Orchestina sp. 1 (Chile)

SPERM TRANSFER FORM (figs. 26, 27): Long (.80 Mm), tubelike synspermia (fig. 26),

comprising two sperm (fig. 26) that are arranged consecutively to each other (fig. 26). A thick electron-dense secretion sheath (, 800 nm) surrounds the sperm conjugates (fig. 27 A–D). Sperm cell components are uncoiled (fig. 26) and surrounded by a small amount of conspicuous electron-dense fibrils, mitochondria are present (fig. 27B).

SPERMATOZOA (fig. 27): Acrosomal complex: AV small, cylindrical. AF originates from the subacrosomal space and extend into the nuclear canal. Nucleus: prcN tubelike and

elongated (,19.2 Mm) with deep implantation fossa that extends as far as the anterior pole of the nucleus and is filled with a distinct, electron-dense centriolar adjunct (fig. 27C). peN absent (fig. 27E). NC located in the periphery. Axoneme: short (,19.2 Mm); 9+3 microtubular pattern.

NOTES ON SPERMIOGENESIS (fig. 28): Within the testis all stages of spermiogenesis are visible. A small, developing AV is attached to the cell membrane (fig. 28A, inset) and extends toward the anterior pole of nucleus, from which it is separated by a distinct electron-dense plate (fig. 28A). The AF originates from the subacrosomal space. During development of the spermatids the chromatin condenses and appears fibrillar in midspermatids (fig. 28 B–D). The deep implantation fossa of early and midspermatids is filled with numerous microfilaments (fig. 28 C, D) and few electron-dense secretions (fig. 28C, D) that form a distinct centriolar adjunct in late spermatids, which completely covers the proximal centriole (fig. 28 E–G). In the periphery of the developing spermatids numerous looplike constrictions are visible (fig. 28H inset), resulting in a fringed appearance of the latter (fig. 28H, I).