Candona quasiakaina, Karanovic, Ivana & Lee, Wonchoel, 2012

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 : 9-15

Candona quasiakaina sp. nov.

( Figures 1–4 )

Etymology. The new species is named after Fabaeformiscandona akaina Smith & Janz, 2008 , because of their close resemblance. The specific name is composed with the Latin adjective quasi, meaning “appearing as if”, which was prefixed to the specific name akaina . Gender feminine.

Material examined. Holotype male (soft parts dissected on one slide, shell not preserved NIBRIV0000245048), allotype female (soft parts dissected on one slide, shell mounted on micropaleontological slide NIBRIV0000245049); 9 paratypes (1 male soft parts dissected on one slide, shell mounted on micropaleontological slide NIBRIV0000245050; 1 female soft parts dissected on one slide, shell not preserved NIBRIV0000245051; 7 females in ethyl alcohol kept for future DNA studies), from (type locality) South Korea, Choenggye Mountain, freshwater stream, 37 0 25’25” N 127 0 03 ’55.2”E; 15/05/2011, collectors Hyunsu Yoo & Ivana Karanovic.

Description. Male. Carapace subtriangular in shape ( Figure 1 A) with the greatest H lying behind middle L, equaling 48% of total L. Size: L= 1.3 mm. Dorsal margin highly arched and with slightly sharp angle at point of greatest H, then slightly sinusoid towards posterior and gently sloping towards anterior end. Anterior and posterior margins both broadly rounded and equally wide. Ventral margin concave around mouth region. Calcified inner lamella narrow on both ends, 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 wart-like structures. No other surface ornamentation present. LV overlapping RV on all free margins, dorsally with narrow flange.

A1 (Figure 2A). Appendage 7-segmented. First segment with two setae anteriorly and two posteriorly. One anterior seta situated more proximally, the other distally on segment. Posterior setae originate from same (or very close) spot. All setae pappose. Second segment with one anterior pappose seta, reaching distal end of fourth segment. Third segment with one anterior pappose seta slightly exceeding distal margin of fourth segment. Fourth segment with one short posterior seta (exceeding distal end of the same segment), and two anterior, longer setae (exceeding distal end of terminal segment); all these setae pappose. Fifth segment with same chaetotaxy as fourth one. Penultimate segment with total of five setae; posteriormost seta “d” present. Alpha seta slightly exceeding distal end of terminal segment. Seventh segment (Figure 2C) with posterior, claw-like seta which is as long as terminal segment, one aesthetasc (ya) of the same L, and two longer pappose setae. L ratio of five distal segments equaling 1: 1.25: 1.5: 2: 1.9. Rome and Wouters organs not present.

Candona quasiakaina sp. nov., holotype (male): A, A1; B, A2; C, terminal segment of A1; D, Md; E, Mxl. Scales = 0.1mm.

A2 (Figure 2B). Basal segment with total of three setae: one short, well-sclerotized and pappose, other two smooth and longer. One of the long setae situated dorsally and one ventrally on segment. Distal segment of 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 aesthetasc “Y” and antero-ventrally with two long setae (almost equally long). Second segment with one medio-dorsal (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. Third endopodal segment with claws G1, G2, z1 and z2, and setae G3 and z3. Claw G1 short (60% of first endopodal segment); G2 long (1.3 times longer than first endopodal segment); z1 slightly shorter than z2 and both approximately as long as first endopodal segment; G3 and z3 thin setae and half as long as z2 claw. Terminal segment with one long claw, Gm (approximately as long as first endopodal segment) and one short claw, GM (1.5 times longer than terminal segment). Terminal segment also armed with aesthetasc y3 (as long as terminal segment) and one thin seta accompanying y3. Claws very gently serrated.

Md (Figure 2D). First segment of palp with one plumose seta (S1), one pappose, short seta (S2), a short alpha seta, and one additional seta situated proximally on segment. Second segment dorsally with two setae, reaching distal end of following segment, ventrally with four setae originating from a small plate and one plumose seta; beta seta not observed. Penultimate segment dorsally with three almost equally long setae, gamma seta smooth, and three additional setae of which one originating medially and two ventrally. Terminal segment with two strong, well-sclerotized claws (medial one pappose distally) and two setae more ventrally.

Mxl (Figure 2E). Palp 2-segmentd, first segment with four setae: three originating antero-distally, and one medio-distally. All these setae pappose. Terminal segment with two claw-like setae and four setae, one situated between claws, and three situated more posteriorly.

Prehensile palps ( Figure 3 C, D). Palps slightly asymmetrical, right one with more curved dorsal margin and more strongly pronounced ventral chitinous enlargement situated close to tip of finger. Finger on right palp slightly shorter in comparison to the body than on left palp. Both palps with well-developed subterminal structures.

L6 ( Figure 3 A). Basal segment with one seta (d1). Endopod 4-segmented (on one leg penultimate segment distally subdivided, creating a 5-segmented endopod). 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.

L7 ( Figure 3 B). Basal segment with “d1” and “dp” setae. Seta “d2” missing. Endopod 4 segmented, and only “g” seta present distally. Terminal segment armed with two long and one short seta. L ratios between three “h” setae equaling: 1: 1.8: 1.8.

UR ( Figure 3 E). Slightly asymmetrical: on one ramus claws almost equally long, on other posterior claw clearly shorter than anterior one. Posterior seta very long and by far exceeding postero-distal margin of the ramus. Anterior seta much shorter and only ¼ L of anterior claw. Both claws faintly serrated. L ratio between anterior margin, anterior caw, posterior claw and posterior seta equaling: 1.75: 1.2: 1: 1.4.

Hemipenis ( Figure 4 A). Medial lobe well-sclerotized with evenly rounded distal margin. Lobe “h” squareshaped and with sclerotized margins. Lobe “a” with wavy distal margin ( Figure 4 B) and pointed, elongated outer end. Same lobe also sclerotized, sclerotized structure on inner margin with small septae, giving striate appearance. Inner duct not coiled.

Zenker organ with seven rows of spines.

Female. Slightly smaller than males ( Figure 1 B, C), L= 1.15 mm, otherwise very similar to male. Posterodorsal margin not as sinusoid as in males, and wider anterior inner calcified lamella than in male.

A2 ( Figure 4 C). Endopod 3-segmented. All “t” setae on penultimate segment present, subequally long and pappose; exceeding distal end of terminal segment. None of “z” setae transformed into claws, and only two “z” setae visible, slightly exceeding distal end of terminal segment. Claw G2 equaling 2/3 of claw G1, which slightly longer than first endopodal segment. Claw G3 same as claw G1. Terminal segment with long claw Gm and short Gm. All claws gently serrated.

L5 ( Figure 4 D). Two setae present in exopod, one “a”, one “b” and one “d” seta present. Distal setae on endopod relatively short and two subequally long, one half as long.

UR ( Figure 4 F) Similar to male, two rami slightly asymmetrical: on one, claws almost equally long, on other posterior claw obviously shorter. Posterior seta very long. Ramus also much wider proximally than in males. L ratios between anterior margin, anterior, posterior claw and posterior seta equaling: 1.5: 1.1: 1: 1.3.

Genital field ( Figure 4 E, F). Well-sclerotized around margins and consisting of anterior and posterior parts. Anterior part with one narrow but rounded end ( Figure 4 E), posterior part with one large square-like structure whish dorsally extends into relatively small, narrow, but rounded process.

All other appendages same as in male.

Remarks and affinities. Morphological data suggest that the new species is probably most closely related to Fabaeformiscandona akaina Smith & Janz, 2008 , described from Lake Biwa, Japan. Smith & Janz (2008) placed the species in the genus Fabaeformiscandona Krstic, 1972 , accepting the “broad” diagnosis of the genus, which follows Meisch (2000) who includes all species with a smooth “gamma” seta on the penultimate segment of the Md-palp, W/L ratio less than 40% and three ( fabaeformis -group), four ( acuminata - and breuli- group), and five setae ( balatonica -group) internally on the second segment of Md-palp, into the genus Fabaeformiscandona .

Petkovski & Karanovic (2000, 2004) questioned the validity of the genus Fabaeformiscandona , because the type species of the genus Eucandona Daday, 1900 , E. balatonica (Daday, 1900) (poorly known at the time) is placed into the genus Fabaeformiscandona , although this species differs in many details (including the carapace shape) from other Fabaeformiscandona species. Karanovic (2006) redefined the genus Fabaeformiscandona , proposing that it should include only species with a very low carapace in lateral view, without the most posterior (“d”) seta on the fifth segment of the A1, with a group of three setae on the internal margin of the second segment of the Mdpalp, and, with a peculiar appearance of the male prehensile palp. The genus at the moment includes 39 Recent species ( Karanovic 2012), but not all of those conform to the definition of the genus proposed by Karanovic (2006). The following species currently assigned to the genus should be given a new systematic position (in the genus Candona Baird, 1845 or Eucandona ): F. acuminata (Fischer, 1851) ; F. akaina Smith& Janz, 2008 ; F. bilobata ( Klie, 1938) ; F. bilobatoides (Löffler, 1961) ; F. breuili (Paris, 1920) ; F. brevicornis (Klie, 1925) ; F. caudata (Kaufmann, 1900) ; F. danielopoli Yin & Martens, 1998 ; F. h y a l i n a (Brady & Robertson, 1870); F. latens (Klie, 1940) ; F. levanderi (Hirschmann, 1912) ; F.nishinoae Smith & Janz, 2008 ; F. siliquosa (Brady, 1910) . We are here not proposing any new combinations, because the taxonomy and systematic of the genus Candona is far from being resolved and the actual relationship among many of the groups is still unknown, therefore the generic position may easily change in the future. On the other hand, we decided not to include Candona quasiakaina into the genus Fabaeformiscandona , although it is very closely related to some of its current representatives, because the genus Fabaeformiscandona should be much narrower (following Karanovic 2006) and all the species C. quasiakaina is related to, definitely do not belong there.

Candona quasiakaina , Fabaeformiscandona akaina , F. n i s h i n o a e Smith & Janz, 2008, F. danielopoli and F. hyalina from a group of very closely related species, in which the outer lobe of the hemipenis (lobe “a”) has a tapering/pointed tip. The second and third species are described from Lake Biwa and both differ from the Korean species by the long and finger-like process on the genital field in females; by a shorter posterior seta on the UR, and many details of the hemipenis. Fabaeformiscandona danielopoli , described from China (Yin & Martens 1998) also has a finger like genital process, more robust right prehensile palp, a shorter posterior seta on the UR and a quite different hemipenis. The carapace shape is very similar among the four species. Fabaeformiscandona hyalina has a supposedly Holarctic distribution ( Meisch 2000) but has never been recorded in East Asia. It has a much smaller projection on the genital lobe, but, in contrary to the new species, it is broad and triangular. The posterior seta on the UR is also much shorter in F. hyalina and the outer lobe on the hemipenis is not as rectangular as in C. quasiakaina . The new species is also lower in lateral view, and the posterior margin is less inclined.

Figures

FIGURE 1. Candona quasiakaina sp. nov., A, holotype (male); B, C, allotype (female): A, carapace, lateral exterior view from the right side with Zenker organ indicated; B, LV, exterior view; C, RV, interior view. B and C with ovary indicated. Scales = 0.1 mm.

FIGURE 3. Candona quasiakaina sp. nov., holotype (male): A, L 6; B, L 7; C, left prehensile palp; D, right prehensile palp; E, UR. Scales = 0.1 mm.

FIGURE 4. Candona quasiakaina sp. nov., A, B, holotype (male); C – F, allotype (female): A, hemipenis; B, variability of outer lobe of hemipenis; C, A 2; D, L 5; E, genital field; F, UR. Scales = 0.1 mm.