Onychoteuthis aequimanus Gabb, 1868

Introduction

Gabb (1868) described Onychoteuthis aequimanus from two specimens collected near the Society Islands.  Although it was synonymized with Os. banksii by Adam (1962) and Voss (1962), several subsequent authors have recognized the existence of multiple banksii-affiliated species in the Pacific (Young & Harman 1987, Bolstad 2008).  Examination of the syntypes suggests that Os. aequimanus is the correct name for one of these Pacific species.  

Characteristics

Figure. O. cf. aequimanus, in dorsal arm-curl posture, side view (in situ photograph, same squid as in title photograph). Top insert: Enlargement showing gladius rostrum (top yellow arrow) and gladius conus (bottom yellow arrow. Bottom insert: Enlargement of club showing terminal pad of right club (yellow arrow) apparently locked to aboral surface of terminal pad of left club.  © 2016 Jeffrey Milisen

1. Photophores
   1. Two circular intestinal photophores present. Anterior photophore ~40-60% diameter of posterior photophore.
   2. Ocular photophore a long whitish patch on ventral surface of each eyeball.
   
   
2. Measurements of larger syntype
   1. Mantle length - 93 mm
   2. Arm lengths - 37-50 mm
   3. Fin length - 49 mm
   4. Fin width - 56 mm (damaged)
   5. Club length - 24 mm (right)
   6. Club hook numbers - 23
      
   7. Largest hooks - Hooks V6 and V7
   8. Smallest mid-series dorsal hooks - Hooks D4 and D5
   
   
3. Tentacle club
   1. Length ~28% ML, with 20–23 hooks.
   2. Distal-most ventral hook bases not produced into spike below ML ~90 mm; may develop small spike at greater MLs.
      
      

      Click on an image to view larger version & data in a new window

      

      Click on an image to view larger version & data in a new window

      
      

      Figure. O. aequimanus, left tentacular club, oral view, female, 70 mm ML. Note the suckers of the terminal pad (see above photograph. ©

   Comments

   Gabb (1868) remarked that the Os. aequimanus syntypes (two males, ANSP 6444) had been long preserved in alcohol before he received them, and had lost much pigmentation. Their soft tissues have also hardened, the tentacles appear stretched, and the hooks somewhat desiccated.  However, most of the important characters (photophores, club morphology overall body proportions, beak and radula) are in reasonable condition.
   

Life History

Click on an image to view larger version & data in a new window

Figure. Growth stages of O. aequimanus, dorsal and ventral views. Top left _ 138 mm ML, female. Top right - 66 mm ML, sex unknown. Bottom left - 37 mm ML, sex unknown. Bottom right - 15 mm ML, sex unknown. ©

Distribution

References

Adam, W. 1962. Céphalopodes de l’Archipel du Cap–Vert, de l’Angola et du Mozambique. Memórias da Junta de Investicacões do Ultramar, second series, 33: 9–64, pl. 1.

Bolstad, K.S. 2008. Two new species and a review of the squid genus Onychoteuthis Lichtenstein, 1818 (Oegopsida: Onychoteuthidae) from the Pacific Ocean. Bulletin of Marine Science, 83: 481–529.

Bolstad, K.S.R. 2010. Systematics of the Onychoteuthidae Gray, 1847 (Cephalopoda: Oegopsida). Zootaxa, 2696: 186 pp.

Gabb, W.M. 1868. Description of a new species of cephalopod from the South Pacific. American Journal of Conchology, 4: 23–24, 1 pl.

Voss, G.L. 1962. List of the types and species of cephalopods in the collections of the Academy of Natural Sciences of Philadelphia. Notulae Naturae, 356: 1–7.

Young, R.E. & Harman, R.F. 1987. Descriptions of the larvae of three species of the Onychoteuthis banksii complex from Hawaiian waters. The Veliger, 29: 313–321.