Helicorthomorpha holstii (Polydesmida: Paradoxosomatidae): a new introduced millipede in Brazil and updated list of introduced species

ABSTRACT

We report the occurrence of the paradoxosomatid Helicorthomorpha holstii (Pocock, 1895) in Brazil, expanding the known distribution of this East Asian millipede to South America. Specimens were collected from potted plants in urban areas of São Paulo city in 2024, suggesting accidental introduction via imported ornamental plants. The species is readily recognized by its distinctive color pattern - dark brown to black with a broad longitudinal orange stripe - and by the structure of the gonopods, with an elongate telopodite bearing three apical terminations. This finding brings the total number of introduced millipede species in Brazil to 16, distributed across five orders, seven families, and 15 genera, highlighting the ongoing introduction and establishment of alien taxa in the country.

KEYWORDS:
Adventive species; arthropod invasions; Diplopoda; Myriapoda; Neotropical Region; non-native fauna

With over 975 described species, Paradoxosomatidae is the most speciose family within Diplopoda and occurs across most biogeographical regions, being especially diverse in Southeast Asia, Australia, and the Neotropics (Nguyen and Sierwald 2013). In addition to this wide-ranging natural distribution, several paradoxosomatid species have been reported from regions outside their native ranges, primarily as a result of human-mediated introductions (Stoev et al. 2010, Nguyen and Sierwald 2013, Iniesta et al. 2021, Almeida et al. 2022). Such anthropogenic dispersal has facilitated the establishment of alien taxa in new environments, occasionally resulting in invasive populations.

Records of introduced millipedes, particularly paradoxosomatids, have a long history in Brazil, with some species considered agricultural pests since the early 20th century (Schubart 1942a, Lordello 1954, Iniesta et al. 2021), yet their ecological impacts in protected forest habitats remain poorly understood (Iniesta et al. 2020, 2022). At present, 15 species of introduced millipedes, including three paradoxosomatids, are known from Brazil (Iniesta et al. 2021, 2022, Almeida et al. 2022). Orthomorpha coarctata (Saussure, 1860) and Oxidus gracilis (C.L. Koch, 1847) are widely distributed in northern Brazil and the Atlantic Forest (Iniesta et al. 2021), while Chondromorpha xanthotricha (Attems, 1898) was recently documented from the Amazon region (Almeida et al. 2022).

Helicorthomorpha Attems, 1914 comprises three species from Southeast Asia and Melanesia (Nguyen and Sierwald 2013). The orange rosary millipede, Helicorthomorpha holstii (Pocock, 1895), is notable for its anthropogenic affinities and human-aided dispersal. Native to Vietnam, China, Taiwan, and the Ryukyu Archipelago in Japan, H. holstii is very common in southern China and Southeast Asia, where it predominantly occurs in disturbed habitats (Nguyen and Sierwald 2013, Golovatch 2017). It has been reported as an adventive species in Hawai’i and Florida, USA (Nguyen and Sierwald 2013), but had not previously been recorded from South America.

Here we document the occurrence of H. holstii (Fig. 1) in Brazil, demonstrating its continuing range expansion in the New World. This finding adds to the growing list of introduced millipede species in the country and emphasizes the need for ongoing monitoring of non-native arthropods with the potential to affect native biodiversity and ecosystem functioning.

Figures 1-6
(1) Habitus of living Helicorthomorpha holstii; (2) garden where the specimens were collected, São Paulo, Brazil; (3-4) habitus of ethanol-preserved specimen, IBSP 16026; (5-6) right gonopod (IBSP 16026): (5) mesal view; (6) ectal view. Scale bars: 3−4 = 1 mm; 5−6 = 500 μm.

One female and four male specimens were obtained from potted plants at residences in São Paulo, São Paulo State, Brazil, between April and September 2024 (Fig. 2). Specimens were preserved in 70% ethanol and deposited in the myriapod collection of Instituto Butantan (IBSP; curator: A.D. Brescovit). Photographs were taken with a Leica DFC 500 digital camera mounted on a Leica MZ16A stereomicroscope, and extended focal range images were composed using Leica Application Suite ver. 2.5.0 (Leica Camera, Wetzlar, Germany) at IBSP. Specimens were compared with the original description by Pocock (1895). Geographical coordinates were obtained directly from the labels of all examined specimens.

TAXONOMY

Order Polydesmida Leach, 1814

Paradoxosomatidae Daday, 1889

Tectoporini Jeekel, 1968

Helicorthomorpha Attems, 1914

Helicorthomorpha holstii (Pocock, 1895)

Figs 1, 3-6

Strongylosoma holstiiPocock, 1895: 355, fig. 3.

Chinosoma hoditesChamberlin, 1923: 166. Synonymized by Jeekel, 1980: 664.

Kochliopus trivittatusVerhoeff, 1933: 20, figs 12-14. Synonymized by Attems, 1936: 215.

Kochliopus trilobatusVerhoeff, 1936: 310, figs 14-15. Synonymized by Attems, 1936: 215.

Diagnosis. Helicorthomorpha holstii can be distinguished from all other South American paradoxosomatid species by its distinctive color pattern and gonopod structure. Color (Fig. 1): dark brown to black with a broad longitudinal orange stripe extending from the collum to the telson; stripe narrow on the prozona but expanded and somewhat egg-shaped on the metazona; paranota greatly reduced, rounded, with orange tips; sterna and legs orange. Gonopods (Figs 5-6): telopodite elongate, narrow, branches helically intertwined, with three apical terminations.

Descriptive notes. Male. Body length 18-19 mm. Coloration (specimens preserved in 70% ethanol): body dark brown, with a yellowish longitudinal stripe; paranota tips, sterna, and legs yellowish (Figs 3-4). Integument smooth. Body rings subcylindrical; metazonite with a transverse sulcus; paranota reduced, rounded (Figs 3-4). Sterna of 5th body ring with a ventral subrectangular projection. Telson triangular (Fig. 4). Legs unmodified. Gonopods. Coxa curved caudad, less than 1/2 the length of telopodite, with distal anterior setae (Figs 5-6). Prefemur densely setose, approximately 1/3 the length of telopodite (Figs 5-6). Telopodite divided near base, with a distinct cingulum (Fig. 6); basal part sharply delimited, arising distad of prefemur, giving rise to solenomere medially (Fig. 5). Solenomere long, unbranched; solenophore broad, lamelliform, twisted, forming a groove accommodating the apical portion of solenomere, tip with three small apical terminations (Figs 5-6).

Female. Body length 20 mm. Coloration and other somatic characters as in male, except sterna of 5th body ring without projection.

Material examined. BRAZIL • 1♀, 2♂; São Paulo, São Paulo, Cangaíba neighborhood, Zona Leste (23°30’26.3”S, 46°32’24.2”W); 05 Apr 2024; C.T. Paranhos col. (IBSP 16026) • 2♂; Vila Maria Alta neighborhood, Zona Norte (23°30’31.8”S, 46°34’36.8”W); 22 Sep 2024; R.C.R. Nicolau col. (IBSP 16027).

To date, no published records of H. holstii from Brazil existed prior to this study. Its absence from previous checklists of introduced species (Brölemann 1902, Schubart 1947, Iniesta et al. 2021) suggests that its discovery in São Paulo is likely the result of a recent introduction event. Given that the specimens were found in potted plants in urban areas, the species was most likely accidentally introduced via imported plants from Asia or the United States. This finding is consistent with other records of anthropogenic dispersal of paradoxosomatid millipedes in Brazil, which are often associated with the movement of soil and ornamental plants (Iniesta et al. 2020).

Updated list of introduced millipede species in Brazil

A preliminary list of introduced millipedes in Brazil was provided by Iniesta et al. (2021), with subsequent additions by Almeida et al. (2022) and Iniesta et al. (2022). The list, arranged in taxonomic order, now comprises 16 species from 15 genera, seven families, and five orders.

Order Julida

Julidae

Cylindroiulus britannicus (Verhoeff, 1891)

Distribution in Brazil: Rio de Janeiro and São Paulo states (Schubart 1942b, 1944, 1945a, 1947).

Cylindroiulus truncorum (Silvestri, 1896)

Distribution in Brazil: São Paulo state (Schubart 1946a).

Ommatoiulus moreletii (Lucas, 1860)

Distribution in Brazil: São Paulo state (Iniesta et al. 2022).

Order Polydesmida

Haplodesmidae

Cylindrodesmus hirsutus Pocock, 1889

Distribution in Brazil: Pernambuco, Rio de Janeiro and São Paulo states (Scubart 1945b).

Prosopodesmus jacobsoni Silvestri, 1910

Distribution in Brazil: Espírito Santo, Minas Gerais, Rio de Janeiro and São Paulo states (Schubart 1945b, 1947, Romero-Rincon et al. 2026).

Paradoxosomatidae

Chondromorpha xanthotricha (Attems, 1898)

Distribution in Brazil: Amazonas state (Almeida et al. 2022).

Helicorthomorpha holstii (Pocock, 1895)

Distribution in Brazil: São Paulo state (present study).

Orthomorpha coarctata (Saussure, 1860)

Distribution in Brazil: Acre, Alagoas, Amazonas, Espírito Santo, Goiás, Mato Grosso, Minas Gerais, Pará, Paraíba, Paraná, Pernambuco, Rio de Janeiro, Rondônia, São Paulo, and Tocantins states (Schubart 1939, 1942a, 1944, 1945b, 1958a, Brölemann 1904, Hoffman et al. 2002, Iniesta et al. 2021).

Oxidus gracilis (C.L. Koch, 1847)

Distribution in Brazil: Amazonas, Distrito Federal, Espírito Santo, Mato Grosso do Sul, Minas Gerais, Paraná, Rio de Janeiro, Rio Grande do Sul, Santa Catarina, and São Paulo states (Schubart 1944, 1945a, 1945b, 1953, Rodrigues et al. 2017, Iniesta et al. 2021).

Order Polyzoniida

Siphonotidae

Rhinotus purpureus (Pocock, 1894)

Distribution in Brazil: Amazonas state (Hoffman et al. 2002, Iniesta et al. 2022).

Order Spirobolida

Pachybolidae

Epitrigoniulus cruentatus (Brölemann, 1903)

Distribution in Brazil: Amazonas and Pará states (Schubart 1947, Hoffman et al. 2002).

Leptogoniulus sorornus (Butler, 1876)

Distribution in Brazil: Bahia, Espírito Santo, and Rio de Janeiro states (Brölemann 1929, Schubart 1947, 1958b).

Trigoniulus corallinus (Gervais, 1842)

Distribution in Brazil: Amazonas, Pará, Pernambuco, Rio de Janeiro, Roraima, and Tocantins states (Brölemann 1902, Schubart 1958b, Hofffman et al. 2002, Antunes et al. 2016, Iniesta et al. 2022).

Spirobolellidae

Paraspirobolus lucifugus (Gervais, 1837)

Distribution in Brazil: Espírito Santo, Rio de Janeiro, and São Paulo states (Brölemann 1902, Schubart 1947).

Order Spirostreptida

Cambalopsidae

Glyphiulus granulatus (Gervais, 1847)

Distribution in Brazil: Rio Grande do Sul state (Iniesta et al. 2021).

Trachyjulus calvus (Pocock, 1893)

Distribution in Brazil: Bahia and Rio de Janeiro states (Schubart 1946b, Iniesta et al. 2021).

ACKNOWLEDGMENTS

We thank the editors and anonymous reviewers for their comments on the manuscript. This research is associated with the project Biodiversidade de Diplopoda no Brasil (Arthropoda, Myriapoda): Sistemática e Biogeografia (PIF3437-2025), coordinated by LFMI.

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• ZooBank register
  https://zoobank.org/AB1094BD-8EEE-4459-B0CD-496E2C264EA3
• Data Availability Statement
  All data generated and/or analyzed are included in this article.
• Funding Statement
  This study was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP; grants 2022/12588-1 to ADB and 2024/16377-0 to RSB) and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES; Finance Code 001).
• Ethical Statement
  Not applicable. This study was based exclusively on specimens deposited in scientific collections and did not involve field collection or handling of live vertebrate animals.
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  No artificial intelligence tools were used in the preparation of this manuscript.
• How to cite this article
  Bouzan RS, Brescovit AD, Means JC, Ivanov K, Paranhos CT, Nicolau RCR, Romero-Rincon J, Iniesta LFM (2026) Helicorthomorpha holstii (Polydesmida: Paradoxosomatidae): a new introduced millipede in Brazil and updated list of introduced species. Zoologia 43: e25086. https://doi.org/10.1590/S1984-4689.v43.e25086
• Published by
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Edited by

• Editorial responsibility
  Michel P. Valim

Publication Dates

• Publication in this collection
  07 Sept 2026
• Date of issue
  2026

History

• Received
  26 Sept 2025
• Accepted
  19 Mar 2026