Dolerocypria mukaishimensis Okubo, 1980

Karanovic, Ivana & Lee, Wonchoel, 2012, A review of candonid ostracods (Crustacea: Ostracoda: Podocopida) from East Asia, with descriptions of five new species from South Korea *, Zootaxa 3368, pp. 7-49 : 41-45

Dolerocypria mukaishimensis Okubo, 1980

( Figures 20 , 21 )

Synonymy. Dolerocypria mukaishimensis Okubo, 1980 : p. 20, Fig. 2, Pl. 1g, h.

Dolerocypria mukaishimensis Okubo—Nakao & Tsukagoshi, 2002 : p. 71, Figs 2E–J, 3,4.

Material examined. Two males and one female (soft parts dissected on slides, shell of 1 male and of 1 female kept on micropaleontological slides NIBRIV0000245063, NIBRIV0000245064, NIBRIV0000245065), 2 females (in ethyl alcohol NIBRIV0000245066), from South Korea, Yigidae rocky shore, near Busan, rock pool, 35 0 07’27.30” N 129 0 07 ’25.50”E; 25/04/2011, collector Hyunsu Yoo; temperature = 24.10 0C, salinity = 35.2‰.

Two females (soft parts dissected on slides, shell kept in ethyl alcohol NIBRIV0000245067, NIBRIV0000245068) from South Korea, Hwapyeonggyo, 37o49’46” N 128o51’40” E; 06/08/2008, collector Dongju Lee.

Redescription. Male. Carapace subtriangular in lateral view ( Figure 20 A, B) with the greatest H lying in front of middle L, equaling 40% of total L. Size: L= 0.62 mm. Dorsal margin highly arched on point of greatest H, with sinusoid margin towards anterior and gently inclined (almost rounded) towards posterior margin. Posterior margin much narrower than anterior one. Ventral margin slightly concave around mouth region. Calcified inner lamella narrow on both ends, anteriorly equaling 16% of total L, posteriorly equaling less than 1% of total L. Fused zone also very narrow and marginal pore canals short, straight and denser anteriorly than posteriorly. Surface of shell covered with fine setulae, originating from small, but clear wartlike structures. No other surface ornamentation present. LV overlapping RV on all free margins.

A1 ( Figure 21 A-C). Appendage 7-segmented. First segment with one seta anteriorly and two posteriorly. One anterior seta situated more proximally. Posterior setae originate from same (or very close) spot. All setae pappose. Second segment with one anterior pappose seta, reaching middle of following segment. Rome organ welldeveloped ( Figure 21 C), Wouters organ not observed. Third segment with one posterior short seta, and one anterior longer seta. Fourth and fifth segments with two anterior, long setae (exceeding distal end of terminal segment), and one short posteriorly. Penultimate segment with total of four setae; posteriormost seta “d” present. Alpha seta absent. Seventh segment with aesthetasc (ya) twice as long as terminal segment. L ratio of five distal segments equaling: 2.2: 1.7: 1: 1: 1.45.

A2 ( Figure 21 H, I). Protopod with one, distally pappose seta exceeding distal margin of fourth endopodal segment. Exopod consisting of plate carrying one long (almost reaching distal end of first endopodal segment) and two short, pappose setae. Endopod 4-segmented, penultimate segment being divided, carrying two male sexual bristles. First endopodal segment with one relatively long aesthetasc “Y” and antero-ventrally with one strong seta. Swimming setae longer than claw, except for first and sixth ones, which are much shorter. Sixth swimming seta at some distance from the group. Second segment with two medio-dorsal setae (one being “t4” seta); setae t3 and t2 transformed into sexual bristles (exceeding distal end of terminal segment) and one antero-ventral seta (t1). Same segment medio-ventrally with short aesthetasc y1, y2 also short. Third endopodal segment with claws G1, G2, z1 and z2, and setae G3 and z3. Claw G1 short (less than 50% of G2); G2 long (1.2 times longer than first endopodal segment); z1 slightly shorter than z2 and both slightly shorter than G2. G3 and z3 thin setae and as long as G1 claw. Terminal segment with one long claw, Gm (approximately as long as first endopodal segment) and one short claw, GM (1.5 times shorter than Gm). Terminal segment also armed with aesthetasc y3 (1.5 times as long as terminal segment) and one thin seta accompanying y3.

Md ( Figure 21 E). First segment of palp with two plumose setae (S1 and S2), and one pappose seta; alpha seta not observed. S2 seta bent. Second segment dorsally with two setae, reaching distal end of following segment (one apparently smooth other plumose), ventrally with three smooth setae originating from a small plate, one plumose shorter seta and beta seta. Penultimate segment dorsally with four almost equally long setae, gamma seta pappose, and five additional setae, one of which originates medially and four ventrally. Terminal segment short with two claws and two setae.

Prehensile palps ( Figure 20 H, I). Palps 2-segmented and finger on right palp more robust. Each palp bearing ventrally on body three long, pappose setae. More than two “a” setae present on protopod, exopod with five long and pappose setae and one very small. Distally to exopod one additional seta present.

L6 ( Figure 20 G). Basal segment with three setae (d1, d2, dx). Endopod 4-segmented. Setae “e”, “f”, and “g” all relatively short and pappose. Terminal segment with distal claw and two lateral, short setae (h1 and h3). Distal claw as long as combined L of three distal segments. Appendage very hirsute, some setulae very strong and exiting from their own canals.

L7 ( Figure 21 F). Basal segment with three setae. Endopod 4-segmented, with all setae present, “g” being very short and accompanied by four small setulae. Terminal segment armed with two very short and one long seta. Long seta covered with setulae which are very strong and long distally. Terminal segment elongated. Appendage very hirsute.

UR ( Figure 20 D). Symmetrical, with two distinct posterior setae and with stiff setulae along posterior margin. Posterior claw with strong teeth, while anterior one with fines setulae. L ratio between anterior margin, anterior claw and posterior claw equaling: 1.7: 1.4: 1. Attachment ( Figure 20 F) with one dorsal branch. One caudal seta present.

Hemipenis ( Figure 20 J). Lobe “a” (outer lobe) almost square shaped, lobe “b” triangular. Inner duct coiled. The presence of three setae on the basal segment of the L6 ( Fig. 20 G) is only an abnormality found on one leg of a male.

Female. Carapace ( Figure 20 C, D) very similar to male. L= 0.65 mm.

A2 ( Figure 21 G). Endopod 3-segmented. All four “t” setae on penultimate segment present, and second endopodal segment postero-medially with one seta. All “z” setae seta-like, second segment with one additional seta medio-distally positioned on dorsal side of appendage. Claw G2 2/3 of other claws.

UR ( Figure 21 D) Similar to male, symmetrical.

Genital field ( Figure 21 D). Rounded and without projections but densely covered with spines.

All other appendages same as in male.

Remarks and affinities. The genus Dolerocypria at the moment comprises 12 species ( Maddocks 2005), and they occur in the tropical Pacific and Atlantic Oceans, but also in the subtropical and moderate regions of Japan ( Wouters 2001). Dolerocypria mukaishimensis Okubo, 1980 was described only after females ( Okubo 1980), but the males were latter on collected and described by Nakao & Tsukagoshi (2002). The species is relatively common in Japan living from marine to brackish waters, reaching the highest abundance in brackish environment ( Smith & Kamiya 2003). The male upon which Nakao & Tsukagoshi (2002) based their description was probably subadult, because the chitinous rows on the Zenker organ are not fully developed and some additional soft tissue (like a small flap) accompanies the hemipenis on the internal side. Unfortunately, the authors never described both prehensile palps, so only the appearance of the right one is known and it looks very much like the one found in males of the Korean population. Since our males were fully developed, they had a normal Zenker organ and the flap on the hemipenis was not observed. There are, however, several differences between the Japanese and the Korean populations. The first, probably the most important one, is the number of posterior setae on the UR. While on the drawings of Okubo (1980) and Nakao & Tsukagoshi (2002), there is only one (more distal seta), we have found one more seta situated more proximally. However, because the posterior margin of the UR is densely covered with spines, the second, very short seta could be easy overlooked. In the entire genus Dolerocypria the number of posterior setae on the ramus varies from none to two and they are always very short, like in D. mukaishimensis . Similar miscalculations of the number of posterior setae on the UR have already occurred in this genus (see McKenzie 1979). The other difference is related to the fact that the L6 and L7 are covered with conspicuous setulae, not illustrated in Nakao & Tsukagoshi (2002) for neither of these legs, but in Okubo (1980) the L7 has also some sort of long setulae along the margins of the appendage, but not the L6. In addition, the genital field in the Korean population is covered with tiny spinules, not described for the Japanese species. Despite these differences we believe that the investigated Korean population is conspecific with the Japanese one and thus belong to D. mukaishimensis . It is most probable that they represent interspecific variability. Other than that, the carapace shape and structure, as well as the appearance and the chaetotaxy of all other appendages are the same in these two populations.

The systematics of the entire subfamily Paracypridinae is in an urgent need of revision, and although several attempts of improvement were made (see Maddocks 1992, 2005), none has resolved the current problems, such as many overlapping morphological characters between different genera and no clear synapomorhies.

Figures

FIGURE 20. Dolerocypris mukaishimensis Okubo, 1980, A, B, E-I, male; C, D, female: A, RV, outside view; B, LV, inside view; C, RV, inside view; D, LV, inside view; E, UR; F, end of the body showing caudal seta and UR attachment; G, L 6; H, right prehensile palp; I, left prehensile palp; J, hemipenis. Scales = 0.1 mm.

FIGURE 21. Dolerocypris mukaishimensis Okubo, 1980, A. B, C, E, F, H, I, male; D, G, female: A, terminal segment of A 1; B, A 1; C, Rome organ; D, UR, arrows pointing on two posterior setae; E, Md palp; F, L 7; G, terminal part of A 2; H, proximal part of A 2; I, distal part of A 2. Scales = 0.1 mm.