Abstract
Gordius chiashanussp. nov., a newly described horsehair worm that parasitizes the Spirobolus millipede, is one of the three described horsehair worm species in Taiwan. It is morphologically similar to G. helveticus Schmidt-Rhaesa, 2010 because of the progressively broadening distribution of bristles concentrated on the male tail lobes, but it is distinguishable from G. helveticus because of the stout bristles on the mid-body. In addition, a vertical white stripe on the anterior ventral side and areoles on the inside wall of the cloacal opening are rarely mentioned in other Gordius species. Free-living adults emerged and mated on wet soil under the forest canopy in the winter (late November to early February) at medium altitudes (1100–1700 m). Mucus-like structure covering on the body surface, which creates a rainbow-like reflection, might endow the worm with high tolerance to dehydration. Although Gordius chiashanussp. nov. seems to be more adaptive to the terrestrial environment than other horsehair worm species, cysts putatively identified as belonging to this hairworm species found in the aquatic paratenic host, Ephemera orientalis McLachlan, 1875, suggest the life cycle of Gordius chiashanussp. nov. could involve water and land. The free-living adults emerged from the definitive hosts might reproduce in the terrestrial environment or enter an aquatic habitat by moving or being washed away by heavy rain instead of manipulating the behavior of their terrestrial definitive hosts.
Highlights
In addition to the two previously described species of horsehair worm (Chiu et al 2011, 2017), Gordius chiashanus sp. nov. is the third described species in Taiwan, and one among 90 valid Gordius species reported worldwide (Schmidt-Rhaesa 2010, 2014)
The aforementioned complex life cycle has been reported in multiple Gordius species (e.g., G. robustus Leidy, 1851 and G. difficilis Smith, 1994) (Thorne 1940; Bolek and Coggins 2002); it has not been reported in some species that parasitize aquatic definitive hosts (e.g., G. villoti Rosa, 1882 and G. albopunctatus Müller, 1926) (Valvassori et al 1988; Schmidt-Rhaesa and Kristensen 2006) or in species that reproduce in terrestrial environments (G. terrestris Anaya et al, 2019) (Anaya et al 2019)
Unlike the two low-altitude species, Gordius chiashanus sp. nov. inhabits medium altitude areas (1100–1700 m), which matches the distribution of its millipede host, Spirobolus sp. nov. (Hsu and Chang, unpublished), in Taiwan (1100–1600 m) (Hsu 2008)
Summary
In addition to the two previously described species of horsehair worm (Chiu et al 2011, 2017), Gordius chiashanus sp. nov. is the third described species in Taiwan, and one among 90 valid Gordius species reported worldwide (Schmidt-Rhaesa 2010, 2014). Many host records might be questionable because the genus Gordius (G. aquaticus Linnaeus, 1758) had been used to represent the entire members of horsehair worms, Gordius species might parasitize several insect orders, Chilopoda, Diplopoda, and Araneae as their definitive hosts (Schmidt-Rhaesa 2012; Bolek et al 2015). Are frequently found in foggy forests situated at altitudes of 1100–1700 m in Taiwan Their taxonomic status was first examined in the present study by using a description of morphology and phylogenetic comparison of partial mitochondrial DNA cytochrome oxidase subunit I (mtDNACOI) genes. Based on our field observations on adult free-living worms, cysts and their hosts, along with our laboratory observations of non-adult stages for this gordiid species, we suggest the possible life history of Gordius chiashanus sp. Based on our field observations on adult free-living worms, cysts and their hosts, along with our laboratory observations of non-adult stages for this gordiid species, we suggest the possible life history of Gordius chiashanus sp. nov
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