Proceroecia joseondonghaensis, Choi & Karanovic & Lee & Angel, 2020

Choi, Eunha, Karanovic, Ivana, Lee, Wonchoel & Angel, Martin V., 2020, Description of two new Proceroecia species (Ostracoda: Halocyprididae) from neritic waters off South Korea with an insight into the morphological and molecular diversity of the genus, Zootaxa 4896 (2), pp. 180-200 : 190-194

Proceroecia joseondonghaensis sp. nov.

( Figs 3C , 7–9 )

Material examined: Holotype, 1 female mounted in CMC mounting medium on 3 slides (NIBRIV0000867286) ; Allotype, 1 male mounted in CMC mounting medium on 3 slides (NIBRIV0000867287) .

Type locality: South Korea, Korea Strait , 33°25’12” N, 127°53ʼ24” E, depth range 0–127 m, 14 September, 2018 ; collectors Jisu Yeom, Jaehyun Kim and Wonchoel Lee.

Etymology: The specific name refers to the East Sea (in the Korean language “joseondonghae”), because the type locality lies in the Korea Strait, which is the border between the Yellow and East Sea (Sea of Japan).

Female.

Carapace ( Fig. 7A ). Carapace length (measured only for one specimen) 1.12 mm; height 0.48 mm; height/length ratio 42.8%. Morphological differences between the carapace of this species and P. hwanghaensis are subtle: The posterior margin less bowed, carapace less tapered and the right asymmetrical gland opening closer to the posterior margin. The right asymmetrical gland opening at 12.5% of the carapace length measured from posterior margin.

Frontal organ ( Fig. 7B ). Similar to P. hwanghaensis , but thicker. Capitulum of uniform thickness and more smoothly curved and not divided from the stem. Also relatively shorter than in P. hwanghaensis , only twice the length of the first antenna.

First antenna ( Fig. 7B ). Similar to Proceroecia hwanghaensis , but with slightly longer segments. The e–seta carrying sensilla, which gradually shorten towards the end of the seta (the seta damaged in Fig. 7B ).

Second antenna ( Fig. 7C, E ). Protopodite about 1/2 the length of carapace (46%). Endopodite with a–seta 1/2 the length of b–seta. Thirteen thick spinules present on the b–seta, and 6 spinules on the first segment near the bases of the a– and b–setae. Nine long and 4 short spines present on the fused second and third endopodite segment. The g–seta clearly the longest, f–seta slightly shorter and the remaining three setae about 1/2 the length of g–seta.

Mandible ( Fig. 8A, B ). Coxale with 6 uneven teeth; endites covered with sensilla, and with 2 subequally long setae. Basale ventro-distally with 2 setae (almost subequally long), and 1 seta close to endopodite. Exopodite reduced to a plumose seta. First endopodite with 1 plumose dorsal seta (slightly longer than in P. hwanghaensis ) and 2 ventral setae (one 3 times longer than the other). Eight tiny spines present on the second segment dorsally. Same segment with 3 dorsal, almost claw-like setae: 2 short and only reaching distal margin of the terminal segment, and 1 ringed, long seta, by far exceeding terminal segment. Second segment ventrally with 2 subequally long setae. Terminal segment with 2 strong, ringed setae, 1 short claw inserted between these two and 4 setae more ventrally on the segment of 1/3 of the length of the longer of the two ringed setae.

Maxilla. No significant sexual dimorphism observed. Similar to male.

Fifth limb ( Fig. 7D ). First endite of coxale with 2 setae (one much shorter than the other); second endite with 3 plumose, ringed setae; third endite with 5 setae (some claw-like and ringed) in the ventral group of setae, and with another 2 setae ventro-proximally (one plumose and more distal to the ventral group, other smooth and more proximal). Basale with 2 dorso-lateral setae, 3 ventro-proximal group of setae, and 2 ventro-distal setae. All setae on basale smooth, including the remnant of the exopodite.

Sixth limb ( Fig. 7F ). Basis with 5 ventral setae (2 proximally and 3 distally; 1 proximal and 1 distal plumose, other smooth) and 1 plumose dorsal seta. Exopod reduced. Endopod with the same chaetotaxy like P. hwanghaensis .

Uropodal lamellae ( Fig. 7G ). Similar to P. hwanghaensis , without an unpaired seta.

Male.

Carapace ( Fig. 3C, D ; 9A ). Length 0.94 mm; Height 0.40 mm; height/length ration equalling 42.5%. Surface without ornamentation. Left asymmetrical gland opening at typical location on the dorsal margin, just anterior to the back end of the hinge between the carapace valves. Right asymmetrical gland opening at 10.5% length of carapace measured from posterior margin.

Frontal organ ( Fig. 9B ). Stem similar in length to the limb of the first antenna. The capitulum angled ventrally. Basis broad and narrowing towards the rounded end. Medially with long sensilla on its ventral surface.

First antenna ( Fig. 9B ). The a– and c–setae missing. The b– and d–setae almost as long as e–seta, which has a central armature of 12 pairs of spines.

Second antenna ( Fig. 9C, D, E ). First segment of the exopodite short, about 1/3 the length of the protopodite. Hook appendages on the endopodites slightly asymmetrical: the right hook having a pointed tip, whereas the left hook with a rounded tip. The a–seta bare and 1/2 length of b–seta, which carries 2 spinules. Second endopodite segment with c–seta 3/5 length of d–seta. The f– and g–setae long and slightly unequal, h–, i– and j–setae with thin wall and similar in length to b–seta.

Mandible ( Fig. 8C ). Similar to female, with slightly longer ventral setae on the first endopodite segment and with 12 (instead of 8) small spines on the second segment distally.

Maxilla ( Fig. 9 F ). Similar to P. microprocera , with 5 anterior and 3 posterior setae on the first endopodite.

Fifth limb. Same as in female.

Sixth limb ( Fig. 8D ). Similar to P. hwanghaensis , all 3 terminal setae carrying long sensilla. All setae on the basis non-plumose, and one more seta present ventrally (only one in P. hwanghaensis ).

Copulatory appendage ( Fig. 9 G ). Relatively thin (214 μm high, 36 μm wide). Height 22.7% of carapace length. Oblique muscles could not be observed.

Figures

FIGURE 3. SEM photographs: A, B—Proceroecia hwanghaensis sp. nov., female; C—P. joseondonghaensis sp. nov., male; A—right valve, external view; B—right valve postero-dorsal view; C—detail of the postero-dorsal spine on the right valve. The arrow indicates the position of the right asymmetrical gland.

FIGURE 7. Line drawings of Proceroecia joseondonghaensis sp. nov., female: A—carapace; B—first antenna and frontal organ; C—protopodite of the second antenna; D—fifth limb; E—endopodite of the second antenna; F—sixth limb; G—uropodal lamellae.

FIGURE 8. Line drawings of Proceroecia joseondonghaensis sp. nov. A, B, female; C, D, male: A—mandible; B—ventrodistal seta on the basis of mandible; C—mandible; D—sixth limb.

FIGURE 9. Line drawings of Proceroecia joseondonghaensis sp. nov., male:A—carapace; B—first antenna and frontal organ; C—endopodite of the second antenna; D—left hook appendage of the second antenna; E—protopodite of the second antenna; F—mandible; G—copulatory appendage.