Pseudocandona atmeta, Smith & Kamiya, 2015

Smith, Robin James & Kamiya, Takahiro, 2015, Four new species of the subfamily Candoninae (Crustacea, Ostracoda) from freshwater habitats in Japan, European Journal of Taxonomy 136, pp. 1-34 : 11-17

Pseudocandona atmeta sp. nov.

urn:lsid:zoobank.org:act:CE81B0CC-F7FD-46EF-87DD-CCD6907068ED

Figs 2 F–I, 6B, 7A–B, 8–10

Diagnosis

Carapace relatively large (approximately 1.2 mm in length) and high (height/length = 0.67), with maximum height posterior of mid-length, marked by dorsal hump. Hinge slightly curved anterior of dorsal hump, steeply sloping down towards anterior margin. Male antenna with undivided second endopodal segment, and with no male bristles. Female antennal claw G2 approximately half length of claw G3. Mandible with 3+1+beta setae on second segment of palp, and with long gamma seta and very short alpha and beta setae; beta slightly shorter than alpha. Walking leg with long d1 seta, and with e, and f setae shorter than next segment respectively. Seventh limb with five segments, terminating with long h2 and h3 setae of approximately equal length, and short, reflexed and curled h1 seta. Medial lobe (h) of hemipenis extending beyond outer lobe (a); outer lobe distally sub-quadrate, inner lobe (b) folded at inner edge. Female genital lobe triangular in shape with apical protuberance.

Etymology

From the Greek atmetos, meaning “undivided”, and referring to the second endopodal segment of the male antenna, which is undivided in this species.

Type material

Holotype

♂ ( LBM 1430006270 ), dissected with appendages sealed in a glass slide and valves stored dry in a micropalaeontological cavity slide. Collected from the type locality on 27 Sep. 2004.

Allotype

♀ ( LBM 1430006271 ), dissected with appendages sealed in a glass slide and valves stored dry in a micropalaeontological cavity slide. Collected from the type locality on 27 Sep. 2004.

Paratypes

1 ♂ ( LBM 1430006272), whole, stored dry in a micropalaeontological cavity slide. 1 ♀ ( LBM 1430006273) whole, stored dry in a micropalaeontological cavity slide. 1 ♀ ( LBM 1430006274) valves, stored dry in a micropalaeontological cavity slide. All collected from the type locality on 27 Sep. 2004.

Type locality

Sarugamori, Higashidori, Shimokita District, Aomori Prefecture, Japan, 41º16’00.6” N, 141º22’38.4” E. Boggy, marshy area with little standing water, lots of reeds, and sodden ground. Locality 4 on Fig. 1 .

Other material examined

68 ♂♂, 33 ♀♀, from the type locality, collected 27 Sep. 2004. 1 ♂ from a small swampy area surrounded by trees, reeds and moss at Higashidori, Shimokita District, 12.

Description

Carapace ( Figs 2 F–I, 7A–B, 8A–B). Male length 1137–1227 µm, height 657–760 µm. Female length 1028–1157 µm, height 631–689 µm. Male with distinctive dorsal hump posterior of mid-length. Hinge slightly curved anterior of dorsal hump, steeply sloping down towards anterior margin. Anterior margin unevenly curved, with apex of curve below mid-height. Posterior margin more inflated than anterior margin and unevenly curved, with apex below mid-height. Ventral margin slightly concave. Dorsal view ovoid, anterior slightly more pointed than posterior. Inner calcified lamella wide anteriorly and narrow posteriorly, narrowest along posterior margin, widening slightly at postero-ventral margin. Six to seven small adductor muscle scars in tight formation at mid-height, anterior of mid-length. Indistinct dorsal scars near dorsal margin. Female similar to male, but slightly less elongate. Colour, white. Surface covered with stiff setae and small, shallow pits (observed with scanning electron microscopy) ( Fig. 7B ).

Antennule with seven articulated segments ( Fig. 8C ). First segment large, supporting two setae on dorsal edge and two long setae on ventral-apical corner. Second and third segments quadrate each with one dorsal-apical seta each. Fourth and fifth segments each with two long dorsal-apical setae and one short ventral-apical seta. Sixth segment with two long and two short apical setae. Final segment with two long and one short setae, and aesthetasc ya.

Male antenna with three-segmented endopodite (second endopodal segment not divided and with no male bristles) ( Fig. 8 D–E). Setae z2 and z3 very short. Claw G1 about half length of claw G2 and z1. Claw Gm on final segment half length of claw GM.

Female antenna ( Fig. 8F ) with claw G2 about half length of G1, z1 stout and claw-like, about half length of G2, setae z2 and z3 very short. Claw Gm approximately three-fourths length of claw GM.

Mandibular palp ( Figs 8G , 9A & B ) with four segments. Alpha and beta setae very small, sub-equal in length. Inner edge of second segment with 3+1+beta arrangement of setae. Outer edge with two apical setae. Third segment with three long sub-apical setae on outer edge, and three long and one short setae arranged along apical edge; outer-most gamma seta, long and without obvious setules. Final segment with two claws and three setae. Number of rays on branchial plate not observed.

Maxillula ( Fig. 9C ) palp first segment with three setae on apical outer margin, and one apical seta offset towards inner edge. Second segment with stepped apical margin, with outer part more distal than inner part. Outer part of apical margin with two long and one short setae, and inner part with three mid-length setae. Branchial plate with morphology typical of subfamily, consisting of 18 normal and six reflexed rays.

Fifth limb palps of male asymmetrical ( Fig. 9 E–F). Right palp widens distally to large bulbous hookshaped end, with two sub-apical setae towards inner edge. Left palp distally narrower than right, sinuous, with finger-like, crooked distal hook, and with two sub-apical seta.

Fifth limb of female ( Fig. 9D ) with one a-seta, and setae b, c and d present; b and d long. Endite with approximately 15 apical setae. Palp (endopodite) stout, terminating with three short setae of differing lengths. Branchial plate with one long and one short ray.

Sixth limb ( Fig. 9G ) first segment bearing long d1 seta. Setae e and f of second and third segments respectively, both less than half length of next respective segment. Fourth segment with g seta reaching to end of fifth segment. Fifth segment with short h1 seta, tiny h3 seta and well-developed claw h2.

Seventh limb with five segments ( Fig. 9H ). First segment with long dp seta, medium-length d1 seta and shorter d2 seta. Second and third segments with no setae. Fourth segment with long g seta. Fifth segment approximately quadrate, h2 and h3 long and of equal length, h1 short, hook-like and reflexed.

Male caudal ramus ( Fig. 10B ) with inflated base, tapering distally, slightly curved to straight. Claw Ga straight proximally, curving distally. Claw Gp slightly shorter and thinner than Ga and slightly sinuous. Seta sa short, seta sp long, approximately two-thirds length of claw Gp. Caudal ramus attachment with rounded dorsal end, and with one posterior branch and two anterior branches on dorsal-most half.

Female caudal ramus ( Fig. 10A ) similar to male, but claws slightly more robust. Caudal ramus attachment with one posterior branch and two anterior branches, lowest of which curves to posterior edge of female genital lobe. Female genital lobe ( Fig. 10A ) large and triangular, with distinctive projection on apex.

Hemipenis ( Fig. 10C ) relatively large and wide. Outer lobe (a) tongue-like, with sub-quadrate distal end. Base of outer lobe with rounded, well chitinized protuberance that contacts M-process (marked with asterisk on Fig. 10C ). Inner lobe (b) folded, producing angular projection on inner edge. Medial lobe (h) unevenly rounded, extending beyond both outer and inner lobes. M-process with rounded proximal base, tapering to curved middle section with small lobe on inner edge, and expanding distally to small, quadrate end. Notch on outer edge near tip contacting protuberance of outer lobe (a). Bursa copulatrix (e) elongate, tapering distally, and with backward curled tip.

Remarks

The carapace of Pseudocandona atmeta sp. nov. in lateral view is most similar to that of Pseudocandona marchica (Hartwig, 1899) . However, these two species can be distinguished by the following features: the penultimate segment of the antennae is sub-divided and has male bristles in P. marchica , whereas Pseudocandona atmeta sp. nov. lacks this sub-division and male bristles; the Gp claw of the male’s caudal ramus is reduced in P. marchica , whereas in Pseudocandona atmeta sp. nov. this claw is of typical length, albeit slender and slightly sinuous. The hemipenes of P. marchica are noticeably of different shape compared with those of Pseudocandona atmeta sp. nov., in particular the outer lobe (a) of Pseudocandona atmeta sp. nov. is more quadrate, and the inner lobe (b) smaller, while the entire body of the hemipenes are relatively wider compared with those of P. marchica ; the female genital lobe is triangular in Pseudocandona atmeta sp. nov. whereas it is rounded in P. marchica . Other species of the rostrata -group have lower lateral views of the carapace, and all have differently shaped hemipenes and female genital lobes compared with Pseudocandona atmeta sp. nov. Additionally, Pseudocandona atmeta sp. nov. is the only member of the rostrata -group without a sub-division of the second endopodal segment of the male antennae and lacking male bristles.

Ecology and distribution

The type locality of Pseudocandona atmeta sp. nov. is a small boggy area covered by reeds and grasses, surrounded by trees. At the time of collecting, there was very little standing water, although the ground was sodden. Pseudocandona atmeta sp. nov. was found in a small, shallow pool amongst the vegetation, and in a small overgrown channel.

A second locality (also in Higashidori, Aomori Prefecture) yielded one male specimen of Pseudocandona atmeta sp. nov., together with Pseudocandona tenuirostris Hiruta & Mawatari, 2013 (see under Pseudocandona tenuirostris for a description of this locality). Currently, this species is only known from the Higashidori region of Aomori Prefecture.

Figures

Fig. 2. A–E. Pseudocandona becca sp. nov. A. Right view of male carapace (LBM 1430006268). B. Right view of female carapace (LBM 1430006269). C. Dorsal view of female carapace, anterior to left (LBM 1430006269). D. Internal view of female left valve (LBM 1430006269). E. Internal view of female right valve (LBM 1430006269). F–I. Pseudocandona atmeta sp. nov. F. Right view of male carapace (LBM 1430006272). G. Right view of female carapace (LBM 1430006273). H. Internal view of female left valve (LBM 1430006274). I. Internal view of female right valve (LBM 1430006274).

Fig. 1. Map of the main islands of Japan, showing the localities mentioned in the text.

Fig. 7. A–B. Pseudocandona atmeta sp. nov. A. Dorsal view of male carapace, anterior to left (LBM 1430006272). B. Detail of external surface of male right valve (LBM 1430006272). C–F. Pseudocandona falcula sp. nov. C. Right view of female carapace (LBM 1430006278). D. Dorsal view of female carapace, anterior to left (LBM 1430006278). E. Internal view of female left valve (LBM 1430006277). F. Internal view of female right valve (LBM 1430006277). G–H. Candona candida (O.F. Müller, 1776) G. Internal view of female left valve. H. Dorsal view of female carapace, anterior to left. Scale bar: A, C–F = 500 µm; B = 134 µm; G–H = 412 µm.

Fig. 8. Pseudocandona atmeta sp. nov. A. Internal view of male left valve (LBM 1430006270). B. Internal view of female left valve (LBM 1430006271). C. Male antennule (LBM 1430006270). D. Male antenna (LBM 1430006270). E. Detail of male antenna (LBM 1430006270). F. Detail of female antenna (LBM 1430006271). G. Male mandible (LBM 1430006270). Scale bar: A–B = 710 µm; C–D, G = 200 µm; E–F = 122 µm.

Fig. 9. Pseudocandona atmeta sp. nov. A. Male mandibular palp (LBM 1430006270). B. Detail of alpha and beta setae of mandibular palp (LBM 1430006270). C. Male maxillula (setae on endites not drawn) (LBM 1430006270). D. Female fifth limb (LBM 1430006271). E. Male left fifth limb palp (LBM 1430006270). F. Male right fifth limb palp (LBM 1430006270). G. Male sixth limb (LBM 1430006270). H. Male seventh limb (LBM 1430006270). Scale bar = 200 µm.

Fig. 10. Pseudocandona atmeta sp. nov. A. Female caudal ramus and genital lobe (LBM 1430006271) (FGL = female genital lobe). B. Male caudal ramus (LBM 1430006270). C. Hemipenis (M-process shaded grey) (LBM 1430006270), asterisk marks protuberance of outer lobe (a) that contacts M-process. Scale bar = 200 µm.