Neonesidea edentulata, Maddocks, Rosalie F., 2013

Maddocks, Rosalie F., 2013, New and poorly known species of Neonesidea (Bairdiidae, Ostracoda, Crustacea) from French Frigate Shoals, the Hawaiian Islands, Zootaxa 3608 (6), pp. 457-510 : 502-504

Neonesidea edentulata n. sp.

( Figs. 2 , 35–37 )

Etymology. Latin edentulatus, toothless; referring to the shape of the Kauplatte of the masticatory organ.

Material. Four specimens at two localities, including one adult male and three juveniles.

Types. Holotype male 3958M, and three paratype juveniles.

Type locality. French Frigate Shoals, Hawaiian Islands, station FFS–TC–15, 23 o 46.107 N, 166 o 15.689 W, 14 Sep 2000. Central lagoon, W side of La Perouse Pinnacle, depth 3– 7 m.

Dimensions. Holotype male 3958M L 690 μm, H 373 μm. Paratype juvenile L 418 μm, H 212 μm. See also Figure 2 .

Description. Carapace ( Figs. 35 A–H) bairdian in shape, nearly symmetrical, with angular contours and valves of nearly equal size; greatest height located at about one-third length (0.34), greatest thickness located a little anterior to midlength (0.43). Lateral outline of LV with tripartite dorsal margin, anterodorsal segment straight; median segment nearly straight, only very slightly arched, sloping gently from well-marked anterodorsal angle; posterodorsal angle broadly rounded but distinct, posterior segment nearly straight, sloping steeply to distinct, obtuse angle; anterior margin obliquely rounded; ventral margin deeply indented in mouth region; posteroventral margin at first weakly convex, then nearly straight, rising smoothly; posterior end a narrowly rounded, acute angle, subtly caudate, located at one-fourth height (0.26); caudal process flanged but not humped. Fused marginal zone narrow, vestibules deep and broad; false RPC not observable (obscured by setae). LV margins smooth, lacking marginal denticles; RV with narrow chitinous flange along anterior margin and narrow frill along posteroventral margin. Selvage distinctly indented at the posterior end of both valves. NPC simple, most without walls.

Carapace setae ( Figs. 35 A–H) numerous, conspicuous, both light and dark; of many lengths, somewhat longer posteriorly, but none trailing; all of simple form, with thick shafts, stiff, tapering to point, erect or oriented slightly posteriorly. Eyelash setae regularly arrayed along anterior margins of both valves, recognizable by regular spacing, uniform length and curvature, and light color; crowded by numerous simple setae of many sizes and colors, which are also densely, untidily packed at very edge of valve. Posteroventral and ventral margins of both valves have numerous simple setae of all sizes. Caudal process with only simple setae, caudal setae absent; anchor setae absent.

Male antennal claw ( Figs. 35 F, 36F–G, H–J, 37A–B) weakly curved, anterior horn continues profile of claw; anterior horn longer than posterior horn, slender, tapering, with sigmoid posterior margin; posterior horn about the same thickness with similar curvature, tapering; thin tips of both horns bent inward (curved) through 90o; cleft between horns weakly sigmoid with broad opening.

Hemipenis ( Figs. 36 A–E, M, 37F) with wedge-shaped, muscular basal segment; large, oval, folded-lamellar median segment, with reinforced inner edge that projects beyond terminal segment; terminal segment an oblong plate, bluntly terminated except for one long, curved, pointed spine located at upper-inner edge; copulatory tube curved, tapering to a thin, looped thread beyond terminal segment.

Kauplatte ( Figs. 36 L, 37G) of chewing organ lacking marginal teeth along most of the perimeter, having only end teeth separated by gaps from a broad, smooth, nearly straight margin, without any median cleft. Comparisons. None of the species described from Midway or the Hawaiian Islands (Holden 1967, 1976) closely resemble this species.

The carapace shape is rather ordinary, but there are no close similarities to any species of Neonesidea for which the soft parts have been described.

N. edentulata differs from most members of the N. schulzi species-group by the more emphatically bairdian carapace shape (rather than streamlined, teardrop-shaped), the rather small size, and the absence of marginal denticles, terminal spine, and caudal setae. In carapace and soft parts the species shows no close affinity to the N. pateriformis or N. dinochelata species-groups.

The antennal hook is unique, with horns of nearly equal size curved through more than 90o.

The distal spine on the terminal segment of the hemipenis of N. edentulata is a configuration that is shared by several species. In N. edentulata the single spine is on the inner edge; in N. obscura it is also on the inner edge, but much thicker and separated by a deep cleft from the rounded outer lobe; in N. manningi and perhaps in N. maddocksae the spine is on the outer edge. In N. decipiens and N. frequens there are two spines, of which the inner spine is the longer one in N. decipiens and the shorter one in N. frequens . In most of these species the terminal segment is ovate to nearly equant, rather than the more oblong proportions of N. edentulata .

The toothless Kauplatte of the masticatory organ is unique in Neonesidea .

Figures

FIGURE 35. Neonesidea edentulata n. sp., all male specimen 3958 M. A, RV exterior; B, left side of entire animal; C, interior of LV with body; D, anterior margin of LV; E, posterior end of LV; F, right antennal claw, as seen through carapace before dissection; G, posterior end of entire animal from right side, showing numerous simple setae but no caudal setae; H, anterior end of entire animal from right side. Scale bar = 50 μm.

FIGURE 36. Neonesidea edentulata n. sp., all male specimen 3958 M. A – C, dorsal view of right hemipenis, focused from higher to lower; D, E, dorsal view of left hemipenis, focused higher and lower; F, G, right antennal claw; H – J, left antennal claw; K, mouth; L, Kauplatte of masticatory organ; M, dorsal view of both hemipenes and furcae; N, wedge-shaped ends of two proximal segregated setae of vibratory plate of fifth limb. Scale bar = 10 μm.

FIGURE 37. Neonesidea edentulata n. sp., all male specimen 3958 M. A, B, antenna; C, sixth limb; D, seventh limb; E, mouth, F, posterior of body with hemipenis, furca and post-abdominal bristle; G, masticatory organ.

FIGURE 2. L – H scatter plot for Hawaiian records of Bairdia amygdaloides of Brady (1880) and similar species.