Proceroecia hwanghaensis, 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 : 184-190

Proceroecia hwanghaensis sp. nov.

( Figs 2 , 3A, B , 4–6 )

Material examined: Holotype, 1 female mounted in CMC mounting medium on 3 slides (NIBRIV0000867284) ; Allotype, 1 male mounted in CMC mounting medium on 3 slides ((NIBRIV0000867285); Paratypes, 9 females dissected on 27 slides and 3 males dissected on nine slides.

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 Yellow Sea (in Korea language) 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. 3 A, B ; Fig. 4 A ). Carapace length ranging between 0.89 and 1.21 mm; height ranging between 0.39 and 0.55 mm; height/length ratio ranging between 41.6 and 45.8% (Mean= 43.2%, N=10). The right posterior dorsal corner of carapace with a distinct spine inserted slightly below the corner. The left asymmetrical gland opening present on the dorsal surface of the carapace just anterior to the posterior back of the hinge between the two carapace valves, i.e. the most common place in halocyprids. A few tiny sensilla present near the gland. The right asymmetrical gland opening anteriorly to the posterior ventral corner, at 19.5% length of carapace from the posterior margin. Surface of the carapace smooth and lacking ornamentation.

Frontal organ ( Fig. 4D ). Typical for the genus: stem long and projecting well beyond the end of the first antenna. No suture present between the capitulum, which is slightly bent down and with a pointed tip. Frontal organ ventrodistally covered with short sensilla. Whole organ 2.5 times length of the first antenna.

First antenna ( Fig. 4D ). Dorsal seta on the shaft absent, all segments very short (including shaft). The longest terminal e–seta about 2x length of a–d setae. Ventral surface of the distal half of the e–seta lined with sensilla, which gradually shorten towards the end of the seta.

Second antenna ( Fig. 4B, E ). Typical of halocyprids. Muscular protopodite occupying about 1/2 the length of carapace (mean size = 44.8%). First endopodite segment with b–seta 2x the length of a–seta, and armed with 4-10 thick spinules. A line of 4-5 spines present near the bases of these two setae. Second and third endopodite segments with 8-11 long spines and 4-7 shorter spines, respectively. Four terminal setae present, of which the g–seta the longest, and others subequally long.

Mandible ( Fig. 5A ). Coxale with 6 uneven teeth; endites covered with sensilla, and with 2 subequally long setae. Basale venro-distally with 2 setae (almost subequally long), and 1 seta close to endopodite. Exopodite reduced into a plumose seta. Endopodite 3-segmented. First segment with 1 short plumose seta dorsally, and 1 long seta ventro-distally. Second segment with 3 claw-like setae dorso-distally (two of which short and one long, annulated seta), and 2 setae ventro-distally (one 2/3 of the other). Terminal segment with total of 6 claw-like setae: 2 long and ringed, and 4 short on the ventral side of the appendage.

Maxilla ( Fig. 4C ). The overall structure of the maxilla typical of the subfamily Conchoeciinae . A stout basal seta present. First segment with 6 anterior setae, 3 posterior setae, and a single lateral seta, all of which are bare. Second segment angled anteriorly and with 3 claw-like setae and a pair of subterminal thin setae. A patch of long sensilla present near the base of the shortest claw-like seta there.

Fifth limb ( Fig. 5B ). Protopodite with an array of plumose, and spine-like setae, typical of the family. Coxale with 2 setae on the first endite, 2 on the second, 6 on the third (ventral group of setae), and 1 additional plumose seta ventrally to the latter group. Basale with 4 setae in the ventro-proximal group, 2 in the ventral group, 1 dorso-lateral seta, and a dorsal seta (vestige of the exopodite). First endopodite segment with a medio-dorsal seta and a pair of ventral setae; all setae bare and extending just to the end of the segment. Second segment carrying the usual 3 setae, central one being the longest (broken on the Fig. 5B ).

Sixth limb ( Fig. 5C ). Two plumose setae present on coxale endites. Basale with 2 plumose ventro-proximal setae, and 3 (one plumose) ventro-distal setae; one dorso-lateral seta plumose and short. Exopod reduced to a smooth seta. First segment of endopodite with 1 smooth seta ventro-medially; second segment with 1 plumose seta ventromedially and 1 smooth seta ventro-dorsally. Terminal segment with 3 setae (but only one illustrated on Fig. 5C ).

Seventh limb. Reduced with only one whip-like seta terminally.

Uropodal lamellae ( Fig. 4F ). With 8 paired spinose claws.

Male

Carapace ( Fig. 2B , 6A ). As usual in the subfamily there is a slight, but noticeable dimorphism in the carapaces between the sexes present: the male carapace is slightly shorter and broader and with a straighter posterior margin than the female carapace. Length varying between 0.99 and 1.03 mm, height between 0.44 and 0.45 mm; height/length ratio ranging between 43.7 and 45.4% (Mean= 44.5%). The right asymmetrical gland also opening at 14–16% of carapace length (measured from the posterior margin). A spine present slightly below the postero-dorsal corner of the right valve; slightly below the spine a group of gland cells present that open on the posterior edge of the carapace. These glands discharge just where the long, curved, plumose terminal setae of the sixth limb projects through the gap between the valves of the carapace.

Frontal organ ( Fig. 6B ). Anchored medially of the second segment, with stem almost as long as the first antenna. The capitulum ventrally right-angled and divided from the stem by a septum. Frontal organ constricted centrally, and with proximal half lined with long sensilla along trailing edge.

First antenna ( Fig. 6B ). The limb clearly segmented with terminal setae very different to those of the female. The a– and c–setae poorly developed or missing, and could not be observed of the dissected animals. The b– and d–setae long and of a similar length, and longer than the e–seta (e–seta on the slide snapped off on the illustration). The b–, d–, e–setae with thin cuticular wall. The e–seta medially carrying a row of 14-15 paired spines, all straight and angled at approximately 45˚to setae axes.

Second antenna ( Fig. 6C, E, F ). Protopodite more than 1/2 length of carapace (mean size 51.2%). Endopodite with a–seta 1/2 length of b–seta, which carries 6-10 spinules; d–seta 1/2 length of c–seta; e–seta very short; setae h, I, and j with thin cuticular wall, and as short as the b–seta; g–seta slightly longer than f–seta. Hook-like appendages asymmetrical and with pointed tip. Left hook appendage with a straight distal end, while distal end curved on the right appendage.

Mandible, maxilla and fifth limbs show no sexual dimorphism and are similar to those of female.

Sixth limb ( Fig. 6D ). Overall morphology of this limb very similar to Drapun’s (2012) illustration of the limb of P. procera , especially the number, location and size of the setae. All three of the terminal setae have long terminal sensilla.

Copulatory appendage ( Fig. 6G ). One spine on the distal end. The size of the appendage: 217 μm high, 54 μm wide, the height equaling 21.3% of the carapace length. Similar to Drapun & Smith’s (2012) description of P. microprocera with 4 oblique muscles.

Figures

FIGURE 2. Light microscope photographs: A—Proceroecia hwanghaensis sp. nov., female: B—P. hwanghaensis sp. nov., male.

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 4. Line drawings of Proceroecia hwanghaensis sp. nov., female:A—carapace; B—endopodite of the second antenna; C—maxilla; D—first antenna and frontal organ; E—protopodite of the second antenna; F—uropodal lamellae.

FIGURE 5. Line drawings of Proceroecia hwanghaensis sp. nov., female: A—endopodite of mandible; B—fifth limb; Csixth limb.

FIGURE 6. Line drawings of Proceroecia hwanghaensis sp. nov., male: A—carapace; B—first antenna and frontal organ (indicated by an arrow); C—endopodite of the second antenna; D—sixth limb; E—protopodite of the second antenna; F—left hook appendage of the second antenna; G—copulatory appendage.