Phylogenomics and genital morphology of cave raptor spiders (Araneae, Trogloraptoridae) reveal an independent origin of a flow-through female genital system

Abstract

The monotypic family Trogloraptoridae was only recently described from caves and old-growth forest of Oregon and California (Western USA). These enigmatic spiders are characterized by striking raptorial claws, and based on their spinneret morphology, a close relationship to dysderoid spiders, a large clade within Synspermiata, was suggested. Here, we used a phylogenomic framework using transcriptomes to test the phylogenetic position of Trogloraptor marchingtoni. Our analysis placed this taxon within Synspermiata, which is supported by the presence of synspermia. Furthermore, a sister group relationship with Dysderoidea is strongly supported. In a second step, we reinvestigated the female genitalia using a non-destructive approach. Our data revealed that Trogloraptor has a flow-through genital system (entelegyne condition) and is not haplogyne as previously described based on dissections. The Trogloraptor female genital system consists of paired large spermathecae, which connect by a fertilization duct to a wide bursa. The copulatory duct arises from the sclerotized anterior margin of the bursa, and its organization is likely related to the organization of the male intromittent organ. Based on our phylogenetic data, we show that the entelegyne condition evolved at least six times independently within spiders. Moreover, our results indicate that the peculiar organization of the dysderoid female genitalia with an additional posterior sperm storage site is a synapomorphy of this Synspermiata clade.