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Comprehensive Description

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Description

Onykia rancureli n. sp.

 

(Figs. 1-9)

 

 

Onychia carribaea: OKUTANI, 1968, p. 22, pl. 4, fig. 6 (non LESUEUR, 1821).

 

Onychia sp.: RANCUREL, 1970, p. 18, figs. 12-16.

 

 

Description. The body is muscular throughout. The mantle is rather short, with the width being almost half the dorsal mantle length, short cylindrical anteriorly and abruptly tapering behind. The dorso-anterior edge of the mantle forms a blunt triangular angle and a dark and slightly raised streak of the gladius runs along the mid-dorsum from the anterior end to the halfway point of the fin base. There is a shallow ventral excavation on the free mantle margin.

 

The fins are broad and never sagittate but semi-oval in outline. The posterior margin of both lobes exceeds beyond the level of the posterior extremity of the mantle. Fin length is about 45 % and fin width about 100 % of the dorsal mantle length, respec­tively.

 

The head is semi-cubic in shape with a moderate-sized funnel which reaches as far as the midpoint of the eye. The neck carries a small olfactory crest at the posterior edge of the broad and smooth funnel groove and another small fleshy crest at the antero­dorsal corner. The funnel element of the mantle-funnel locking apparatus is a simple leaf-shaped cartilage with a shallow longitudinal groove corresponding to a slender fleshy ridge of the mantle element. The dorsal element of the funnel organ is V-shaped, with round tipped rami on which a distinct ridge runs. There is no papilla at the apex. The nuchal cartilage is straight but moderately widened anteriorly and posteriorly. There is a shallow longitudinal groove running in the middle, which is margined by the ridge on both sides.

 

The eye-opening is rather small, quadrate in outline with a deep sinus. The eye-opening is frequently closed by a shrinkage of the muscle.

 

The arms are muscular and stout, armed by biserial suckers. The Arm I is slightly shorter than the others which are subequal in length. The Arm I is trapezoid in cross-section, without aboral keel but with a low undulating protective membrane on both sides of the sucker-bearing surface. There are some 50 suckers on the Arm I. The Arm II has a low aboral keel in its entire length. There is also a very low protective membrane on both sides of sucker-bearing surface where 50-52 suckers are present. The Arm III is very much alike the Arm II in general characters except a slight promi­nency of the aboral keel in comparison to that of the Arm II. The Arm IV also has an aboral keel which is broadly extended proximally forming a web covering the basal portion of the tentacular stalk. No hectocotylization was observed. The chitinous rings of all arms have no teeth along the internal margin.

 

The tentacle is rather short, only slightly longer than the longest arm. There is a low membraneous carina running along the aboral side of the stalk. This carina barely reaches to the club part. The club is slightly expanded with a protective membrane on the dorsal side extending from the midpoint of the club to the distal tip. The sucker-bearing part has distinct carpal group, manus and dactylus. The carpal group is well defined as a fixing apparatus consisted of nine suckers and nine fleshy knobs. The armature of the manus is consisted of a double row of hooks, of which the ventral row is distinctly larger than the dorsal row. On the ventral row, there are 13 hooks among which the fourth and fifth from the proximal are largest of all. The dorsal row has 10 hooks of which medial ones are slightly stronger than the proximal and distal ones. The hooks are all basally covered with fleshy hood. There are very small suckers between proximal hooks one each per interval between hooks; two on the ventral side and four on the dorsal side. There are only even to nine small suckers in the well-defined dactylus. A very weak fleshy ridge runs from the proximal peri­phery of the fixing apparatus towards the base of the tentacle.

 

The buccal connnective attaches to the ventral side of the Arm IV (DDVV-type).

 

The gladius is lanceolate in general shape, widened at about posterior two-thirds of the length. The rhachis is rather wide and solid. The posterior end is slightly solidified with a minute cap-like structure.

 

The upper jaw plate has a strong rostrum and triangular lateral wall which is mostly stained in amber color with transparent margin. The rostrum gently curves with an acute jaw angle. The hood is moderately apart from the crest at the posterior end. The lateral wall is not notched behind. The crest is rather narrow. The wing shoulder is sharp with an oblique profile in cross-section.

 

The lower jaw plate is typical onychoteuthid type. The rostrum has a sharply defined cutting edge with a usual degree of protrusion. The wing fold is moderately distinct as an obtuse jaw angle is hidden behind. There is a sharp edge, which is chipped a little, on the outer surface of the wing fold. The wing shoulder is also ridged. The hood is rather short and situated rather low on the crest which is narrow on top. The lateral wall is auriculated in outline with a distinct ridge running about halfway between the crest and the inner posterior corner. The hood notch is shallow and wings are widely spread with lateral wall close together.

 

The transverse row of the radula is composed of seven teeth. The central tooth has three sharp cusps of which the central one is the most prominent of all. The inner lateral tooth is curved with a rather obtuse tip. The medial lateral tooth is the smallest of all with a low triangular outline. The outer lateral is large and sickle-shaped in outline terminating with a rather sharply pointed tip.

 

Type series. Holotype specimen (NSMT Mo-59489): Female, 68.0 mm DML, removed from the stomach of a lancetfish measured 1410 mm FL fished at 07°51'S, 88°02.5'E in the central Indian Ocean by the Sagami-Maru, August 3, 1975.

 

Paratype No. 1 (NSMT Mo-59490): Female, 43.5 mm DML, removed from the stomach of a lancetfish measured 850 mm FL fished at 09°15'S, 83°45'E in the central Indian Ocean by the Sagami-Maru on July 28, 1975. Paratype No. 2 (NSMT Mo­59491): Female, 57.6 mm DML, removed from the stomach of a lancetfish measured 1390 mm FL fished at 09°21'S, 81°42'E in the central Indian Ocean by the Sagami‑Maru, August 6, 1975. Paratype No. 3 (NSMT Mo-59492): Female, 57.6 mm DML, removed from the stomach of a lancetfish measured 742 mm FL fished at 11°16.2'S, 109°29.5'E in the eastern Indian Ocean by the Shonan-Maru, December 25, 1975.

 

Table 1. Measurements and indices of Onykia rancureli n. sp.

                                                                                                            
 

 
 

Holotype

 
 

Paratype No.1

 
 

Paratype No.2

 
 

Paratype No.3

 
 

Mean for 26 specimens

 
 

Sex

 
 

Female

 
 

Female

 
 

Female

 
 

Female

 
 

 
 

Dorsal mantle length (mm)

 
 

68.0

 
 

43.5

 
 

57.6

 
 

57.6

 
 

22.0-102.9*

 
 

MWI

 
 

42.5

 
 

48.5

 
 

41.7

 
 

41.7

 
 

46.1

 
 

HWI

 
 

36.8

 
 

40.0

 
 

35.6

 
 

35.6

 
 

37.0

 
 

FLI

 
 

47.1

 
 

38.4

 
 

46.9

 
 

46.9

 
 

42.5

 
 

FWI

 
 

105.3

 
 

97.5

 
 

100.7

 
 

100.7

 
 

94.2

 
 

I

 
 

72.4

 
 

52.9

 
 

67.7

 
 

67.7

 
 

59.5

 
 

II

 
 

86.5

 
 

69.0

 
 

78.8

 
 

78.8

 
 

75.6

 
 

III

 
 

90.0

 
 

69.9

 
 

81.6

 
 

81.6

 
 

78.3

 
 

IV

 
 

82.2

 
 

41.1**

 
 

77.4

 
 

77.4

 
 

70.7

 
 

TLI

 
 

104.3

 
 

92.9

 
 

101.9

 
 

101.9

 
 

101.3

 
 

CLI

 
 

42.6

 
 

39.5

 
 

42.2

 
 

42.2

 
 

41.2

 
 

* Range. ** The tip mutilated.

 

 

 

Measurements. See Table 1.

 

Comparison. This species is distantly larger than Onykia carribaea LESUEUR 1821, which is an only species of this genus and is a cosmopolitan epipelagic squid. The original description of O. carribaea says it measures "body 1 inch" (LESUEUR 1821). The largest specimen recorded by CLARKE (1966) is 36 mm in mantle length. A speci­men measured 43 mm ML reported by OKUTANI (1968) under the name of Onychia carribaea apparently belongs to the present new species.

 

This new species lacks bluish chromatophores which are common to epipelagials. This also differs from Onykia carribaea in having less number of marginal suckers in manus (2-4 vs 6), less number of carpal suckers (9 vs 11) and more hooks (10-12 vs 9).

 

Since OKUTANI (loc. cit.) discovered this species from the stomach contents of a scombrid fish, Euthynnus yaito, fished in the Kuroshio area, south of Honshu, Japan, RANCUREL (1970) described five speciemens from stomachs of fish including Alepisaurus ferox in the southwestern Pacific. The type series in this paper came from stomachs of A. ferox taken with tuna longline operated in the central and eastern Indian Ocean. But, additional materials reveal that this new species is widely dis­tributed in the whole range of the Tropical Indian and Pacific Oceans (OKUTANI et al., MS).

 

Remarks. For the generic name, Onychia has been more universally used than Onykia. The reader should refer TAKI (1964) for the correct usage of Onykia.”

 

 

(Okutani, 1981: 155-159)

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Creative Commons Attribution Non Commercial 3.0 (CC BY-NC 3.0)

© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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