Fabaeformiscandona pedana, Smith & Janz, 2008

Smith, Robin J. & Janz, Horst, 2008, Recent species of the Family Candonidae (Ostracoda, Crustacea) from the ancient Lake Biwa, Central Japan, Journal of Natural History 42 (45 - 46), pp. 2865-2922 : 2894-2898

Fabaeformiscandona pedana sp. nov.

( Figures 17 A–D, 18 and 19)

Type locality

Lake Biwa – eastern coast of north basin, locality 42 (35 ° 13954.10N; 135 ° 57949.60E), depth 2 m, substrate large pebbles, sand and gravel.

Type material

Holotype LBM 1430003316 , male, appendages mounted on a glass slide, valves stored in a micropalaeontological cavity slide . Allotype LBM 1430003317 , female, appendages mounted on a glass slide, valves stored in a micropalaeontological cavity slide .

Derivation of name

From the Greek pedanos, meaning short, and referring to the short, stumpy nature of the h lobe of the hemipenis ( Figure 19C ).

Diagnosis

Carapace with dorsal hump at posterior third of length. Male carapace, anterior and posterior margins equally rounded. Female carapace, posterior margin more tightly curved than anterior margin and with sinuous ventral margin. Male right L5 palp rounded and inflated distally. Left palp with elongate finger-like projection distally. L7 limb with five segments. Posterior projection of FRO elongate and well developed. Hp with rounded distal end of m process, h lobe small and slightly curved, a lobe large and rounded along distal edge.

Description

Male carapace length 928 Mm, height 461 Mm, H/L50.5, female length 905 Mm, height 428 Mm, H/L50.47. Dorsal margin of carapace with angular hump at approximately one-third of length from posterior margin. Anterior and posterior margins of male carapace equally rounded. Female posterior margin more tightly curved than anterior margin and with sinuous ventral margin. Both valves of female with large posterodorsal flaps; left valve also with smaller anterodorsal flap. Male carapace with very narrow calcified margin along posterior and posteroventral margins. Female with sinuous calcified lamella along posteroventral margin, wider than male’s. Surface of valves smooth, colour translucent white.

An1 with eight segments, first two of which fused together to produce one large article, with two long setae near apical–ventral corner, and two long setae along dorsal edge. Third segment with one dorsal–apical seta. Fourth segment with one dorsal–apical seta. Fifth and sixth segments both with two dorsal–apical setae and one short ventral–apical seta each. Seventh segment with two long and two shorter apical setae. Final segment with three setae of differing lengths and one aesthetasc.

An2 with slender Y aesthetasc. Male t2 and t3 setae with rounded ends, and claw GM twice length of Gm. Claw G2 of female approximately 60% length of claw G1, Gm about 75% length of GM.

Md with 3+1+beta setae on second segment of palp.

L 5 male palps large and asymmetrical. Left palp with slender, finger-like distal projection. Right palp very inflated distally with pointed anterior edge.

L6 with elongate second segment. Setae e, f and g all approximately equal in length to next segment respectively. Claw h2 relatively long.

L7 five-segmented. Seta d1 short, seta g long, seta h1 relatively short, setae h2 and h3 long and sub-equal in length.

UR male and female with no significant sexual dimorphism, claw Gp approximately 75% length of Ga and seta Sp short. Ramus slightly curved and with inflated, rounded base.

Hp with large striated a lobe with curved distal margin. m process with inflated, bulbous distal end. h lobe short and stubby, slightly curved.

FRO sub-rounded with well-developed, sub-triangular FRO projection.

Remarks

This species is most similar to F. yajimae sp. nov. However, male F. yajimae sp. nov. have a maximum height situated further towards the mid-length of the carapace than male F. pedana sp. nov. Other differences include a shorter G2 claw on the female An2, a much smaller h lobe and a differently shaped a lobe on the hemipenis, and a proportionally smaller FRO projection in F. pedana sp. nov. compared with F. yajimae sp. nov.

Only one male and one female were found of this species in 2 m of water on a substrate of large pebbles, sand and gravel on the western side of the north basin. Locality 42 in Figure 1 .

Figures

Figure 1. Location of Lake Biwa and sampling localities.

Figure 17. (A–D) Fabaeformiscandona pedana sp. nov. (A) Male, right valve, external view (LBM 1430003316); (B) female, right valve, external view (LBM 1430003317); (C) dorsal view of female left valve (LBM 1430003317); (D) dorsal view of female right valve (LBM 1430003317). (E–G) Fabaeformiscandona nishinoae sp. nov. (E) Male, whole carapace, right lateral view (LBM 1430003318); (F) female, whole carapace, right lateral view (LBM 1430003319); (G) dorsal view of female, anterior to right (LBM 1430003320). (H–J) Fabaeformiscandona akaina sp. nov. (H) Male, whole carapace, right lateral view (LBM 1430003324); (I) female, whole carapace, right lateral view (LBM 1430003325); (J) dorsal view of female, anterior to right (LBM 1430003325). (K,L) Pseudocandona sarsi. (K) Female, whole carapace, right lateral view (LBM 1430003328); (L) female, whole carapace, dorsal view, anterior to right (LBM 1430003328). Scale bar below L represents 515 Mm for A–D, 618Mm for E–G, 761Mm for H–J, 510Mm for K and L.

Figure 19. Fabaeformiscandona pedana sp. nov. (A) L6 (LBM 1430003316); (B) female UR and FRO (LBM 1430003317); (C) Hp (m process shaded grey) (LBM 1430003316).