◂Fig. 5 Gametogenesis in male and female Veneriserva pygoclava. A–D Semi-thin histological sections of female Veneriserva pygoclava, stained with toluidine blue. A Cross-section of a female Veneriserva. B Close-up of large mature oocytes without discernible nurse cells. C Developing oocytes attached to mesenteries (mes), and oogonia proliferating from the ventral side of the dorsal blood vessel (bv). D Details of vitellogenic oocytes and nurse cells. Arrowheads indicate brownstained yolk platelets and yolk bodies. E Live sperm cells captured in a light micrograph. F–G Cross-sections of male Veneriserva. Note the absence of a gut in the cross-sections. Abbreviations—ac acicula, acr acrosome, bv blood vessel, coe coelomic cavity, mes mesentery, nc nurse cell, nn nurse cell nucleus, nu sperm cell nucleus, Oo oocyte, on oocyte nucleus, sp spermatogonia, vnc ventral nerve cord in Hardly Venus's servant-morphological adaptations of Veneriserva to an endoparasitic lifestyle and its phylogenetic position within Dorvilleidae (Annelida)