JOURNAL OF EXPERIMENTAL ZOOLOGY 292:187–199 (2002) © 2002 WILEY-LISS, INC. DOI 10.1002/jez.1154 Female Sperm Storage in Reptiles DAVID M. SEVER 1 * AND WILLIAM C. HAMLETT 2 1 Department of Biology, Saint Mary’s College, Notre Dame, Indiana 46556 2 Indiana University School of Medicine, South Bend Center for Medical Education, Notre Dame, Indiana 46556 ABSTRACT Internal fertilization and oviparity most likely are symplesiomorphies for modern reptiles, and viviparity has evolved independently numerous times in Sauria and Serpentes. Ovidu- cal sperm storage is known in females of all taxa except Amphisbaenia. However, in Rhynchocephalia and Crocodilia, sperm storage is poorly studied, and specialized sperm storage tubules (Ssts) are unknown. We use the molecular phylogenetic hypothesis [(Chelonia+ Archosauria) (Squamata)] to trace evolution of sperm storage characters. Ssts arose independently in Chelonia and Squamata. Turtles possess albumen-secreting glands in the anterior half of the oviduct (the tuba or isthmus), and the most distal of these glands also serve as Ssts; in addition, some turtles possess Ssts in the adjacent segment of the oviduct, the uterus. Squamates lack albumen-secreting glands, and the ancestral state is possession of Ssts in the posterior infundibulum (uterine tube). Secondarily, iguanids have evolved vaginal Ssts. In this paper, we present the first ultrastructural observations on vaginal Ssts in lizards, using Anolis sagrei (Polychrotidae). Proximally, the neck of these simple tubular glands continues the alternation of ciliated and secretory cells lining the lumen of the vagina. How- ever, the epithelial cells of the distal sperm storage area are neither secretory nor ciliated. The Ssts of Anolis are more similar to those of birds more than to infundibular receptacles in snakes and lizards. J. Exp. Zool. 292:187–199, 2002. © 2002 Wiley-Liss, Inc. Female, as well as male, sperm storage is an obligatory part of the reproductive cycle in many reptiles. Sperm production, mating, and ovulation are out of phase with one another in numerous species (Fox, ’52; Saint Girons, ’82; Schuett, ’92). Thus, storage by either males or females promotes the wide dissemination, over time, of gametes pro- duced in a narrow time window (Gist and Jones, ’87). The selective advantage of sperm storage in reptiles does not involve long-term production of multiple clutches from a single mating, but rather the facilitation of female choice and sperm com- petition (Olsson and Madsen, ’98). The role of sperm storage in behavioral and eco- logical aspects of the reproductive biology of rep- tiles has been reviewed extensively (Saint Girons, ’73; Devine, ’84; Schuett, ’92; Olsson and Madsen, ’98), and this paper is not concerned with these subjects. This paper also is not directly concerned with the physiology of sperm storage; our knowl- edge about how viability is maintained and ca- pacitation is achieved is quite limited (Hoffman and Wimsatt, ’72; Depeiges et al., ’87; Averal et al., ’92; Manimekalai and Akbarsha, ’92). Rather, herein we consider the anatomy and phylogeny of sperm storage in reptiles and extend observations made by Gist and Jones (’87) in the last review on these topics. We actually know very little about the anatomy of sperm storage in reptiles. Ultrastructural stud- ies, especially using transmission electron micros- copy (TEM), are essential to study sperm/epithelial interactions during sperm storage. Yet, out of 5,400+ species of reptiles, we have TEM observa- tions on female sperm storage tubules (Ssts) for just one turtle (Gist and Fischer, ’93), one lizard (Bou-Resli et al., ’81), and two snakes (Hoffman and Wimsatt, ’72; Sever and Ryan, ’99). We are unaware of any ultrastructural study devoted to male sperm storage in the reptilian epididymis or vas deferens. A number of papers, however, deal at least peripherally with the cytology of male sperm storage in reptiles (Weil, ’84; Esponda and Bedford, ’87; Carcupino et al., ’89; Gist et al., ’92; Newton and Trauth, ’92). A review of male sperm storage in reptiles, however, seems premature, so this paper is limited to female sperm storage in the oviduct. The purpose of this paper is three-fold. First, we consider current views on evolutionary rela- tionships among reptiles and propose general hy- *Correspondence to: Dr. David M. Sever, Department of Biology, Saint Mary’s College, Notre Dame, Indiana 46556. E-mail: dsever@saintmarys.edu Received 14 September 2001; Accepted 14 September 2001