Evolutionary morphology of sperm in pholcid spiders (Pholcidae, Synspermiata)
Published in BMC Zoology 7: 52. https://doi.org/10.1186/s40850-022-00148-3

In this study we reconstruct the evolution of sperm traits in pholcid spiders, based on the currently largest taxon sampling in any spider sperm study (46 species representing 35 genera). Using transmission electron microscopy and character maping, we document several sperm characters that are unique for individual pholcid caldes, such as a helical band (Pholcinae) or a lamellate posterior centriolar adjunct material (Modisiminae). At the same time, our data reveal a highly dynamic evolution of sperm characters, with convergences across all subfamilies and a high level of homoplasy.

With regard to sperm transfer forms, we found that synspermia occur only in the subfamily Ninetinae, whereas the other subfamilies have cleistospermia. This supports the idea that Ninetinae are an ancestral clade within Pholcidae that have retained synspermia and that synspermia represent the ancestral sperm transfer form of Pholcidae.

Coiled spermatid of Mesabolivar iguazu (left) and 3D surface reconstruction of a cleistosperm of Mesabolivar cyaneotaeniatus.