Sarsiella nereis, Karanovic, Ivana & Soh, Ho-Young, 2015

Karanovic, Ivana & Soh, Ho-Young, 2015, Five Sarsiellidae ostracods (Crustacea: Myodocopida) from the South Coast of Korea (East China Sea), Zootaxa 3947 (4), pp. 451-488 : 476-480

Sarsiella nereis sp. nov.

( Figures 18–20 )

Etymology. The species name is the Greek word “ Nereis ”—sea nymph, a daughter of Nereus.

Material examined. Holotype female dissected on one slide, shells on micropaleontological slide ( NIBR IV 0000287244), one paratype female dissected on one slide, shell on micropaleontological slide ( NIBR IV 0000287245), from (type locality): from South Korea, East China Sea, Maemul Island, 34°36’47”N 128°20’46”E, 0 7 September 2012, collector H. Y. Soh.

Description. Female. Shell ( Figure 18 D, E) with only faint, short ridges anteriorly. Surface covered with wide, shallow pits (fossae), and two types of setulae: short ones on lateral surface and longer ones marginally. Caudal process ( Figure 18 B, C) short and not sharply pointed. Postero-dorsal bulge not clearly outlined. Dorsal margin of carapace straight medially, abruptly sloping down posteriorly and with sinusoid curve anteriorly. Anterior margin slightly protruding. Ventral margin rounded. Long pore canals lead from posterior process to inside of valves, shorter ones present along entire anterior and ventral margin. Anterior infold without bristles. Posterior infold with two dorsal bristles. Infold of caudal process with only few short bristles running along caudal process. Shell L (including caudal process)= 1.2 mm.

A1 ( Figures 18 F, 19A). First segment long and bare. Second segment with annulated, bare, dorsal bristle reaching 1/2 of following segment. Third and fourth segment fused; third with annulated, bare dorsal bristle exceeding distal margin of same segment and one longer, pappose ventral bristle. Fourth segment with short, bare, annulated dorsal bristle not reaching distal end of following segment, and two, annulated bristles ventrally (one longer than other). Fifth and sixth segments fused. Bristle of fifth segment long, annulated and with one sensory seta; seta on sixth segment short, bare. Seventh segment: a-bristle about five times longer than sixth segment’s bristle; b-bristle slender, and about as long as a-bristle; bristles from b- to g- all almost subequally long and without sensory setae.

Bellonci Organ ( Figure 19 B). Cylindrical, not segmented and short, distally with small protuberance.

Eyes. Both medial and lateral eyes present. Medial eye with scattered pigment, lateral eye with four ommatidia.

A2 ( Figure 19 C). Prp bare. Enp with two short basal bristles (annulated and bare), and no bristles situated on terminal node. Exp: first segment with small terminal medial recurved tubular bristle; bristle on second segment with thick proximal ventral spines and distal swimming setae; bristles on segments 3–8 without thick spines proximally and with swimming setae distally; ninth segment with two bristles (one short, bare and other longer with swimming setae).

Md ( Figure 19 D). Cx endite elongated and with short, thick spines, Cx with long slender spines near ventral margin. Bs: ventral margin with three short bristles medially and two cuticular spine-like extensions distally; dorsal margin with one distal spine. Exp present and very small. First Enp segment with one stout claw distally, segment covered with small spines; second Enp segment with strong claw ventrally, and one tiny spine dorsally; third Enp segment with stout terminal claw and small dorsal and ventral spines.

Mxl ( Figure 18 A). Cx with short, bare dorsal bristle. Endite I with total of five claws/bristles; endite II with three claws/bristles; endite III with about eight claws/bristles. Exp with two subequally long bristles. First Enp segment with spinous alpha- and beta-bristles. Second Enp segment with four pectinate claws, two a- and one cbristle.

L5 ( Figure 20 A). Lobe one with one short bristle; lobe two with two bristles (one longer than other, both pappose); lobes 3–5 fused and with total of seven bristles, five long and annulated and with setulae, two bare, short bristle. Entire appendage hirsute.

L6 ( Figure 20 C). One endite with two ringed bristles (one bare, other pappose). Terminal segment with nine annulated bristles, three bare, five pappose, one with spines. Two bristles long, one very short and other subequally long. Nine bristles followed by space and two long plumose bristles. Entire appendage covered with fine, short setulae.

L7 ( Figure 20 B). Proximal group with two bristles (one on each side), each with three or four bells. Terminal group with two bristles on each side, each with five bells. Terminus without opposing combs.

UL ( Figure 20 E). Each lamella with five claws. Only claw one non-articulated; claws with long and short teeth along posterior edge. Right lamella with bunch of setulae dorsally to first claw, left lamella with long setulae following terminal claw. Copulatory apparatus shown in Figure 20 D.

Remarks and affinities. The new Korean species differs from all other Sarsiella representatives by the specific shell morphology. All other species have either more prominent ridges, are completely smooth, or covered with dense spines. Sarsiella nereis is also one of the rare species with only two bristles distally on each side of the L7. Of the species where this appendage has been described, only S. spinulosa ( Poulsen, 1965) has the same morphology.

Figures

FIGURE 18. Eusarsiella nereis sp. nov., holotype female: A, Mxl; B, detail of the caudal process, RV, inside view; C, detail of the caudal process, LV, inside view; D, RV, lateral view from the inside; E, whole animal, lateral view from the left side; F, distal segments of A 1. Scales = 0.1 mm.

FIGURE 19. Sarsiella nereis sp. nov., holotype female: A, A 1 without distal segments; B, Bellonci Organ; C, Enp and first segment of Exp A 2; D, Md. Scale = 0.1 mm.

FIGURE 20. Sarsiella nereis sp. nov., holotype female: A, L 5; B, distal part of L 7; C, L 6; D, part of female copulatory apparatus; E, UL. Scales = 0.1 mm.