This study provides the first descriptions of sperm storage at the tissue and cellular levels in a female frog or toad. Oviducal anatomy was studied by light and electron microscopy in Ascaphus truei from north coastal California. Ascaphus truei is one of the few species of anurans in which fertilization is internal. Unlike other anurans with internal fertilization, however, mating in A. truei consists of a unique combination of amplectic and copulatory mechanisms that we term "copulexus." Posterior to a short, aglandular infundibular region, the oviduct possesses: 1) a proximal, convoluted ampullary region where intrinsic tubular glands secrete gelatinous envelopes around eggs; 2) a middle ovisac region where fertilization occurs; and 3) a distal oviducal sinus formed by medial junction of the ovisacs. Sperm storage tubules (SSTs) occur in the anterior portions of the ovisacs and consist of simple tubular glands. SSTs and the rest of the oviducal lining stain positively with the periodic acid-Schiff's procedure for neutral carbohydrates and this reaction is especially intense in reproductively active females. Sperm were found in the SSTs of gravid females as well as some nonvitellogenic females. The sperm are in orderly bundles in the SSTs, and although occasionally sperm nuclei were embedded in the epithelium, no evidence for spermiophagy was found. Oviducal sperm storage in A. truei is homoplastic, with closest structural similarities to squamate reptiles. Oviduct/sperm design constraints appear to limit the options for expression of features associated with oviducal sperm storage.
Females of the marbled salamander, Ambystoma opacum, store sperm in exocrine glands called spermathecae in the roof of the cloaca. Eggs are fertilized by sperm released from the spermathecae during oviposition. Some sperm remain in the spermathecae following oviposition, but these sperm degenerate within a month and none persists more than 6 mo after oviposition. Thus, sperm storage between successive breeding seasons does not occur. Apical secretory vaculoes are abundant during the fall mating season and contain a substance that is alcian blue+ at pH 2.5. Production of secretory vacuoles decreases markedly after oviposition, and the glands are inactive by the summer months. Ambystoma opacum is a terrestrial breeder, and some mating occurs prior to arrival at pond basins where oviposition occurs. Mating prior to arrival at the ovipository site may prolong the breeding season, leading to fitness implications for both males and females. Females have opportunities for more matings, and the possibilities for sperm competition in the spermathecae are enhanced. © 1995 Wiley-Liss, Inc.
Female sperm storage was studied in a population of Notophthalmus viridescens from South Carolina. Spermathecae initiate production of a glycoprotein secretory product in October. At this time ovarian follicles are immature (0.5–0.9 mm dia), and mating does not occur despite spermiation in males. Six of the 10 females collected in December had sperm in their spermathecae, indicating onset of mating. Unmated females collected in October and sacrificed in February and March possessed mature ovarian follicles (1.3–1.4 mm dia), and the spermathecae contained large secretory vacuoles 2–3 μm dia. Release of secretory product is concomitant with the appearance of sperm in the spermathecae. Thus mated females lack secretory vacuoles in the spermathecal epithelium, and additional synthesis of secretory product does not occur. All females collected in February and March have mated. Sperm are embedded in the spermathecal epithelium and are undergoing degradation in February. Degradation of sperm in the lumen and epithelium is evident in specimens examined from May and June. Atresia of ovarian follicles begins in April in captive specimens, and specimens captured from the bay in May are spent. A general postbreeding emigration from the pond occurs in summer. Fourteen females collected 7 March were injected with human chorionic gonadotropin (hCG) on 9 March and laid fertile eggs 10–18 March. Two of these females were sacrificed each month from April‐September; all retained some sperm in their spermathecae, but further oviposition did not occur. Four females were kept 1 year after oviposition of fertile eggs, and oviposition again was induced with hCG; these eggs were infertile, and spermathecae lacked sperm. Spermathecae are inactive from June‐September in captive and wild‐caught specimens. Sperm may be stored effectively up to 6 months (December‐May), and no evidence was found for retention of viable sperm from one breeding season to the next. © 1996 Wiley‐Liss, Inc.
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