Promachoteuthis megaptera Hoyle 1885

Introduction

Promachoteuthis megaptera is known from only two specimens: the holotype, 15 mm ML captured during the Challenger Expedition in the late 19th century and a female, 52 mm ML, captured 105 years later (1980) from nearly the same locality. It is most easily distinguished from congeners by the lack of a head-mantle fusion in the nuchal region, the long arms and tentacles, and a dark band at the base of the tentacles (see arrow in title photograph).

Diagnosis

• without nuchal fusion between head and mantle.
• with 2 series of suckers on arms.
• with pigment band around tentacle at base and without papillae on tentacles.

Characteristics

1. Tentacles
   1. Long, thick (length >2 times ML); base appears much wider than arm III (judging from title photograph).
   2. Club with many series (number uncertain) of small suckers.
   3. Suckers with smooth inner rings.
   4. Large arm suckers approximately four times the diameter of large club suckers (see drawings with same magnification on the right).
   5. Dark pigment band near tentacle base present (see title photograph above and drawing of head below).
      

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      Figure. Comparison of a club sucker (left) and an arm sucker (right) of P. megaptera, 52 mm ML. Drawing from Okutani (1983).

2. Arms
   1. Arms long (60-90% of ML)
   2. Suckers with smooth inner rings and pegs on outer rings.
      
      
3. Head and funnel
   1. Eyes small (1.6 mm in 15 mm ML squid).
   2. Eyes embedded in head and connected to exterior by narrow canal (drawing below).
   3. Mantle free from head in nuchal region; nuchal cartilage present (drawing below).
      
      

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      Figure. Left - Lateral view of the head showing the eye canal of P. megaptera, 52 mm ML. Right - Dorsal view of the nuchal cartilage of P. megaptera. Drawings from Okutani (1983).

Comments

This description, except for comments reflecting uncertainty, is taken from Okutani (1983). Additional details of the description can be found here.

Life History

Distribution

This species is known from two localities, both near Japan: 34°37' N, 140°32' E (type locality; 0-3690 m) and 31°00' N, 147°00' E (2750 m).

References

Okutani, T. 1983. Rare and interesting squid from Japan. VIII. Rediscovery of Promachoteuthis megaptera Hoyle, 1885 (Oegopsida: Promachoteuthidae). Venus 42: 241-247.

Roper, C. F. E. and R. E. Young (1968). The family Promachoteuthidae (Cephalopoda: Oegopsida). I. A re-evaluation of its systematic position based on new material from Antarctic and adjacent waters. Ant. Res. Ser., 11: 203-214.