Oribatella oregonensis, Behan-Pelletier & Walter, 2012

Behan-Pelletier, Valerie M. & Walter, David E., 2012, 3432, Zootaxa 3432, pp. 1-62 : 31-34

Oribatella oregonensis sp. nov.

( Figs. 15, 16, 18B, C, 28F, 30D)

Material examined. Holotype: female USA: Oregon, Tillamook Co., Cliff Creek Trail, 19.xii.1976 (L. Russell) deposited in the CNC, type number 24042 . Paratype s: 9 females 10 males with same data as holotype . Paratypes deposited in the CNC, RNC and the USNM.

Diagnosis. Total length of adult 405–460 µm. Rostral margin medially flattened or undulating with two small lateral teeth; rostrum without strong medial crest. Lamellar cusps parallel medially and contiguous, separated posteromedially so that prodorsum visible through oval opening, about 5 µm wide; translamella without tooth, about 5 µm at greatest width, 10 µm deep. Dentes on lamellar cusp very short: medial dens 18–21 µm long, without teeth, lateral dens 21–23 µm long with 1–2 teeth. Bothridial seta 88–139 µm long, with barbed head, isodiametric along length, tapered distally. Custodium about 48 µm long, very narrow along length. Female with four welldefined pairs of porose areas without deep pore canals; male with two pairs, Aa, and fused A1–A3, in approximately same position as A 3 in female. In female, setae lm posteriad Aa, and lp anteriad A1. In male, setae lm posteriad Aa, lp, h 3 and h 2 closely adjacent and borne approximately in middle of fused porose area A1–A3. In both sexes setae h 1 shorter than other h setae, projecting posteriorly. Tarsi monodactylous.

Description. Adults. Dimensions: Total length: females (n = 10) 451 µm (range 430–460); males (n = 10) 433 µm (range 405–450). Notogastral width: females (n = 9) 305 µm (range 300–315); males (n = 8) 298 µm (range 280–310).

Integument: Prodorsum, notogaster, anal plates, genital plates, venter and mentum micropunctate. Lamellae with distinct irregular striae laterally with finer striae medially; pedotectum I and pteromorph with short irregular striae.

Prodorsum: Rostral margin medially flattened or undulating with minute lateral teeth. Lamella 148–152 µm long, of which cusp 94–97 µm long, 38–45 µm wide at level of insertion of seta le. Lamellar cusps parallel medially; separated posteromedially leaving prodorsum visible through oval opening, about 5 µm wide; translamella without tooth, about 5 µm at greatest width, 10 µm deep ( Figs 15, 18B). Dentes on lamellar cusp very short ( Fig. 18B): medial dens 18–21 µm long, without teeth, shorter than lateral dens 21–23 µm long with 1–2 teeth ( Figs 15, 18B). Seta ro 74–101 µm long, strongly barbed along length, acuminate, curved anteromedially. Seta le about 56 µm long, thick, heavily barbed, tapered. Seta in 115–142 µm long, thick (less so than le), barbed, tapered, parallel; mutual distance of pair 46–49 µm. Bothridial seta 88–139 µm long, with barbed head, isodiametric along length, tapered distally ( Figs 15, 18B). Exobothridial seta about 16 µm long, thin, smooth.

Lateral region of podosoma: Genal tooth broad, subrectangular, with dens ventrodistally, with longitudinal ridge ventrolaterally. Tutorium broad rectangular about 154 µm long, of which cusp about 86 µm long, rectangular, distal margin with about 6 teeth. Custodium about 48 µm long, very narrow along length ( Fig. 28F). Porose area Al about 8 µm in diameter.

Notogaster: Length subequal to width. Anterior margin undulating, convex region lateral of bothridium with 8–11 transverse ridges. Pteromorph with irregular striae; with small dens on anteroventral margin. Octotaxic system in form of relatively large porose areas, without deep pore canals. Female with four well defined pairs 13–15 µm arranged as in Fig. 16; porose areas A1–A3 more closely positioned than in other known species of Oribatella . Male with two pairs: Aa, and fused A1–A 3 in approximately same position as A 3 in female, Aa about 18 µm, fused porose area about 27 µm wide, 34 µm long ( Fig. 15, 18C, 30D). Ten pairs of weakly barbed notogastral setae present, about 25–68 µm long, with c seta longest. In female, setae lm posteriad Aa, and lp anteriad A1 ( Fig. 16). In male, setae lm posteriad Aa, lp, h 3 and h 2 closely adjacent and borne approximately in middle of fused porose area A1–A3 ( Figs 15, 18C, 30D). In both sexes seta h 1 shorter than other h setae, projecting posteriorly rather than curved as other notogastral setae ( Figs 15, 16). Mutual distance of h 1 –h 1 45–49 µm, and p 1 –p 1 27–29 µm; mutual distances subequal in both sexes ( Figs 15. 16). Lenticulus not evident.

Ventral Region: Epimeral setae mostly about 13–48 µm long, all weakly barbed acuminate, with 3c thickest; 3b, 3c and 4b longest epimeral setae, about 30–38 µm long, with 3c longest ( Fig. 28F). Genital, anal and adanal setae weakly barbed, about 10–13 µm long; genital setae in a curved row on plates, 1+5. Aggenital setae about 12 µm. Lyrifissure iad anterolateral of anal plate. Postanal porose area about 25 x 5 µm.

Gnathosoma : Anterior border of mentum without thickened transverse ridge, without tectum. Axillary saccule about 6 x 2 µm.

Legs: Setation (I to IV): trochanters, 1-1-2-1; femora, 5-5-3-2; genua, 3(1)-3(1)-1(1)-2; tibiae 4(2)-4(1)-3(1)- 3(1); tarsi, 20(2)-15(2)-15-12. Seta l” genua I and II about 29 and 18 µm, respectively; l” of tibiae I and II about 27 µm. Tarsi monodactylous.

Etymology. This species is named for the State of Oregon, the only place in which it has been found to date.

Remarks. This is the second species of Oribatella known to have distinct sexual dimorphism. As in the other species, O. canadensis , dimorphism is expressed as a modification of the octotaxic system in the male. In both species there is a fusion of porose areas: A1–A 3 in O. oregonensis , A2 and A 3 in O. canadensis . This variation in expression of sexual dimorphism is similar to that found in some genera of the Oripodoidea, Ceratozetoidea and Galumnoidea ( Behan-Pelletier & Eamer 2010). However, only in O. oregonensis is there a close association of notogastral setae with the modified porose area.

Distribution and Ecology. This species is known only from Oregon. The specific habitat of the type series is unknown, other than the type locality is in an area of mixed west-coast forest.