male, 24 mm ML. Drawing from Harman and Seki (1990). 

5. Fins
   1. Fins with pointed posterior lobes.
      
      

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      Figure. Dorsal view of the left fin of Iridoteuthis sp. A, female, showing sharp angle (arrow) of posterior fin lobe. Photograph by R. Young.

6. Photophores
   
   1. Visceral photophore papillae each with two large, laterally-visible tubes.
   2. Photophore tubes located at lateral edges of photophore; do not penetrate photophore "lens" apparently entering glandular photophore between "lens" and ink sac.
      
   

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   Figure. Lateral view of the visceral photophore of Iridoteuthis sp. A showing two tubes (arrow) leading into the photophore at the side of the lens. Photograph by R. Young.

Comments

The above generic characteristics are mostly those that separate the genera Iridoteuthis and Stoloteuthis. The other genera are very different from these two and the reader is referred to the Heteroteuthinae page for comparisons of all genera.

Species comparisons 

The two species of Iridoteuthis are very different in the sexual modification of the arms (See table below for most striking differences).

Distribution

I. iris is known from the Hawaiian Archipelago and Iridoteuthis sp. A from off New Caledonia.

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.