Page 1 VENUS 60 (4): 237-260, 2002 Descriptions of Eucleoteuthis

Home , Ommastrephidae, Ornithoteuthis, Ornithoteuthis volatilis

VENUS 60 (4): 237-260, 2002

Descriptions Descriptions of Eucleoteuthis luminosa (Sasaki, 1915) and Ornithoteuthis Ornithoteuthis volatilis (Sasaki, 1915) Paralarvae in in the Northwestern Pacific

Toshie Toshie Wakabayashi1, Kazunori Saito2, Kotaro Tsuchiya1 and Susumu Segawa1 1Tokyo 1Tokyo University of Fisheries, 4-5 ース Konan, Minato-ku, To 卸0 180-847 スJapan; twakab α＠to わ10-u-fish.ac.jp 2Asahikawa 2Asahikawa University, 3ゾo, 23, Nagayama, Asahikawa, Hokkaido 079-8501, Japan

Abstract: Abstract: Eucleoteuthis luminosa paralarvae ranging from 1.4 to 12.4 mm in mantle length (ML) and Ornithoteuthis volatilis paralarvae ranging from 2.4 to 5.4 mm ML are described bas 巴d on specimens collected from waters off the Ogasawara Islands and from off Shikoku to the the Philippine Sea. E. luminosa paralarvae are characterized by having subocular and intestinal photophores, photophores, a relatively long proboscis with a mean proboscis index (ratio of proboscis l巴ngth to to mantle length) of 0.70, and mod 巴rately enlarged lateral proboscis suckers with a mean ratio of of lat 巴ral sucker diameter to medial sucker diameter ratio of 1.57. 0. volatilis paralarvae are characterized characterized by having subocular and intestinal photophores, a relatively short proboscis with a mean proboscis index of 0.49, and considerably enlarged lateral proboscis suckers, with a mean ratio of lateral sucker diameter to medial sucker diameter of 2.09.

Keywords: Keywords: Eucleoteuthis luminosa, Ornithoteuthis volatilis, paralarvae, Ommastrephidae

Introduction

The family Ommastrephidae consists of 11 genera and 21 species (Wo ロnuth, 1998) and is one of of the largest families of Oegopsid squids. It includes many commercially important species, and more studies have been made of the fisheries biology of this family than for any other squid family ly (e.g. Araya, 1967; Murata & Araya, 1970). Ommastrephids spawn egg masses that r巳semble large g巴latinous balls (Hamabe, 1961; Bower

& Sakurai, 1996), and their paral 紅 vae ar 巴 commonly found in t巴mperate to tropical surface waters (Saito (Saito & Kubodera, 1993). Morphological growth sequences of ommastrephid paralarvae have been traced in only a few species in the northwestern Pacific (Hamabe, 1961; Okiyama, 1965; Okutani, Okutani, 1965) and in Hawaiian waters (Harman & Young, 1985; Young & Hirota, 1990). The present sent study describes the growth sequences of two ommastrephid species in the northwestern Pacific, Pacific, Eucleoteuthis luminosa and Ornithoteuthis volatilis. E. E. luminosa is distributed between 20°and 40°N across the North Pacific and at similar latitudes in in the southern hemisphere (Wormuth, 1998). 0. volatilis is distributed throughout the tropical and subtropical subtropical Indo-Pacific (Dunning, 1998). of Paralarvae both species occur in Japanes 巴 waters (Saito (Saito & Kubodera, 1993). Nesis (1979) described th 巴 stages of photophore appearance, the differ entiation entiation of Arm III and Arm IV, the beginning of proboscis division, and relative size of proboscis suckers suckers in E. luminosa and 0. volatilis. More detailed observations of featur 巴s such as the structure of of the sucker rings on the proboscis, the beaks and the chromatophore patterns of th 巳se two species would b巴 useful in comparing their morphology and life history with other ommastrephid sp 巴cies. The present study describes the morphological features of the paralarval stages of E. luminosa and 0. volatilis based on characters viewed und 巴r an optical microscope and several new charac-

ters ters observed for th 巴 first time with a scanning electron microscop 巴． 238 238 T. Wakabayashi, K. Saito, K. Tsuchiya & S. Segawa

Materials and 恥1ethods

Specimens used for the present study were collected from 3 areas (Fig. 1): 1) 1) East of the Ogasawara Islands during April and May in 1990-1992 by the R 八fHokko-Maru; 2) 2) At 142°30'E 仕om 25°to 35°N in January 1997 by the R 八f Shunyo-Maru; 3) 3) At 134°E from 15°to 33°from May to June 1994 by the R 八f Kaiyo-Maru. Samplings east of the Ogasawara Islands and at 142°30'E were taken with a bongo net (0.7 m in in mouth diameter), a large larva net (2 min mouth diameter) and a conventional larva net (1.3 m in in mouth diameter) (Table 1). Sampling at 134°E was carried out using a MOCNESS (0.33 mm

40 N Sea of Japan

Northwest Pacific Pacific 35

ζフ

of 30

Nansei Nansei グ Islands Islands • n J"' J"' Ogasawara , Islands Islands ' 25

200 200

a Apr.-May, 1990 RIV Hokko-Maru 15° 15° Philippine d I b Apr., 1991 RIV Hokko-Maru Sea c Apr., 1992 RIV Hokko-Maru d May-June, 1994 RIV Kaiyo-M α ru e Jan., 1997 RIV Shunyo-Maru

lO lO 125 125 E 130 135 140 145 150°

Fig. Fig. 1. Location of sampling stations in the 回 st off Ogasawara Islands and the off Shikoku to th 巴 Philippine Sea by res 巴arch vessels and by ye 訂 S Descriptions Descriptions of Eucleoteuthis luminosa and Ornithoteuthis volatilis Paralarvae 239

Table Table 1. V 巴ssels, sampling gear and towing methods. Year Year Vessel Bongo net Large larva net Larva net 1990 1990 Hokko-Maru Oblique tow Stepwise horizontal tow Surface honzontal tow (200-0m) (200-0m) (200-100 50-20-0 m) for 5 min. (2 kt) for for 15 min. at each depth 1991 1991 Hokko-Maru Stepwise horizontal tow Stepwise horizontal tow Surface horizontal tow (200 (200 75 50-20-0 m) (200-75 50-20-0 m) for 15 min. (2 kt) m 15 min. each stratum for 15 min. at each depth 1992 1992 Hokko-Marn Oblique tow Oblique tow Surface horizontal tow (100 心 m) (100-0m) for 30 min. (2 kt) Surface Surface hori 回目al tow for for 30 min. (2 kt) 1997 1997 Shunyo-Maru Oblique tow Surface horizontal tow (150-0m) (150-0m) for 10 min. (1.5 kt)

Table Table 2. Sampling gears and towing data. Vessel Vessel MOCNESS IKMT 1994 1994 Kaiyo Maru Oblique tow Oblique tow 。－ !Om 100 125 m 400-450m (0-300m) 10-20m 10-20m 125-150 m 450-500m 20-30m 20-30m 150-175 m 500-550 m 30-40m 30-40m 175 200 m 550-600m 40-50m 40-50m 200 250m 600-700m 50-60m 50-60m 250 300 m 700-800 m 60-75 60-75 m 300-350 m 800-900m 75 75 100 m 350-400 m 900-1000 m 10 10 min. (2 kt) at each stratum mesh) mesh) at 2 knots ship speed between 0 and 1000 min depth through 24 discrete layers, and with an IKMT (1 mm mesh) in oblique hauls from 300 to 0m at the same stations (Table 2). All the samples ples except those from the 142 。30 ’E line were fix 巴d with 10 % formalin on board, and later pre- served served in 40 % isopropanol. Specimens from the 142°30'E line were deep-frozen on board and fixed fixed with 10 % formalin after being thawed in the laboratory. 百ie measurements, indic 巴s and terminologies used below follow those of Roper & Voss (1983). Measurements Measurements of proboscis length and sucker rings, knob counts and calculations of proboscis indices indices follow those of Harman & Young (1985). Suckers Suckers on Arms II were used for measurement and for knob count of 征 m suckers. A binocu- lar lar microscope with a micrometer was used for measurements. A JEOL JSM-100 scanning electron microscope microscope (SEM) was used for observation and measurement of beaks and suckers. The specimens used for SEM observations were dehydrated in a graded series of ethanol and t-butyl alcohol, dried dried using a freeze dryer, and finally coated with gold. Data from specimens of different sizes were statistically tested using analysis of variance, and significance was accepted at 出ep= 0.05 level. level. Abbreviations Abbreviations used in the text to describe the specimens: ML, mantle length; MW, mantle width; width; MWI, mantle width index= percentage of MW to ML; FL, fin length; FW, fin width; HW, head head width; HWI, head width index = percentage of HW to ML; PL, proboscis length; Pl, proboscis boscis index= ratio of PL to ML; PSP, percentage of separated p訂 t length to the total PL. All All examined specimens are deposited 白巴 Laboratory of Aquatic Biology of Tokyo University of of Fish 巴ries. 240 240 T. Wakabayashi, K. Saito, K. Tsuchiya & S. Segawa

Descriptions

Eucleoteuthis Eucleoteuthis luminosa (Sasaki, 1915) (Figs. (Figs. 3-12, Tables 3, 4)

A total of 53 sp 巴cimens ranging from 1.4 mm to 12.4 mm ML were identified as Eucleoteuthis luminosa. luminosa. They were collected at between 26°30 ’N and 33 。N (Fig. 2). The mantle is rather thin, oval, broadest at the middle and rounded posteriorly in specimens smaller smaller than 2.2 mm ML. The antero-dorsal margin is bluntly angulate (Fig. 3A), while the antero-

Sea of Japan

Northwest Pacific Pacific e

ιコ

ol 30

Nansei グ Islands Islands • n ~ Ogasawara , Islands Islands ' 25

20° 20°

a Apr.-May, 1990 RIV Hokko-Maru 15° 15° Philippine d I b Apr., 1991 RIV Hokko Maru Sea c Apr., 1992 RIV Hokko-Maru d May June, 1994 RIV Kα iyo M α ru e Jan., 1997 RIV Shunyo-Maru

10° 10° 125° 125° E 130° 135 140 145° 150'

Fig. Fig. 2. Distributions of Eucleoteuthis luminosa and Ornithoteuthi~ voL αtilis. Solid circles indicate occurrence of E. luminosa luminosa and solid triangles, 0. volatilis. Descriptions Descriptions of Eucleoteuthis luminosa 加 d Ornithoteuthis volatilis Paralarvae 241

川町一志τ才官 a ・後一 ‘骨ヤ ≫ . .' .. ' ・, . ，’ e ' . •' 官官事 . . i雪 q ・ ~ 辱 ' I '' ' ' ' " . 唱 . 奄 S u ¥ ' ;, 時寺手陶 A －・・、、句物色 ’‘ ． J '/ K G ’h H 車 ‘

Fig. Fig. 3. Paralarvae of Eucleoteuthis luminosa. A. 2.2 mm ML, dorsal vi 巴w. B. 2.2 mm ML, ventral view. C. 2.2 mm ML, oral view. D. 4.4 mm ML, dorsal view. E. 4.4 mm ML, ventral view. F. 4.4 mm ML, oral view. G. 6.4 mm ML, dorsal vi 巴W H. 6.4 mm ML, ventral view. I. 6.4 mm ML, oral vi 巴w. J. 9.1 mm ML, dorsal view. K. 9.1 mm ML, ventral view. L. 9.1 n立n ML, oral view. Scale bars = 1.0 mm. 242 242 T. Wakabayashi, K. Saito, K. Tsuchiya & S. Segawa ventral ventral margin is gently concave (Fig. 3B). At 4.4 mm ML, the mantle has a sac-like shape (Fig. 3D, 3D, E). The antero-ventral margin is g巴ntly excavated with blunt lateral angles (Fig. 3E). At 6.4 mm ML, the mantle becomes cylindrical for the anterior two-thirds and terminates in a pointed posterior terior end (Fig. 3G, H). At 9.1 mm ML, the mantle is rather firm and cylindrical, and tapers abruptly ly to the pointed posterior end (Fig. 3J, K). In general, M 羽TI tends to decrease as ML increases from from 2.0 to 5.0 mm; however, the MWI values varied widely between 40 and 80. There is a slight decrease decrease in MWI as ML increases from 5.0 to 12.4 mm (Fig. 4). The fins are attached to the posterior end of the mantle. At 2.2 mm ML, they are very small, delicate delicate and oval. The posterior margin of the fins extends beyond the posterior end of the mantle (Fig. (Fig. 3A, B). In specimens ranging from 4.4 to 9.1 mm ML, FW is greater than FL. The posterior margin margin of each fin is gently concave in 4.4 to 6.4 mm ML specimens (Fig. 3D, E, G, H). At 9.1 mm ML, the fins becomes semicircular, and the posterior margin of each fin is n巴arly straight (Fig. 3 J, K). The FW: FL ratio is 4.56, 3.25, 3.20 and 2.16 for specimens of 2.2, 4.4, 6.4 and 9.1 mm 恥 1L respectively, showing that this ratio decreases as body size increases. The head is subcubic with large eyes on both sides. HW is slightly na 町 ower than the mantle opening. opening. HLI varies from 26.5 to 52.9 in specimens ranging from 1.4 to 4.0 mm ML and declines with with growth (Fig. 5). The funnel is slender and long, and almost reaches the base of the arms in 2.2 mm ML specimen (Fig. 3B). In specimens ranging from 4.4 to 9.1 mm ML, the funnel reaches halfway between the the base of the arms and the mantle margin (Fig. 3E, H, K). Th 巴 funnel cartilage shaped like an inverted T (Fig. 6A, B) and in specimens smaller than 9.0 mm ML is not fused with the mantle cartilage. This fusion occurs at 9.0-10.0 mm ML. The arm formula is II >I> III> IV in specimens ranging from 1.4 to 2.7 mm ML. The arm formula formula of specimens ranging from 2.8 to 12.4 mm ML is variable: II >I >III >IV, II >I = III III > IV or II > III > I> IV. At 2.2 mm ML, Arm II reaches about 20 % of ML (Fig. 3A), Arm III III is one quarter the length of Arm II (Fig. 3C) and Arm IV is much shorter than the others (Fig. 3B). 3B). At 4.4 mm ML, Arm II reaches about 30 % of ML (Fig. 3D), Arms I and III 紅巴 slightly shorter er than Arm II (Fig. 3D-F), and Arm IV is about one quarter 出e leng 白 of Arm II (Fig. 3E). At 6.4 mm ML, the length of Arm II is half ML (Fig. 3G), Arms I and III are slightly shorter than Arm II (Fig. (Fig. 3G, H), and Arm IV is about half the length of Arm II (Fig. 3G). At 9.1 mm ML, Arm II reaches reaches about 40 % of ML (Fig. 3J), and Arm IV is two-thirds the length of Arm II (Fig. 3K). Arm III III has an aboral keel in specimens larger than 6.0 mm ML. At 1.4 mm ML, there is one large sucker each on Arms I and II, with no suckers on Arms III or IV. IV. At this size, the diameter of the outer chitinous sucker ring of the first sucker of Arm II is 52 μm, with 15 and 16 knobs on the inner and middle whorl, respectively (Fig. 7A, Table 3). At 2.1 mm ML, there is one large sucker on Arm I, one large basal sucker on Arm II, 1-2 small bud-like suck 巴rs on Arm III, and no suckers on Arm IV. At 5.5 mm ML, there are 14, 18 and 16 suckers on Arms I, II and III, respectively, and 12 small suckers without chitinous rings on Arm IV. At this size, size, the diameter of the outer chitinous ring on the first sucker of Arm is II 75 μm, with 12 knobs on the inner whorl and 11 on the middle whorl (Fig. 7B, Table 3). The fifth sucker of Arm II of this specimen specimen has 16 knobs on the inner whorl and 22 on the middle whorl, and the diameter of the outer outer chitinous suck 巴r ring is 90 μm (Fig. 7C, Table 3). At 8.5 mm ML, there are 16, 24, 20 and 24 suckers on Arms I, II, III and IV respectively. At 9.7 mm ML, there are 20, 26, 22 and 26 suckers ers on Arms I, II, III and IV respectively. The diameter of the outer chitinous sucker ring on the first first sucker of Arm II at this size is 92 μm, with 13 knobs on the inner whorl and 14 knobs on the middle middle whorl of the outer chitinous ring (Fig. 7D, Table 3). The 18th sucker of Arm II bears 21 knobs knobs on the inner whorl and 58 knobs on the middle whorl, and the knobs on the middle whorl form rows (Fig. 7E, Table 3). The 24th sucker of Arm II bears 21 knobs on the inner whorl and 63 knobs knobs on the middle whorl (Fig. 7F, Table 3). The number of knobs on the middle whorl increases Descriptions Descriptions of Eucleoteuthis luminosa and Ornithoteuthis volatilis Paralarvae 243

1刷 100

80 80 80 ．－．－．．をR ．、・． E 曲．・．主柑ロ．宣君 4 －．告．携・・・、．－．・． ~ 言 40 ．官 40 ・・－・・．．耳．韮－、‘・・．、＿，.．・‘.，.！. ・- ．－・．．・. －・ 6 ・． 20 20

0 00 20 4.0 60 8.0 10.0 120 140 00 20 4.0 6.0 8.0 100 120 140 Mantlo longth (mm) Mantlo longth (mm)

Fig. Fig. 4. Relationship between ML and MWI in Fig. 5. Relationship between ML and HLI in Eucleoteuthis Eucleoteuthis luminosa. Eucleoteuthis luminosa.

A B

Fig. Fig. 6. Funnel locking cartilage and intestinal photophore of Eucleoteuthis luminosa paralarvae. A. 2.1 mm ML, funnel funnel cartilage. B. 9.7 mm ML, funnel cartilag 巴. C. 3.3 mm ML, v巴ntral views showing photophores with mantl 巴 opened. Scale bars = 1.0 mm. with with growth in all but the first (Table sucker 3). The proboscis is much longer than the longest arm and twice HL, with a proboscis index (PI) of of 0.77 in specimens of 2.2 mm ML (Fig. 3A-C). At this size, it has not yet begun to divide. At 4.4 mm ML, proboscis length is about two times greater than the 1巴ngth of the longest arm and almost 巴qual to HL, with a PI of 0.73 (Fig. 3D, E). At this stage, the proboscis has begun to divide at its base ，組d the separated part measures 9.4 9もof total proboscis length (PSP) (Fig. 3F). At 6.4 mm ML, the proboscis is as long as the longest arm (Fig. 3G, H), and PSP is 22.6 %. At 8.5 mm ML, the the proboscis is clearly separated at the base with a PSP of 90 % (Fig. 8A), and the distal tip of the proboscis proboscis is also slightly divided. The sides of the proboscis tip become slightly extended, and small small suck 巴rs appear there (Fig. 8B). At 9.1 mm ML, the proboscis has completely separated to form the tentacles (Fig. 3J-L). At 9.7 mm ML, the tentacles are very thin and the half l巴ngth of Arm II II (Fig. 3L), with small suck 巴r buds that lack chitinous rings a町 anged in 8 transverse and 4 longitudinal tudinal rows on the distal half (Fig. 8C). Proboscis Proboscis length increas 巴s from 1.0 to 4.4 mm in specimens of between 1.4 and 5.8 mm ML, 244 T. Wakabayashi , K. Saito, K. Tsuchiya & S. Segawa

Fig. Fig. 7. Scanning electronmicrographs of suckers on Arm II in Eucleoteuthis luminosa. A. 1.4 mm ML, !st suck 巴r. B. B. 5.5 mm ML , 1st sucker. C. 5.5 mm ML , 5出 sucker. D. 9.7 mm ML , 1st sucker. E. 9.7 mm ML , 18th sucker. sucker. F. 9.7 mm ML , 24 出 sucker. Scale bars = 50 μm. decreases decreases from 4.4 to 1.0 mm in specimens of from 6.0 to 8.5 mm ML, and increases again after 8.5 8.5 mm ML (Fig. 9). Pl ranges from 0. 12 to 1.14 (n = 43) and decreases with growth (Fig. 10). The proboscis proboscis has not separated in 17 of 20 specimens ranging from 1.4 to 3.9 mm ML. The PSP in specimens of from 4.3 to 8.0 mm ML ranges from 5 to 50 %. The proboscis has separated completely pletely in specimens larger than 8.6 mm ML (Fig . 11) . Descriptions Descriptions of Eucleoteuthis luminosa and Ornithoteuthis volatilis P 紅 alarvae 245

Table Table 3. Number of knobs on Arm II suckers in Eucleoteuthis luminosa. ML Sucker Diameter No. of knobs (mm) (mm) (μm) Inner whorl Middle whorl 1.4 1.4 1st 46 14 15 1.4 1.4 !st 52 15 16 2.1 2.1 1st 60 14 17 3.1 3.1 1st 64 12 14 3.1 3.1 2nd 64 15 18 3.1 3.1 3rd 61 14 21 3.5 3.5 1st 59 11 14 3.5 3.5 2nd 53 16 18 4.9 4.9 1st 68 12 14 4.9 4.9 2nd 57 14 17 4.9 4.9 3rd 57 14 21 4.9 4.9 6th 57 20 27 5.5 5.5 1st 75 12 11 5.5 5.5 1st 80 12 14 5.5 5.5 5th 100 17 24 5.5 5.5 5th 90 16 22 5.5 5.5 12 出 61 20 25 6.0 6.0 1st 67 13 14 6.0 6.0 3rd 87 20 23 6.0 6.0 5th 97 18 27 8.5 8.5 9th 173 19 50 9.7 9.7 1st 92 13 14 9.7 9.7 1st 100 9 14 9.7 9.7 8th 204 17 44 9.7 9.7 10 白 207 18 50 9.7 9.7 18 出 170 21 58 9.7 9.7 24th 123 21 63

There are 8 suckers on the tip of th 巴 proboscis (Fig. SD) in specimens ranging from 1.4 to 8.0 mm ML. The two lateral suckers are larger than the six medial suckers. The ratio of the diameters of of th 巴 lateral to medial suckers ranges from 1.31 to 1.90 (x = 1.57, n = 29 in 9 specimens ranging from 1.4 to 8.5 mm ML). This ratio does not differ significantly among sp 巴cimens of different sizes. sizes. The number of knobs on the lateral suckers in specimens ranging from 1.4 to 8.5 mm ML rang 邸 from 14 to 22 on the inner whorl and from 18 to 24 on the middle whorl (Table 4). The number of knobs on th 巴 medial suckers in specimens ranging from 1.8 to 8.5 mm ML ranges from 9 to 13 on the inner whorl, and from 11 to 16 on the middle whorl, respectively (Table 4). The number of knobs on the proboscis suckers is similar in specimens ranging from 1.4 to 8.5 mm ML (Table (Table 4). Subocular Subocular and intestinal photophores are not yet differentiated at 2.2 mm ML (Fig. 3B). At 3.3 mm ML, a single round photophore is present between the intestine and digestive gland (liver), located located halfway betw 巴en the anus and the posterior curve of the intestine (Fig. 6C), but no subocular ular photophores occur in this size. At 4.4 mm ML, a single round photophore is also pres 巴nt on the the ventral surface of each eye (Fig. 3E). The epidermal layer of specimens smaller than 2.0 mm ML collected in the present study were damaged during collection, so their chromatophores could not be d回 cribed. At 2.2 mm ML, four chromatophores chromatophores are arranged in an irregular transverse row in the middle of the dorsal mantle, with a single chromatophore at the posterior end. On the ventral mantle, four chromatophores are arranged arranged in a trapezoid pattern. One or two pairs of chromatophores are present dorsally on the head, head, and one pair is present on the posterior V巴ntral m 紅 gin of the head (Fig. 3A, B).

At 4.4 mm ML, five chromatophores are arranged in an i打 egular transverse row in the middle 246 T . Wakabayashi, K. Saito, K . Tsuchiya & S . Segawa

Fig. Fig. 8. Scanning electronmicrographs of proboscis of Eucleoteuthis luminosa. A . 8.5 mm ML, proboscis. B. 8.5 mm ML , tip of proboscis . C. 9.7 mm ML, suckers of tentacular club. D . 5.5 mm ML, proboscis sucke rs. Scale bars bars = 100 μm .

5.0 5.0 150

I 4.0 4.0 ．．．．．．も・・．・ I 00 ． i 3.0 ．．．．．『料百t戸~』・．・．，司：九; 旬~。'0 ．．．．．．．．．．．呈－・．．．．．． ,. 。- ．••• ．．・．・．．孟主5。ヨ 2.0 ．．．． 050 ．．．．．．．．．．．－．】。．．．． :•

0.0 0.0 。。。 0.0 2.0 40 6.0 80 10 .0 12.0 14 0 。。 20 40 6.0 8.0 100 Manti< longth (mm) Manti< longth (mm)

Fig. Fig. 9. Relationship betw 巴en ML and proboscis Fig. 10. Relationship between ML and proboscis length length (t 巴ntacle 1巴ngth) in Eucleoteuthis ind 巴X (PI) in Eucleoteuthis luminosa . luminosa. luminosa. Descriptions Descriptions of Eucleoteuthis luminosa and Ornithoteuthis volatilis Paral 紅 va 巴 247

100 100 －・・・．

ヨ旨 d宮崎討品 22 6408 言語停兎a 3aaMA弓

H94同居【阿古ち．． dSA432 言宗．．．．．． 20 －，．・．．．．．．・． 0 0.0 0.0 2.0 4.0 6.0 8.0 10.0 120 140

Montleleng 曲（ mm)

Fig. Fig. 11. Relationship betwe 巴n ML and percentage of separat 巴d part length to total proboscis length (PSP) in Eucleoteuthis Eucleoteuthis luminosa.

Table Table 4. Counts of knobs on proboscis s川ckers in Eucleoteuthis lu 澗 inosa.

Lateral Lateral suckers 乱1edial suckers ML(mm) Inner whorl Middle whorl Inner whorl Middle whorl 1.4 1.4 22 24 1.8 1.8 12 14 1.9 1.9 15, 18 22 10, 13 11, 14 2.1 2.1 9, 12, 11, 13 15, 14, 12, 16 1222281211 3.1 3.1 14 11, 13, 13 15, 14, 15, 16 3.5 3.5 14, 17 11 16 5.5 5.5 16 10, 10, 11 15, 12, 12 6.0 6.0 15 11 13 8.5 8.5 17 10 12 *Bars *Bars indicate lack of data due to damage. of of the dorsal mantle, with a single chromatophore between the fins. Five chromatophores occur along along the anteroventral margin of the mantle, and the four in a trapezoid arrangement are still present sent in the middle of the ven 住al mantle. A single pair of chromatophores is present at the posteri- or or end of the dorsal mantle (Fig. 3D, E). At 5.0 mm ML, there ar 巴 7-11 chromatophores dorsally on the head and four ventrally. Arms I, II II and III have one to three chromatophores on the aboral side. Two chromatophores are present on the the surface of the outer lip between the bases of Arms II and III. At 6.4 mm ML ，出 ere are about 30 chromatophores on the dorsal mantle and about 20 chromatophores matophores on the ventral mantle, with 11-15 chromatophores dorsally on the head, and 6 ventrally. ly. Arms I, II and III hav 巴 two, five and five chromatophores respectively on the aboral side (Fig. 3F, 3F, G). A single pair of chromatophores is present on the outside of the outer lip between th 巴 bases of of Arms II and III. At 9.1 mm ML, chromatophores become more crowded on the mantle and the dorsal surface of the the head. There are 6 chromatophores on the ventral surface of the head and 5- 7 chromatophores on each arm (Fig. 31, J). A pair of chromatophores is still present on the surface of the outer lip between Arms II and III, and a single chromatophore is present between both Arms I. The buccal connective is of DDVD type (Fig. 3C, F, I, L). In specimens smaller than 2.0 mm 248 248 T. Wakabayashi, K. Saito, K. Tsuchiya & S. Segawa

Fig. Fig. 12. Scanning elec 仕onmicrographs of the mouth parts of Eucleoteuthis luminosa. A. 2.1 mm ML, B. 2.1 mm ML, C. 3.5 mm ML, D. 5.5 mm ML. Scale bars = 100 μm.

ML, the conn 巴ctives between the buccal m 巴mbrane and 紅 ms are not traceable. In a6 .0 mm ML specimen specimen with its proboscis split at the base, the connectiv 巴 with both Arms IV pass 巴S through the foramen foramen of th 巴 proboscis base (Fig. 31). The tips of th 巴 upper and lower beaks are not pointed at 2.1 mm ML (Fig. 12A) . Minute denti- tions tions are present on the cutting edge of th 巴 lower beak (Fig. 12B), and lip cilia are present (Fig. 12A). 12A). At 3.5 mm ML, the rostrum of the upper beak is pointed and developed, while the tip of the lower lower beak is not yet pointed '(Fig . 12C). At 5.5 mm ML, the rostra of the upper and lower beaks ar 巴 well developed (Fig. 12D) . The numbers of demibranch leaflets are 8, 16, 22, 29 and 35 for specimens of 2.1, 4.9, 5.5, 8.5 and and 9.7 mm ML respectively , showing that they increase with mantle size .

Ornithoteuthis Ornithoteuthis volatilis (Sasaki, 1915)

(Figs. (Figs. 13-23 , Tabl 巴s5 , 6)

A total of 47 specimens ranging from 2.4 mm to 5.4 mm ML were identified as Ornithoteuthis volatilis. volatilis. Of these, 96 % were collected at 31 'N, 134 。E and 32'N, 134'E (Fig. 2). Around the Ogasawara Islands, only 2 specimens were captured at 25'N, 142'30 ’E and 25'30 ’N, 142'30 ’E. 0. volatilis volatilis was collected from depths of between 20 and 70 m, with the largest catches occurring at Descriptions Descriptions of Eucleoteuthis luminosa and Omithoteuthis volatilis Paralarvae 249

No. No. of paralarvae 。 5 10 15 20

0-10

10-20

20-30

30-40

e 40 訓

卓早唱 50 ・60

60-70

70-80

80-90

90-100

Fig. Fig. 13. Vertical distribution of Ornithoteuthis volatilis paralarvae.

50-60 50-60 m depth (Fig. 13). The mantle in all the specimens examined is rather thin and sac-like in shape (Fig. 14A, B, D, E, E, G, H). The dorsal mantle edge is bluntly triangular (Fig. 14A, D, G), while the ven 住al margin is gently gently excavated with blunt lateral lobes on both sides (Fig. 14B, E ，町. MWI slightly declines with increasing increasing body size (Fig. 15).

The fins are small, delicate and semicircular in outline (Fig. 14A, B ヲ D, E, G, H). At 2.5 mm ML, the posterior margin of the fins extends beyond ilie posterior end of the mantle (Fig. 14A, B). At 5 .1 mm ML, the fins are 住ansversely oblong and attached to the posterior end of the mantle (Fig. (Fig. 14G, H). The FW: FL ratio is 3.0 and 2.5 at 2.5 and 5.1 mm ML resp 巴ctively. The head is subcubic in shape, with large eyes (Fig. 14A, B, D, E, G, H), and slightly narrow- er er than the mantle opening. HLI is relatively consistent at around 30 to 50 % in all specimens examined examined (Fig. 16). The funnel is slender and relatively long, extending to the middle of the head at 2.4 mm ML (Fig. (Fig. 14B). In sp 配 imens larger than 4.0 mm ML, the funnel is moderate in size (Fig. 14E, H). The funnel-mantle locking cartilage is shaped like an inverted T, and the longitudinal groove has has a round edge (Fig. 17 A). The arm formulas in specimens from 2.4 to 5.4 mm ML were II> I >III >IV, II> I = III III >IV and II >III> I >IV. At 2.5 mm ML, Arm IV is much shorter than the other ぽ ms and Arm II which is the longest, is one-quarter of ML. Arms I and III are of almost the same length

(Fig. (Fig. 14A 田 C). At 4.0 mm ML, Arm II is slightly longer than Arms I and III, and is one-third of ML (Fig. (Fig. 14D-F). At 5.1 mm ML, the longest Arm II is half ML, and Arm IV is about 40 % the length of of Arm II (Fig. 14G-I). At 2.4 mm ML, there are three, five and five suckers on Arms I, II and III, respectively, and 250 T. Wakabayashi, K. S氾to, K. Tsuchiya & S. Segawa

A B D E

G H c～／

Fig. Fig. 14. Paralarvae of Ornithoteuthis volatilis. A ・C. 2.5 mm ML; dorsal (A), ventral (B) and oral (C) views. D ・F. 4.0 4.0 mm ML; dorsal (D), ventral (E) and oral (F) views. G ・I. 5.1 mm ML; dorsal (G), ventral (H) and oral (I) (I) views. Scale baIS = 1.0 mm. Descriptions Descriptions of Eucleoteuthis luminosa and Ornithoteuthis volatilis Paralarvae 251

100 100

。。 80 。。 0 0 00 0 0 喧）主 60 0 0 "o O 。 ~o00 t 60 d 。 o0ef' o0 ロ。。 0 0 Q。。。。。 ] t日。可- 」『】乍~ 。。。。。0 • o vooo 'b 。、~f 。。三 40 宮 40 。o 0 v《 0 oO ~ ヨο回。。0 0 0 00 0 。

20 20

0 00 1.0 2.0 3.0 40 5.0 60 0.0 1.0 2.0 3.0 40 50 6.0 Manti< longth (mm) Manti< longtb (mm)

Fig. Fig. 15. Relationship betw 巴en ML and MWI in Fig.16. R 巴lationship between ML and HLI in Ornithoteuthis Ornithoteuthis volatilis. Ornithoteuthis volatilis.

Fig. Fig. 17. Funnel locking cartilage and intestinal photophore of Ornithoteuthis νolatilis paralarva 巴 A. 4.2mmML, funnel funnel cartilag 巴. Scale bar = 1.0 mm B. 4.2 mm ML, ventral views showing photophores with mantle opened. opened. Scale bar = 100 μm. none on Ann IV. At 2.8 mm ML, there is a single sucker bud on Arm IV, and five, ten and eight suckers suckers on Arms I, II and III, respectively. In this specimen, the ofdiameter the outer chitinous sucker sucker ring on the first sucker of Arm III is 65 μm, with 12 and 16 knobs respectively on the inner and middle whorl (Fig. 18A, Table 5). The fourth sucker of Ann II has 17 knobs on the inner whorl and 23 knobs on the middle one, with an outer chitinous sucker ring of 75 μmin diameter (Fig. 18A, 18A, Table 5). Th 巴 s巴venth sucker of Arm II has 20 knobs on the inner whorl and 8 knobs on the middle middle one, with an chitinous outer sucker ring of 54 μmin diameter (Fig. 18C, Table 5). At 3.6 mm ML, 10, 12 and 10 suckers with chitinous rings are present on Arms I, II and III, respectively, and six small suckers buds ar 巴 present only on Ann IV. At 4.0 mm ML, there are 10, 14 and 12 suckers suckers with chitinous rings on Arms I, II 姐 d III, respectively, and six suckers without chitinous rings rings on Arm IV. At 5.1 mm ML, 12, 18, 16 and 12 suckers are present on Arms I, II, III and IV, respectively. respectively. At 2.5 mm ML, the proboscis has not yet begun to separate and is 1.5 times longer than the longest longest arm (Arm II), with a PI of 0.36 (Fig 14A-C). At 4.0 mm ML, the proboscis splits off by a qu 紅 t巴r of its full length at the base and is 1.5 times long 巴r than the longest 征 m (Arm II) with a PI 252 T. Wakabayashi , K. Saito, K. Tsuchiya & S. Segawa

Table Table 5. Number of knobs on Arm II suckers of Ornithoteuthis volatilis. ML Diameter No .of knobs (mm) (mm) Sucker (μm) Inner whorl Middle whorl 2.4 2.4 1st 57 13 14 2.4 2.4 2nd 51 13 13 2.8 2.8 1st 70 13 14 2.8 2.8 2nd 69 13 18 2.8 2.8 3rd 75 16 22 2.8 2.8 4th 73 17 23 2.8 2.8 7出 54 20 3.6 3.6 1st 76 13 15 3.6 3.6 3rd 93 15 16 3.6 3.6 4th 100 15 18 3.6 3.6 5th 70 18 15 3.6 8th 93 20 18 4.0 4.0 2nd 85 16 21 4.2 4.2 !st 81 14 15 4.2 4.2 2nd 89 17 20

Fig. Fig. 18. Scanning 巴lectronmicrographs of suck 巴rs on Arm II in Ornithoteuthis volatilis. A. 2.8 mm ML, 1st . B. 2.8 mm ML, 4th sucker. C. 2.8 mm ML , 7th sucker. Scale bars = 50 μm.

of 0.40 (Fig . 14D-F). A t 5.1 mm ML , the proboscis is slightly longer than the longest arm (Arm II) (Fig . 14G , H) with a PI of 0.49. The proboscis splits broadly at the base (Fig. 141), and the lateral sid 巴 of the proboscis tip becomes slightly longer, with a PSP of 48.0 %. Proboscis Proboscis length increases from 0.8 to 2.5 mm in specimens between 2.4 and 5.4 mm ML (Fig. 19) . PI varies widely , but tends to decr 巴ase with increasing ML (Fig. 20) . In 17 of 28 specimens ranging ranging from 2.4 to 4.0 mm ML, the proboscis had started to separat 巴. The maximum PSP r巴cord- 巴d was 76 .99 もin a 5.0 mm ML specimen (Fig. 21) . In In specimens ranging from 2.4 to 5.4 mm ML, there are eight suckers on the tip of the proboscis. boscis. The lateral suckers are considerably larger than them 巴dial ones (Fig . 22A). The ratio of lateral eral sucker diameter to medial sucker diameter ranges from 1.72 to 2.60 （主＝ 2.09, n = 50 in 9 specimens) . This ratio does not differ significantly among specimens of differ 巴nt sizes. The number of knobs on lateral suckers on the tip of the proboscis in specimens ranging from 2.8 to 5.3 mm ML ranges from 12 to 18 on th 巴inn 巴r whorl, and from 7 to 19 on the middle whorl (Table (Table 6) . In specimens ranging from 2.4 to 5.3 mm ML, the number of knobs on medial suckers Descriptions Descriptions of Eucleoteuthis luminosa and Ornithoteuthis volatilis Paralarvae 253

3.0 3.0 0.80

2.5 2.5 。。。。。。。 0.60 。 20 。。。。。。。。吉。。。。 cρ 国。。。。。 vd 。。－EHaoAOS 吾。。。幼 α0 0 。。。 § 15 。。。。。。。。。判。。。♂ g。泊。・o ・o 。。。。。。。。。。。 Hh。 o~ 。 o 2 00 v 。。。 0 。 ~ 10 。。。 cρ 。。。 0.20 0.20

0.5 0.5

0.0 0.0 0.00 o目。 1.0 20 3.0 40 5.0 6.0 0.0 1.0 2.0 3.0 4.0 so 6.0

M 田 tie length (mm) Mantle l四回＞（ m 皿）

Fig. Fig. 19. R 巴lationship betwe 巴n ML and proboscis Fig. 20. Relationship betwe 巴n ML and proboscis length length in Ornithoteuthis volatilis. index (PI) in Ornithoteuthis νolatilis.

100

80 。層仏古担当昔告 2AA 6400 。ヨ。 4020HESSQ 刊官官。。 τ 。。。ヨ宮崎ザ岳。 S 。 cρ cρ 0 0 ~，..， 20 0 0 －。。。。0 》。~ - 。0 000 －ら。 0 00 1.0 2.0 3.0 4.0 50 6.0 Mantle length (mm)

Fig. Fig. 21. Relationship between ML 組 d percentage of separated rated part length to total proboscis length (PSP) in Ornithoteuthis Ornithoteuthis volatilis.

Table 6. Counts of knobs on proboscis suckers in Ornithoteuthis volatilis.

Lateral Lateral sud 担問 Medial suckers ML(nun) Inner whorl Middle whorl Inner whorl Middle whorl 2.4 2.4 ＊ 9,10 5,11 山一時一則一日一同 2.8 2.8 15, 16 8, 9, IO 5, 2, 11 3.6 3.6 14 12 2 4.0 4.0 17, 19 9, 13, 14 6, 11, 14 4.0 4.0 10, 10, 12 1, 2, 9 4.2 4.2 18 12, 14 3, 13 4.2 4.2 11, 12 12 4.9 4.9 12, 12 7, 11 12, 10, 12, 13 2, 10, 12, 12 5.3 5.3 14 12, 11, 10, 13 4, 8 *Bars *Bars indicate lack of data due to damage. 254 254 T. Wakabayashi, K. Saito, K. Tsuchiya & S. Segawa

Fig. Fig. 22. Scanning electronmicrographs of the proboscis tip of Ornithoteuthis volatilis. A. 3.6 mm ML, proboscis. Scale Scale bar= 100 μm. B. 4.2 mm ML, medial sucker of proboscis. Scale bar= 10 μm. C. 3.6 mm ML, m 巴di al al sucker of proboscis. Scal 巴 bar= 10 μm.

Fig. Fig. 23. Scanning electron micrographs of the mouth parts of Ornithoteuthis volatilis. A. 2.8 mm ML. B. 3.1 mm ML. C. 4.2 mm ML. Scale b紅白＝ 100 μm.

ranges ranges from 8 to 14 on th 巴 inner whorl, and from 1 to 14 on the middle whorl (Table 6, Fig. 22B, C). C). Subocular Subocular and intestinal photophores cannot be distinguished in specimens small 巴r than 2.5 mm ML. In sp 巴cimens larger than 3.0 mm ML, an int 巴stinal photophore is appar 巴nt near the anus (Fig. 17B). 17B). Subocular photophores 紅巳 distinguishable at about 3.0 mm ML, but are often indistinct. In specimens specimens ranging from 4.6 to 5.4 mm ML, both subocular and intestinal photophores are appar - ent. ent. At 2.5 mm ML, four chromatophores are arrang 巴d in a diamond shape on th 巴 posterior half of the the dorsal mantle, with a single chromatophore at the post 巴rior end. On the ventral mantle, six chromatophores matophores are a汀 anged in a circl 巴， with a single pair at the posterior end of the mantle .Th 巴r巴 are six six chromatophores on the dorsal surfac 巴 of the head, two on the ventral surface near the eyes, and a single pair on the posterior margin of the ventral surface . Two chromatophores are present at the anterior anterior end of the funnel, and two more are present on the surface of th 巴 outer lip between the bas 巴s of Arms II and III (Fig. 14A, B) . At 4.0 mm ML, fiv 巴 chromatophores are arrang 巴d in a diamond shape in the middle of the dorsal sal mantle, with a single chromatophore between the fins. There are five chromatophores along the anteroventral anteroventral margin of th 巴 mantle, and eight a汀 ang 巴d in a circle in the middl 巳 of the ventral man- Descriptions Descriptions of Eucleoteuthis luminosa and Omithoteuthis volatilis Paralarvae 255 tle. tle. There are two pairs of chromatophores at the posterior end of the dorsal mantle, eight on 出c dorsal dorsal surface of the head, and four on the ventral surface. Two chromatophores are present at the anterior anterior end of the funnel; two more are present on the surface of the outer lip between the bases of of Arms II and III. One chromatophore is present between 白e bases of both Arms I (Fig. 14D, E). At 5.1 mm ML, five chromatophores are arranged in a diamond shape in the middle of the dorsal sal mantle, with a single one between the fins. There are five chromatophores along the anteroventral tral margin of the mantle, eight arranged in a circle in the middle of the ventral mantle, two on the anteroventral anteroventral mantle, and seven on the posteroven 住al mantle. There are 10 chromatophores on the dorsal dorsal surface of the head, 6 on the ventral surface, and two at the anterior end of the funnel. Two chromatophores 紅 e present on the surface of the outer lip between Arms II and III (Fig. 14G, H). The buccal connective is of DDVD type (Fig. 14C, F, I). In small specimens whose proboscis has has not yet begun to separate, the buccal membrane is not connected to the bases of Arms IV. In specimens specimens whose proboscis has separated widely, th 巴 buccal membrane is connected to Arms IV through through the foramen of the separated proboscis (Fig. 141). The tip of the lower beak is not pointed and bears minute dentition on the cutting edge at 2.4 mm ML. At 3.1 mm ML, the tip of the lower beak begins to become acute, but the dentition still remains remains (Fig. 23B). At 4.2 mm ML, the rostrum of th 巴 lower beak is pointed (Fig. 23C). The upper beak beak is not well developed. Lip cilia 創・e pres 巴 nt in specimens smaller than 2.8 mm ML (Fig. 23A). There There are 15, 18 and 23 demibranch leaflets at 2.8, 4.0 and 5.3 mm ML, respectively.

Discussion Discussion

Important Important taxonomic characters of ommastrephid paralarvae include the number and location of photophores, photophores, mantle size at photophore differentiation, PI, proboscis length relative to that of the longest longest arm, relative size of suckers on the proboscis tip and mantle size at complete proboscis separation aration (Wormuth et al., 1992; Table 7). Although most ommastrephine paralarvae can be identified fied based on a combination of these characters, it is v巴巧 f hard to identify certain stages of some species species which have similar taxonomic features. The present study shows that chromatophore patterns terns on the head and mantle, and characters of the proboscis and photophores ar 巴 useful in id 巴nti- fying fying paralarvae of E. luminosa. In In the present study, subocular photophores in E. luminosa appeared at 4.0 mm ML, and a single gle intestinal photophore appeared at 3.5 mm ML. Proboscis division in E. luminosa started at about about 3.0 mm ML and was completed at about 9.0 mm ML. Fusion of the funnel-mantle cartilage occurred occurred at 8-11 mm ML. These results 紅 e similar to 白ose of Nesis (1979), except that in the present sent study, proboscis separation occu 町 ed at a greater ML (Table 7). The PI or Tentacular Index is a good character for identifying ommastrephid paralarvae (Sato, 1973; 1973; Harman & Young, 1985). The PI of E. luminosa in the pr 自己nt study ranged from 0.12 to 1.14 1.14 (x = 0.70). Since there is a variation in PI with a tendency to decline with increase of ML, PI is is still useful character for identification. In In Ommastrephes bartramii (Naef, 1923), Rhynchoteuthion type C (Sato, 1973) and Illex argentinus argentinus (Vidal, 1994), proboscis suckers can be clearly seen in the carpal part of the tentacular club club after the proboscis has completely sep 紅 ated. However, we observed no proboscis suckers on the the tentacles of E. luminosa after the tentacles had separated. Wormuth (1976) and Roeleveld (1988) considered E. luminosa to be taxonomically close to Hyaloteuthis Hyaloteuthis pelagica. These two species have similar morphological characters during th 巴 paralarval alarval stage (i.e. a relatively long proboscis, moderately large lateral suckers on the proboscis tip, a single photophore on the intestine and a photophore on the ventral surface of each eye); however, er, there ar 巴 some criteria that can be used to sep 紅 ate these two species. In E. luminosa, the photophores tophores occur at a later stage than in H. pelagica (Table 7). The mean proboscis index and the Nua

Table 7. Morphological comparison of ommastrephine paral 紅 vae. 日当係各担吉田 ML(mm) Proboscis Index Ratio of the diameter Size (mm ML) at Number of Size (mm ML)

Speci 巴S of examined (m 巴an± S.D. of lateral to m 巴dial suckers proboscis division photophores at photophores

specmens specmens or range) of prboscis Begin Complete Subocular Intestinal appe 紅 anc 巴

Ommastrephes bartramii 吋 1.0-12.5 ca. 0.4 吋 ca. 2.0 5.0 7.0 。。 no photophore E ・関・∞阻止 Dosidicus Dosidicus gigas η 3.0-5.8 0.2-1.0 ca. 1.0 no data no data 。。 no photophore

Sthenoteuthis Sthenoteuthis oualaniensis ・3 ca. 1. 0-10.0 0.81 士0.25 1.19 士0.01 S.D. 3.0-5.0 8.5 2 3.5 4.0 PH Omithoteuthis Omithoteuthis i olatilis 叫 no data 0.50-0.75 1.5 2.0 4.0-5.0 6.5-7.0 2 3.5-4.0

1 '10 円・ Ornithoteuthis Ornithoteuthis volatilis 府5 2.4-5.4 0.43 土0.10 2.09±0.21 S.D. 2.5 no data 3.0-4.0 42znE Eucleoteuthis Eucleoteuthis luminosa '' ca. 2.0-11.0 0.5-0.67 ca. 1.5 '9 5.0-5.5 9.0-10.0 3.0-3.5

Eucleoteuthis Eucleoteuthis luminosa 巧 1.4-12.4 0.70±0.28 1.57 士 S.D. 0.14 4.0 8.0 4.0 苫

Hyalot 印， this pelagica " ca. 1.0-8.0 0.61 土0.25 1.44±0.03 S.D. 3.5-4.0 6.5 <1.5 hw ∞－官官 Rhynchoteuthion Rhynchoteuthion Type A ’η1.00-7.25 0.45±0.16 cι2.0 句 3.0 4.0-5.0 2.0

Rhynchoteuthion Rhynchoteuthion Type B ’咋 2.06-3.75 0.90±0.29 c仏 1.2 匂 4.0< no data 4.0< S Rhynchoteuthion Rhynchoteuthion Type A 句 2.0-5.3 0.43 2.0 no data no data no data no data 5.0-6.0 吋Young & Hirota (1991) ，傘 2Yatsu et al. (1999),''Harman & Young (1985 ），叫 Wormuth et al. (1992 ），吋 Present study, ''Nesis (1979),

咋 Roper & Lu (1979 ），切 Sato (1973 ）四 dY 創 namoto & Okutani (1975), ''Measurement from illus 仕組ons in 出1e literature,

•in Only one photophore ne 紅白巴anus is p民間 nt in the examined size range. Descriptions Descriptions of Eucleoteuthis luminosa and Ornithoteuthis volatilis Paralarvae 257 number of knobs on the proboscis suckers in E. luminosa are both slightly larger than in H. pelagica ica (Harman & Young, 1985), but these differences are not significant (Table 7). In specimens smaller smaller than 4.0 mm ML, the mantle chromatophore pattern differs between E. luminosa and H. pelagic α. H. pelagica has a single conspicuous chromatophore on the dorsal mantle (Harman & Young, 1985; Young & Hirota, 1990), but E. luminosa examined in the present study have several chromatophores chromatophores arrang 巴d in irregular transv 巴rse rows. As was point 巴d by Young & Harman (l (l 985a, 1987), th 巴 chromatophore patterns on the mantle are a useful criterion for identifying Enoploteuthid Enoploteuthid and Onychoteuthis paralarvae. Saito et al. (1990) suggested that th 巴 chromatophore pattern pattern on the dorsal surface of the head is useful in distinguishing E. luminosa from other ommastrephid trephid paralarvae. The pres 巴nt study corroborates their suggestion. In In summ ぽ y, the key characters for distingushing E. luminosa paralarvae from thos 巴 of H. pelagica pelagica are : The presence of subocular and intestinal photophores and the chromatophore pattern on the dorsal surface of the head in specimens smaller than 4.0 mm ML; the mantle chromatophore pattern pattern in specimens ranging from 4.0 to 5.0 mm ML; the degree of proboscis division in specimens ranging from 5.0 to 6.5 mm ML, and the d巴gree of proboscis separation in specimens larger than than 6.5 mm ML. The present observations on 0. volatilis agre 巴with those of Nesis (1979) in that subocular photophores tophores appeared at 4.0 mm ML, and the intestinal photophore appeared at 3.0-3.5 mm ML. N 巴ither posterior intestinal photophores nor complete division of the proboscis were observed in the the pr 巴印刷 specimens. The proboscis at 5.4 mm ML is almost completely split and has small sucker er buds on th 巴 tip. The chromatophore pattern of specimens of 0. volatilis at 4.0 mm ML agrees well well with the descriptions of Wormuth et al. (1992). The PI of 0. volatilis in the present study ranged from 0.24 to 0.66 (x = 0.43). The ratio of lat- 巴ral to medial sucker diameters on the proboscis did not vary significantly among specimens of diι ferent ferent siz 巴. Although the number of knobs on the middle whorl of the lateral suckers and on the inner inner whorl of th 巴 lateral and medial suckers are relatively consistent among species, there is some intraspecific intraspecific variation in the number of knobs on the middle whorl of the medial suckers. There are only only one or two knobs on 白巴 middle whorl of the medial suckers of 0. volatilis. Although the features tures of sucker knobs in other ommastrephid paralarva 巴 hav 巴 not been described, they could be useful ful in distinguishing 0. volatilis from Nototodarus hawaiiensis and Ommastrephes bartramii, which have lateral suckers considerably larger than the m 巴dial ones (Harman & Young, 1985; Young & Hirota, 1990). The Rhynchoteuthion Type A ’ of Roper & Lu (1979) from the northwestern Atlantic was thought thought to belong to the genus Ommastrephes, but do 巴s not agree with paralarvae of Ommastrephes, Ommastrephes, because 0. bartramii paral 訂 vae have no photophores; Type A ’ is Ornithoteuthis antillarum. antillarum. On the other hand, Rhynchoteuthion B ’ of Roper & Lu (1979), which they identified as 0.α ntillarum, has the characters of either Sthenoteuthis or Hyaloteuthis pelagica, i.e. two lateral suckers suckers slightly larger than the m 巴dial ones and a moderately long proboscis (Table 7). Type A ’ has greatly greatly enlarged lateral suckers and a short to moderate proboscis, features similar to those of 0. volatilis volatilis in the present study (Table 7). Nesis (1979) suggested that Rhynchoteuthion type A of Sato (1973) (1973) and of Yamamoto & Okutani (1975) is 0. volatilis. The present study supports this vi 巴w based based on the chromatophore pattern, Pl, and enlarged lateral suck 巴rs on the proboscis (Table 7). The tips of the upper and lower beaks of E. luminosa and 0. volatilis of less than 3.0 mm ML were not pointed, but the lower b巴aks bore minute dentition and lip cilia were present. The presence ence of such minute dentition on the cutting edge of beaks is common in ommastrephids (Harman & Young, 1985) and other Teuthoid paralarvae (Boletzky, 1971; Young & Harman, 1985b). Boletz 匂（ 1971) mentioned that the mandibular structure of juvenile cephalopoda is related to their feeding feeding s佐ategy. A Sthenoteuthis oualaniensis paralarva of 5.4 mm ML had a few crustacean frag- ments ments in its caecum (Vecchione, 1991). An Illex argentinus Rhynchoteuthion paralarvae of 3.7 mm 258 258 T. Wakabayashi, K. Saito, K. Tsuchiya & S. Segawa

ML had cop 巴pod appendages in its digestive tract (Vidal & Haimovici, 1998). Vidal & Haimovici (1998) (1998) suspected that filaments on the lips of the buccal mass may represent an adaptation for the manipulation manipulation and ingestion of microorganisms or small pieces of enriched mucus. Morphological changes in the beaks and the disappearance of lip cilia occurred at 2.0-4.0 mm ML in E. luminosa 姐 d 2.4-4.0 mm ML in 0. volatilis in the present study, which may reflect changes in their feeding behavior behavior at these sizes. Young & H ぽ man (1988) defined the term ‘paralarva ’ as 'a cephalopod of the first post-hatch- ing ing grow 由 stage that is pelagic in near-surface water during the day and 出at has a distinctively different ferent mode of life from that of older conspecific individuals. ’However, the criteria that define the end of the paralarval stage differ among families. In the Ommastrephidae ，出 e paralarval stage ends when the proboscis separates (Young & Harman, 1988). In the present study the proboscis in E. luminosa luminosa separated completely at 8.0-10.0 mm ML and 出e numbers of chromatophores and suck-

er er knobs increased abruptly. In addition, lip cilia that disappear before the separation of the pro 咽 boscis boscis may be an important criterion in determining the close of the paralarval stage. Further research research on the morphological characters of paralarvae in other families may provide clues for understanding understanding more clearly the changes that occur during the paralarval stage.

Acknowledgements

We thank the captains 拍 d crews of the RIV Hokko-Maru, RIV Kaiyo-Maru and RIV Shunyo-Maru for their their effort in sampling during the cruises. We thank Mr. K. Mori, Hokkaido National Fish 出 es Research Ins Ins ti tut 巴； Mr. J. Mori, formerly of th 巴 National Research Institute of Far Sea Fisheries, and Mr. Y. Hirota and and M. Ishida, National Research Institute of Fisheries Science for providing samples. Thanks 紅 e also due to to Dr. A. Yatsu, National Research Institute of Fisheries Science, for his helpful advice, and to Dr. J. R. Bower, Bower, Hokkaido University for reading the manuscript and making helpful comments. We are grateful to Dr. Dr. T. Okutani, for his valuable comments and criticisms.

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北西太平洋で採集されたスジイカおよびヤセトビイカ稚仔の形態について

若林敏江・斎藤和範・土屋光太郎・瀬川進

要約

小笠原周辺海域および四国沖からフィリピン海で採集された，外套長 1.4 ～ 12.4 mm のスジイカ稚仔 53 個体と，外套長 2.4 ～ 5.4 mm のヤセトピイカ稚仔 47 個体を用いて記載を行った。スジイカ稚仔は眼胞上に 1 個，直腸上中央に 1 個の発光器をもち，それらの出現時期は外套長 4.0 mm であった。また融合触腕は，外套長 4.0 mm で分離が始まり，外套長 8.0 mm で完全に分離する。融合触腕指数の平均値は 0.70 0.70 ± 0.28 (S.D .）で，融合触腕先端の吸盤は側部の 2 個が中央の 6 個よりやや大きく，中央の吸盤に対する側部の吸盤の大きさの平均は， 1.57 ± 0.14 (S.D. ）であった。ヤセトビイカ稚仔は眼胞上に 1 個，内臓上に 2 個の不等大の発光器をもち，それらの出現時期は外套長 3.0 ～ 4.0 mm であった。また融合触腕の分離は外套長 2.5 mm で始まるが，本研究では完全に分離した個体はなかった。融合触腕指数の平均値は0.43 ± 0.10 (S.D .）で，融合触腕先端の吸盤は側部の 2 個が中央の 6 個より顕著に大きく，中央の吸盤に対する側部の吸盤の大きさの平均は， 2.09 ± 0.01 (S.D. ）であった。