Friday, October 16, 2020

[Diplopoda • 2020] Dichromatobolus elephantulus • A New Genus of Spirobolidan Millipedes (Spirobolida, Pachybolidae) from Madagascar

 Dichromatobolus elephantulus Wesener, 2020

A new genus, Dichromatobolus gen. nov., belonging to the genus-rich mainly southern hemisphere family Pachybolidae of the order Spirobolida, is described based on Dichromatobolus elephantulus gen. et sp. nov., illustrated with color pictures, line drawings, and scanning electron micrographs. The species is recorded from the spiny bush of southwestern Madagascar. Dichromatobolus elephantulus gen. et sp. nov. shows an unusual color pattern, sexual dichromatism with males being red with black legs and females being grey. Males seem to be more surface active, as mainly males were collected with pitfall traps. Females mainly come from the pet trade. The body of this species is short and very wide, being only 8 times longer than wide in the males. Live observations show the species is a very slow mover, digging in loose soil almost as fast as walking on the surface. The posterior gonopods of Dichromatobolus gen. nov. are unusually simple and well-rounded, displaying some similarities to the genera Corallobolus Wesener, 2009 and Granitobolus Wesener, 2009, from which the new genus differs in numerous other characters, e.g., size, anterior gonopods and habitus. Despite several attempts with fresh tissue samples and different primers, molecular barcoding did not work for Dichromatobolus gen. nov. Any relationships to the other 15 genera of Pachybolidae indigenous to Madagascar remain unknown.

 Keywords: biodiversity, Mahafaly Plateau, spiny forest, sexual color dimorphism, soil arthropod

Fig. 1. Dichromatobolus elephantulus gen. et sp. nov. 
A. Living ♂ (red; FMNH-INS 55888) and ♀ (grey; FMNH-INS 55887) from Odenwald Exoten 2007 import, photo by P. Decker. B–C. Living immature ♂, 2019 import (ZFMK MYR8708), photo by L. Moritz. B.  Head.  C. Whole body. D–F. ♂ (ZFMK MYR8745), multi-layer photographs.  D. Anterior body, lateral view; E. Leg pairs 1–7, ventral view. F. Posterior body end with telson.
Abbreviations: av = paraprocts; C = lips of paraprocts; Ca = cardines; Co  =  collum  (ring  1);  Gn  =  gnathochilarium;  Go  =  gonopods;  IL  =  incisura  lateralis;  ms  =  marginal  setae; P-M = parasitic(?) mites; Pre = epiproct; St = stipes; sub = hypoproct. Not to scale.

Class Diplopoda de Blainville in Gervais, 1844
Order Spirobolida Cook, 1895
Family Pachybolidae Cook, 1897 sensu Hoffman 1980

Dichromatobolus gen. nov.

Diagnosis: Massive, short, differs from all other known genera of Pachybolidae in mature males being only eight times longer than wide. Coloration uniquely differing between sexes, females grey, males red (Fig. 1A). Transverse  ridge  on  mentum  of  gnathochilarium  absent  (Fig.  4A).  Male  legs  with  tarsal  pads  and  unusually spinose tarsi (Fig. 4D). Shares anterior telopods with apical process of telopodite (Fig. 4E–F) with Zehntnerobolus Wesener, 2009, from which Dichromatobolus gen.    nov. differs strongly in habitus and  posterior  gonopods.  Simple,  apically  swollen  posterior  gonopods  (Fig.  5A–C)  are  shared  with  Corallobolus  Wesener,  2009,  from  which  Dichromatobolus  gen.  nov.differs in habitus and anterior telopods.

Etymology: After the differences in the color pattern between the sexes, and ʻ-bolusʼ, a common suffix for genus names of the Spirobolida. Masculine.

Taxonomic position: The posterior gonopods being connected by a sclerotized sternite as well as the absence of apodemes on the anterior  gonopods  (Fig.  4E–F)  place Dichromatobolus gen.  nov.  in  the  suborder Trigoniulidea Attems, 1909, family Pachybolidae. The closest relative of Dichromatobolus gen. nov. is unknown.

Remarks: There is a second potential species, > 100 mm in length, with specimens from Manongarivo, Ananambao (FMNH-INS 56254), all unfortunately female. Their  wide body with  short  legs  and  grey color (all other larger Spirobolida genera on Madagascar are black/red, Wesener et al. 2009)  might indicate  a  relationship to Dichromatobolus gen. nov.

Dichromatobolus elephantulus gen. et sp. nov.

Diagnosis: Body 60–80 mm long, massive, bulky spirobolidan. Epiproct not projecting. Males red, females grey, ozopore  openings  in  both  sexes  marked  by  a  black  circle.  Males  with  tarsal  pads,  coxa  projections  absent.  Legs  and  antennae  short.  Anterior  gonopods,  telopodite  process  well-developed  and  at  apex  curved laterally. Posterior gonopod slender and elongated, telopodite simple, rectangular, apically with opening of efferent duct.

Etymology: Elephantulus, diminutive noun in apposition, after the resemblance to an elephant in the female grey color, as well as a hint referring to the width of the species.

Thomas Wesener. 2020. Dichromatobolus, A New Genus of Spirobolidan Millipedes from Madagascar (Spirobolida, Pachybolidae). European Journal of Taxonomy.  720(1); 107-120. DOI: 10.5852/ejt.2020.720.1119