Abralia heminuchalis Burgess 1992

Introduction

A. heminuchalis is a small sized species, less than 40mm DML, found in the tropical  Pacific. It is very similar to A. siedleckyi from off South Africa and may prove to be a junior synonym of the latter. It is characterized by its proportionally short, robust mantle and a photophore arrangement on the ventral head and mantle in which large photophores have a space surrounding each organ.

Brief diagnosis:

An Abralia (Heterabralia) with ...

• anterior ocular photophore comparable in size to largest of 3 medial ocular photophores but much smaller than posterior ocular photophore. 
• irregular photophore series on mid-region of arms IV.
  

Characteristics

1. Tentacle clubs
   1. Two or three hooks on ventral side.
   2. Two rows of large suckers on dorsal side of manus.
   

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   Figure. Oral view of the tentacular club of A. heminuchalis. Drawing from Burgess (1991, p. 121, Fig. 2J)
   

2. Hectocotylus
   1. Left ventral arm of male hectocotylized.
   2. Hectocotylus with two different sized off-set flaps: an elongate, proximal flap on ventral margin and much shorter, distal flap on dorsal margin.
   

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   Figure. Oral view of the distal portion of the hectocotylus of A. heminuchalis. Drawing from Burgess (1991, p. 121, Fig. 2I).
   

3. Eye Photophores
   1. Five, complex organs: two terminal opaque organs and three intermediate silvery organs. Posterior opaque organ much larger than others; anterior opaque photophore about the same size as the largest intermediate organ.
      

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      Figure. Ventral view of the ocular photophores of A. heminuchalis, anterior is at left. Top - Drawing from Burgess (1991, p. 121, Fig. 2B). Bottom - Photograph of a damaged, preserved eye. Note the pale color of the two terminal photophores and the orange color of the three medial photophores. Photograph by R. Young.
      

4. Integumental Photophores
   1. Arms IV with scattered photophores between the two photophore series (the series on the edge of the lateral memberane constitutes a third series).
   2. Ventral mantle and head with scattered arrangement of integumental organs.
   3. Large organs each surrounded by space lacking photophores (black arrows in photograph). Their appearance (which is poorly defined in the photograph) varies depending on the contraction state of nearby chromatophores.
   4. Scattered, small photophores on midregion of arms IV between medial and lateral arm photophore series (white arrow in photograph). These photophores apprear at about 25 mm ML and are absent in A. andamanica and A. trigonura.
      
      

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      Figure. Ventral view of the head, posterior region of arms IV and anterior region of mantle of A. heminuchalis, 35 mm ML, equatorial pacific, mature male. Note the small photophores present in the mid-region of arms IV (white arrow).  Note, also, the large photophores surrounded by a ring of smaller photophores, two of which are indicted by the black arrows.  Photograph by R. Young.

5. Reproductive structures
   
   1. Posterior region of nuchal cartilage replaced by part of the receptacle for spermatangia in females.
      
   

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   Figure. Dorsal (top) and dorsolateral (bottom) views of the receptacle for spermatangia in female A. heminuchalis. Anterior is right. Note that the posterior region of the nuchal cartilage is covered by the organ and that permatangia attach to ruguose areas (not a deep pit) on posterior portion of nuchal cartilage and gladius.  Mantle, gladius and attachment area folded posteriorly.  Drawing from Burgess (1991, p. 121, Fig. 2K). Photograph by R. Young.
   

Distribution

Geographical distribution

References

Burgess, L.A. 1992. Squids of the genus Abralia (Cephalopoda) from the central equatorial Pacific with a description of Abralia heminuchalis, new species. Bulletin of Marine Science, 49(1-2):113-136.

Hidaka, K. and T. Kubodera. 2000. Squids of the genus Abralia (Cephalopoda: Enoploteuthidae) from the western tropical Pacific with a description of Abralia omiae, a new species. Bulletin of Marine Science, 66(2):417-443.

Okutani, T. 1974. Epipelagic decapod cephalopods collected by micronekton tows during the EASTROPAC expeditions, 1967-1968 (systematic part). Bull. Tokai Reg. Fish. Res. Lab., 80: 29-118.