Comparative Anatomy and Phylogeny of the Cloacae of Salamanders (Amphibia: Caudata). II. Cryptobranchidae, Hynobiidae, and Sirenidae
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چکیده
Cloacae were examined from salamanders representing the three families in which fertilization of eggs is known or inferred to occur externally. The cloacae of male and female sirenids are aglandular and lack cilia. Sexual dimorphism in sirenid cloacae occurs only in the extent of epithelial stratification in the cloacal chamber in females (entire chamber) versus males (posterior angle of the vent). Both male and female Cryptobranchus alleganiensis possess ventral glands that secrete an acid mucopolysaccharide and have ciliated cloacal linings. The ventral glands are more numerous and hypertrophied in breeding male than female C. aZZeguniensis, but in males, ventral glands secrete only onto the surface of the cloacal lips along the anterior three-fifths of the cloacal orifice, whereas in females, the glands secrete onto the border of the entire cloacal orifice. Except for male Onychodactylus japonicus, male and female hynobiids also possess only ventral glands and have ciliated cloacal linings. Hynobiid ventral glands secrete a glycoprotein. Much variation occurs, however, among these hynobiids in cloacal conformation, extent of epidermis into the cloaca, and anatomy of the ventral gland. Male O.$aponicus possess an unciliated cloaca in which three types of cloacal glands occur, each giving unique reactions to tests for carbohydrates and proteins. The glands in male 0. japonicus do not seem to be homologous to those found in spermatophore producing salamanders in the Salamandroidea, but this does not negate the possibility that 0. japonicus makes spermatophores. Examination of cloacal characters in additional species of hynobiids may be useful in resolving intrafamilial phylogenetic relationships. Extant salamanders are placed into three suborders, Sirenoidea, Cryptobranchoidea, and Salamandroidea (Duellman and Trueb, '86). The Salamandroidea contains six families in which specialized cloacal glands exist for spermatophore formation (males) and sperm storage (spermathecae of females), reflecting internal fertilization. The Sirenoidea, consisting of the family Sirenidae, and the Cryptobranchoidea, composed of Cryptobranchidae and Hynobiidae, contain species in which external fertilization occurs or is inferred, because male spermatophore producing glands and female sperm storage glands are unknown. However, only a few studies deal with cloacal histology of sirenids, cryptobranchids, and hynobiids. Descriptions of female cloacae are limited to cursory observations on the presence of cloacal glands (Sever, '87). No histological descriptions exist for male cloacae except for a recent study on the ventral gland in Hynobius nigrescens (Hasumi et al., '90). Sever ('91) provides presenceiabsence data for 25 cloacal characters used in cladistic analyses but no histological descriptions. The present paper contains detailed descriptions of cloacal histology in representatives of the Cryptobranchidae, Hynobiidae, and Sirenidae. It extends the observations of Sever ( '87) and Hasumi et al. ('90) and provides the morphological basis for the character state polarities used by Sever ('91). MATERIALS AND METHODS Snout-vent length (SVL) refers to the distance from the tip of the snout to the posterior edge of the vent. Cloacal anatomy was examined grossly or following histological preparations for light microscopy. Speciu 1991 WILEY-LISS, INC.
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Cloacae, Cloacal Glands and Female Sperm Storage in Giant Salamanders
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