Pratherodesmus voylesi Shear

Shear, William A., Taylor, Steven J., Wynne, Judson & Krejca, Jean K., 2009, Cave millipeds of the United States. VIII. New genera and species of polydesmidan millipeds from caves in the southwestern United States (Diplopoda, Polydesmida, Macrosternodesmidae), Zootaxa 2151, pp. 47-65 : 51-54

Pratherodesmus voylesi Shear , new species

Figs. 2 , 6 , 9 , 11–14 , 19, 33, 36.

Types: Male holotype, five male and seven female paratypes from Millipede Cave, Mojave Co., Arizona, collected 16 February 2003 by K. Voyles, J. Jasper, M. Porter and K. Dittmar de la Cruz, deposited in FMNH. Four male and sixteen female paratypes from October Gyp Cave, collected 27 March 2004 by same collectors. All specimens deposited in FMNH and CPMAB.

Description: Male. Length, 7.5 mm, width 0.75 mm. Antennae long, extended backward reaching to posterior border of sixth segment. Head 20–25% wider than collum, anterior margin of collum ( Fig. 2 ) nearly semicircular, with 10 marginal setae, posterior margin with six marginal setae, nearly straight; middle row with four setae. Typical midbody segment (segment 10; Fig. 6 ) with metazonite as broad as long, three prominent lateral marginal teeth, posteriolateral angles moderately extended beyond ozopores; marginal teeth each with seta; anterior setal row recurved, with six setae, posterior row nearly straight, with four setae, posterior marginal row with four setae; three setae arranged around ozopore. Posteriorly, setation of anterior row increases to eight. Pygidium ( Fig. 9 ) nearly hemispherical in dorsal view, with about 10 setae visible dorsally, pygidial process short, with four spinnerets arranged in square, typical of polydesmideans. Legs long, slender.

Pregonopodal legs slender, unmodified. Gonopods ( Figs.11–14 , 33 ) with hemispherical coxae filling gonostome, tightly appressed, probably immovable, anteriorly excavate to receive telopodites. Prefemora strongly transverse, sparsely setose, distally narrowed to short stem connecting to acropodite. Exomere absent. Endomerite large, blunt, complex, with prominent lateral notch. Course of seminal canal along femorite straight. Solenomere with fine cuticular scales near seminal opening, subtended by short process; apical zone small, flattened, curved, ridged.

Female. Length, 8.2 mm, width, 0.9 mm. Nonsexual characters as in male, but segmental setae longer, more acute, body less slender. Cyphopods as single fused organ (Fig. 19), evidently permanently extruded, with two anterior pores.

Distribution and habitat: Known only from the two caves named above, located in the northeastern corner of Mohave Co., Arizona, on BLM-Arizona Strip Field Office lands. The exact location of the caves is not given because of conservation concerns.

Millipede Cave (elevation 1371 m [4497 ft.]) is a limestone and gypsum cave with 274 m (900 ft.) of mapped passage. This cave has a vertical entrance approximately 2 by 4m. Average passage height is <2m. The cave floor is characterized by areas of medium to small breakdown, with unconsolidated silts and sands, stream gravels and exposed bedrock. A single trunk passage is characterized by medium-sized rooms; cave roof height varies from walkable to crawling passage. At the back of the cave, there are three large pools which create ~100% rH (relative humidity) at this depth, where the accessible cave ends in a sump. Floods periodically transport significant amounts of vegetation into this cave, including various types of weeds e.g., Russian thistle ( Salsola kali ), black brush ( Coleogyne ramosissima ), rabbit brush ( Chrysothamnus molestus ) and creosote ( Larrea tridentata ). Logs and branches have also been washed in; however, the source of this larger material is unknown. Detritus often covers portions of the cave floor and forms mounds towards the back of the cave. P. voylesi is commonly observed on this material; we suggest this animal is either feeding on detritus, or on fungus or bacteria growing on detritus. Individuals of P. voylesi occur from approximately 60 m (200 ft.) within the cave to ~ 121 m (400 ft.) up to the sump. Unflooded passage does occur beyond the sump; however, it is unknown whether this species occurs in that part of the cave. Other arthropods detected in the cave include spiders (spp. not known) and pillbugs ( Porcellio laevis , det. Stefano Taiti). Surface vegetation is inter-mountain basins mat saltbush shrubland (SWReGAP land cover type; Lowery et al. 2006).

October Gyp Cave (elevation 1392 m [4566 ft.]) is a linear phreatic tube with two levels, and consists of 269 m (882 ft.) of passage. This cave has a vertical entrance ~ 2m in diameter. The upper extent is characterized by dry limestone passage, while the lower passageway is moist to wet gypsum. The lower passage contains 30m (100 ft.) of walkable passage tapering to a series of belly crawls to hands-and-knees crawls. The upper level is exposed hardpan with no millipeds, while the lower level is silt to silty clay; this is where the millipeds occur. This cave receives little to no flood detritus. Millipeds are observed from ~ 134 m (440 ft.) onward to the terminus of the cave. Other arthropods observed in the cave include crickets ( Ceuthophilus sp.) and beetles (Family Tenebrionidae ). Surface vegetation is inter-mountain basins mixed salt desert scrub (SWReGAP land cover type; Lowery et al. 2006).

There is one cave within two miles of Millipede and October Gyp caves that contains polydesmid milllipeds. While unconfirmed, this likely represents an additional locality of this new species. In the course of the survey that produced this species, about 300 individual caves were visited, and only the three mentioned here were found to support milliped populations. This does not prove the millipeds are absent from these caves, but they were not found during the time available for exploration.

Etymology: Named for Kyle Voyles, Arizona BLM Cave Coordinator, who organized and led the collecting effort that resulted in the type specimens.

Figures

FIGURES 1, 2. Heads, collums and first two segments of males, dorsal view. Fig. 1. Pratherodesmus despaini. Fig. 2. P. voylesi.

FIGURES 3 – 6. Segments 10, dorsal view. Fig. 3. Nevadesmus ophimontis. Fig. 2. Pratherodesmus ecclesia. Fig. 3. P. despaini. Fig. 6. P. voylesi.

FIGURES 7 – 10. Figs. 7 – 9. Pygidia, dorsal view. Fig. 7. Nevadesmus ophimontis. Fig. 8. Pratherodesmus despaini. Fig. 9. P. voylesi. Fig. 10. Metazonital setae anterior to ozopore of segment 10, Nevadesmus ophimontis.

FIGURES 11 – 14. Gonopods of Pratherodesmus voylesi. Fig. 11. Gonopods in gonostome, ventral view. Fig. 12. Posterior view. Fig. 13. Lateral view. Fig. 14. Solenomere, distal zone, and subtending process, posterior view.

FIGURES 30 – 35. Drawings of gonopods. Figs. 30, 31. Nevadesmus ophimontis. Fig. 30. Lateral view. Fig. 31. Mesal view. Fig. 32. Pratherodesmus despaini, posteriolateral view. Fig. 33. P. voylesi, mesal view. Figs. 34, 35. P. ecclesia. Fig. 34. Posterior view. Fig. 35. P. despaini, mesal view.