Black-yellow pill millipede (Rhopalomeris nigroflava) is 5.1-9.7 mm long from Myanmar

NEWS - Black-yellow pill millipede (Rhopalomeris nigroflava Likhitrakarn sp. nov.) found in Linno Gu, Kayin State, Myanmar, 5.1-9.7 mm long and yellow with contrasting brown to blackish markings on certain terga, also the position of the syncoccital lobe of the telopod relative to the lateral syncoccital horns separates it from other Rhopalomeris species.

Currently, pill millipede (Rhopalomeris Verhoeff, 1906) consists of 7 species distributed in Vietnam (4 species), Myanmar (2 species), Thailand and Malaysia (1 species each) with no documented species overlap.

The distribution pattern, especially the higher species diversity in Vietnam compared to neighboring countries, suggests that there is still a high possibility of new species being discovered in Cambodia and southern Thailand through future surveys.

Rhopalomeris species are found at elevations of 5-1600 meters. Most are narrow endemics restricted to the type site. The exceptions are R. sauda which has a distribution of 180 km and R. carnifex which shows a range exceeding 1200 km and extends from southern Myanmar through Thailand to northern Malaysia.

R. nigroflava differs from other Rhopalomeris species by its yellowish body with contrasting brown to blackish markings on terga 4-9. In addition, the body is 5.1-9.7 mm long and 2.6-4.7 mm wide, with a lower syncoccytial lobe of the telopods than the lateral syncoccyte horns.

A female and two males were found guarding a clutch of eggs near the head, beneath the thoracic shield. This behavior deviates from the typical reproductive strategy known throughout the order Glomerida, where females deposit eggs in special clay chambers and allow them to develop independently.

This newly discovered species exhibits interesting traits that deserve special study. The specific epithet nigroflava is derived from the Latin niger meaning black and flavus meaning yellow, referring to the dark bands on the yellowish back.

The low intraspecific genetic divergence observed in R. carnifex (1.75%) and the newly described R. nigroflava (0%) is consistent with previous reports in Peplomeris magna (0.2%), some species of Hyleoglomeris (0-1.19%) and Hyperglomeris (0.45-5.30%).

Unfortunately, phylogenetic relationships do not seem to be sufficient to resolve genus-level relationships within the family, as shown in other studies. Future studies should include other genetic markers, such as 16S and 28S ribosomal RNA genes, and more advanced techniques, such as transcriptomic and phylogenomic data.

Studies combined with analyses of morphological, distributional and ecological traits are needed to gain a more integrative understanding of the evolutionary relationships among glomerid species, especially regarding the intraspecific variation observed within the R. carnifex complex.

Original research

Likhitrakarn N, Golovatch SI, Srisonchai R, Jirapatrasilp P, Sapparojpattana P, Jeratthitikul E, Panha S, Sutcharit C (2024). A new species of the pill millipede genus Rhopalomeris Verhoeff, 1906 (Diplopoda, Glomerida, Glomeridae) from Myanmar, and notes on Rhopalomeris carnifex (Pocock, 1889). ZooKeys 1215: 235-257. https://doi.org/10.3897/zookeys.1215.130919, DOI:10.3897/zookeys.1215.130919

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