Gonatopsis borealis Sasaki, 1923

Gonatopsis borealis: Holotype (23 cm ML) collected off eastern coast of Hokkaido, Japan. Drawing from Sasaki (1923).

Introduction

Gonatopsis borealis was described by Sasaki (1923) based on 8 specimens (140-255 mm ML) donated by Mr. G. Yamaguchi. Most of the specimens were caught on 28 July 1922, 15-30 miles off Kushiro, Hokkaido, Japan. Although Sasaki did not designated type specimens nor provide accurate measurements, his careful description and drawing are enough to specify this species is valid.

Various authors have reported the presence of 3 distinct morphs of G. borealis, namely: large, small and slender. The morphological and molecular status of these morphs have not been critically reviewed.

Based on differences in the number of teeth in the radula Nesis (1971) erected a new subgenus, Boreoteuthis, for G. borealis to separate it from other species in the genus Gonatopsis. Several subsequent authors have elevated this name to genus status (see Katugin, 2004). The issue of generic placement has not been resolved for borealis.

Diagnosis

A Gonatopsis with ...

• 7 radular teeth per transverse row.
• short arms; distal tips not attenuated
  
• with suckers in 4 rows near arm tips.
• muscular mantle.
  

Characteristics

1. 1. Arms stout, moderately long; length ca. 40-45% ML.
   2. Arms subequal; arm formula: II=III>I>IV.
   3. Aboral keels distinct and well developed on arms III
   4. Armature in 4 rows (quadriserial) in mid-region of all arms.
   5. Mid-region of arms I-III with 2 rows of medial hooks in mid-region (39-48 per arm); arms IV with 2 medial rows of suckers.
   6. Proximal region of arms with 5-10 suckers.
   7. Fistal region of arms with 4 rows of suckers; total sucker counts ca. 56-63 per arm.
   8. Arm suckers with ca. 12-15 pointed teeth on distal half of inner rings, often grading to small knobs on proximal margins.
   9. Hectocotylized arms not present.
      image info

      Figure. Arm armature of G. borealis, 200 mm ML, off Southern California. All suckers maintain relative sizes; hook one half size relative to suckers. Arm III (left to right) - Largest hook; largest marginal sucker, medial sucker from arm tip, marginal sucker from arm tip. Arm IV (left to right) - Largest medial sucker; largest marginal sucker. Suckers are inner rings only. Drawings from Young (1972).

2. Tentacles
   1. Tentacles absent beyond paralarval stage (above 8-10 mm ML).
3. Head
1. Eyes very large.
2. Occipital crest with 4 distinct longitudinal folds.
3. Buccal membrane with 7 lappets; suckers absent.
4. Beaks. Information on the beaks of G. borealis can be found here.
5. Radula with 7 teeth per transverse row; rachidian tricuspid; 1st lateral bicuspid.
4. Funnel
1. Funnel valve present.
2. Funnel organ V-shaped with short anterior papilla; 2 large, oval-shaped ventral pads also present.
3. Funnel cartilage lanceolate with single long straight groove.
4. Nuchal cartilage large, panduriform, constricted in middle.
5. Mantle cartilage straight, ridge-like.


5. Mantle
1. Mantle wall very thick and muscular.
2. Mantle cylindrical; tapered posteriorly at level of anterior fins to blunt point.
3. Skin pigmentation dark reddish or purplish brown.
4. Maximum lengths of mature males, 27 cm ML; mature females, 33 cm ML.
   
6. Fins and tail
   1. Fins short (length over 40% ML); broad (ca. 65-70% ML).
   2. Fin shape rhombic; with sharp lateral angles, tapered posteriorly to broadly rounded apex.
   3. Tail absent.
7. Photophores
   1. Photophores absent.
8. Gladius
   1. Gladius shape penniform; length 11 times width.
   
   
9. Viscera
   1. Gills with ?? lamellae per outer demibranch.
   2. Mature eggs not described.
   3. Spermatophores not described.
10. Measurements and counts (taken from Young, 1972).

    Character/catalog no.		000000	60897	000000
    Institution		USNM	SBMNH	SBMNH
    Velero station		10402	10401	8697
    Sex		male	male	male
    Maturity
    ML		200	257	240
    MW		44	60	61
    HW		41	--	49
    FL		85	110	107
    FW		137	164	155
    AL	1	99	101	104
    	2	108	113	110
    	3	107	110	113
    	4	88	99	93
    Arm formula		2=3>1>4	2=3>1=4	3=2>1>4
    Hook counts (max)	1	40	42	45
    	2	40	44	48
    	3	39	44	47
    Sucker counts	4
    Depth (m)		925	1845	3695

Comments

Information on characters listed above taken from Young (1972). The characters are based on animals from southern California that appear to represent the "large morph" mentioned by a number of authors.

Life History

Paralarvae can be identified by the dorsal-head chromatophore pattern which is Type II (three transverse rows of chromatophores with one chromatophore in the anterior row, two in the middle row and three in the posterior row); the mantle has 6-10 dorsal chromatophores (Jorgensen, 2006).

image info

Figure. Dorsal views of the chromatophores of a G. borealis paralarva, 4.5 mm ML, Gulf of Alaska. Left - Head. Right - Paralarva. Drawing from Jorgensen (2006).

Distribution

Type locality: Western North Pacific Ocean, Japan, eastern Hokkaido Island, 15-30 miles off Kushiro; depth of capture not indicated.

image info

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

References

Jorgensen, E. M. 2006. Identification, distribution and relative abundance of paralarval gonatid squids (Cephalopoda: Oegopsida: Gonatidae)from the Gulf of Alaska, 2001-2003.Journ. Molluscan Studies. In Review.

Katugin, O.N. 2004. Squids of the family Gonatidae from the North Pacific Ocean and their genetic differentiation: controversial issues in the systematics and phylogeny. Ruthenica, 14(1): 73-87. [In Russian, English summary].

Nesis, K.N. 1971. The family Gonatidae - abundant squids of the North Pacific (their distribution, ecology, systematics and phylogeny), Pp. 63-65. In: Fourth Meeting of the Investigation of Molluscs: Molluscs Trends, Methods and Some Results of Their Distribution. Moscow: Academy of Sciences USSR Zoological Institute. [Abstract; in Russian].

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

Sasaki, M. 1923. On a new eight-armed squid from Hokkaido, Gonatopsis borealis n. sp. Annotationes Zoologicae Japonenses, 10: 203-207.

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 10): 1-357.

Young, R.E. 1972. The systematics and areal distribution of pelagic cephalopods from the seas off southern California. Smithsonian Contributions to Zoology, 97: 1-159.