Parapolycope uncata, Tanaka & Tsukagoshi, 2013

Tanaka, Hayato & Tsukagoshi, Akira, 2013, The taxonomic utility of the male upper lip morphology in the ostracod genus Parapolycope (Crustacea), with descriptions of two new species, Journal of Natural History (J. Nat. Hist.) 47 (13 - 14), pp. 963-986 : 975-983

Parapolycope uncata sp. nov.

( Figures 8–13 )

Type series

Holotype. Adult male (SUM-CO-2079), appendages mounted on slides and valves preserved in a cardboard cell slide.

Paratypes. Six adult males (SUM-CO-2080–2085) and seven adult females (SUM-CO- 2086–2092). All specimens were collected on 22 November 2007.

Type locality

The holotype specimen was collected from the Koajiro Beach , Ito City, Shizuoka Prefecture, the Pacific coast of central Japan, 34 ◦ 57 ′ 15 ′′ N, 139 ◦ 08 ′ 31 ′′ E ( Figure 1 ; Table 2); interstitial environment at 20 cm below the shoreline sand surface. Substrate consisting of coarse sand with shell fragments .

Diagnosis

Carapace nearly round in lateral view. Carapace surface covered with a large number of fine pits. Male upper lip with hook-shaped structure. Male copulatory organ bearing one long tube. Male furcal lamella with three stout claws and one distal hamulus; right lamella with four stout claws and one distal long furcal projection (right flagellum) toward dorsal at distal end. Both of female furcal lamellae with four stout claws.

Description of adult male

Carapace ( Figures 8A–E , 9 , 10 ). Right valve length 232–248 µm and height 175–194 µm, left valve length 230–246 µm and height 174–196 µm ( Table 1). Nearly round in lateral view ( Figures 8A, B , 10 ). Surface covered with a large number of fine pits ( Figure 8A, B ). Serration along anterior margin with 28 and 26 sharp processes in right and left valve, respectively ( Figure 10 ). Marginal infold of each valve developing along anterior to posteroventral margins ( Figure 8C, D ). Along inner margin of right valve, anterodorsal bar and groove ( Figure 9B ), posteroventral groove ( Figure 9F ), posterior element of hinge structure ( Figure 9E ), posterodorsal bar ( Figure 9D ) and one socket (part of hinge structure) developed at the dorsal end ( Figure 9C ). Along inner margin of left valve, anterodorsal bar ( Figure 9H ), posteroventral bar ( Figure 9L ), posterior element of hinge structure ( Figure 9K ), posterodorsal bar ( Figure 9J ) and one knob (part of hinge structure) developed on dorsal end ( Figure 9I ). Adductor muscle scars oval, consisting of three closely spaced scars ( Figure 10 ).

Frontal organ. Absent.

Antennula ( Figure 11C). Uniramus, four articulated podomeres. First podomere quadrate, with two tufts and one tuft of setulae on anterior margin and lateral surface, respectively. Second podomere about 1.2 times as long as first podomere, with one annulated setulous seta on anterior proximal end, one cluster of hairs on anterior margin, and two minute spines on anterodistal end. Third podomere same length as first podomere, with one short annulated seta at anterodistal end and five posterodistal setae consisting of one seta with large disk-shaped sucker, one short tip furnished seta with a row of short setulae, one thick medium seta with comb-like setulae at tip, and two medium simple setae, respectively ( Figure 11 C′). Fourth podomere small, with three long and two very long annulated setae.

Antenna ( Figure 11E). Typically biramous, with exopodite and endopodite consisting of nine and three podomeres, respectively. Exopodite: first podomere about one-third as long as basis; podomere length decreasing in size from second to eighth, each podomere with one long annulated seta, respectively; ninth podomere small, with one long seta on proximal, one medium, and one short annulated seta on distal ends. Endopodite ( Figure 11 E′): first podomere same length as first podomere of exopodite; second podomere about four-fifths as long as first podomere, with three simple setae along dorsal margin consisting of one medium and two short, and seven annulated setae on distal end consisting of four long, two medium, one short. Third podomere about one-third length of second podomere, with one strong hook-shaped claw extending backward, and two long annulated setae on distal end.

Mandibula ( Figure 12A). Coxal endite with five teeth. Basis with three annulated plumose setae along ventral margin and small tufts of setulae on ventrodistal and dorsodistal surface. Exopodite reduced as one annulated setulous seta. Endopodite consisting of two podomeres. First podomere with two annulated setulous setae along ventral margin near proximal end and two long annulated plumose setae on dorsodistal end. Second podomere very small, with two setulose setae and small tuft of setulae on distal.

Maxillula ( Figure 12B). Precoxa ( Figure 12B ′′) with eight setulous setae (endites) of different lengths. Coxa ( Figure 12 B′) with three short plumose setae (endites) on medial surface near ventral margin, three long plumose setae on ventral margin, setulae on dorsal margin. Basis and first podomere of endopodite fused. Basis with setulae along dorsal margin and one medium and two long plumose setae along ventral margin. First podomere of endopodite with one long seta at dorsodistal end and two annulated long setae on middle of ventral margin. Second podomere very small, with four setae consisting of two long annulated setulous and two long stout with some bilateral spines and setulae. Exopodite consisting of two almost fused podomeres. First podomere with tuft of hairs on dorsal margin. Second podomere with tuft of hairs on dorsal margin and eight annulated setae consisting of one very long stout, one very long, three long, two medium, and one short along ventral margin.

Fifth limb ( Figure 12C). Coxa bearing branchial plate (epipodite) with 12 long plumose setae ( Figure 12 C′), and two short setulous setae on dorsal margin. Basis with three plumose setae along dorsal margin, one annulated setulous seta on ventral margin. Endopodite small, with two plumose and two slender simple setae of different length on distal margin. Exopodite very small, with one stout setulous seta at distal end.

Furca ( Figure 13A ). Left lamella with three stout claws and one distal hamulus ( Figure 13 A′ ). Right lamella with four stout claws and one distal long furcal projection toward dorsal on distal end ( Figure 13A ′′).

Male copulatory organ ( Figure 13A ). Arising from outer surface of body on left side of terminal trunk segment as a slender long curved tube.

Upper lip ( Figure 11A). Dorsal margin straight and ventral margin semicircular downward in left lateral view. Hook-shaped structure with ventral side. Numerous setulae on left lateral surface.

Description of adult female

Mandibula, maxillula, and fifth limbs similar to those of adult male.

Carapace ( Figure 8F–J ). Right valve length 258–272 µm and height 194–207 µm, left valve length 252–267 µm and height 196–209 µm ( Table 1). Slightly depressed round in lateral view ( Figure 8F, G ).

Antennula ( Figure 11D). Uniramus, four articulated podomeres. First podomere quadrate, with two tufts of setulae along anterior margin. Second podomere about twice as long as first podomere, with one long annulated setulous seta and cluster of hairs on anterior margin. Third podomere two-fifths as long as second podomere, with one and two short setae at anterior and posterior distal ends, respectively. Fourth podomere very small with five annulated distal setae.

Antenna ( Figure 11F). Only second and third podomeres of endopodite different from those of adult male. Endopodite consisting of three podomeres. Second podomere widened distally, with one simple seta at anterodistal end and five annulated setae of different length on posterodistal end. Third podomere about one-third length of second podomere, with two long annulated distal setae.

Furca ( Figure 13 B′ , B ′′). Each lamella with four short stout claws.

Female copulatory organ ( Figure 13B ). Spermatheca extended S-shaped in lateral view. Genital opening sclerotized.

Upper lip ( Figure 11B). Semicircular in lateral view. Larger than male’s.

Occurrence

See Figure 1 and Table 2. All specimens were collected by the authors from interstitial pore water.

Etymology

Specific name uncata , adjective derived from Latin uncus (hook), referring to the hookshaped structure of male upper lip.

Remarks

The carapace and appendage morphologies of Parapolycope uncata sp. nov. and P. germanica are similar to each other. However, this new species is distinguished by the morphology of the male upper lip (basal part of a hook-shaped structure in the lateral view is without a “waist” in P. uncata sp. nov. versus narrow in P. germanica ). Parapolycope uncata sp. nov. is clearly distinguishable from four other described species except for P. kunashiri by the shape of male upper lip. Parapolycope kunashiri is distinguishable from P. uncata sp. nov. by possessing a longer copulatory duct and a larger number of furcal claws in both furcal lamellae. Parapolycope uncata sp. nov. has a narrower distribution along the Pacific coast than P. psittacina sp. nov., extending from Nahama ( Figure 1 , Loc. 3) to Oura ( Figure 1 , Loc. 11), about 150 km in linear distance. Along the Sea of Japan, on the other hand, P. uncata sp. nov. is found in a zone from Omonogawa ( Figure 1 , Loc. 1) to Yatsumata ( Figure 1 , Loc. 12), a distance of about 600 km. This result suggests that P. uncata sp. nov. is widely distributed along the Sea of Japan rather than the Pacific. But the authors have researched only two sites along the coast of the Sea of Japan (Yatsumata, Fukui Prefecture and Omonogawa, Akita Prefecture). Therefore further research may show a broader distribution for P. uncata sp. nov.

Figures

Figure 1. Map showing the distribution of Parapolycope psittacina sp. nov. and Parapolycope uncata sp. nov. See Table 1 for locality details.

Figure 8. Scanning electron micrographs of valves of Parapolycope uncata sp. nov., male paratype (SUM-CO-2080) (A, B); male paratype (SUM-CO-2081) (C, D); male paratype (SUM- CO-2082) (E); female paratype (SUM-CO-2088) (F, G); female paratype (SUM-CO-2089) (H, I); female paratype (SUM-CO-2090) (J). (A) External lateral view of right valve; (B) external lateral view of left valve; (C) internal lateral view of left valve; (D) internal lateral view of right valve; (E) dorsal view of carapace; (F) external lateral view of right valve; (G) external lateral view of left valve; (H) internal lateral view of left valve; (I) internal lateral view of right valve; (J) dorsal view of carapace.

Figure 9. Scanning electron micrographs of valves of internal lateral views of valve in Parapolycope uncata sp. nov., male paratype (SUM-CO-2081). (A) Anterior part of marginal infold; (B) anterodorsal bar and groove; (C) socket at dorsal end of hinge structure; (D) posterodorsal bar of hinge structure; (E) posterior element of hinge structure; (F) posteroventral groove; (G) anterior part of marginal infold; (H) anterodorsal bar; (I) knob at dorsal end of hinge structure; (J) posterodorsal bar of hinge structure; (K) posterior element of hinge structure; (L) posteroventral bar.

Figure 10. Parapolycope uncata sp. nov., male holotype (SUM-CO-2079). (A) Internal lateral view of left valve; (B) internal lateral view of right valve.

Figure 13. Parapolycope uncata sp. nov., male holotype (SUM-CO-2079) (A); female paratype (SUM-CO-2087) (B). (A) Left lateral view of posterior trunk segment, furca, and copulatory organ of male; (A′) left furca; (A′′) right furca; (B) left lateral view of posterior trunk segment, furca and copulatory organ of female; (B′) left furca; (B′′) right furca. Abbreviations: cd, copulatory duct; fp, furcal projection; fs, female spermatheca.