Amplaria nazinta ( Chamberlin), 1910

Shear, William A., Nosler, Philip & Marek, Paul, 2017, The identity of Amplaria nazinta (Chamberlin, 1910): a century-old millipede mystery resolved (Diplopoda, Chordeumatida, Striariidae), Zootaxa 4311 (2), pp. 233-240 : 234-239

Amplaria nazinta ( Chamberlin), 1910

Figs. 1–15

Striaria nazinta Chamberlin 1910 , p. 242; Loomis 1936, p. 408.

Amplaria nazinta, Chamberlin, 1941 , p. 9; Causey 1958, p. 180; Shear & Krejca 2007, p. 26.

Designation of neotype. In the absence of a type specimen, we designate the following as the neotype: male specimen from Oregon, Multnomah Co., Portland , Powell Butte Park , 45.488820, –122.513119. Specimen deposited in the Virginia Museum of Natural History , Martinsville , Virginia ( VMNH) . Additional specimens from nearby Towle Butte (45.467431, –122.449857) have also been deposited at VMNH .

Diagnosis. Amplaria nazinta differs from other known species of Amplaria in the form of the gonopods, in the reduced spines of the male labrum, in the presence of needle-like setae on the first legs of the males and the scarcely detectable (but present, see below) segmental setae.

Etymology. Chamberlin, in addition to his biological work, was an ethnographer who lived with and studied the Goshute Indians of Utah. He often used Goshute words as genus or species names, and in 1908, he published a list of anatomical terms and animal names in the Goshute language. Chamberlin (1908) explained that na as a prefix designates a support, instrument or means. An example he gives is na’dzi ta, meaning a walking stick, or cane. While the connection with the millipede is unclear, we suspect that this is the source of the name, though the spelling “ nazinta ” does not appear in the 1908 publication.

Description of male from Powell Butte Park: Length, about 10 mm, width about 0.9 mm. Color pale creamy tan, with mottled purplish highlights along crests and segment margins; legs mottled purple. Head ( Fig. 2 ) robust, with central and posterior areas of nodular sculpture. Three to 5 poorly pigmented ocelli on each side. Antennae typical. Labrum (lab) with slightly produced posteriolateral corners. Collum (col) and succeeding metazonites with 12 crests, the 6th (lateralmost) crest on collum about one-fourth length of 5th. Anterior region of collum set off by distinct depression, strongly rimmed anteriorly, with nodular sculpture ( Fig. 2 ). First to 4th metazonites broadly expanded ventrolaterally; first metazonite (collum) with ventrolaterally flared lateral margins, appearing as earflaps of an aviator hat. Crest 6 complete on metazonites posterior to collum, crests 2, 3 the largest, crest 1 lower, distinctly angled posteriorly ( Fig. 3 ). Between crests scattered nodules present; entire surface covered with cerotegument (secreted epicuticular waxy covering), including microscopic granules ( Figs 11, 12 ). Segmental setae ( Fig. 7 ) not visible using light microscopy, highly reduced (40–50 micrometers long) but still present; sockets short-tubular, setae ending in multiple teeth. Central posterior margin of metazonites with limbus consisting of 8– 12 rounded tabs ( Fig. 12 ). Epiproct ( Figs. 3 [ep], 13) deeply trilobed, lacking crests, dense sculpture of distinct knobs densely covered by tiny granules. Legpair 1 ( Fig. 4 ) robust, prefemora (pf), tibiae (ti), tarsi (t) set ventrally with long, needle-like setae ( Fig. 10 ). Second leg trochanters bearing ventral knob. Third legpair with coxae modified (cp3, Fig. 5 ), closely appressed in midline; telopodites reduced, prefemora (pf3, Fig. 5 ) with ventrodistal processes. Legpairs 4–7 incrassate, strongly flattened dorsoventrally, set with setae typical of Amplaria ( Fig. 8 ).

Gonopods ( Figs. 14, 15 , 17, 18 ) with well-sclerotized colpocoxites (cpx) laterally, bearing one large, one small tooth distally and small array of denticles. Anterior angiocoxites (aacx) closely appressed in midline, with simple termination and small lateral hook. Flagellocoxites (f) 4, sheathed by short anterior branch of posterior angiopocoxite (pacx). Posterior branch of colpocoxite strongly arcuate, terminus resembling crested head of a bird. In situ, gonopods lie in depression in coxosternum (st) of legpair 9 ( Fig. 16 ), locked in position by singlearticled telopodites (tel); telopodites of legpair 9 with setae similar to those on walking legs but slightly modified in different regions ( Figs. 6, 8 ). Coxal part of coxosternum with gland pores and posteriolaterally curved distal process (sp, Fig. 16 ).

Female ( Fig. 1 ): similar to male in nonsexual characters. Ventrolateral margin of metazonite 2 broadly enlarged.

Notes. Habitat: Amplaria nazinta was collected on two forested, extinct cinder cones in the Boring Volcanic Field near Gresham, OR, USA. Amplaria nazinta has so far been confirmed from only Powell Butte (45.488820, – 122.513119) and Towle Butte (45.467431, –122.449857), but it can likely also be found on any of the other, similar buttes in the Boring Volcanic Field. The forest habitat is representative of the Portland, OR region, comprising lowland mixed coniferous/deciduous forests, with a plant community similar to that of Forest Park to the west. Characteristic plant species of these forests are Douglas Fir ( Pseudotsuga menziesii (Mirb.) Franco ), Big-leaf Maple ( Acer macrophyllum Pursh ), Red Alder ( Alnus rubra Bong. ), Western Red Cedar ( Thuja plicata Donn ex D. Don ), Vine Maple ( Acer circinatum Pursh ), Red Elderberry ( Sambucus racemosa Linnaeus ), Huckleberry ( Vaccinium Linnaeus ), Western Sword-fern ( Polystichum munitum (Kaulf.) C. Presl ), Stinging Nettle ( Urtica dioica Linnaeus ), Oregon Grape ( Mahonia aquifolium (Pursh) Nutt. ), Bedstraw ( Galium sp.), and Fringe Cup ( Tellima grandiflora (Pursh) Douglas ex Lindl. ).

The soil type at the Powell Butte collection locality is Quatama loam, and the slope is 15–30% (on a slope of a seasonal creek gully, USDA Web Soil Survey). The soil type at the Towle Butte collection locality is Cascade silt loam, and the slope of the land is 30–60% (USDA Web Soil Survey). The underlying lava flow has weathered to create a 1.5–4.5 m layer of red clay soil ( Trimble 1963).

All specimens were found under fallen Big-leaf Maple ( Acer macrophyllum Pursh ) branches that averaged 75 to 100 mm in diameter. Common co-inhabitants of this micro-habitat include isopods, lancetooth snails, beetles, ants, springtails, and soil mites.

Most often, A. nazinta occurred as small, localized groups of individuals. Within a 12-m2 area, seven individuals (four males, three females) were found on Towle Butte. The only two Powell Butte collections known were made within ca. 15 meters of each other, although the entire gully and the adjacent ridge were also searched. This clumped distribution could be explained by a life history where the millipedes remain relatively sedentary during initial development and throughout the relatively drier summer, and then disperse when individuals are closer to maturity later in the year, when the temperature cools and rain starts falling more consistently. The patchy distribution may also be a result of scattered Big-leaf maples, upon which A. nazinta may feed. On 9th April 2017, an adult male was found in the company of two juveniles, so breeding may occur in late winter to early spring, the time period in which adult male specimens have been recorded. The presence of mid-instar juveniles and mature males at the same time may indicate a two-year or multi-year life history.

Distribution. Amplaria nazinta is the northernmost of the described species of the genus; others are from the San Francisco Bay region, the Sierra Nevada of California and caves in Shasta Co., California [ Amplaria shastae ( Causey, 1958) ], so a considerable gap including most of southern Oregon seems to intervene. However, an undescribed species of Amplaria from Humboldt and Mendocino Counties, California; and a second from Linn, Morrow and Tillamook Counties, Oregon, bridge this geographic gap, and further undescribed species have been collected in Washington and Idaho. The southernmost named species is A. muiri Shear & Krejca, 2007 from caves in Tulare Co., California, and an undescribed species has been collected from Mt. Palomar, San Diego Co. These new species will be named and described in a subsequent paper.

Morphology and systematics. Among the many peculiarities of striariids among chordeumatidan millipedes are their unusually heavy sclerotization, cerotegument, hood-like collum, unique ridged tergal sculpture, and the remarkable array of specialized setae on the appendages, as well as a reduction in many taxa of the characteristic chordeumatidan metatergal setae to very small, unusually shaped remnants.

The heavy cuticle, broad collum and tergal ridges may be associated with life in the soil, as adaptations to resist crushing forces as the animals push their way among soil particles. When disturbed, the millipedes roll into a disc with the head concealed and the heavy cuticle may also be an adaptation to protect against predation. The cerotegument could be an adaptation to, in the case of all western North American species, seasonal drought. The eastern species are often found in habitats generally considered too dry for most millipedes, which lack a waxy epicuticle. The cerotegument of the legs and pleurotergites seems to consist not only of a layer of wax, but also of tiny granules. Where the cerotegument has been scraped away, the underlying cuticle appears very smooth, with scattered nodules each bearing a pair of acute projections ( Fig. 11 ). At very high magnification (>3000X), a small pore can be made out between these projections, and this may be the source of the cerotegument itself; between the nodules there are no discernable pores.

To our knowledge, the limbus illustrated here is the first found in the order Chordeumatida . Schmidt (1962) did not find a limbus in three European chordeumatidan species she examined, but of course many more species remain unstudied. The elaborately specialized setae on the legs often have their details obscured by the cerotegument; some of them occur only in the males and may have a role in detecting and identifying females; this may be the case in the long, rigid, needle-like setae found only on the first legs of the male.

Shear and Krejca (2007) provided detailed descriptions and illustrations of two species, A. muiri Shear & Krejca, 2007 and A. adamsi Shear & Krejca, 2007 . Both of these species inhabit Sierra Nevada caves at the southern end of the known range of the genus and differ from A. nazinta in several respects. The setae of the first legs of males, while modified, are dissimilar to those of A. nazinta (cf. Fig. 6 in Shear & Krejca 2007), the third coxae are differently modified, the spines at the corners of the mentum are long and sigmoid and the telopodites of the ninth leg of the two Sierra species do not have a long distal process. These species also have obvious, easily seen segmental setae, especially on the anterior segments. The setae on the legs of A. nazinta differ from those of the two Sierra species in having a dorsal crest of filaments ( Fig. 10 ). Nevertheless, the conformation of the gonopods establishes A. nazinta as a member of the genus.

Figures

FIGURES 1, 2. Amplaria nazinta (Chamberlin, 1910). Fig. 1, habitus of adult female. Fig. 2, frontal view of head and collum of mature male. Col, collum; lab, labrum.

FIGURES 3 – 5. Amplaria nazinta (Chamberlin, 1910) male. Fig. 3, posterior end of male. Fig. 4, legpair 1 of male. Fig. 5, legpairs 3 – 5 of male. cp 3, coxal processes of legs 3; cx, coxa; f, femur; ep, epiproct or telson, L 3 – 5, legs 3 – 5; pf, prefemur; pf 3, prefemur of leg 3; t, tarsus; ti, tibia; tr, trochanter; numbers of diplosegments.

FIGURES 6 – 9. Amplaria nazinta (Chamberlin, 1910) male. Fig. 6, specialized setae of the upper distal part of the telopodite of leg 7. Fig. 7, typical segmental seta. Fig. 8, specialized setae of tarsus 5. Fig. 9, specialized setae of the lower distal part of the telopodite of leg 7.

FIGURES 10 – 13. Amplaria nazinta (Chamberlin, 1910) male. Fig. 10, modified needle-like setae from the ventral surface of the tibia and tarsus of leg 1. Fig. 11, Dorsal surface of penultimate segment, showing central region where the cerotegument has been scraped away. Fig. 12, limbus of metazonite 26. Fig. 13, nodular ornamentation of epiproct. 29, segment 29; n, intercrest nodules; pc; paramedian crest.

FIGURES 14 – 16. Amplaria nazinta (Chamberlin, 1910) male. Fig. 14, right gonopod, lateral view. Fig. 15, left gonopod, mesal view. Fig. 16, legpair 9, anterior view. Aacx, anterior angiocoxite; pacx, posterior angiocoxite; cpx, colpocoxite; f, flagellocoxites; tel, telopodite; sp, coxosternal process; st, sternum.

FIGURES 17 – 18. Amplaria nazinta (Chamberlin, 1910) male. Fig. 17, tip of right gonopod, lateral view. Fig. 18, tip of left gonopod, mesal view. Aacx, anterior angiocoxite; pacx, posterior angiocoxite; cpx, colpocoxite; f, flagellocoxites.