北海道産カイミジンコScleroconcha属のI新種
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(2) Journal of Hokkaido University of Education (Section II B) Vol. 31, No. 2 Bg% 56 -^ 3 ^. -Ib^^aW^^ffiS (^2^B) ^31^^2-t March, 1981. A New Species of the Genus Scleroconcka Skogsberg. from Hokkaido (Ostracoda: Myodocopina)l). Shinlchi HIRUTA Biological Laboratory, Kushiro College, Hokkaido University of Education, Kushiro 085. ^ s ^ —: -Ib^it^^ ^f $ >>' > r? Scleroconcha J^CT) 1 ^. witOT^iu i^^wa^. Abstract A new species of the genus Scleroconcha is reported from Uchiura Bay, Hokkaido. The species resembles S. ochotensis in the general appearance of its carapace and several ap-. pendages but is distinguishable from the latter in the detailed structure of carapace and appendages, especially the seventh limb.. Introduction The present paper deals with a new species of the genus Scleroconcha Skogsberg, 1920 from Uchiura Bay, Hokkaido. This is the second record of the genus from Japan and its adjacent seas (Chavtur, 1978). The materials were collected by using a Smith-McIntyre grab during the survey of benthos by Japan Data Service & Co., Ltd., and were placed at my disposal for my taxonomic work on ostracods from Hokkaido through the courtesy of M.r. Sh. Kubota of Hokkaido University. The type specimens are deposited in the Zoological Institute, Faculty of Science, Hokkaido University.. Scleroconcha kubotai n. sp.. (Figs. 1-8) Female. Carapace (Fig. 1-1—3) oval with semiquadrate rostrum and caudal process; surface. 1) Studies on the recent marine Ostracoda from Hokkaido, VIII.. (59).
(3) Shinlchi HIRUTA. reticulate, with a rib along anterior half of dorsal margin and two midribs of which upper one continues anteriorly to rostrum; two juxtaposed obtuse processes present below rostral incisur.. Eight long bristles present on rostral infold; anterior infold below incisur with eleven bristles and several striations; ventral infold bare; posteroventral and posterior list with a number of minute spines in groups of one to three spines; ridge with five spines present between posterior list and outer edge of valve, posteromost spine longer and stronger than others; one spine present near edge of caudal process. Selvage with striated lamellar prolongation. which has a fringe of hairs along outer margin.. Fig. 1 Scleroconcha kubotai n. sp. Female. (Holotype). 1. lateral view; 2. medial view of anterior part of right valve; 3. medial view of posterior part of right valve.. (60).
(4) A New Species of Scleroconcha from Hokkaido. Size (mm). length. height. width. Holotype. ^ .. 3.15. 2.00. 1.50. Paratype. 1. .. 3.13. 2.00. 1.45. 2. .. 3.15. 2.10. 1.50. 3. .. 3.20. 2.00. 1.50. First antenna (Fig. 2-1). First segment slightly longer than second; second segment with clusters of hairs along dorsal margin, combs of hairs on distolateral surface, and four (generally. three) bristles, one dorsal, one lateral, two (generally one) ventral, all with stiff hairs; third segment about one-fifth length of second, with minute spines on dorsal margin and three bristles, two dorsal, one ventral, all with stiff hairs; fourth segment about 1.5 times as long as third, with six bristles, two dorsal, four of different lengths ventral, all except shortest ventral bristle with stiff hairs; fifth segment as long as fourth, with one long distoventral bristle, which is furnished with proximal and distal filaments as shown in figure; sixth segment very short, with one distal bristle. Seventh segment : a-bristle similar to bristle on sixth segment but longer; b-bristle longer than a-bristle, with filaments; c-bristle as long as and similar to bristle of fifth segment. Eighth segment: d- and e-bristles bare, about the same length as c-bristle; f- and g-bristles as long as and similar to c-bristle.. Second antenna (Fig. 2-2—4). Endopodite two-segmented; first segment with five proximal bristles and one longer distal bristle on dorsal margin; second segment with one long proximal bristle wreathed with stiff hairs and one bare terminal bristle. Exopodite: third to eighth segments with a basal spine; end segment with seven bristles of which ventral three are short and furnished with hairs, others long, bare; bristles on second to eighth segments almost bare.. Mandible (Fig. 3-1, 2). Coxale endite large, bifurcate, with secondary teeth and clusters of spinules, accompanied with small bristle near its base. Basale: five bristles of which three are spine-like with secondary teeth present on medial surface near proximal margin; dorsal margin. with two terminal and one subterminal bristles, all with stiff hairs; ventral margin with eight bristles, all with stiff hairs; mediocentral surface with one bristle; medial surface with several clusters of long hairs. Exopodite about five-ninths length of dorsal margin of first endopodite segment, with two long terminal bristles and fine hairs on distal half of dorsal surface. Endopodite: first segment with four bristles on ventral margin, all with stiff hairs; lateral and medial surfaces bare; second segment about twice as long as first; dorsal margin with three proximal and six distal bristles; ventral margin with three terminal and three subterminal bristles; medioproximal surface with several clusters of hairs; end segment small, with three claws and four bristles of different lengths on distal margin. Maxilla (Fig. 3-3, 4). Coxale with one plumose bristle on dorsal margin; first endite with eleven distal bristles; second endite with six distal bristles; third endite with eight distal bristles and one proximal bristle. Basale with one short dorsal bristle and two long ventral bristles. Exopodite with three bristles of which subterminal one is short, others long with stiff hairs. Endopodite: first segment with one a?-bristle with stiff hairs, five ft -bristles, and clusters of long hairs along dorsal margin; second segment with three stout claws and eight bristles of which. (61).
(5) Shinlchi HIRUTA. \. F"2 ^"t^:^^^,. ^ 3_A:tto: .end:pZeanr^prlop^e_a"rend^^^ organ and median "eye" wwl exopodite' 5. rod-shaped'. (62).
(6) A New Species of Scleroconcha from Hokkaido. juxtaposed three (a-bristles) rise from the mediodistal surface, spinous one from dorsodistal surface, and the other four from ventral surface.. Fifth limb (Fig. 3-5; Fig. 4-1). Epipodial appendage with 55 bristles; first endite with six bristles; second, endite with seven bristles; third endite with about eleven bristles. Exopodite: first segment with two bristles of subequal length on anterior side and two bristles on posterior. Fig. 3 Scleroconcha kubotai n. sp. Female. (Holotype ; 3-5 paratype). 1. mandible; 2. ditto, endite; 3. maxilla; 4. ditto, endites; 5. teeth of fifth limb.. (63).
(7) Shinlchi. Fig. 4. &^^".sp. J- fifth I»nh. 7:^ "• SP- pemaie.. HJRUTA. Kk^;t?^%ess (64).
(8) A New Species of Scleroconcha from Hokkaido. side, one of which is present near base of proximalmost tooth of main tooth; main tooth consists of four constituent teeth, distalmost tooth accompanied by a large triangular tooth; second segment with one short bristle on anteroproximal surface near large process, a group of three. bristles of different lengths and one long proximal bristle on posterior side, and a large distal tooth; outer lobe of third segment with two bristles, one of which is twice as long as the other; inner lobe with four (or three) bristles; end segment (fourth and fifth segments) with six bristles. Sixth limb (Fig. 4-2). Epipodial appendage with four (sometimes three) bristles; first endite with three bristles; second endite with four bristles, one proximal, others distal; third endite with eight or nine bristles, one proximal, others distal; fourth endite with seven or eight bristles, one proximal, others distal; and segment with 26—36 bristles; all bristles on sixth limb plumose or with hairs; surface of endites and end segment hirsute. Seventh limb (Fig. 4-3) . Each limb with six distal bristles (three on each side) and ten to thirteen proximal bristles; each bristle with three to seven bells and marginal hairs; terminal comb with eight teeth, some of which are provided with short lateral spine(s) ; one peg with a lateral spine present opposite comb.. Furca (Fig. 4-4) . Each lamella with eleven to thirteen claws; claw 3 longer than claw 4 but more slender, claw 1 to 4 with rows of teeth along posterior margin; remaining smaller claws with spinules along anterior and posterior margins; several long hairs present on near proximal. edge of claw 1; lamellae near base of claws hirsute. Rod-shaped organ and median eye (Fig. 2-5). Rod-shaped organ elongate, with about thirteen sutures on middle part; tip of the organ tapers to a fine point, with minute hairs; minute hairs also present along margins. Median eye as shown in figure. Lateral eye not observed. Eggs. about 400// in diameter; three individuals examined with 2, 19, 21 eggs in brood pouch. Brushlike organ and genitalia (Fig. 4-4). Genitalia on each side as shown in figure; brush-like organ consisting of ten short bristles is present above genitalia. Male. Carapace (Fig. 5-1—4) about same length as the female's but compressed; incisur. more open than that of female; shell thin, with a rib which is barely perceptible along anterior half of dorsal margin, two midribs which lie on posterior half of surface, and a short ridge on rostrum ; two processes below incisur similar to those of female but not so conspicuous ;. posterodorsal margin and upper midrib with long bristles ; surface covered with small hollows of different size. Thirteen bristles of different lengths present on rostral infold ; two short bristles present at inner corner of incisur ; anterior infold below incisur with ten bristles ; posteroventral and posterior list with a number of minute spines in groups of one to three spines ; ridge with three spines between posterior list and outer edge of valve, posteromost spine longer than others ; one spine present between ridge and outer edge of valve. Selvage has striated lamellar prolongation with a fringe of hairs along outer margin.. Size (mm) length height width Allotype ^ . . . 3.00 1.50 1.35 Paratype 4. ... 3.15 1.50 1.40. (65).
(9) Shinlchi HIRUTA First antenna (Fig. 6-1). First segment five-sevenths length of second; second segment. with some clusters of hairs along ventral margin, eight combs of hairs on distolateral surface, and three bristles, one dorsal, one lateral, one ventral, all with stiff hairs; third segment onefifth length of second, with three britsles, two dorsal, one ventral, all with stiff hairs; fourth segment one-fourth length of second, with six bristles, two with stiff hairs dorsal, four with marginal hairs ventral ; fifth segment inset ventrally between fourth and sixth segments; sensory bristle on fifth segment with numerous long filaments on proximal half of ventral. Fig. 5 Scleroconcha kubotai n. sp. Male. (Allotype). 1. lateral view; 2. dorsal view; 3. medial view of anterior part of left valve; 4. medial view of posterior part of left valve; 5. rod-shaped organ an(i median eye.. (66).
(10) A New Species of Scleroconcha from Hokkaido. margin, where the bristle is thickened, and terminal filaments; sixth segment as long as fourth, with one distal bristle and some clusters of short hairs on surface. Seventh segment: a-bristle somewhat shorter than bristle of sixth segment; b-bristle stout, with filements; c-bristle extremely long, with stiff long filaments. Eighth segment: d- and e-bristles slender, bare, as long. Fig. 6 Scleroconcha kubotai n. sp. Male. (Allotype; 2,4 paratype). 1. first antenna; 2. second antenna: protopodite and endopodite; 3. ditto, endopodite; 4. ditto, exopodite.. (67).
(11) Shinlchi HIRUTA. as b-bristle; f-bristle about same length as c-bristle, with stiff long filaments; g-bristle similar to b-bristle. Second antenna (Fig. 6-2—4) . Protopodite semitriangular. Endopodite three-segmented;. first segment short, with five proximal and one distal bristles; second segment elongate, with one proximal bristle and four distal bristles of subequal length near middle of anterior margin; third segment elongate, reflexed, somewhat shorter than second, with about ten teeth along inner margin, one short bristle near proximal edge, two short subterminal bristles, and terminal. ridges. Exopodite: The length ratio of first three segments 14: 5: 6 ; bristle of second segment with several spines on anterior margin; ninth segment with five bristles of which four are long with natatory hairs, one short with marginal hairs; third to eighth segments with very short basal spines.. Mandible (Fig. 7-1—3) . Coxale endite weakly developed, bifurcate, accompanied with a small bristle near its base. Basale: five bristles on medial surface near proximal margin; dorsal margin with two terminal bristles and one subterminal bristle, all with long hairs; ventral margin with eight bristles, all with long hairs; mediocentral surface with one bristle; medial surface covered with many combs of long hairs. Exopodite four-sevenths length of dorsal. margin of first endopodite segment, with two long terminal bristles with long hairs. Endopodite: first segment with five bristles on ventral margin; medial surface with some clusters of hairs; second segment 1.75 times as long as first; dorsal margin with ten bristles of different lengths; ventral margin with three terminal and three subterminal bristles; medial surface with clusters of long hairs; end segment small, with three claws and four bristles on distal margin. Maxilla (Fig. 7-4) weakly developed. Exopodite with three bristles. First endopodite segment with one a -bristle and five ^-bristles. Fifth limb (Fig. 7-5) weakly developed; epipodial appendage with about 55 bristles; endites with about 25 bristles. Exopodite: first segment with four thin lamellar teeth; second segment with one long thin lamellar tooth; outer lobe of third segment with two plumose bristles; inner lobe with three bristles; end segment with six bristles and long hairs along posterior nargin. Sixth limb (Fig. 8-1) . Epipodial appendage with three bristles; first endite with three bristles; second endite with four or five bristles; third endite with nine bristles; fourth endite with seven or eight bristles; end segment with 24—29 bristles; all bristles on sixth limb plumose or with hairs; surface of the limb hirsute. Seventh limb (Fig. 8-2) . Each limb with four distal bristles (two on each side) and ten to thirteen proximal bristles; each bristle with three to six bells; terminal comb with four teeth; one peg present opposite comb. Furca (Fig. 8-3) . Each lamella with seven or eight claws; claw 3 somewhat shorter and more slender than claw 4; lamella near base of claws hirsute. Rod-. shaped organ (Fig. 5-5) elongate with 22 sutures on middle part; tip of organ tapers to a fine point, with minute haris; minute hairs also present along margins. Eyes. Median eye (Fig. 5-5) similar to that of female; lateral eyes well-developed, with about 30 ommatidia. Copulatory limb (Fig. 8-3,4) as shown in figure; each limb consists of three lobes with total six bristles.. (68).
(12) A New Species of Scleroconcha from Hokkaido. Remarks. The females of the present new species resemble 5. ochotensis Chavtur, 1978 from. the Kurile Island in the general appearance of carapace and the structure of appendages, but are distinguishable from the latter by the following characteristics. The reticulation of the shell in 5. ochotensis is finer than that of the present new species. The number of striations on the anterior infold in S. ochotensis is about twice as many as those of 5. kubotai n. sp. In S. kubotai,. the seventh limb is provided with six terminal bristles, three on each side, while only 2-3 bristles. Fig. 7 Scleroconcha kubotai n. sp. Male. (Allotype). 1. mandible; 2. ditto, distal part; 3. ditto, endite; 4. maxilla; 5. fifth limb.. (69).
(13) Shinlchi HIRUTA are recognized on the corresponding area in 5. ochotensis. The terminal comb of the seventh. limb in S. kubotai has eight teeth, while in 5. ochotensis the comb consists of ten teeth. On the other hand, in the previously known species within the genus, the only species whose male is fully described is 5. arci^ata Poulsen, 1962 (Kornicker, 1975). Though males of the present new species have no conspicuous structure which differs from that of 5. arcuata, it is. to be noted that the second endopodite segment of the second antenna in 5. kubotai is provided with five bristles, while the male of 5. arcuata has only three bristles on the corresponding segment. In this connection, the segment with three bristles is also detected in the male of 5. flexilis (Brady, 1898) (Kornicker, op. cit). Specimens examined. Holotype ^-; allotype c71; paratypes 3 ^--^ and 1 ^ (10-II-'79). The species name was selected in honour of Mr. Sh. Kubota who gave me a chance to examine these. J 1-5. Fig. 8 Scleroconcha kubotai n. sp. Male. (Allotype; 4 paratype). 1. sixth limb; 2. seventh limb; 3. furca and copulatory limb; 4. copulatory limb.. (70).
(14) A New Species of Scleroconcha from Hokkaido specimens.. Locality. Uchiura Bay: 2000m off Sahara fishery harbor; depth 51m; dark brown mud (coase sand 13.8%, sand 29.3%, mud 56.9%); bottom mud temperature 4.5°C.. Acknowledgements I wish to express my thanks to Mr. Sh. Kubota of Hokkaido University who gave me the opportunity to study the interesting animal reported in this paper, and to Mr. T. Watanabe of Japan Data Service & Co., Ltd. foi his kindness in giving me the data of the collecting station. This study was supported in part by the Grant-in-Aid for Co-operative Research of the Ministry of Education, Science and Culture, project no. 434042.. References. Chavtur, V. G. 1978. Euphilomedes nipponica Hiruta, Scleroconcha ochotensis n. sp. and Empoulsenia kurilensis n. sp. (Ostracoda, Myodocopina) from the region of the Kurile Islands. Pages 149-158. In Kussakin 0. G., editor, Fauna and vegetation of the shelf of the Kurile Islands. Publshing House Nauka, Moscow (In Russian). Kornicker, L. S. 1975. Antarctic Ostracoda (Myodocopina). Smiths. Contr. Zool. 163:1-720.. (71).
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