Ishizakiella supralittoralis ( Schornikov, 1974 )

Yoo, Hyunsu, Karanovic, Ivana & Lee, Wonchoel, 2012, First record of Ishizakiella supralittoralis (Ostracoda, Cytheroidea, Leptocytheridae) from South Korea with a key to species of the genus, Journal of Species Research 1 (1), pp. 68-77 : 69-75

Ishizakiella supralittoralis ( Schornikov, 1974)

( Figs. 2-5 )

Synonymy. Tanella supralitoralis Schornikov, 1974: 158 , fig. 11.

Ishizakiella supralittoralis (Schornikov) - Tsukagoshi (1994): 303, figs. 7A, 8A-J, 12A.

Material examined. 2 males ( NIBRIV0000245044 , NI BRIV0000245045 ) and 2 females ( NIBRIV0000245046 ,

NIBRIV0000245047 ) dissected, approximately 15 specimens kept undissected in 99% Et-OH, and 1 male and 1 female on one SEM-stub from Rock Pools in Igidae (35̊ 07′20.2′′N, 129̊07 ′30.1′′E), Busan, South Korea, 25 th of April, 2011, collected by Hyunsu Yoo.

Redescription. Male: Shell subrectangular in lateral view ( Figs. 2C, D , 5C, D ), with greatest H situated on the first third of L equaling 50% of total L. Dorsal margin slopping gently down from anterior to the posterior end with a small bend around middle L. Both anterior and posterior margins widely rounded and equally wide. Ventral margin almost straight. From inside view, flange narrow and running around anterior, ventral and posterior margin. Calcified inner lamella well-developed on both ends.

Line of concrescence narrow and marginal pore canals very short, but dense. Hinge merodont: LV anteriorly and posteriorly with sockets ( Figs. 5D, F ), medially with shallow continuous socket ( Fig. 5E ), while RV anteriorly and posteriorly with teeth ( Figs. 5H, J ), while medially with single continuous bar ( Fig. 5I ). Surface ornamentation consisting of relatively small pits. One anterior and one posterior more prominent ridge present, along with numerous smaller and discontinuous ones. Surface also relatively densely covered with hair-like setae, which specially dense frontally and caudally. Muscular scar imprints consisting of a row of four vertical scars, dorsally to which another three larger scars present. In dorsal view ( Fig. 2B ) carapace narrow, slightly constrict anterior to middle L. Greatest W equaling 38% of L. One eye prominent and pigmented. L= 0.48 mm.

A1 ( Fig. 3C ): 5-segmented. First segment bare, second segment postero-dorsally with one short (not reaching distal end of same segment) plumose seta. Third segment short, and anteriorly with strong, distally plumose seta, which reaching distal end of fourth segment. Fourth segment with total of seven setae: three situated more medially and four more distally. Two proximal setae short (one situated dorsally bare, one situated ventrally plumose); third medial seta three times longer, distally plumose and with terminal spinula. Two distal setae on fourth segment long (one bare, other plumose and with terminal spinula), and two three times shorter (one dorsal bare, ventral plumose). Terminal segment with one plumose seta terminating with spinula, and one smooth seta proximally fused with aesthetasc. Length ratio of four distal segments equaling 2.8: 1: 1.15: 1.15. Almost all setae on A1 very strong, all segments hirsute on their distal margins.

A2 ( Fig. 3D ): 4-segmented. Exopod transformed into spinneret seta which with two sutures. First endopodal segment with one strong seta postero-distally with overpassing middle of following segment. Second endopodal segment with two equally long setae postero medially (exceeding distal end of terminal segment), and accompanied with one short aesthetasc; postero-distally second endopodal segment with one plumose seta; anteriorly with two setae (one exceeding distal end of terminal segment, other two times shorter) situated more distally. Terminal segment with two strong claws. Length ratios of three endopodal segments equaling: 2.8: 5.4: 1.

Md ( Fig. 3A ): Exopod with one long vibratory seta. First segment of the palp with one posterior, plumose seta. Second segment with two long setae, each carrying distally spin-like setulae, and two short (situated mediodistally) plumose setae. Third segment with three subequal, plumose setae which only reaching distal end of terminal segment; two setae postero distally (one long and with long spine-like setulae, other short) and one posterodistal seta. Terminal segment square-shaped and with four strong setae.

Mxl ( Fig. 2B, E ): Exopod without reflexed setae. Palp 2-segmented. First segment with three setae: two lateral and one medial. Terminal segment with three setae, one completely fused with segment. Masticatory lobes small and each with two or three setae.

L5 ( Fig. 4A ): First segment dorsally with two tiny setae and two long setae distally; ventrally same segment with one long, plumose, proximal seta. Second segment with one distal plumose seta. Third and fourth segments bare. Terminal claw gently curved and short, slightly longer than two terminal segments combined. All segments hirsute especially along margins.

L6 ( Fig. 3C ): First segment dorsally with two short setae situated more proximally on the segment and one ventral, long seta; dorso-distally same segment with one plumose seta. Second segment with one distal seta, exceeding distal end of following segment. Third and fourth segments bare. All segments hirsute especially along margins

L7 ( Fig. 4B ): Similar to L6 except than seta on second segment much shorter.

Hemipenis ( Fig. 4D ): Distal lobe triangular and with antero-distal end sharply pointed. Postero-ventral end of distal lobe cylindrical. Ejaculatory tube smooth around margins. Clasping part cylindrical with rounded tip. Hemipenis capsule with couple of sclerified rods, but no musculous net present.

Female: Carapace: Strong sexual dimorphism present especially in dorsal view ( Fig. 1A ). Females with much broader posterior end, -transformed into brooding pouch. In lateral view ( Figs. 2E , 5A, B ) dorsal margin with more prominent medial bend. Calcified inner lamella posteriorly narrower than in males. Hinge same as in males. L= 0.51 mm.

A1 ( Fig. 2H ): Similar to male, except that posterior seta on second segment longer, and all setae appearing more slender than in males.

A2 ( Fig. 2G ): Exopod with only one suture observed.

Md palp ( Fig. 2F ): long setae on second and third segment of palp with less developed spine-like setae.

Genital filed and end of the body ( Fig. 2E ): Two setae representing UR present. Body ends in conspicuous process with two main branches each with numerous filaments.

Other appendages same as in male.

Remarks. The population collected in Korea slightly differs from the original description from Kuril Island ( Schornikov, 1974) and subsequent finding in Japan ( Tsukagoshi, 1994). Females of the Korean population seem to be much narrower in dorsal view. The other two findings are also different from each other, and in the original description the females have the broadest posterior end, while the Japanese population is somewhere in-between these from Kuril Island and Korea. The hinge part in the Japanese population is slightly different, as the teeth and sockets on the posterior part are much better differentiat- ed, i.e. one can easily observe up to six sockets/teeth in the population from Japan, while in the Korean specimens the teeth/sockets seem rather fused together. Tsukagoshi (1994) did not provide drawings or descriptions of the soft parts. In comparison to Schornikov’s (1974) description of the soft parts, the Korean population differs in the following: 1. all the setae on the A1 are slightly shorter and stronger; 2. setae on A2, especially antero-distal ones on the second endopodal segment are also shorter, and the terminal claws are equally long, while in the Kuril Island population the more posterior (inner claw) is shorter; 3. spinulae on the long setae of the Md palp are better developed in the Korean population; 4. both tiny dorsal setae are present on the L 7 in the Korean population, while on the drawings of Schornikov (1974) none is apparent, but because of their small size the setae may have been overlooked; 5. end of the female body looks different in two populations, namely the one from Korea has slightly stronger main process (in the Kuril Island specimens it is more slender), and the second branch coming ventrally has less filaments. The importance of the last character is not clear, and the appearance of it may be influenced by the slide preparation, since many of the filaments may become folded.

We have also noticed some variability within the Korean population: one or two setae internally on the first segment of the Md palp, and three or four setae on the first segment of the Mxl palp.

Figures

Fig. 2. Ishizakiella supralittoralis (Schornikov, 1974). A, E, F-H. female; B-D. male: A, B. shell, dorsal view. C, E. RV-lateral view from the inside. D. LV-lateral view from the inside. F. second, third and fourth segments on the Md palp. G. A2. H. A1. A-E Scales 0.1 F-H Scales 0.05 mm.

Fig. 3. Ishizakiella supralittoralis (Schornikov, 1974). Male: A. Md. B. Mxl. C. A1. D. A2. E. vibratory plate of the Mxl. Scales=0.05 mm.

Fig. 4. Ishizakiella supralittoralis (Schornikov, 1974). A-D. male, E. female: A. L5. B. L7. C. L6. D. Hemipenis. E. UR and the posterior end of the body. Scales=0.05 mm.

Fig. 5. SEM photos of Ishizakiella supralittoralis(Schornikov, 1974). A, B. female, C-K. male: A. LV, lateral view from the outside. B. RV, lateral view from the outside. C. LV, lateral view from the inside. D. anterior part of the hinge on the LV. E. medial part of the hinge on the LV. F. posterior part of the hinge on the LV. G. RV, lateral view from the inside. H. anterior part of the hinge on the RV. I. medial part of the hinge on the RV. J. posterior part of the hinge on the RV. K. muscular scars imprints.

Fig. 1. Sampling locality, Rock Pools in Igidae (35̊07′20.2′′N, 129̊07′30.1′′E), Busan, South Korea.