Gonatopsis okutanii Nesis 1972

Introduction

The original description of Gonatopsis okutanii by Nesis (1972) was based on a holotype and 4 paratypes plus reference to another specimen described by Okutani (1967) and a brief description by Okiyama (1969) of an animal represented in 2 photographs. All appear to be spent females.

The species was later considered by Nesis (1987, 1997) to represent spent females of Gonatus madokai. Okutani (2005), in contrast, treats Gonatopsis okutanii as a valid species because it is much smaller at maturity than G. madokai (25 vs 44 cm ML). In addition, the fins of G. madokai are larger and the arms shorter than G. okutanii. Nesis (1972) found remnants of tentacles in the spent female types of G. okutanii which we now know indicates that prior to sexual maturity the squid had tentacles and therefore does not belong in Gonatopsis. In addition, O. Katugin (personal communication) recently found large Eogonatus tinro in the size range of G. okutanii, and he suspects that G. okutanii is a junior synonym of E. tinro.

Clearly the status of G. okutanii is in limbo but we retain it here until evidence for its correct position is available.

Diagnosis

A Gonatopsis with ...

• 5 radular teeth per transverse row.
• long, slender arms.
• soft, gelatinous body.

Characteristics

1. Arms
   1. Arms II & III very long and slender; equal to or longer than ML.
   2. Arm formula: II=III>I>IV.
   3. Arms thick in proximal region; weak and thin in distal half.
   4. Armature in 4 rows: arms I-III with 2 medial rows of hooks and 2 marginal rows  of small suckers; arm IV with suckers only.
   5. All arms with 5-10 pairs of widely spaced or sparsely arranged medial hooks or suckers.
   6. All arm suckers with 7-9 teeth on distal edge of ring.
2. Tentacles
   1. short rudiments of tentacle stalks present in adults between bases of arms III and IV.
3. Head
   1. Eyes very large.
   2. Buccal membrane with 7 lappets.
   3. Beaks
   4. Radula with 5 teeth per transverse row.
   5. Occipital crest present with 3-4 weak longitudinal folds on each side of head.
4. Funnel
   1. Funnel valve present.
   2. Funnel organ V-shaped; 2 oval-shaped ventral pads also present.
   3. Funnel cartilage slender, slightly curved.
   4. Nuchal cartilage elongate rectangular shape, almost quadrangular with rounded corners.
5. Mantle
   1. Mantle thick, but soft and gelatinous (all specimens are spent females).
   2. Mantle length of holotype 18 cm; other specimens reported to 25 cm.
   3. Mantle cone-shaped; tapered posteriorly.
   4. Skin color dark purplish; eye "patches" present.
6. Fins
   1. Fins short; 35-45% length of mantle.
   2. Fins shape rhomboidal; slightly wider than long.
   3. Short tail present.
7. Photophores
   1. Photophores absent.
8. Viscera
   1. Gladius shape penniform.
   2. Mature ovarian eggs relatively large; maximum diameter 2.6 mm.
   3. Spermatophores unknown; spermatangia illustrated by Nesis (1972).
9. Measurements and counts

   Character/catalog no.		??	??
   Institution		ZIN	NSMT
   Status		Holotype	--
   Sex		female	female
   Maturity		spent	spent
   ML		170	230
   MW		40	90
   HW		30	--
   FL		55	100
   FW		40	160
   AL	1	125	150
   	2	130+	140+
   	3	135	170
   	4	105	110
   Arm formula		3=2>1>4	3>2>1>4
   Hook counts 1-3		18-20	10-18
   Teeth on sucker rings		7-9	--
   Depth (m)		525-550	sperm whale
   Source		Nesis (1972)	Okutani (1967)

Comments

Characteristics listed above are taken from Nesis (1972) and Okutani (1967).

Hatchlings and paralarvae are not known for this species.

Life History

The species is reported to have relatively large eggs, to copulate "head to head", and adult females do not appear to die after the first spawning (Nesis, 1972).

Distribution

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

Figure. Distribution of G. okutanii. Dark pink area indicates known range; light pink area indicates inferred range. ©

References

Nesis, K.N. 1972. Two new species of gonatid squids from the North Pacific. Zoologichesky Zhurnal, 51(9): 1300-1307 [In Russian].

Nesis, K.N. 1987. Cephalopods of the World; Squids, Cuttlefishes, Octopuses, and Allies. T.F.H. Publications: Neptune City, NJ. 351 pp.

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.

Nesis, K.N. & G.A. Shevtsov. 1977. The first data on abyssal cephalopods of the Okhotsk Sea. Biologiya Morya, 5: 76-77 [In Russian, English summary].

Okiyama, M. 1969. A new species of Gonatopsis from the Japan Sea, with the record of a specimen referable to Gonatopsis sp. Okutani 1967 (Cephalopoda: Oegopsida: Gonatidae). Publications of the Seto Marine Biological Laboratory, 17(1): 19-32.

Okutani, T. 1967. Preliminary note on a hitherto unknown form of the eight-armed squid, genus Gonatopsis, from northern North Pacific. Venus (Japanese Journal of Malacology), 25(2): 65-68.

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