The malacologicalsocietymalacological society of Japan a Preliminary Note on Hitherto Unknown Form of the Eight-Armed Squid, Genus Gonatqpsis,from Northern North Pacific Takashi OKu'rANi <Tokai Regional Fisheries Research Laboratory) ".'"B vT) '( d lt Jit ilZ ?r llki ft[. fide rai Ul i .h IEfi dD 1 Jtc ttd ESI NI IC L s (I ex) N Z} kM (witu)x:zi<tsMljX}lfi) (paJtt Plate 5) During the course of study on squids in the stomach contents of sperm whales taken from the northern North Pacific and the Bering Sea (OKuTANi & NEMo'ro, 1964), a single specimen of strange eight-armed squid was found. As the specimen was almost spoiled superficially, it was erroneously misidentified in the previous report. The re- sult of close observation of the specimen finally revealed that this belongs to the genus Gonatopsis (Gonatidae) and shows some differences from the known three forms of the genus, namely, Genatopsis octopedatus SAsAKT, G. borealis SAsAKr and G. borealis makho OKuTANi & NEMoTo. It may be described as a new species or subspecies, but a new name will be deferred until better specimens wil! be availab!e in future. The precise locality of the specimen is not known, but it might be taken near the Aleutian Chain. The present report is aiming at providing an information of existence of a probable differentiated form of Gonatopsis borealis-group which may be one of the puzzling groups of squid. It is interesting to find the fact that the present specimen retains the trace of degenerated tentacle as a fleshy process between third lateral and ventral arms. Observation of the specimen The external shape agree with general Gonatid squid. The epithelium with dark purplish (in preserved condition) chromatophores are almost stripped off on the mantle, while it is retained on the head, funnel and proximal portions of the arms. The in- tegument is rather thick but very soft. The softness of integument may not be due to digestive fluid of a sperm whale, because other types of Gonatid examined on the same occasion never lost robustness of integument even they were more badly digested (Fig. 1). The dorsal mantle length measures 230mm. and width of the mantle at the an- terior end, about 90mm. The mantle tapers gradually towards the posterior end. The NII-Electronic Library Service TheThemalacological malacological society of Japan 66 VENUS: 25 (2) 1967 middle of the dorsal free rnargin terminates in a prominant triangular end, while ex- cavation on the ventral margin is very shallow. The fin is rhomboidal or sagittate, and is soft but muscular and thick. The length of the fin is about 100mm. and the width to is presumed be 160mm. or so; the marginal portion is badly nipped and torn. The head is not larger than the mantle opening. Neck is strongly constricted and clearly marked off from the head. Eye is very large, with a wide opening which has a deep sinus in front. A minute olfactory crest is present on both posterior ends of the funnel excavation wliich is very smooth and has no ridges at the circumference (Fig. 4). Funnel is of moderate size, with a large semilunar valve. Dorsal funnel organ is inverse V-shaped and a ramification measures about 25mm (Fig. 10). The ventral organ consists of a pair of ovoidal pads which measure 18mm. in major diameter and 8mm. in minor diameter. Funnel cartilage is slender, slightly curved renal form and 26rnm. in length (Fig. 6). The Iocking socket is very shallow and widened posteriorly. The plug on the mantle is very short and nearly hemi-rodshaped (Fig. 9). Nuchal cartilage almost quadrangular with rounded corners and its middle portion being feebly concave (Fig. 5). Arms are remained only in proximal portion and, consequently, armatures on the distal are not measurements of remained parts known. The part of respective arms are as follows: right left Dorsal 130 mm. 150 mm. 2nd lateral 140 105 3rd lateral 170 160 Ventral 110 100 The outer suckers are all lost, but weak and short pedicels on which suckers might be present are remained (Figs. 7, 8). All of arms except the dorsal ones seem to have a pair of rows of small hooks between outer rows of suckers on both sides of sucker- bearing faces of the arms. The hooks are situated apart from each other in an oblique positions and 2-3 pairs on the proximal portions are immature hooks that retain nature of suckers. Of the dorsal arm, middle pair of armature is not hooks but small suckers. Five to nine pairs of hooks or suckers of the middle rows are observed on the entire length of remained portion of the arms. Between the ventral and third arms, a pair of short fleshy process is present. It is laterally compressed and semi-quadrilateral in profile. The anterior margin is cut in a knife-edge, but the posterior to distal margin are widened and roundish with purplish chromatophores. This strange fleshy process is considered to be a remains of the degenerated tentacle (Figs. 2, 3). Buccal membrane seems to be supported with 7 ribs. Gladius is apparently a pen- niform one, but almost broken into pieces. NII-Electronic Library Service The malacologicalsocietymalacological society of Japan OKv[v,tNT: Unknown Form of Eight-Armed Squid 67 ' Comparison to G. boreatis is decidedly GonataPsis boreatis Although the closest species to the present specimen SAsAKi, there are found a number of different characteristics from G. borealis: Mantle : The mantle of G. borealis is quite muscular and robust even it is badly digested in sperm whale's stomach. There was not any examples that have such a soft and loose musculature as is observed on the present specimen. of the head but Olfactory crest: G. boreaiis has four crests on the posterier part only a single minute crest was found on the present specimen, Locking cartilage: The general shape of funnel cartilage ef both species are similar each other, but the socket groove of th/ present specirnen seems to be shal- lower than that of G. borealis. The mantle plug of G. borealis is elongated wedge- shaped and that of the pres-.a.nt specimen is short hemi-rod-shaped. Armature of brachial arms: The principle of arrangement of hooks and suckers is common to that of G. borealis, ie. the dorsal arm has four series of suckers only and other arms have two sL'ries of hooks in the middle and two pairs of suckers outside. Even on those arms, s:veral proximal pairs of hooks are immature and re- main nature of suckers. The most remarkable difference between G. borealis and the hooks present specimen is size and density of hooks. On the former, large and strong are arranged very closely each other and they cover the major pertion of the sucker- bearing face of arms, On the latter, small and weak hooks are so sparsely arranged The on the arms that the large portion of naked sucker-bearing face of arm is seen. comparison of armature on the distal portion could not be made as the only proximal portion of arms are remained on the present specimen. of degenerat- The most noteworthy finding on the present specimen is a remnant ed tentacles. Result of examination on small adolescent specimens Qf G. borealis revealed that the species does not retain any remnants ef tentacle despite this seems to have normal tentacles in early stage of the life (OKuTANi 1966). The internal characteristics so far observed do not seem to be different from those of G. borealis. The visceral organs of the present specimen were badly invaded by number of large nemathelminths which are parasitic to the sperm whale. Consideration appendage seems to As far as the present specimen is concerned, a short fleshy be a normal remnant of degenerated tentacle and not a remains of accidentaly cut tentacle. If this is not abnormal, this is an exceptional case among eight-armed squids and rnay be an important phylogenic link between Gonatzts and GonatQPsis. This fact may be suggested that this specimen is a contingent or belongs one of probable poly- typic subspecies of G. borealis. NII-Electronic Library Service The malaoologioalmalacological societysooiety of Japan 68 VENUS ： 25 （2） 1967 摘 要 北 部 太 平 洋 産 の マ ッ コ ウ ク ジ ラ の 胃中 か ら発 ．見 さ れ た イ カ 類 中 に GonatePsis 属 に 属 す る 未 記 載 の 1 種 を 一 認 め た 。 単 慓 本 で も あ り，か な り破 損 し て い る の で ， 現 段 階 で 新 種 名 を 与 え る こ と は さ し 控 え た が ， 複 雑 て い と こ の い で に 分 化 し る 思 わ れ る Gonatidae に 更 に よ う な 型 が あ る と う 情 報 を 与 え る 意 味 予 報 す る 。 octoPedatus bore α iis makho 標 本 は 同 属既 知種 ， G ． SASAKI，G ．borealisSASAKI お よ び G ． OKVTANI ＆ 一 NE 皿 orrO の 何 れ と も 異 る 特 徴 を も っ て い る が ， 明 ら か に G ． borealis 種 群 の 員 と 考 え ら れ る 。典 型 的 な G ． borealis と は 次 の よ うな点 で 異 な る 。 （1） 外 套膜 ： G ．boreagis の よ う に 強 靱 な 筋 肉質 で な く柔 か く締 りが な い 。 こ れ は 必 ず し も マ ッ コ ウ タ ジ ラ の 消 化 液 の せ い で は な い と 考 え られ る 。な ぜ な ら ば ， こ の 標 本 よ り更 に 消 化 度 の 進 ん だ 他 の Gonatidae と ． い え ど も筋 肉 質 の 陸質 が 失 わ れ て い な い 。 2 ： の は ． の と い （） 外 套 軟骨 器 漏 斗 軟 骨 器 形 状 G borealis そ れ 殆 ど 変 らな が ，外 套 軟骨 器 が 極 め て 短 く， 漏 ．斗軟 骨 器 の 溝 も 浅 い よ うで あ る 。 腕 ： 先 端 の 部分 は 各 腕 と も失 わ れ て い て 比 較出 来 な い e 残 さ れ た 部分 を 見 る 限 りで は ，吸 盤 と 鉤 の 配 列 の 原 則 は G ．borealis と 変 ら な い が ， G ． boreaiis の そ れ は 強 力 な 鉤 が 密 生 し て い る の に 比 し ，弱 く小 さ い 鉤 が 広 い 間 隔 を あ け て 並 ん で い る 点 明 らか な相 異 で あ る n 〔4） 触 腕 ： GonatoPsis 属 は 幼 時 触 腕 を 持 っ て い る と 推 察 さ れ る が ， 触 腕 を 失 っ た 痕 跡 は 何 も認 め る こ と い の で で は こ 1cm の が 出来 な が 普通 あ る 。 本 標 本 れ が 長 さ 程 側 扁 し た 肉 質 の 附 属肢 的 な 痕 跡 と し て 残 っ て い る 点 他 に 類 例 を 見 な い 特 徴 で あ る 。 References OKul ］ANr ， T ．，1966 ： Planktonic larvae of decapodan cephalopods from the Northern North Pac 三且c summer seasons 1952−1959 Bu 〃 Toleai fteg Fisher Res 五 ab − in during ． 。 ． ． ． ．45 ； 61 79 ， 3pls ． OKuTANI ， T ．＆ T ． NE