Oxidus gracilis (C.L. Koch, 1847 )

Parra-Gómez, Antonio, 2022, Records about the alien millipede Oxidus gracilis (C. L. Koch, 1847) (Diplopoda: Polydesmida: Paradoxosomatidae) in continental Chile, Revista Chilena de Entomología (Rev. Chil. Entomol.) 48 (1), pp. 73-79 : 74-77

Oxidus gracilis (C.L. Koch, 1847)

( Figs. 1-4 )

Fontaria gracilis C.L. Koch 1847: 142 .

Oxidus gracilis : Verhoeff 1924: 416, fig. 18; Chamberlin 1957: 12.

Orthomorpha gracilis : Skottsberg 1956: 418.

Material examined. Oxidus gracilis . 1 male. CHILE. Coquimbo, Choapa, Salamanca , in a water fountain MLP (sic.), 17-V-2011, col. P. Baéz, B. Collado and S. Letieler [ MHNH]. 5 females, 5 males. Limarí, Bosque Fray Jorge National Park , under a log close to reedbed, park administration, 30°40’31.12” S - 71°38’9.57” W, 5-X-2017, col. Jorge Pérez Schultheiss [ MHNH]. 9 females, 5 males. Santiago, Linderos, Buin, under ornamental stones in a house garden, 33°45’09” S - 70°44’16” W, 16-I-2019, e-13 (field code), col. Patricio Farah [ APG] .

Additional records: CHILE.> 10 specimens (sic.). Valparaíso, Quillota, La Cruz , 18-I-1973, Col. Walter C. Sedgwick. Det. Herbet W. Levi (presumably) (Coordinates incorrectly given as “ 34°30’30.6720” S - 71°53’45.7404” W ”) ( MCZBASE 2021) .

Descriptive notes. Length ca 18-19 mm in males, ca 20-21 in females. Width of midbody pro- and metazonae in males and females ca 1.3-1.4 and ca 1.9-2 mm respectively. General coloration dark brown with yellowish paranota; legs also yellowish. Body with 20 segments. Antennae long, extending back behind 2nd segment when stretched dorsally (a little shorter on females). Terga with transversal sulcus. Paraterga developed, anterolateral margin rounded, posterolateral margin dentiform. Epiproct tip bilobulated. Gonopods as Nguyen et al. (2017) and Rojas-Buffet et al. (2020): Femorite (fe) expanded distally; postfemoral lamina (l) with a rectangular shape; postfemoral spine (z) tubercular and spiniform; postfemoral process (h) thin and serrated at the distolateral part; basal part of process (h) and spine (z) noticeably separated; solenophore (sph) with a lamelliform mesal lobule; tips of mesal lobule and solenophore circular ( Fig. 3 ).

Remarks. The species differs from Ologonosoma Silvestri, 1897 congeners, by the presence of prominent paranota with yellowish lateral margin ( Figs. 1-2 ).

Oxidus gracilis is widely distributed over the world primarily in warm temperate areas ( Nguyen et al. 2017). The material from Chile has been collected in Rapa Nui (Easter Island) ( Verhoeff 1924) and also in continental Chile in 1973 by Walter C. Sedgwick, as other invertebrates were collected in the same date and locality by this author and possibly identified by Herbet W. Levi as he worked with spiders from the same batch ( MCZBASE 2021, 2022), no subsequent publication has been issue citing this last sample. Although records from GBIF show O. gracilis to be a very common species in central Chile ( GBIF 2021), especially in urban environments, it is worth noting that some of our specimens were collected in the park administration zone of the Bosque Fray Jorge National Park, near manmade structures ( Fig. 4 ).

Apart from Oxidus , only one Paradoxosomatidae genus from Chile is known: Ologonosoma ( Fig. 5 ). Species from this genus have been recorded from Bosque Fray Jorge National Park and Valparaíso in the case of Ologonosoma robustum ( Attems, 1898) and Valdivia and nearby places for Ologonosoma ecarinatum ( Attems, 1898) and Ologonosoma primum ( Chamberlin, 1957) , all 3 of them endemic to the Chilean territory ( Attems 1898, 1903; Chamberlin 1957; Silva & Sáiz 1975; Parra-Gómez unpublished). Only O. rubustum seems to overlap its known distribution with the records of O. gracilis . Impacts of exotic diplopods on native species in Chile is still unknown as no study has ever been conducted in the country.

According to the records known in the literature, the exotic milliped fauna of continental Chile contains a total of six species: B. guttulatus (Bosc, 1792) , B. pusillus (Leach, 1814) , C. britannicus (Verhoeff, 1891) , C. latestriatus (Curtis, 1845) , N. kochii (Gervais, 1847) ( Attems 1903; Verhoeff 1924; Schubart 1964), and O. gracilis which extends from Caballo Muerto near Ovalle to Chillán, based on the additional records herein ( Fig. 4 ).

Figures

Figure 3. Male right gonopod view under compound microscope, lateral view. Nomenclature by Nguyen et al. (2017): h = postfemoral process; sph = solenophore; sl = solenomere; z = postfemoral spine; l = postfemoral lamina; fe = femorite; co = coxa; pf = prefemorite. Scale: 0.1 mm / Gonópodo derecho del macho visto bajo microscopio compuesto, vista lateral. Nomenclatura por Nguyen et al. (2017): h = proceso postfemoral; sph = solenóforo; sl = solenómero; z = espina postfemoral; l = lámina postfemoral; fe = femorito; co = coxa; pf = prefemorito. (nota: la translación de algunos términos al español es tentativa, debido a que en muchos casos no existe una traducción oficial). Escala: 0,1 mm.

Figure 4. Oxidus gracilis distribution in continental Chile. / Distribución de Oxidus gracilis en Chile continental.

Figure 5. Ologonosoma sp. from Nahuelbuta locality, Chile. / Ologonosoma sp. de la localidad de Nahuelbuta, Chile.

Figures 1-2. Oxidus gracilis. 1. Lateral view, female. 2. Dorsal view, male, collum broken. Scale: 1 mm. / Oxidus gracilis. 1. Vista lateral, hembra. 2. Vista dorsal, macho, collum roto. Escala: 1 mm.