Illex Steenstrup 1880

Introduction

This subfamily, as currently recognized, contains only the genus Illex. These are commercially important species found in neritic waters of the North and South Atlantic (Roper et al., 1998). The number of species in the North Atlantic has been controversial, with the validity of I. oxygonius repeatedly questioned. Carlini et al. (2006) used molecular methods to confirm that three species are present in the North Atlantic, although morphological identification of specimens other than mature males can be quite difficult.

Brief diagnosis:

Ommastrephids with ... 

• suckers in eight series on tentacular club dactylus. 

Characteristics

1. Arms
   1. Either right or left ventral arm hectocotylized.
   2. Hectocotylus with distal protective membranes absent.
      
   

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   Figure. Oral views of the distal region of the hectocotylus of Illex oxygonius. Top - Photograph by M. Vecchione. Bottom - Drawing from Roeleveld (1988). v - Ventral side.
   
2. Tentacles
   1. Large, medial club suckers with smooth or bluntly crenulated inner rings.
   2. Dactylus of tentacular club with suckers in eight series.
   3. Carpal locking-apparatus absent.
      
   

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   Figure. Oral view of the dactylus of the tentacular club of Illex sp. Photograph by M. Vecchione.
3. Head
   1. Funnel groove without foveola or side pockets.
      
      
4. Photophores
   1. Photophores absent.

Behavior

All species of Illex appear to congregrate, at least on occasion, near the ocean floor and spend time sitting on the ocean floor. Videos of Illex swimming near the ocean floor can be seen here.

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Figure. Left - Group of Illex sp., swimming near the ocean floor at about 600 m. Right - Illex coindetii sitting on the ocean floor. ©

Distribution

Found only in the Atlantic Ocean. Western Atlantic Ocean from Equator to Iceland and from southern Brazil to Patagonia, and eastern Atlantic from 20°S to 60°N, including Mediterranean Sea. These species are generally confined to continental shelf and slope areas, or nearby oceanic waters, perhaps because of their habit of sitting on the bottom at depths of up to 1000 m.

References

Carlini, D.B., L.K. Kunkle, and M. Vecchione. 2006. A molecular systematic evaluation of the squid genus Illex (Cephalopoda: Ommastrephidae) in the North Atlantic Ocean and Mediterranean Sea. Molec. Phylog. Evol. 41:496-502.

Roper, C.F.E., C. C. Lu, and M. Vecchione. 1998. Systematics and distribution of Illex species; a revision (Cephalopoda, Ommastrephidae). In: Voss, N.A., et al. (eds.) Systematics and Biogeography of Cephalopods. Smithson. Contr. Zool. 586:405-423.