Mastigoteuthis dentata Hoyle, 1904

Introduction

Hoyle (1904) based his description of M. dentata on two specimens from the Eastern Tropical Pacific off Panama, neither had tentacles.  The type description with relevant notes can be seen here.

We describe here specimens taken from the central Equatorial Pacific and from the central North Temperate Pacific. At present we consider these all belong to M. dentata. 

Brief diagnosis:

A Mastigoteuthis with ...

• a Pacific Ocean habitat.
• two primary rows of photophores on each arm IV.

Characteristics

1. Tentacles
   1. Club suckers vary in size and packing density depending on position on club (a Mastigoteuthis characteristic).
      
   

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   Figure. Oral view of different portions of the tentacular club of M. dentata, mature male, 135 mm ML, 6°N, 150°W. 1 - Proximal end of the club. 2 - Middle of the club. 3 - distal region of the club. Photograph by R. Young.

Scanning electron micrographs of the arm and tentacle suckers can be seen here.

2. Head
   1. Beaks. Description of the beaks can be found here.
      
      
3. Funnel
   1. Funnel locking-apparatus without a distinct antitragus.
   2. Posterior margin of funnel component strongly undercut, matching hook-shaped mantle component.
      
      

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      Figure. Funnel locking apparatus of M. dentata, 48 mm ML, central equatorial Pacific. Left - Anterofrontal view of funnel component. Left middle - Frontal view of funnel component. Right middle - Frontal view of mantle component. Right - Side view of mantle component. Blue tint from methylene blue stain. Photographs by R. Young.

      

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      Figure. Funnel locking apparatus of M. dentata, 135 mm ML, central equatorial Pacific. Left - Anterofrontal view of funnel component. Right - Side view of mantle component. Blue tint from methylene blue stain. Photographs by R. Young.

   
   
4. Mantle
   1. Tubercules absent.
   
   
5. Fins
   1. Slightly wider than long.
      
   
   
6. Photophores
   1. Integumental photophores in two series on arms IV.
   2. Eyelid photophore present and and small as in all members of Mastigoteuthis.
      
   

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   Figure. Ventral view of the head and arms IV of M. dentata. Photograph by R. Young.

7. Measurements

   Source	Hoyle, 1904
   Mantle length	72
   Mantle width	17
   Head width	17?
   Fin length	48
   Fin width	52
   Arm I, length: Right / Left	37 / 38
   Arm II, length	44 / 47
   Arm III, length	45 / 42
   Arm IV, length	87 / 78

   *Measurements in mm.

Comments

We have examined few specimens from the Pacific Ocean. At present there are no reliable characters that separate M. dentata from M. agassizii. Genetic data is needed to determine if the Pacific form is distinct from that of the Atlantic.

Distribution

Type locality: Gulf of Panama, off Cape Mala, Panama at 7°21'N, 79°35'W. In the Central Pacific M. dentata is found in Equatorial and Temperate waters but not in between around the main Hawaiian Islands. It appears to be absent from the Eastern Pacific in waters occupied by Mastigotragus pyrodes. In the Western North Pacific it occurs as far north as the Kurile Islands (Nesis, 1982/87). In the South Pacific it is known from southern Australia, New Zealand and off central Chile and in the Indian Ocean it is known from Southern Africa (Nesis, 1982/87).

References

Hoyle, W.E. 1904. Reports on the Cephalopoda. Bulletin of the Museum of Comparative Zoology at Harvard College, in Cambridge, 43(1):1-72.

Young, R. E. 1972. The systematics and areal distribution of pelagic cephalopods from the seas off Southern California. Smithson. Contr. Zool., 97: 1-159.