S caphios yanayacu Platnick and Dupérre´, 2010

SPERM TRANSFER FORM (fig. 35): Synspermia that comprise four sperm. The entire sperm conjugate is rather large and unsheathed. Within the lumen of the proximal deferent ducts, the nuclei of sperm of one sperm conjugate appear still spotted (fig. 35A, B), while a distinct vesicular area that is composed of numerous electron-dense vesicles surrounds the main sperm cell components (fig. 35A, B). In the distal deferent ducts this vesicular area is homogeneously electron dense (fig. 35C, D). The periphery of the sperm conjugate is built by large quantities of granular cytoplasm of the syncytium, which contains numerous mitochondria and vesicles (fig. 35C). Only the axonemes coil within the membrane of the syncytium (fig. 35 D–E).

SPERMATOZOA (fig. 35): Acrosomal complex: AV conical with moderately widened subacrosomal space (fig. 35F). AF originates from the subacrosomal space and extends into the nuclear canal but clearly ends before the base of the axoneme. Nucleus: prcN elongat- ed, compact, and tubelike (fig. 35C) with a small implantation fossa that comprises only the two centrioles. peN not identifiable. NC located in the periphery, in late spermatids not identifiable. Axoneme: 9+3 microtubular pattern (fig. 35D, E).

NOTES ON SPERMIOGENESIS (fig. 36): The periphery of spermatids of all developmental stages is frequently invaginated and folded, resulting in a loose and spongy appearance (fig. 36A). Early spermatids are characterized by a large, oval nucleus with already irregularly condensed chromatin (fig. 36A). The subacrosomal space of the developing AV is enlarged (fig. 36B). The AF extends into the NC (fig. 36B) but clearly ends before the end of the axonemal base (fig. 36B, E inset). The AV is surrounded by electrondense material in mid spermatids (fig. 36C). The chromatin condenses irregularly, resulting in a spotted appearance of the nucleus of mid- and late spermatids (fig. 36D, E). Conspicuous membrane whorls, as well as electron-dense vesicles are in close association to the nucleus (fig. 36D). At the end of spermiogenesis, four spermatids fuse, while the main sperm cell components arrange in the center of the developing sperm conjugate (fig. 36F).