Sepiola Leach, 1817

Introduction

Members of Sepiola are small, mostly less than 25 mm ML.

Brief diagnosis:

A sepiolin ...

• with arm suckers in two series.
• with bean-shaped visceral photophores.

Characteristics

1. Arms
1. Arm suckers in two series.
   
   
2. Hectocotylus typically with:
• 3-4 suckers at the base of the hectocotylus (left arm I).
• Stalks of the subsequent 4 suckers form tubercules of the copulatory apparatus which can be transformed into hooks or lobes.
• Distally the arm is thickened and suckers and stalks of the two series are somewhat separated forming a basket; some suckers often enlarged.


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Figure. Oral views of arms I of mature males of S. aurantiaca (A), S. steenstrupiana (B), S. ligulata (C), S. robusta. Drawings from Naef (1921-23).

2. Tentacles
1. Tentacular clubs with suckers in 8 or fewer series.
   
   
3. Head
   
   1. Beaks: Descriptions can be found here: Lower beak; upper beak.
      
      
4. Mantle
1. Anterior margin of ventral mantle with narrow indentation for funnel and adjacent rounded projections.
   

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   Figure. Ventral view of the mantle of S. aurantiaca, mature female, 13 mm ML . Compare with title illustration. Drawing modified from Naef (1921-23).

5. Photophores.
1. Pair of bean-shaped visceral photophores.
   
   
6. Gladius
1. Gladius present as a distinct rudiment

Comments

These characteristics are from Naef (1921-23). Naef places Inioteuthis as a subgenus of Sepiola.

Distribution

Along the eastern margin of the Atlantic Ocean from Norway to western Africa; along the western margin of the Pacific Ocean from Sakhalin and the South Kuril Islands off Russia, Japan, Philippines and Singapore (Nesis, 1982/87).

References

Naef, A. 1921-1923. Die Cephalopoden. Fauna e Flora del Golfo di Napoli, Monographie 35, Vol I, Parts I and II, Systematik, pp 1-863.

Nesis, K. N. 1982/87. 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