Research Article |
Corresponding author: Aleksandr P. Evsyukov ( aevsukov@mail.ru ) Academic editor: Pavel Stoev
© 2022 Aleksandr P. Evsyukov, Boyan Vagalinski, Igor Y. Zabiyaka, Evgeniy V. Sadyrin.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Evsyukov AP, Vagalinski B, Zabiyaka IY, Sadyrin EV (2022) A new millipede genus and species of the tribe Pachyiulini from the Caucasus (Diplopoda, Julida, Julidae). ZooKeys 1097: 47-63. https://doi.org/10.3897/zookeys.1097.81792
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A new genus and species of the millipede tribe Pachyiulini, Bellatoiulus golovatchi gen. et sp. nov., is described from the Lesser Caucasus, Azerbaijan. Cybertypes of the new species are created from the physical holotype male and from a paratype female. The distribution and ecological features of the new species, and the position of the new genus within Pachyiulini are discussed.
Azerbaijan, Bellatoiulus golovatchi, cybertype, taxonomy
The tribe Pachyiulini, also referred as the subfamily Pachyiulinae, is a monophyletic trans-Palaearctic group (
In the Caucasus sensu lato, the tribe is represented by three genera: Pachyiulus Berlese, 1883, Amblyiulus Silvestri, 1896, and Syrioiulus Verhoeff, 1914 (
Here we describe a new genus for a tiny new species of this tribe from the Azerbaijani part of the Lesser Caucasus and create cybertypes of the new species from the physical male holotype and a female paratype. Until now cybertypes have not been very common in millipede taxonomy and are known only for two species (
The specimens were stored in 70% ethanol. All material has been shared between the collections of the Zoological Museum of the Moscow State University, Russia (
Scanning electron micrographs were taken with a Zeiss CrossBeam 340 (Don State Technical University, Rostov-on-Don, Russia). For SEM micrographs, the gonopods, legs etc. were dehydrated in alcohol (96 and 100%) and acetone, glued to aluminium SEM-stubs and air dried.
Creation of cybertypes was carried out using a Zeiss Xradia Versa 520 X-ray computed micro-tomography unit (Don State Technical University, Rostov-on-Don, Russia). X-ray projections acquisition parameters were as follows: X-ray tube voltage 60 kV, power 4.5 V, magnification objective 0.4×, sample rotation 360°, exposure time 4 s, X-ray tube filter LE6. For each scan 2001 projections in total were obtained. The source-object-detector distances were adjusted according to the sample sizes to give the desired field view for each sample. Thus, the voxel sizes were 4.7 and 5.8 µm for the male holotype and the female paratype, respectively. For each scanning, the tube with the sample was placed at the closest possible distance to the X-ray source. The 2048 × 2048-pixel CCD camera was kept at –59 °C and the acquisition was performed with camera binning factor = 2, which resulted in up to 1024 × 1024-pixel sized projection images. The X-ray source filter was selected based on the observed transmittance values according to the recommendations of the Xradia Versa 520 User’s Guide A003030 Rev. B. The exposure time was selected to maintain count (intensity) values >5000 with the selected source parameters and filter. The option for Dynamic Ring Removal, which enables small random motions of the sample during acquisition, was enabled for all projections. During each tomography procedure, 10 reference (air) X-ray images were acquired with equal time intervals between them. Average of these references was applied to each projection. An up to one-hour warm-up scan was performed with the same source parameters before each acquisition. X-ray projections were reconstructed using XRMReconstructor 12.0.8086.19558 software with manually adjusted center shift values, σ = 0.5 Gaussian blur filter and BH = 0.05 standard beam hardening correction.
The reconstructed tomographic images were exported as 16-bit DICOM image stacks (without compression and retaining the original voxel values) for volume rendering in VGStudio MAX 3.5 software (Volume Graphics GmbH, Heidelberg, Germany). The DICOM files were rendered using Volume renderer (Phong). The Draw instrument was used to highlight individual structures, and after initial highlighting the region of interest was modified using Smoothing tool.
For contrasting before micro-CT examination samples were soaked in 100% alcohol for 2 h and then transferred to a 1% iodine alcohol solution for 48 h (
The distribution map was created using Google Earth Pro 7.3.4.
All images were processed in Adobe Photoshop CS6.
BRF body ring formula. Indicates the number of podous (including collum and the gonopod-bearing segment/ring) and apodous segments/rings in an individual. This formula is p+a+T, where p is the number of podous body rings, a is the number of apodous body rings, and T represents the telson (
H vertical body diameter measured at a mid-body ring
L body length measured at the ozopore level
Order Julida Leach, 1814
Bellatoiulus golovatchi gen. et sp. nov., by present designation.
A genus of the julid tribe Pachyiulini, distinguished from all contribal genera by the unique presence of a lateral process on the opisthomere, as well as by the following combination of gonopodal and external somatic characters: promere with mesal ridge distally extending in a strong process, caudal face without apical denticles/ridges; opisthomere without anterior and caudal lamellae or these being vestigial, mesomeral process well-differentiated, crest-like, solenomere with a deep and narrow apical fovea; ommatidia absent, mandibular stipites in males not expanded, vertigial and metazonal setae present, pre-anal ring with an epiproct.
Derived from the Latin bellator meaning “soldier”, “warrior”, after the remarkably “armed” appearance of the gonopods including the club-like mesal and lateral processes of the promere and the opisthomere, respectively, and the apically serrated mesomeral process; plus Julus, the type genus of the family Julidae. Masculine.
Holotype
: ♂ (unbroken) (
7 ♂♂, 12 ♀♀, 2 juv. (
http://morphobank.org/permalink/?P4180. Created from the physical ♂ holotype and a ♀ paratype.
The new species honours our friend and colleague, Prof. Sergei Golovatch (Moscow, Russia), an outstanding myriapodologist and one of the collectors of the material used for the present species description.
Measurements: holotype with BRF 45+2+T, L = 12 mm, H = 0.6 mm; paratype and non-type ♂♂ with BRF 40–46+1–3+T, L = 10–12 mm, H = 0.5–0.6 mm; paratype and non-type ♀♀ with BRF 37–51+1–4+T, L = 9.5–14 mm, H = 0.5–0.7 mm.
Colouration (Fig.
Head (Figs
Bellatoiulus golovatchi gen. et sp. nov., male paratype (
Trunk and legs: collum mostly smooth, with only two or three faint longitudinal grooves just next to posterolateral corner. Body rings (Figs
Telson (Fig.
Male sexual characters: leg-pair 1 (Fig.
Bellatoiulus golovatchi gen. et sp. nov., male paratype (
Gonopods (Figs
Bellatoiulus golovatchi gen. et sp. nov., male paratype (
Bellatoiulus golovatchi gen. et sp. nov., male cybertype. A habitus, lateral view B anterior half of body, lateral view C anterior half of body with highlighted gonopods, lateral view D anterior body part with highlighted gonopods, ventral view. Abbreviation: g gonopods. Images not to scale.
Bellatoiulus golovatchi gen. et sp. nov., male cybertype. A gonopods, caudal view B gonopods, frontal view C gonopods, lateral view D gonopods, ventral view E left gonopod, mesal view. Abbreviations: bl basofrontal lobe lp lateral process mp mesal process ms mesomeral process o opisthomere p promere s solenomere. Images not to scale.
Female sexual characters: leg-pairs 1 (Fig.
Bellatoiulus golovatchi gen. et sp. nov., female paratypes (
Bellatoiulus golovatchi gen. et sp. nov., female cybertype. A habitus, lateral view B anterior and posterior body parts, ventrolateral and dorso-lateral views, respectively C anterior and posterior body parts with highlighted vulvae, lateral views D anterior body part with highlighted vulvae, ventral view. Abbreviation: v vulvae. Images not to scale.
Bellatoiulus golovatchi gen. et sp. nov., female cybertype. A vulvae, caudal view B vulvae, frontal view C vulvae, ventral view D vulvae, dorsal view E right vulva, lateral view D right vulva, mesal view. Abbreviations: bu bursa mc median cleft mf median field op operculum. Images not to scale.
Bellatoiulus golovatchi gen. et sp. nov. exhibits a highly distinctive genital (both gonopodal and vulval) morphology, making it hardly comparable to any other genus of Julidae. However, its affiliation to the tribe Pachyiulini seems unquestionable, mainly because of the following male sexual characters: promere without flagellum and with a mesal ridge bearing one or two setae; opisthomere with a well-developed, but not freely articulated, mesomeral process, and with an apical fovea; penis completely non-sclerotised, with relatively long, parallel, apical lobes, without differentiated membranous tubes (corresponding to the “pachyiuline penis type”, as defined by
The classification of the Pachyiulini is still problematic in terms of both delimitations between genera, and the recognition of natural groups of genera based on synapomorphies. One of the few attempts of a subdivision of the tribe is that of
The new genus differs substantially from other tiny pachyiulinine genera (H of males ca 0.5 mm), such as the Carpathian–Balkan Hylopachyiulus Attems, 1904, Geopachyiulus Verhoeff, 1899, and Micropachyiulus Verhoeff, 1899. Apart from the unique lateral process, the opisthomere of Bellatoiulus gen. nov., unlike that in the aforementioned genera, has a fovea and lacks caudal lamella, the latter being well-developed in all three of them. The mesomeral process is well-differentiated in Bellatoiulus gen. nov. and Geopachyiulus, in contrast to Micropachyiulus and Hylopachyiulus, in which it is either poorly developed or mostly fused to the solenomere. Thus, there must be at least two groups of Pachyiulini genera that miniaturised independently of each other.
Apparently, Bellatoiulus golovatchi gen. et sp. nov. is endemic to the eastern part of the Lesser Caucasus within Azerbaijan (Fig.
Despite the absence of ommatidia and body pigmentation, B. golovatchi gen. et sp. nov. can hardly be regarded as an endogean or pedobiont, let alone a subterranean or hypogean form. Judging from both the present habitat information on the new species and personal observations on other blind (or with a strongly reduced number of ommatidia) and pale pachyiulinines, for example, species of Apfelbeckiella Verhoeff, 1901 or Micropachyiulus Verhoeff, 1899, B. golovatchi gen. et sp. nov. must be an inhabitant of the upper-most soil layer, immediately below the leaf litter. It could be thus assigned to the main life-form of Diplopoda–that of the stratobionts (
We are most grateful to S.I. Golovatch and K.Y. Eskov (both Moscow, Russia), the collectors who provided us their material for study. The present study was supported by RFBR, project number 20-54-18008, and BNSF, project number KP-06-Russia/6-11.12.2020. X-ray and SEM study were conducted using the equipment of Research and Education Center “Materials” at Don State Technical University. We are most thankful to Sergei Golovatch (Moscow, Russia), Henrik Enghoff (Copenhagen, Denmark) and Dragan Antić (Belgrade, Serbia), the reviewers, for their very helpful corrections and suggestions that have considerably improved our paper. Pavel Stoev (Sofia, Bulgaria) very helpfully served as the managing editor.
Bellatoiulus golovatchi gen. et sp. nov., male cybertype.
Data type: Video
Explanation note: Volume rendering of microCT image.
Bellatoiulus golovatchi gen. et sp. nov., female cybertype.
Data type: Video
Explanation note: Volume rendering of microCT image.