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Crystal Kelehear - One of the best experts on this subject based on the ideXlab platform.

David M. Sever - One of the best experts on this subject based on the ideXlab platform.

  • cloacae cloacal glands and female sperm storage in giant salamanders
    2013
    Co-Authors: David M. Sever
    Abstract:

    Most of the 620+ species of salamanders are relatively small animals, rarely exceeding 200 mm total length, but members of the families Cryptobranchidae (1800 mm), Sirenidae (978 mm), Amphiumidae (1162 mm), Proteidae (486 mm) and Dicamptodontidae (351 mm) can truly be considered "giant salamanders." These families have few species (Proteidae with six species is the most speciose) and are aquatic paedomorphs except for Dicamptodontidae, in which the four species can metamorphose. All families except Cryptobranchidae, which has single species in China and Japan, are limited in distribution to North America. Cryptobranchidae and Sirenidae reproduce with external fertilization, whereas species in the other families have internal fertilization and females store sperm in cloacal spermathecae. Males of the internal fertilizers possess cloacal glands that make spermatophores. The only sister group relationship that has been proposed is between Sirenidae and Proteidae. This paper brings together and summarizes information from a number of separate studies on histology of the cloaca and cloacal glands and ultrastructure of sperm storage, when it occurs, in the giant salamanders. Proteids have cloacae similar to those of other internal fertilizing salamanders, and if the sister group relationship with sirenids is valid, this means that internal fertilization and associated cloacal structures were lost in sirenids or they evolved independently in proteids. The cloacal evidence, however, supports the proposal in one recent paper to return the Dicamptodon, the only extant genus in the Dicamptodontidae, to its traditional position in the Ambystomatidae.

  • sperm storage in female plethodontids with especial reference to the desmognathinae
    2000
    Co-Authors: David M. Sever
    Abstract:

    Three families of salamanders (Sirenidae, Cryptobranchidae, and Hynobiidae) reproduce by external fertilization (Sever, 1991a; Sever et al., 1996). The remaining seven families, composing the suborder Salamandroidea, undergo internal fertilization (Duellman and Trueb, 1986). Internal fertilization occurs after a sperm-bearing spermatophore produced by the male is introduced directly or indirectly into the cloacal orifice of the female after ritualized courtship (Sever and Houck, 1985). Sperm from the cap migrate into sperm storage tubules in the walls of the female cloaca (Sever and Brizzi, 1998). In the Plethodontidae, these tubules are organized into a single compound tubuloalveolar gland, a complex spermatheca (Fig. 1). Multiple simple tubular glands, simple spermathecae, are found in other families in the Salamandroidea. Sperm are stored in these female cloacal glands in oviparous species until oviposition, when sperm are released onto eggs as they pass through the cloaca, providing the means for internal fertilization (Jordan, 1893). In the few species in the Salamandridae that are ovoviviparous or viviparous, fertilization occurs in the oviduct (Boisseau and Joly, 1975).

  • S perm at h ecae of Salarnandrina terdigita ta (Am p h i b i a: Salamandridae): Patterns of Sperm Storage and Degradation
    1995
    Co-Authors: R. Brizzi, Giovanni Delfino, Maria Gloria Selmi, David M. Sever
    Abstract:

    The spermathecae of female Salamandrina terdigitata were observed using light and transmission electron microscopy during the fall- spring period of sperm storage and secretory activity and during the summer stasis. When sperm are stored inside the spermathecae, the product synthe- sized by spermathecal epithelial cells is exported into the lumen, where it bathes the sperm. During sperm storage some spermatozoa undergo degrada- tion by the spermathecal epithelium. This process, which includes sperm capture by the apical microvilli, formation of endocytic vacuoles and production of lysosomes, becomes prominent shortly after oviposition. In many instances, cells filled with vacuolized spermatozoa andlor residual bodies undergo desqua- mation from the spermathecal epithelium and enter the lumen together with residual sperm. Desquamated cells, together with residual sperm, are a com- mon feature in the spermathecal lumina at the end of the egg-laying season. Concomitant to the activity of the spermathecal epithelium, macrophages move into the spermathecae from the stroma and contribute to the degradation of both the residual sperm and desquamated epithelial cells. As a result of this degradation activity, spermathecae observed during the short summer stasis appear devoid of secretory product and sperm. By late summer, however, the spermathecae already show early signs of an imminent resumption of biosyn- thetic activity. o 1995 Wiley-Liss, Inc. Females of many taxa, including the Am- phibia, are known to posses sperm storage organs associated with their reproductive tracts, which allow the spermatozoa to re- main functional for some time before fertiliza- tion occurs (Joly, '60; Boisseau and Joly, '75; Duellman and Trueb, '86; Selmi, '93; Sever, '91c, '92b). Among Urodela, the occurrence of sperm storage structures (usually defined as receptacula seminis or spermathecae; cf. Dent, '70 for a historical review of these terms) characterizes the female genital appa- ratus of the Salamandroidea (the salamanders which practice internal fertilization: Amphiu- midae, Dicamptodontidae, Proteidae, Am- bystomatidae, Plethodontidae, and Salaman- dridae). Females of the Cryptobranchoidea (Cryptobranchidae and Hynobiidae) and Sire- noidea (Sirenidae) undergo external fertiliza- tion and lack spermathecae (Sever, '78; Duell- man and Trueb, '86; Sever, '87, '88, '91a,b). The presence of spermathecae and male cloa- cal glands involved in internal fertilization were the key characters in establishing the monophyly of the Salamandroidea in a recent analysis using 209 phylogenetically informa- tive characters (Larson and Dimmick, '93). Sperm storage structures have been inves- tigated by light andlor electron microscopy in many salamanders (Dent, '70; Boisseau and Joly, '75; Pool and Hoage, '73; Brizzi et al., '89; Sever, '91a,c, '92a,b; Sever and Brunette, '93; Sever and Kloepfer, '93) and the results show remarkable similarities both in the tubule morphology and storage pat- terns. During storage, a close contact be- tween sperm and spermathecal epithelium occurs and, as a rule, sperm storage does not last long after oviposition. Indeed, following this reproductive stage, most residual sperm seem to undergo degenerative processes and, shortly afterwards, the spermathecae exhibit reduced lumina devoid of secretory product and stored sperm. Only in some cases do a

  • Comparative anatomy and phylogeny of the cloacae of salamanders (Amphibia: Caudata). II. Cryptobranchidae, Hynobiidae, and Sirenidae.
    Journal of morphology, 1991
    Co-Authors: David M. Sever
    Abstract:

    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. alleganiensis, 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. japonicus 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 O. 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 O. japonicus makes spermatophores. Examination of cloacal characters in additional species of hynobiids may be useful in resolving intrafamilial phylogenetic relationships.

  • Comparative anatomy and phylogeny of the cloacae of salamanders (Amphibia: Caudata). I, Evolution at the family level
    Herpetologica, 1991
    Co-Authors: David M. Sever
    Abstract:

    Data on cloacal anatomy were gathered for 128 species of salamanders, representing 48 genera and the nine extant families. Twenty-five characters were recognized, but after resolution of polymorphisms and elimination of autapomorphies, only 12 characters remained for use in phylogenetic analyses at the family level. Weighting the characters equally and using branch-and- bound parsimony algorithms, 15 (PAUP) or 9 (Hennig86), equally parsimonious cladograms were revealed, each with 19 steps and a consistency index of 0.63. The variation in phylogenies is due to opposing hypotheses concerning convergence or reversal in two characters: the extent of epidermal lining in the cloaca, and the presence of primary and secondary folds in the cloacal tube. The strict consensus cladogram gives the topology: Sirenidae (Hynobiidae, Cryptobranchidae (Amphiumidae (Salamandridae (Ambystomatidae, Dicamptodontinae (Rhyacotritoninae, Plethodontidae, Protei- dae))))). These results and consensus analyses with other cladograms based upon morphological data support the notion that the Salamandroidea, as defined by Duellman and Trueb (1986), is a monophyletic group and that internal fertilization evolved once, and is a synapomorphy for the suborder. Male and female cryptobranchids and hynobiids possess one type of cloacal gland that is not highly dimorphic, and may be a courtship gland that functions in the production of chemical signals during reproductive activities. In the Salamandroidea, portions of the cloacal gland mass (male dorsal and vent glands, female ventral glands) retain the ancestral anatomy and presumed function, while other portions have evolved structural and functional differences relating to sper- matophore formation (male pelvic and ventral glands) and storage of spermatozoa (female sper- mathecae). Courtship glands have been secondarily lost or reduced in some of the Salamandroidea, especially in plethodontids, in which selection apparently has led to adaptations for delivery of courtship pheromones by skin glands rather than reliance on a cloacal source.

Sean P. Graham - One of the best experts on this subject based on the ideXlab platform.

James D. Gardner - One of the best experts on this subject based on the ideXlab platform.

  • Revision of Habrosaurus Gilmore (Caudata; Sirenidae) and relationships among sirenid salamanders
    Palaeontology, 2003
    Co-Authors: James D. Gardner
    Abstract:

    The sirenid salamander Habrosaurus is revised and redescribed based on skull elements and vertebrae from the middle Campanian–middle Palaeocene of the North American Western Interior. Habrosaurus differs from the Cenozoic (Eocene–Recent) sirenids Siren and Pseudobranchus in a suite of cranial and vertebral plesiomorphies, one vertebral character of uncertain polarity and five apomorphies describing the structure of the dentary, atlas and tooth crowns. Two species are identified based on dental characters: the type species H. dilatus (late Maastrichtian–middle Palaeocene) has stout marginal and palatal teeth with bulbous crowns and prominent wear facets, whereas H. prodilatus sp. nov. (middle Campanian) has chisel-like marginal teeth (palatal teeth unknown) with weaker wear facets. Habrosaurus is argued to be the geologically oldest, undoubted sirenid and the sister-taxon of Siren + Pseudobranchus. Replacement of marginal teeth with a broad, horny beak in Siren and Pseudobranchus and the broad, bulbous marginal and palatal teeth in H. dilatus are proposed to be convergent strategies for achieving a crushing bite. The chisel-like teeth of H. prodilatus are interpreted as being transitional to the more specialized, crushing dentition of H. dilatus.

Stephen M. Reilly - One of the best experts on this subject based on the ideXlab platform.

  • Cranial Ontogeny in Siren intermedia (Caudata: Sirenidae): Paedomorphic, Metamorphic, and Novel Patterns of Heterochrony
    Copeia, 1996
    Co-Authors: Stephen M. Reilly, Ronald Altig
    Abstract:

    Cranial development and shape was studied in a large series of the salamander Siren intermedia. Six developmental stages were defined based on timing of ossification and other conspicuous events during ontogeny. Ontogeny of cranial shape was quantified by comparing average landmark configurations describing dorsal cranial shape for each of the six developmental stages by using thin-plate spline and resistant fit theta-rho analyses. Cranial elements in Siren have ontogenetic patterns that are truncated, normal, or completely novel as compared to cranial ontogenies of metamorphosing taxa; overall dorsal cranial shape remains remarkably constant throughout ontogeny. The maxillae, palatopterygoid elements, and hyobranchial apparatus display patterns of heterochrony unique to Siren. The mosaic of larval, metamorphic, and unique patterns of development and cranial-shape paedomorphosis exhibited by Siren fundamentally differs from general patterns of paedomorphosis observed in other taxa. Several of the novel traits seem to be functional adaptations for feeding in the close confines of a burrow.

  • Morphology, behavior, and evolution: comparative kinematics of aquatic feeding in salamanders.
    Brain behavior and evolution, 1992
    Co-Authors: Stephen M. Reilly, George V. Lauder
    Abstract:

    The kinematics of aquatic prey capture were studied in species representing six salamander families (Ambystomatidae, Amphiumidae, Cryptobranchidae, Dicamptodontidae, Proteidae, and Sirenidae) to test the hypothesis that the process of aquatic prey capture is similar in these families. Seven variables were digitized from high-speed video records of prey capture, and a nested analysis of variance was performed to test for both significant individual within taxon and among taxa effects. The time-to-peak head angle and gape variables showed no taxon effect, while the other five variables exhibited highly significant differences among taxa. Cryptobranchus and Siren showed the most divergent kinematic pattern from the other taxa in a multivariate analysis of all variables, while Ambystoma, Dicamptodon, and Amphiuma tended to have similar overall patterns of head movement. These results show that kinematic patterns during aquatic feeding are not conserved across salamander taxa, and that phylogenetic differentiation in head morphology has been accompanied by novelties in feeding function. The feeding mechanisms of Cryptobranchus and Amphiuma have a bidirectional hydrodynamic design with kinematic correlates that are similar to kinematic characteristics of aquatic feeding in turtles and transformed ambystomatid salamanders. A general framework is presented as an aid to understanding the interrelationships among muscle activity patterns, morphology, and behavior (kinematic patterns). By considering the distribution of taxa in three multivariate spaces, corresponding to three of the levels at which one might analyze a behavior (kinematics, morphology, and motor pattern), it is possible to identify patterns of correspondence among the levels, which aid in understanding the evolution of behavior.