Choneteuthis tongaensis Lu and Boucher-Rodoni 2006

Introduction

Choneteuthis tongaensis is known from 3 specimens, the largest of which is 33.8 mm ML (holotype), that were taken in the vicinity of the Tonga Islands, South Pacific Ocean. The holotype is a female missing tentacles as is the second paratype. The first paratype is a male known from only the head and brachial crown.

Brief diagnosis: 

A sepiolid with ... 

• mantle free from head in nuchal region.
• large, circular visceral photophore and ventral shield.
• broad keel extending full length of club. 

Characteristics

1. Arms
   1. Suckers in two series to tips on all arms.
      
   2. Males
   1. Suckers on arms I and IV decrease in size from arm base to arm tip.
      
   2. Suckers in dorsal series of arms II increase in size to mid-arm then decrease to arm tip; suckers in ventral series increase in size to mid-arm followed by 3 or 4 abruptly enlarged enormous, somewhat flattened suckers then decrease in size to tip.
      
   3. Suckers in dorsal series of arms III increase in size from arm base for 3 or 4 suckers followed by 2 or 3 abruptly enlarged suckers to mid-arm then decrease in size to arm tip; suckers in ventral series decrease in size to tip.
      
      

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

      
      

      Figure. Ventral view of the head and arms of C. tongaensis, male, showing enlarged suckers on arms II. Photograph by C. C. Lu.

   3. Females
   1. Suckers increase in size from arm base to mid-arm then decrease in size to arm tip.
      
   2. No sucker enlargement.
      
      
2. Web
   1. Web (sector A) between arms I shallow (10% of longest arm in male; 14% in female).
      
      
3. Tentacles
   1. Club (known only for male, paratype 1) slightly expanded with suckers in about 6 series.
      
   2. Keel lies close to dorsal protective membrane from club tip to just beyond carpal region; widest along club manus.
      
      

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

      
      

      Figure. Views of the tenacular club of C. tongaensis, male. Upper left - Aboral view. Upper right - Curving oral view. Upper photographs by C. C. Lu..  Bottom - Oral view. Photograph from Lu and Boucher-Rodoni (2006).

4. Head
   1. Nuchal cartilage present, cartilagenous, broader anteriorly with  matching mantle cartilage.
      
   2. Head not fused to mantle in nuchal region.
      
      

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

      
      

      Figure. Dorsal view of the nuchal locking-apparatus of C. tongaensis with the mantle folded back. Left - Paratype 2. Right - Paratype 1. Photographs from Lu and Boucher-Rodoni (2006).

5. Funnel
   1.  Funnel long, tubular; length over 60% of ML, free from head for 75% of its length.
      
      
6. Funnel/mantle locking-apparatus
   1. Mantle component a simple, curved, raised ridge.
      
   2. Funnel component shoe-shaped with wider anterior end and curved depression.
   

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

   
   

   Figure. Frontal views of the two components of the funnnel/mantle locking-aparatus of C. tongaensis. Photographs from Lu and Boucher-Rodoni (2006).

7. Mantle
   1. Ventral mantle not extending anteriorly beneath head.
      
      
8. Photophores
   1. Single, large round photophore on ventral surface of ink sac.
      
      

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

      
      

      Figure. Ventral views of the mantle cavity and funnel of C. tongaensis with both structures cut open and folded back. Left - Paratype 2. Right - Holotype. Photographs from Lu and Boucher-Rodoni (2006).

Comments

More details of the description of C. tongaensis can be seen here. 

The above description with the exception of a few photographs is taken from Lu and Boucher-Rodoni (2006). 

Distribution

Type locality: The holotype (MNHN 3820) came from the Tonga Islands, N Ha’apai group, 19°42’S, 174°26’W, depth 332m. Paratype 1, male (head only), came from this same station. Paratype 2 (MNHN 3822) came from a seamount in the Tonga Islands at 22°11’S, 175°27’W, depth 385–405m.

References

Lu, C. C. and R. Boucher-Rodoni. 2006. A new genus and species of sepiolid squid from the waters around Tonga in the central South Pacific (Mollusca: Cephalopoda: Sepiolidae). Zootaxa, 1310:37-51.