Description

“Grimpoteuthis antarctica n. sp.

 

(Fig. 1A-F; Plate 1, Figs. A-D)

 

Material examined: Holotype specimen (NSMT Mo-63958) collected at Lat.62º59’S, Long. 62º09’W, 803-804 m (January 30, 1982) and paratype specimen (NSMT Mo-63959) collected at Lat. 61º23’S, Long. 55º11’W, 509-525 m (January 23, 1982) by T. IWAMI. See measurements for size (Table 1). Deposited in National Science Museum, Tokyo.

 

Diagnosis: A cirromorph characterized by transversely semiovoidal fins, short cirri and U-shaped fin support with widened rami.

 

Description: Mantle is short and dome-shaped, flabby to gelatinous, with numerous irregular warts and wrinkles due to preservation (Plate 1, Fig. A). Color dark purplish dorsally, but paler posteriorly and ventrally.

 

Fins are also flabby, ovo-quadrangular in outline, and indistinctly demarcated off the mantle (Fig. 1A). The anterior embayment near the base seems to be deeper than the posterior one. Coloration of the fins is the same as the dorsal surface but paler basally and darker distally.

 

Head is still darker in color than the rest of body. Eyes of moderate size are situated laterally. The mantle opening is moderately wide extending over almost the entire transverse distance of the ventral mantle. Funnel is small and short, tapering distally. Funnel organ is not well preserved, but seems to be almost thick, indistinct W-shaped.

 

Arms are subequal in length. Webs are as broad as half the arm length at medial part, but broadly margining both sides of the arms. Ventrally margining web seems to be somewhat broader than dorsal frill. The arms are sub-trapezoid to sub-triangular in cross section.

 

Suckers are arranged in a single row. They occasionally look like as if sunken below the integumental folds as the integument is so loose that it creates fairly pro­nounced warts (Fig. l D). The number of suckers is 70 to 80 in each arm (because of the skewed posture by fixation, counts not always precise). The suckers of the proximal half are large enough to be counted by the naked eye, but distal 20-30 are very tiny and countable only by means of a magnifying glass (Fig. 1 C). Cirri are not always very apparent but spaced, arranged along both sides of sucker row, and their length is a little shorter or equal to the diameter of adjacent suckers (Fig. 1C–D; Plate 1, Fig. C). The oral surface is also purplish in color but central portions of webs and suckers are much paler than proximal and marginal areas of the web (Plate 1, Figs. B–C).

 

The fin-supporting cartilage is broadly U-shaped. Both rami, particularly at postero-lateral portion, are widened. The posteriormost connective of both rami seems to be weaker than the remaining area (Fig. 1B).

 

The buccal mass is large, but there is no radula except the odontophore of which dorsal surface seems to be lined with a thin chitinous substance.

 

The upper beak has a long rostrum without any groove on either rostral and hood areas. The lateral surface, down to the wing is heavily pigmented leaving only a narrow strip of less darkened area behind. There is a deep notch behind the rostrum. The lateral wall is quadrangular and heavily darkened except a narrow marginal paler belt (Fig. 1F).

 

The lower beak is also well chitinized. The rostrum is blunt and rather short, LRL (lower rostral length) in the Paratype specimen measuring only 4.0 mm. The jaw angle is nearly the right angle with no fold but presents a narrow cutting edge. There are many "radiating" lines on the hood to wing area, which become less darken posteriorly. There are roughly three grades of darkening in this area. No notch present posteriorly in the hood. The lateral wall is moderately apart from the hood and subquadrangular in profile but has a very round top (Fig. I G).

 

Discussion: The establishment of a new species within the genus Grimpoteuthis ROBSON, 1932 was made with some hesitation, because of the still subtle status of the cirromorph taxonomy (ROBSON, 1932). However, some of characters of the present species never accord with those of known members of the genus. Except for fragments and very immature specimens, only two species of the genus have been known from the Antarctic waters. The rest of the members are mostly from the North Atlantic and several tropical localities. They are, Grimpoteuthis mawsoni (BERRY, 1917) from off the Mertz Glacier Tongue, Adelie Land, and G. glacialis (ROBSON, 1930) from the Schollaert Channel, Palmer Archipelago. The former species differs from the present new species in having quite unequal lengths of arms and quadrangular fins. The latter species has a certain similarity of external appearance to the present new species, but differs in having an angulated U-shaped cartilage and very weak and not fully chitinized beaks. In de­scribing G. glacialis (as Chirroteuthis) ROBSON (1930) referred to a North Atlantic species, G. megaptera (VERRILL, 1885), and G. umbellata (FISCHER, 1883). But, it is hardly realistic that the cirromorph fauna in the North Atlantic is common to those in the Antarctic area, judging from the characteristic Antarctic cephalopod fauna of other kinds hitherto known.

 

 

Table 1. Measurement of Grimpoteuthis antarctica n. sp. in mm.

 

   

                                                                                                                                                                                       

Characters			Holotype (NSMT Mo-63958)	Paratype (NSMT Mo-63959)
Sex			-	Female
Eye-Posterior end of mantle			91	180
Eye-Edge of web			120	150
Interocular width			45	100
Body maximum width			95	135
Fin length			80	70
Fin width			40	33
Arm	I	right	200	300
		left	200	310
	II	right	220	280
		left	220	310
	III	right	220	350
		left	225	320
	IV	right	215	260
		left	220	300
Web	A		110	140
	B	right	95	160
		left	105	160
	C	right	100	160
		left	110	150
	D	right	105	155
		left	110	160
	E		55	110
Sucker count	I	right	72	76
	II	right	73	73
	III	right	69	78
	IV	right	73	55+

 

 The paratype specimen is a mature female. Although the visceral organs were so heavily mutilated that the general orientation of them was not clear, several dozens of ripe ova which might have been drived from ovary were found scattered within the cavity. A single ovum measures 12 × 16mm with an ellipsoid shape. There seems to be certain mature stages within them. The probably most advanced egg has longitudinal stripes (Plate 1, Fig. D), but some including the one situated near the oviductial opening have no such stripes. The immature ones were opaque and mostly smashed when they were observed.

 

It is not striking that the present new species lacks radula. Both of two species previously described from the Antarctic, G. mawsoni and G. glacialis, reportedly have no redula.

 

The grade of chinization in beaks of the present new species seems to be far advanced in comparison with ROBSON'S species. The general characters of the lower beak agree well with what CLARKE (1985) described. The specific character on the beak will be hardly designated.”

 

 

(Kubodera & Okutani, 1986: 129-132)