Undulacandona koreana, Karanovic & Cho, 2017

UNDULACANDONA KOREANA SP. NOV.

( FIGS 2–6)

h t t p:/ / z o o b a n k. o r g / u r n:l s i d: z o o b a n k. o r g: a c t: DD91C682-AC36-4D21-ADF2-A6BADD6A7937

Holotype: Male, dissected on one slide ( NIBRIV 0000243281 ), shell on SEM stub ( NIBRIV0000243282 ) . Allotype: Female, dissected on one slide ( NIBRIV 000024328 ), shell on SEM stub ( NIBRIV0000243282 )

Paratypes: Juvenile male, dissected on one slide, shell on micropalaeontological slide ( NIBRIV0000243284 ) ; female with soft parts used in DNA extraction, shell on SEM stub ( NIBRIV0000243282 ) ; 2 juveniles, soft parts used for DNA extraction, shells on micropalaeontological slides; two juveniles, whole on SEM stub ( NIBRIV0000243282 ) and 10 additional specimens in alcohol ( NIBRIV0000243285 ) . All examined material collected from the type locality.

Type locality: River interstitial, Seongdong-ri , Yeongjung-myeon, Pocheon-si, Gyeonggi-do, South Korea, 38°00 ʹ 45.9 ″ N 127°14 ʹ 47.6 ″ E, elevation 73 m, 22 May 2015, collector Joo-Lae Cho. GoogleMaps

Etymology: The species is named after Korea. anterior and inclined towards posterior end. Anterior and posterior margins both rounded, anterior wider than posterior. Ventral margin slightly curved. Surface covered with fine stripes ( Fig. 1C) and with sensory setae exiting from pores ( Fig. 1D, E). Pores rimmed ( Fig. 1F). Surface setae of various lengths. Inner calcified lamellae and line of concrescence narrow ( Fig. 2A, B).

A1 ( Fig. 3C): Five-segmented. First segment with one anterior seta situated proximally and two posterior, more distal setae. Following segment with one short seta anteriorly and peculiar postero-distal margin. The following two segments very long and probably represent fusion of two ancestral segment. Segment number three with only one short, anterior seta, while the following one with three relatively long setae. Terminal segment with a very long aesthetasc (longer Diagnosis: Shell ornamented with fine stripes, elongated in lateral view. LV and RV subequal. A1 five-segmented; A2 with all three exopodite setae short. Prehensile palps almost symmetrical each basally carrying additional spine-like structure. L7 with incompletely subdivided penultimate segment. Uropodal ramus with short and stout ramus and with long claws, anterior claw shorter than posterior, claws not distally curved; posterior seta situated high on the ramus. Hemipenis with lobe ‘a’ higher than lobe ‘h’, and not curved at its tip. Shell and L7 sexually dimorphic.

Description: Male. L of shell 0.8 mm. Greatest H situated around middle L, equalling 40% of L. Valves elongated in lateral view ( Fig. 1A, B). Dorsal margin straight in the middle, broadly rounded towards than the last three segments combined), one shorter posterior seta and two very long medial setae.

A2 ( Fig. 2F): Penultimate segment subdivided with male sensory bristles. Exopod consisting of three short setae. Endopod five-segmented. Aesthetasc Y slightly longer than posterior margin of the first endopodite segment. Same segment with two setae on postero-distal margin: one long and other very short. Beside large male sexual bristles on the margin between second and third endopodal segment also with one anterior (short) and one posterior (longer) seta. Claws G1 and G3, as well as z3 seta reduced, while G2 claw, and z1 and z2 setae long and stout. Terminals segment with long Gm and short Gm claw. Aesthetasc y3 long.

Md ( Fig. 4C): Palp four-segmented. First segment anteriorly bare, posteriorly with four setae. Second segment anteriorly with two setae and posteriorly with 3 + 2 setae in a bunch. Penultimate segment with three setae antero-distally, two long medial setae and two shorter setae situated postero-distally. Terminal segment with two equal, long claws and two setae. Exopod with 7/8 rays.

Mxl-palp ( Fig. 3D): Two-segmented. First segment with total of four long and thin setae. Terminal segment slightly elongated, with two claws and four setae.

Prehensile palps ( Fig. 3E, G): Almost symmetrical. Both with elongated fingers and long subterminal setae. Also, both carrying a spine-like process proximally on the palp.

L6 ( Fig. 4G): Five-segmented. Basal and first endopodal segments without any seta. Second and third endopodal segments with one short seta each. Terminal segment with two short setae and a long claw.

L7 ( Fig. 4E, F): Four-segmented. Penultimate segment incompletely subdivided. Basal segment with all three setae present. Only seta ‘g’ present. Terminal segment with two short and one long seta. L ratio between two short setae equalling 2:1.

UR ( Fig. 4B): Ramus short, posterior setae situated high on the ramus. Both claws well developed, anterior longer than posterior. Anterior setae missing on one ramus. L ratio between anterior margin of the ramus, anterior claw, and posterior claw equalling 1:1:1.2.

Hemipenis ( Fig. 4A): Lobe a higher than h and r e l a t i v e l y s t o u t. I n t e r n a l l y c a n a l s n o t c o i l e d. Ejaculatory process relatively simple.

Zenker organ ( Fig. 4G): With 3 + 2 whorls of spines with wide central tube and inflated anterior end.

Female. L similar to male, but shape of the valves differ: dorsal margin more inclined towards posterior margin than in male ( Fig. 5A, B, E, F). In addition, surface ornamentation different from male: stripes are more clearly defined ( Fig. 5C, D, G). Line of concrescence, and inner calcified lamella ( Fig. 6A, B) same as in male.

A1 ( Fig. 6D): Posterior margin of second segment with clearly pronounced nipple-like extension.

A2 ( Fig. 6F): Four-segmented. Claws G1, G2, G3, and GM all long, seta z1 transformed into claw, two times longer than terminal segment. One seta present antero-medially on penultimate segment and three postero-medially on the same segment.

L5 ( Fig. 6C, I): With asymmetrical chaetotaxy (same in male). On one 2 setae present, probably representing ‘b’ and ‘d’ setae, while on the other only one seta present. One seta in exopod on both limbs.

L7 ( Fig. 6E): One of the two short setae on terminal segment much longer than in males, being over four times longer than the shorter one (only two times in male).

UR and genital field ( Fig. 6G): UR same as in male, genital filed without extensions.

UR attachment ( Fig. 6H): Very long (in both sexes), and much longer than ramus itself.

Remarks: Undulacandona koreana is most similar to U. aeolus sp. nov. (described in the following), but the two species clearly differ in the morphology of the hemipenis, UR and even morphology of prehensile palps. The females of the latter species are not known, so it is not possible to compare characters between these sexes of the two species. Undulacandona koreana clearly differs from U. andromeda (described below) in the shell shape; the latter has a rectangular posterior margin, and is much less elongated. Also, U. andromeda has a very long anterior margin on the UR. The difference between U. koreana and U. cetus is mostly in the peculiar morphology of the hemipenis in the latter species (see description in the following), as well as in the shell shape (asymmetrical and slightly subtriangular in U. cetus ).

The Japanese species, U. spinula Smith, 2011 has a very similar shell shape to that of U. koreana with the same type of sexual dimorphism in the shape, ornamentation and length ratio between setae on the terminal segment of L7, but this species does not have spine-like projections on the prehensile palps and the lobe a on the hemipenis is much thinner, tapering and curving distally. In addition, the posterior seta on the UR is positioned much lower, distal claws are distally curved and the posterior one is shorter than the anterior.