Gonatopsis octopedatus Sasaki, 1920

Introduction

This is the type species of the genus Gonatopsis. It was briefly described by Sasaki (1920) based on a single immature specimen of unknown sex. A more detailed treatment of the same specimen was later provided by Sasaki (1929). A single mature male was described and illustrated by Okiyama (1970) and 4 spent females were treated by Nesis (1993).

Diagnosis

A Gonatopsis with ...

• 5 radular teeth per transverse row.
  
• long, slender arms; arm lengths slightly less than mantle length.
  
• arm tips attenuated; bearing up to 12 rows of tiny suckers.
  

Characteristics

1. Arms
   1. Arms stout, long; equal to or slightly shorter than ML (longest 80-85% of ML).
   2. Arms subequal; arm formula typically: II>III>I=IV.
   3. Armature in 4 rows in proximal region of arms; arms I-III with 2 rows of medial hooks and 2 rows of small marginal suckers; arm IV with 4 rows of suckers.
      
   4. Distal third of arms attenuated, suckers tiny, uniform in size, borne on long stalks; in males arranged in 6-7 rows, in females arranged in 8-12 rows.
   5. Arm hooks first appear when animals are 30-60 mm ML.
   6. Arms I-III with 30-33 hooks; arms IV with 30 large medial suckers.
   7. Sucker rings on arms I-III with 5-7 irregular teeth; rings on arm IV with 9 well defined teeth.
      
      

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

      
      

      Firgure. Oral view of the arms of G. octopedatus, 65 mm ML, holotype. Drawing from Sasaki (1929).

2. Tentacles
   1. Tentacles absent in adults; remnants present as rounded, indistinct tubercules between arms III and IV.
   2. Tentacles disappear when animals between 30-60  mm ML.
      
      
3. Head
1. Eyes large.
2. Occipital crest poorly defined.
3. Buccal membrane with 7 lappets.
   
4. Beaks. Description of the beaks of G. octopedatus from Japanese waters can be found here. Description of the beaks of G. cf. octopedatus from the Gulf of California can be found here: Lower beaks; upper beaks.
   
5. Radula with 5 teeth per transverse row; rachidian tricuspid, lateral 2 teeth unicuspid.
   
   
4. Mantle
   1. Mantle tissue "soft"and watery.
   2. Mantle fusiform-shaped; tapered posteriorly; narrowed anteriorly.
   3. Skin pigmentation dark reddish brown.
   4. Maximum size of mature males 10-12 cm ML; of gravid and spent females. 16-39 cm ML; maximum weights to 2500 g.
      
      
5. Fins and tail
   1. Tail absent.
   2. Fins short (ca. 25-30% of ML); slightly wider than long.
      
   3. Fins rounded, kidney-shaped.
      
      
6. Photophores
   1. Photophores absent.
      
      
7. Viscera
   1. Ink color black.
   2. Mature ovarian eggs ovoid; maximum size, 4.3 x 2.5 mm.
   3. Spermatophore length, 10.7 mm.
      
      
8. Measurements and counts (see sources listed)
   

   Character/Catalog no.		332918	??
   Institution		USNM	NSMT
   Status		Holotype	--
   Sex		ukn	male
   Maturity		immature	mature
   ML		65	99
   MW		22	30
   FL		19	ukn
   FW		30	ukn
   AL (right)	1	45	79
   	2	55	83
   	3	52	82
   	4	53	72
   Arm formula		2>3>4>1	2=3>1>4
   Hook counts	1	27	32
   	2	33	32
   	3	33	32
   Sucker counts	4	30	ukn
   Teeth on sucker rings		ukn	5-7
   Spermatophore L		--	10.7
   Depth		804	810
   Source		Sasaki (1929)	Okiyama (1970)

Comments

Information on characters listed above is taken from Sasaki (1929) and Okiyama (1970). 

Hatchlings and paralarvae have not been described for this species.

Life History

The species is very abundant in the Okhotsk Sea. Mature males are about half the size of mature females. Mating is head to head and spermatophores are transferred to the buccal region of the female. Spawning habits are not known but females are presumed to spawn in deep water. All eggs are spawned in a short time. Spent females often float to the surface and die. The body of spent females is very gelatinous and typically the arm tips and armature are lost. Mature males remain in better condition. Paralarvae move up in the water column shortly after hatching at depth. Juveniles are caught in the upper epipelagic layer at night.

Distribution

Type locality: Okhotsk Sea, Sakhalin Island, near Cape Patience, 48 22'30"N, 145 43'30"; depth of capture 804 m.

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

Figure. Distribution of Gonatopsis octopedatus. Dark pink area indicates known range; light pink area indicates inferred range. Chart modified from Okutani, et al. (1988).

References

Akimushkin, I.I. 1963. Cephalopods of the Seas of the USSR. [English translation 1965 by A. Mercado, IPST: Jerusalem].

Nesis, K.N. 1993. Spent females of deep-water squid Gonatopsis octopedatus Sasaki, 1920 (Gonatidae) in the epipelagic layer of the Okhotsk and Japan seas. Ruthenica, 3(2): 153-158.

Nesis, K.N. 1997. Gonatid squids in the subarctic north Pacific: ecology, biogeography, niche diversity and role in the ecosystem. Advances in Marine Biology, 32: 243-324.

Okutani, T. 2005. Cuttlefishes and Squids of the World. National Cooperative Association of Squid Processors: Tokyo. 254 pp.

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.

Sasaki, M. 1920. Report on cephalopods collected during 1906 by the United States Bureau of Fisheries steamer "Albatross" in the northwestern Pacific. Proceedings of the United States National Museum, 57(2310): 163-203.

Sasaki, M. 1929. A Monograph of the Dibranchiate Cephalopods of the Japanese and Adjacent Waters. Journal of the College of Agriculture, Hokkaido Imperial University, 20 (Supplement): 1-357.