A small school of the bobtail squid Heteroteuthis hawaiiensis was observed on the ocean floor at a depth of 912m near the Ogasawara Islands. This is the first report of an observation on the living deep-sea bobtail squid

Okutani, Takashi

Tsuchida, Shinji

English

OceanRep

VENUS 63 (3-4）ι125-133, 2005 Occurrence and Living Habit of Bathyal Bobtail Squid, Heteroteuthis hawaiiensis (Cephalopoda: Sepiolidae) from off the Ogasawara Islands, Japan Takashi Okutani and Shi吋iTsuchida Japan Agency for Marine-Earth Science and Technology (JAMSTEC), 2-15 Ntsushima-cho, Yokosu化。， Kanagawa237-0061, Japan; okutani@jamstec.go.jp Abstract: A small school of th巴 bobtailsquid Heteroteuthis hawaiiensis was observed on the oce叩日oorat a depth of 912 m near the Ogasawara Islands. This is the first report of an observation on the living deep-sea bobtail squid. Keywords: living habit, S巴piolidae,Heteroteuthis, bathyal, nektob巴nthicIntroduction During the biological and physico-chemical investigations using the ROV Hyper-Dolphin around the Kaikata Seamount, near the Ogasawara Islands, a small school of a bobtail squid of the family Sepiolidae was observed on the sea floor at a depth of 912 m. The video images of this animal were taken and several specimens were then collected by the ROV. Close examination of these specimens rev巴aledthem to be Heteroteuthis hawaiiensis, representing a positive record of this taxon in Japanese waters. Materials Nine specimens were collected with a suction sampler of the ROV Hyper-Dolphin operated by the R八rNatsushima, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), on June 28, 2003, on the Kaikata Seamount at 26°41.25' N, 141°02.72' E, from the bottom at a depth of 912 m (Fig. 1). This dive (HD Dive 188) was aimed at observing and collecting animals in non-chemosynthetic environments on the sea bottom of the southwestern slope of the Kaikata Seamount, between depths of 962 m and 871 m (Watanabe et al., 2003). Observations Living habit Th巴 observationpoint of the ROV Hyper-Dolphin was on a gentle slope of the Kaikata Seamount. The bottom texture was made up of coarse sand in general, with scattered large to small rocks, stones and pebbles, on which occasional growths of cnidarians and sessile crinoids were observed (Fig. 2F). The visible benthos was very intermittent. More than a dozen bobtail squids were found hovering her巴 andther巴 veryclose to the bottom. All specimens under observation were oriented randomly, and se巴m not to have been a庄町tedby water cuπents in this place. Under the light of the ROV, the dorsal surfac巴 ofal specimens was fresh brownish red, and the ventral side was silvery. The dorsal eye-lid and ventral shield, which project forward, exhibit strong iridescent light-reflection (Figs. 2D & E). No special behavior, such as light emitting, inking, copulating, egg-laying, fighting or camouflaging was observed. 126 T. Okutani & S. Tsuchida Fig. 1. Observatory station at the Kaikata Seamount (star). Voucher Specimens Nine female specimens (five in ethanol: JAMSTEC-053574 to 053578 and one frozen lot). Morphology Taxonomy Family Sepiolidae Leach, 1817 Heteroteuthis (Stephanoteuthis) hawaiiensis Berry, 1909 (Figs. 2A-C, 3 ) Animal small with plump body, large oval fins, and short訂ms(Fig. 2A帽 C).Mantle rather muscular, ovoidal to ellipsoidal in shape with round, dome-shaped posterior end. Mantle width (MW) about three quarters of dorsal mantle length (DML). Dorsal surface convex, 組 ddensely speckled by dark reddish-purplish chromatophores. Dorsal margin of mantle bluntly projected in form of broad出angle.Ventral surface likewise convex with dense reddish-purple chromatophores. Prominent ventral shield projects forward beyond dorsal mantle projection or level of eye. Therefore, ventral mantle length (VML) about 20% longer than DML. This ventral shield marked off from ven佐almantle by evident boundary, and more heavily pigmented with weakly plicate skin. Small but distinct funnel excavation in center of ventral margin. Both ventral lobes not acute, but round. Fins oval, separated, almost non-pigmented except small patch of microscopic chromatophores along dorsal distal margin. Posterior margin of fin smoothly round, with small anterior free lobe. Living Habit of Bathyal Bobtail Squid 127 Table 1. Measurements of five selected specim巴nsin ethanol preservation (in mm) #1 #2 #3 #4 #5 Dorsal mantle length (DML) 23.7 22.7 22.1 23.4 23.8 Ventral mantle l巴ngth(VML) 27.9 26.1 27.0 26.5 27.2 Mantle width (MW) 18.0 9.0 16.5 17.3 14.9 Fin length (FL) 17.1 17.2 16.4 17.4 15.3 Fin width (FW) 29.6 32.3 29.4 29.9 32.7 Head width (HW) 16.0 15.1 14.9 15.4 14.8 Right Arm I length (ALI) 7.5 6.0 9.0 9.8 10.8 Right Arm I length (ALII) 11.0 10.0 9.0 9.0 11.9 Right Arm II length (ALIII) 12.5 11.0 9.1 9.5 11.0 Right Arm IV length (ALIV) 7.5 9.0 9.5 9.0 11.2 Arm I sucker count* (AScI) 14 14(L) 14(L) 15 12 Arm I sucker count (AScII) 10 12 12 1 12 Arm II sucker count (AScIII) 22 22 22 22 20 Arm IV sucker count (AscIV) 18+m料 20+m 14+m 14+m 14+m Right t巴ntaclelength (TtL) 20.5 17.0 15.5 16.0(L) 14.4 Right club length (CbL) 2.0 2.0 1.8 1.9 2.1 *All on the right紅mexcept those denoted L (=left arm); ＊＊“＋m”denotes minute distal suckers. Leng出 offin base about 40% DML. Head subcubic, darker in color than mantle, very gradually tapering forward, with large eyes on lateral sides. Funnel moderate in size, tubular, reaching to fork of Arm IV. Dorsal element of funnel organ large, inverted V-shaped. Ventral pads indistinct. Arms short but muscular, subequal in length (Fig. 3A). Arm I with broader aboral side than oral (sucker-bearing) side, trapezoid in cross-section. Some specimens bear short aboral keel on this arm. Aboral side of Arm I dark in color like head surface. Arm I with 7 pairs of globular suckers on proximal two-thirds. Distal one-third totally naked, with several chromatophoric speckles. Interbrachial web (A) between both Arm Is nearly half arm length. Arm I with 5 or 6 pairs of globular suckers at about proximal half of紅 mlength. Distal half of arm totally naked, with shallow longitudinal furrow and only a few chromatophoric speckles. lnterbrachial web (B) between Arms I and I as deep as half of arm length. Arm II with 11 pairs of globul紅 suckersat about proximal three quarters of arm length. Distal quarter naked, ornamented by only a few chromatophoric speckles. Interbrachial web (C) between Arms I and II extended to about the half of Arm I, and two-thirds of Arm II. Aboral side of Arm II less pigmented than that of other紅ms,but ornamented by a longitudinal row of square chromatophore patches. Arm IV with 10-14 pairs of globular suckers on proximal two-thirds followed by more than 20 pairs of very compactly a汀anged,very small suckers diminishing in size towards distal tip. No naked distal portion present on this arm unlike other arms. Int巴rbrachialweb (D) between Arms II and IV reaches about halfway along Arm II, and extends almost entire length of Arm IV. In contrast, interbrachial web (E) between both Arm IVs almost vestigial. Aboral side of Arm IV as dark as head surface, but opaque patch present on wide basal portion (Fig. 2C). No arms or紅m suckers in any specimen under examination exhibit modi白cation,such as hectocotylization and sucker enlargement (al are females). All normal globular suckers similar in 128 T. Okutani & S. Tsuchida Fig. 2. A・C.Lateral (A), dorsal (B) and venral (C) views of Heteroteuthis hawaiiensis （♀： Jj山崎TEC-053574).D・F.Living habit of Heteroteuthis hawaiiensis from the video images taken by the ROY Hyper-Do伊hin.appe紅 ance,with very small apertures armed with minut巴 suckerrings. Sucker rings smooth under light microscop巴， butrevealed to be composed of two zones under the electron microscope. Inner zone simple ring consisted by a series of square, brick-like pegs, while outer zone consists of 2-4 rows of flat-topped, polygonal pegs of various sizes (Fig. 4A, B). Tentacle weak and short, with naked stalk. Club not expanded, with multiseries of microscopic Living Habit of Bathyal Bobtail Squid 129 Funnel org姐Gd! Ovarianeg宮SB Fig. 3. Heteroteuthis hawaiiensis. A. Oral view (JAMSTEC-053574). B. Mantle cavity (JAMSTEC-053578). suckers (Fig. 4C). Tentacle suckers short cylindrical with small aperture. Chitinous rings in two distinct zones; smooth inner zone surrounding aperture, and outer zone with double rows of flat” topped, polygonal pegs that are regularly spaced (Fig. 4D). Buccal membrane not developed, and buccal connectives not apparent except dorsal attachment at Arm I. Lip papillated. Radula ribbon short, c紅巧ringabout 30 transverse rows (Fig. 4E). Radula composed of 7 teeth: 凶cuspidcen佐altooth, triangular lateral teeth and sickle-shaped inner and outer marginal teeth (Fig. 4F). Mantle locking cartilage low, but sharp ridge, well demarcated (Fig. 3B). Cartilage curves slightly, with strongly curved anterior end. Funnel locking cartilage weakly curved, with rounded posterior end and pointed anterior end. Groove also weakly curved and shallow, but slightly deepening anteriorly. Large, round photophore present on ink sac, almost at anterior end of mantle cavity (Fig. 3B). Photophore about a quarter of ML in diameter, opaque and yellowish, with indistinct indention on posterior margin. Gill lamellae 17 or 18 in number. Pair of large nidamental glands occupies more than half of mantle cavity. Ovary filed by ovarian eggs (Fig. 3B). Taxonomic notes Six nominal species of Heteroteuthis from world oceans were reduced to three named species and a single unresolved one by Nesis (1987): Heteroteuthis dispar (Rtippell, 1845) [ =H. atlantis Voss, 1955 (Nesis, 1987)] from the tropical and subtropical Atlantic, H. weberi Joubin, 1902 from the Indonesian waters, H. hawaiiensis Berry, 1909 [?= H. servenηl Allan, 1945 (Nesis, 130 T. Okutani & S. Tsuchida Fig. 4. Heteroteuthis hawaiiensis. A, B. Suckers of Arm II. C, D. Tentacle club. E, F. Radula (al JAお1STEC-053578). Living Habit of Bathyal Bobtail Squid 131 Fig. 5. Heteroteuthis hawaiiensis. A. Aft巴rBerry (1914, Fig. 29). B.Aft巴rLu & Bouch巴rRodoni (2001: fig. 14 as H. cf. hawaiiensis). 1987)] from the仕opicaland subtropical West Pacific, down south to Tasmania, and an unresolved species, H. dagamensis Robson, 1924 from South Africa. Nesis (1987) tr巴atedStephanoteuthis Be町y,1902 (Type species: H. hawaiiensis Berry, 1909) as a subgenus of the genus Heteroteuthis Gray,1849. The subgeneric and species differences are clearer in males than in females, but Nesis (1987) stated that female Heteroteuthis (sふ） are stil separable from female Stephanoteuthis in having a keeled and non-striated oral surfac巴onArm IL The naked part of Arm I of the present specimens is neither keeled nor striated. But the present specimens are closest to H. hawaiiensis Be汀y,1912 (Fig. SA) in many morphological characters. Lu & Boucher-Rodoni (2001) identified a female from the Southw巴stPacific as H. cf. hawaiiensis (Fig. SB). Their hesitation to the final identification may be the difference of arm formula (I, III= IV, I) from that of Nesis (1987), who stated that Arms I and I are the shortest. Nesis’s account may be based on Berry (1914) who gave the formula II, IV, I, I (Be町y’smeasurements were 10 mm, 9-12 mm, 9 mm, and 8 mm, respectively). In our specimens, the紅mformulae are highly variable. Those of five selected specimens are: II, I, I = IV; II, I, IV, I; IV, II, I = 1; I, II, I = IV, and I, IV, II, I. Therefore, arm formula is not a very reliable criterion to separate species. The photophore on the ink sac is oval, and the diameter about 25% ML, agreeing with the description by Lu & Boucher-Rodoni (2001). It di妊ersfrom the photophore of H. atlantis, which is five-lobed (Voss, 1955). Two other species (Heteroteuthis sp. 1 & 2) of Lu & Boucher-Rodoni have similar-shaped photophore, but th巴ydiffer from our specimens, pぽticularlyin the number of arm suckers, and the shape of the locking cartilages among other charact巴rs.The type specimen of H. hawaiiensis was a female, from Albatross St. 3989 near Kauai Island, at 733 fathoms (= 1341 m) collected with a few fragm巴ntedspecimens. But al of them ar巴nolonger extant (Voss, 1955). A single specimen examin巴dby Lu & Boucher-Rodoni from MUSORSTOM 7, St. CP554 at Banc Combe, 795-820 m, was also a female. Our specimens are again al females. 132 T. Okutani & S. Tsuchida A sole male specimen of Heteroteuthis in the collection of the National Science Museum Tokyo (NSM下Mo68348: DML 21.3 mm) from off Sanriku Coast (36°50.28' N, 141°44.65’ E, 0-1000 m) was examined for compぽison.Although some important characters of this specimen are common to those of H. hawaiiensis treated here, this pぽticularspecimen was not conspecific, because it has a peculiar intestinal photophore carrying a pair of mann凶llarypapillae. The future acquisition of a set of male specimens is highly desirable for resolution of Heteroteuthis systematics. Distribution From the above-mentioned capture records, this species is known from the Hawaiian waters, the Southwest Pacific (north of Samoa Islands), and the Ogasawara Islands. Nesis (1982) already gave its distributional range as“Hawaii, Bonin, Ryukyu Islands, Indonesia, Tasman Sea (?), and the Great Australian Bight”， which includes the present locality, but Nesis's voucher specimens have not been examined. Vertical distribution range of this species may range from about 800 m to 1400 m. However, most of the past collections were made by open tow-net or trawl. Nesis (1987) defined the habitat of白isspecies as the “lower epipelagic and mesopelagic zone”. Roper & Young (1975) stated that“Heteroteuthis probably is pelagic throughout its life cycle”， but “the preponderance of specimens taken in bottom trawls compared to midwater captures suggests that these species spend considerable time on or near bottom”. The present direct observation of its habitat proved that their assumption was correct and that出issquid is a bathyal nektobenthic dweller. Acknowledgements We extend our thanks to Dr. S. Kojima, Ocean Research Institute, University of Tokyo, and al other col巴aguesci巴ntistsparticipating in the cruise NT03-06, Leg 2 on board the RIV Natsushima for their cooperation and encouragem巴nt.We also acknowledge the skil and effort of the operation team of the ROV Hyper-Do肺 inand the crew of the RIV Natsushima. We are grateful to Dr. Takenori Sasaki, the University Museum, University of Tokyo, for his warm help and skil in scanning electron microscopy (Fig. 4A干）， and Dr. Tsunemi Kubodera, the National Science Museum Tokyo, for his kind permission to examination of a male specimen of Heteroteuthis under his care. References Berry, S. S. 1914. The Cephalopoda of the Hawaiian Islands. Bulletin of the Bureau of Fisheries 32: 257-362, pls.45-55. Lu, C. C. & Boucher-Rodoni, R. 2001. Cephalopods from the waters around Wallis and Futuna in the central South Pacific. In: Bouchet, P. & Marshall, B. A. (eds.), Tropical Deep-Sea Benthos, vol. 22. Memoires du Museum national d’Histoire naturelle, Paris 185: 369-399. Nesis, K. N. 1987. Cephalopods of the tゐrid.351 pp. T.F.H. Publications, Neptune City, New Jersy. Rop巴r,C. F. E. & Young, R. E. 1975. Vertical distribution of pelagic cephalopods. Smithsonian Contributions to Zoology 209: 1-51. Voss, G. L. 1955. The Cephalopoda obtained by the Harvard-Havana Expedition o紅白ecoast of Cuba in 1938-39. Bulletin of Marine Science of the Gulf and Caribbean 5: 81-115. Watanabe, H., Kado, R., Tsuchida, S., Kano, Y., Kodama, Y., Shimosaka, M., Tao, J., Hayashi, M., Katayama, T., Takizawa, K. & Kojima, S. 2003. Dispersion and reproduction of vent－巴ndemicspecies inhabiting th巴 MyojinKnoll and the Kaikata Seamount -Preliminary report of NT03-06, Leg.2 cruise. JAMSTEC Journal of Deep Sea Research 23: 99-105. (in Japanese with English title and abstract) (Receiv巴dJuly 20, 2004 I Accepted November 19, 2004) Living Habit of Bathyal Bobtail Squid 133 小笠原諸島近海で見られたハワイヒカリダンゴイカの生態奥谷喬司・土田真二要約海洋科学研究開発機構（JAMSTEC）の無人深海探査機ハイパードルフィンによって，小笠原諸島西方の海形海山の中腹，水深 912mにおいてハワイヒカリダンゴイカの小群が発見された。いずれの個体も海底面すれすれのところでホーバリングを行っており，海底に付いているものや高い位置で、遊泳しているものは見られなかった。各個体ともまちまちな方向を向いており，海流に支配されているようには見えない。本種はこれまでもハワイ他西太平洋各地に分布していることは知られていたが，これまでの採集はおおむね開放ネットによるものであり，中層浮遊性とされていたが，今回の観察により漸深海底帯で，近底層性の生活を送っていることが判った。この観察の時， 9標本が採集されたが，いずれも雌で，ハワイから採集されたタイプ標本も，またサモア北方のコンベ礁から採集されたものも雌で，雄の報告はない。また， Nesisは琉球や小笠原など日本近海を分布範囲にあげているが，それらの詳細についての報告は見あたらない。これらの標本と過去の形態記載と比較も行い，腕長式などにかなりの種内変異があることも確かめられた。

Occurrence and living habit of bathyal bobtail squid, Heteroteuthis hawaiiensis (Cephalopoda: Sepiolidae) from off the Ogasawara Islands, Japan

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Occurrence and living habit of bathyal bobtail squid, Heteroteuthis hawaiiensis (Cephalopoda: Sepiolidae) from off the Ogasawara Islands, Japan

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