Gonatus pyros Young 1972

Introduction

Gonatus pyros is a small gonatid. A spent female measured 125 mm ML (SBMNH no. 61050). Nesis (1982/87) states that some individuals are known to be up to 160 mm ML. G. pyros is distinctive in being the only gonatid known to possess photophores.

Diagnosis

A Gonatus with ...

• a large photophore on the ventral surface of each eyeball.
  

Characteristics

1. Arms
   1. Total of 29-33 hooks and suckers present on proximal half of each arm I-III; squid >34 mm GL with 36-41 suckers on proximal half of each arm IV.
2. Tentacles
   1. Clubs 20-25% of GL.
   2. Club dactylus with 7-8 irregular series at proximal end, decreasing to 4 series in mid-dactylus.
   3. Club ventral-marginal zone with 3, sometimes 4, series of suckers in central region all nearly same size.
   4. Club dorsal-marginal zone with 3 irregular series dorsal to large central hook.
   5. Club medial zone with large central hook; distal hook present, occasionally joined by an enlarged sucker with a large tooth; proximal series with usually 3-4 small hooks, occasionally preceeded by a series of suckers. Proximal hooks decrease in size toward club base
      
   6. Total number of suckers (excluding terminal pad and medial zone) on tentacular club: about 151-184.
   7. Median region of tentacular stalk between marginal series with a single, occasionally double and slightly irregular series of sucker adjacent to the ventral-marginal series of the stalk. Lenth variable but usually reaches 3/4 of marginal series length. Medial suckers number between 50-125.
      
   

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   Figure. Oral view of the tentacle of G. pyros. Top - Distal region of tentacle, 35? mm GL. Middle - Enlargement of club from top figure. Drawings from Young (1972). Bottom - Distal region of tentacle, 55 mm ML, preserved. Photograph by R. Young.
   

3. Head
1. Beaks.  Descriptions can be found here: Lower beak; upper beak. See this site also.
   
   
4. Photophores
   1. Large, somewhat oval photophore present on ventral surface of each eye.
   

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   Figure. Ventral view of the head and eyes of G. pyros showing ocular photophore. Left - Eyelid folded back to reveal photophore, preserved, 55 mm ML, immature female. Insert - Drawing of eye and photophore from Young (1972). Right - Fresh squid with the left eye protruding showing the white ocular photophore. Photograph by T. Kubodera. Note the peculiar surface of the photophore which seems to have many small pores.

Comments

More details of the description of G. pyros can be found here.

Life History

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Figure. Chart of the size ranges over which hooks in juveniles of G. pyros first appear. Chart modified from Young (1972).

Distribution

Type locality: 33°37'N, 118°26'W, eastern North Pacific off Southern California. G. pyros is broadly distributed in the central and eastern North Pacific.

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Figure. Distribution of G. pyros. Dark region indicates known range; light areas indicate estimated range. Chart modified from Okutani, et al. (1988).

References

Okutani, T., T. Kubodera and K. Jefferts. 1983. Diversity, distribution and ecology of gonatid squids in the subarctic Pacific: A review. Bull. Ocean Res. Inst., Univ. Tokyo, No. 26 (1):150-192.

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