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PubMed1991

Immunohistochemical localization of components of the immune barrier in the olfactory mucosae of salamanders and rats.

Immunohistochemical techniques were used to investigate the cellular distribution of components of the secretory immune system, including secretory immunoglobulin, secretory piece, and J chain, as well as other immunoglobulins and nonspecific defense factors in the olfactory mucosae of salamanders and rats. In the salamander, secretory immunoglobulin M, and J chain were localized in duct and acinar cells of Bowman's glands, in B lymphocytes, and in sustentacular cells in immature regions of the olfactory mucosa. Lactoferrin and lysozyme were also present in Bowman's glands, in sustentacular cells in immature regions of the olfactory mucosa, and in blood cells in the lamina propria. Olfactory nerve section resulted in the presence of increased numbers of secretory immunoglobulin-immunoreactive B lymphocytes and in an altered distribution of IgM, secretory piece, and lactoferrin. In the rat, secretory immunoglobulin A and J chain were localized in duct and acinar cells of Bowman's glands and in B lymphocytes in the lamina propria. Secretory piece could be demonstrated in Bowman's glands only in rats that had a prior viral infection. Other defense factors, localized in the lamina propria, included IgG in the connective tissue stroma and in B lymphocytes, IgD-immunoreactive B lymphocytes, and IgE-immunoreactive cells that were identified as mucosal mast cells. Lactoferrin and lysozyme were present in serous acinar cells of Bowman's glands and in blood cells. These results demonstrate that the olfactory mucosa is protected from pathogenic invasion by the secretory immune system as well as other immunoglobulins, lactoferrin, and lysozyme.

Ambystoma↗
PubMed2003

Goalpha labels ON bipolar cells in the tiger salamander retina.

By using double-label immunocytochemistry and confocal microscopy, we studied rod and cone synaptic contacts, photoreceptor-bipolar cell convergence, and patterns of axon terminal ramification of ON bipolar cells in the tiger salamander retina. An antibody to recoverin, a calcium-binding protein found in photoreceptors and other retinal neurons in various vertebrates, differentially labeled rods and cones by lightly staining rod cell bodies, axons, and synaptic pedicles and heavily staining cone cell bodies and pedicles. An antibody to G(oalpha) labeled most ON bipolar cells, with axon terminals ramified mainly in strata 6-9 and a minor band in stratum 3 of the inner plexiform layer (IPL). Stratum 10 of the IPL was G(oalpha) negative, and previous studies showed that axon terminals of rod-dominated ON bipolar cells are monostratified in that stratum. The axonal morphology of G(oalpha)-positive cells resembled that of the cone-dominated (DBC(C)) or mixed rod and cone ON (DBC(M)) bipolar cells. The G(oalpha)-positive dendritic processes made close contact with all cone pedicles and superficial contact with some rod pedicles, consistent with the idea that G(oalpha) subunits are present in DBC(C)s and DBC(M)s. The size and density of these cells were analyzed, and their spatial distributions were determined. To our knowledge, this is the first study to characterize photoreceptor inputs and axon terminal morphology of a population of ON bipolar cell with the use of a G(oalpha) antibody as an immunomarker in the salamander retina.

Ambystoma↗
PubMed1989

Distribution of substance P-like, leucine-enkephalin-like, and bombesine-like immunoreactivity and acetylcholinesterase activity in the visual system of salamanders.

In the urodele species Salamandra salamandra and Batrachoseps attenuatus, the distribution of the neuropeptides substance P (SP), leucine-enkephalin (LENK), and bombesine (BOMB) was investigated by means of immunohistochemistry in brain areas containing retinofugal projection sites (tectum mesencephali, praetectum, thalamus) as well as in brain regions postsynaptic to the tectum. The activity of acetylcholinesterase (AChE) was studied histochemically. Despite its simplified, two-layered morphology, the salamander tectum shows a high degree of neurochemical differentiation, characterized by a laminar organization of neuropeptide-like immunoreactivity and AChE-activity comparable to that found in the anuran tectum, which has a multi-layered morphology. SP-like immunoreactivity constituted four tectal laminae, two of them occurring in the stratum opticum. LENK-like immunoreactivity formed three laminae, one in the stratum opticum. BOMB-like immunoreactivity formed one lamina within the stratum opticum and one in the tectal efferent layers. Layers 1 and 2 of the stratum opticum revealed high AChE-activity, whereas low activity was found in deep fiber layers containing tectal efferents. The outer cellular layer also revealed AChE-activity. After enucleation of one eye, the contralateral tectum lacked neuropeptide-like immunoreactivity and AChE-activity in the layers containing retinofugal projection sites. No reduction of immunoreactivity was found in nuclei postsynaptic to the tectum. Our experiments suggest that the secondary simplification that has taken place in salamanders with respect to tectal morphology did not affect the neurochemical differentiation of the tectum.

Acetylcholinesterase↗
PubMed1989

Morphology of retinal ganglion cells in lungless salamanders (fam. Plethodontidae): an HRP and Golgi study.

The family Plethodontidae consists of nearly two-thirds of all living urodeles; most of them possess highly developed visual abilities. We investigated the morphology of retinal ganglion cells (RGCs) in four representative species by means of the horseradish peroxidase method in flatmounts and in transverse sections and with the Golgi method in transverse sections. In flatmount preparations, four classes of RGCs were found, differing in dendritic arborization, dendritic field size, and stratification pattern of dendrites in the inner plexiform layer (IPL). Class-1 cells had small dendritic fields (29-44 microns 2) and arborized throughout the entire depth of the IPL. Class-2 cells had medium to large dendritic fields (75-206 microns 2) and mostly arborized in two or three laminae or in a diffuse fashion in the IPL. Class-3 cells had medium to large dendritic fields (72-200 microns 2) but sparse dendritic arborization. They only arborized in the proximal lamina of the IPL. Class-4 cells had large dendritic fields (273-626 microns 2) and branched in the most sclerad stratum of the IPL. No large differences in intraspecific soma size of the different RGC classes were detected (although interspecific soma size varied to a considerable degree) and no "giant" cells typically found in other vertebrate retinas were present. The results suggest that, with respect to the pattern of arborization and stratification of dendrites, lungless salamanders possess morphological classes of RGC similar to those found in frogs, but the morphology of RGCs in lungless salamanders seems to be simplified in comparison to frog RGCs. This simplification might be a consequence of paedomorphosis.

Animals↗
PubMed1991

Amacrine cells in the tiger salamander retina: morphology, physiology, and neurotransmitter identification.

Amacrine cells of the vertebrate retina comprise multiple neurochemical types. Yet details of their electrophysiological and morphology properties as they relate to neurotransmitter content are limited. This issue of relating light responsiveness, dendritic projection, and neurotransmitter content has been addressed in the retinal slice preparation of the tiger salamander. Amacrine cells were whole-cell clamped and stained with Lucifer yellow (LY), then processed to determine their immunoreactivity (IR) to GABA, glycine, dopamine or tyrosine hydroxylase (TOH), and glucagon antisera. Widefield, ON-OFF amacrine cells were glycine-IR. The processes of these cells extended laterally in the inner plexiform layer (IPL) from 250-600 microns. They were either multistratified in the IPL or monostratified near the IPL midline. Three multistratified ON-OFF narrowfield glycine-IR cells also were found. Four types of ON amacrine cells were found to be GABA-IR; all types had their processes concentrated in the proximal IPL (sublamina b). Type I cells were narrowfield (approximately 100 microns) with a compact projection. Type II cells were widefield (220-300 microns) with a sparse projection. Type III cells had an asymmetrical projection and varicose processes. Type IV cells were pyriform and monostratified in sublamina b. One narrowfield ON-OFF amacrine cell, with processes broadly distributed in the middle of the IPL, was GABA-IR. This cell appeared similar to an ON-OFF cell that was glycine-IR and may comprise a type in which GABA and glycine colocalize. Another class of amacrine cell, with processes forming a major plexus along the distal border of the IPL and a lesser plexus in the proximal IPL, produced slow responses at light ON and OFF; these cells were dopamine/TOH-IR. A narrowfield class of transient ON-OFF amacrine cell, with processes ramifying throughout both sublaminae a and b of the IPL, were glucagon-IR; these cells appeared to be dye-coupled at the soma. We have shown that, with respect to GABA, glycine, dopamine, and glucagon, salamander amacrine cells fall into rather discrete groups on the basis of ramification patterns in the IPL and responses to photic stimulation. The physiological, structural, and neurochemical diversity of amacrine cells is indicative of multiple and complex roles in retinal processing.

Ambystoma↗
PubMed1995

Morphology of ganglion cells in the neotenous tiger salamander retina.

The morphology of retinal ganglion cells in the neotenous tiger salamander (Ambystoma tigrinum) was analyzed with the aid of morphometric techniques to determine the diversity of cell types and to evaluate the widely held notion that this form of Ambystoma has a simple retina, with little variance among its cell morphologies. Single-cell staining was achieved through retrograde labeling with horseradish peroxidase injected around the optic nerve sheath followed by a period of several days before tissue processing; 83 well-labelled cells with axons were studied in detail with light microscopy and a computer-aided reconstruction system. Five different morphological cell classes were devised based on broad morphometric criteria such as the dendritic area of influence; the number, length, and complexity of dendritic branches; and the amount of overlap between neighboring dendrites. These classes included small simple, small complex, medium simple, medium complex, and large cells. In addition, a class of cells with numerous varicosities among the dendrites was separately analyzed. These swellings did not stain for catecholamines. Based on optical determinations of the dendritic sublamination pattern within the inner plexiform layer, presumed On-Off cells are present in all subclasses, whereas On cells predominate in the smaller cell groups. Presumed Off cells are well represented in the large field units, although the small total number of cells in this latter class leads to uncertainty regarding the significance of this observation. The diversity of ganglion cell morphology revealed in the present study argues against the assumption that the neotenous tiger salamander has a simple retina, with a relatively invariant set of ganglion cells. On the contrary, it appears that this aquatic form shows morphological diversity in the retinal ganglion cell population rivaling that reported for other vertebrates, including mammals. A functional role for the different cell classes is briefly considered.

Animals↗
PubMed1995

Sexual and seasonal differences in the vomeronasal epithelium of the red-backed salamander (Plethodon cinereus).

Sexually dimorphic behaviors often are associated with sexually dimorphic neural structures. Perinatal hormonal levels influence structural sexual dimorphism, and seasonal structural changes also can be the result of seasonal hormonal fluctuations. We compared the volume of vomeronasal organs of male and female red-backed salamanders (Plethodon cinereus) throughout the year. Odorants are delivered to vomeronasal receptors through nasolabial grooves when salamanders touch the bases of these grooves to objects (nose tapping). Males may locate and identify potential mates through nose tapping during the prolonged breeding season that lasts from October through May. We compared vomeronasal organ data through multiple regression by using total body size, sex, and season as variables that may influence vomeronasal organ volume. Gonads also were examined as an indicator of reproductive status. Total body size and sex significantly affect vomeronasal organ volume; as body size increases, so does vomeronasal organ volume, and males have significantly larger vomeronasal organs than females at all times of the year. During the summer, both males and females have larger vomeronasal organs than at any other time of the year. Summer also is a period of intense foraging and the initiation of a new cycle of gametogenesis. Previous studies of circulating hormone levels in amphibians have shown that the initial stages of gametogenesis correspond to a period of low estradiol and testosterone levels but high gonadotropin-releasing hormone levels. The functional significance of sexual and seasonal differences in the vomeronasal organs of P. cinereus may relate to the neurogenesis of specialized receptors for courtship and mating.

Animals↗
PubMed2004

Induction of micronucleated cells in the shed skin of salamanders (Ambystoma sp.) treated with colchicine or cyclophosphamide.

The micronucleus (MN) assay can be used to detect the genotoxic effects of chemical agents in virtually any cell that divides frequently. Salamanders (Ambystoma sp.) are amphibians that can be easily maintained and bred in the laboratory and spontaneously shed their skin every 2.5-4 days. In this present study, we have evaluated the usefulness of this shed skin for the MN assay. We exposed salamanders to different concentrations of both the aneugen colchicine (COL) and the clastogen cyclophosphamide (CP) and we determined the frequency of micronucleated cells (MNCs) in their sheds. Fragments of shed skin were placed on clean slides, fixed, stained, observed with a light microscope, and the number of MNCs was counted. The MNC frequency was increased significantly by all doses of COL and CP tested, administered either as single or repeated exposures. The presence of MNCs in the shed skin and the speed of sloughing lead us to propose that the sheds of Ambystoma sp., or other amphibians that slough their skin, are suitable alternative models for detecting genotoxic exposures relevant to aquatic environments.

Ambystoma↗
PubMed2003

Pharmacological characterization of P2Y receptor subtypes on isolated tiger salamander Müller cells.

Müller cells express a variety of neurotransmitter receptors that permit them to "sense" the extracellular environment within the retina. We have used a battery of agonists and antagonists to characterize the purinergic receptor subtypes expressed on isolated tiger salamander Müller cells. Changes in intracellular calcium ion concentration ([Ca(2+)](i)) in Müller cells were measured using the Ca(2+) indicator dye Fura-2 and digital imaging microscopy. ATP, 2-methylthio-ATP, 2-methylthio-ADP, ADP, UTP, UDP, deoxyATP, and 3'-O-(4-benzoyl)benzoyl ATP evoked increases in [Ca(2+)](i) in both the presence and absence of extracellular Ca(2+). Therefore, the increases we observed were likely due to intracellular Ca(2+) release mediated by G-protein-coupled P2Y receptor activation, rather than Ca(2+) influx via P2X receptor channels. The P2Y(1) receptor agonists 2-methylthio-ATP, 2-methylthio-ADP, and ADP evoked increases in [Ca(2+)](i) that were inhibited by the P2Y(1) receptor antagonists adenosine 3'-phosphate 5'-phosphosulfate and 2'-deoxy-N(6)-methyleneadenosine-3',5'-bisphosphate. Responses to ADP were not completely inhibited by the P2Y(1) receptor antagonists. The residual response to ADP could be mediated by P2Y(13) receptors. UTP evoked an increase in [Ca(2+)](i) that was partially inhibited by suramin, suggesting that Müller cells express P2Y(2) and P2Y(4) receptors. The P2Y(6) receptor agonist UDP, and the P2Y(11) receptor agonists deoxyATP, and 3'-O-(4-benzoyl)benzoyl ATP, evoked increases in [Ca(2+)](i) in Müller cells. We conclude that isolated tiger salamander Müller cells express P2Y(1), P2Y(2), P2Y(6), P2Y(11), and possibly P2Y(4) and P2Y(13) receptors. Therefore, the physiological release of ATP, ADP, UTP, and UDP and/or their accumulation in the retina under pathological conditions could stimulate increases in [Ca(2+)](i) in Müller cells.

Adenosine Diphosphate↗
PubMed1987

Carbonic anhydrase cytochemistry in mitochondria-rich cells of salamander larvae gill epithelium as related to age and H+ and Na+ concentrations.

Carbonic anhydrase (CAH) was localized in the mitochondria-rich cells (MRC) of 1-week-old salamander larvae gill epithelium, in both MRC and pavement cells of 6-week-old larvae, and in regenerated stems of previously amputated gills. CAH activity of the MRC was measured quantitatively using a microscope densitometric technique. Changes in CAH activity per cell and changes in the numbers of CAH-positive MRC were followed under different H+ and Na+ concentrations at the two age groups. CAH activity per cell increased with age, whereas the numbers of CAH-positive MRC dropped. CAH activity per cell in the 1-week-old age group reached maximal values at pH 7.4 and stayed relatively high in the more alkaline media. Moderate increases of Na+ concentrations had small but significant effects on increasing CAH activity of gill MRC. When taking into consideration not only the changes in cellular activity but also the changes in the number of CAH-positive cells under the different acclimation media, an activity index (ICAH) was calculated. Thus, the ICAH in the 1-week-old was found to be dependent on the decline of ambient H+ concentrations (expressed as increasing pH), reaching maximal effect at pH 8.0. On the other hand, raising the Na+ concentrations of the acclimation media to 110 and 220 mOsm/liter caused a maximal inhibition of tissue CAH activity as expressed by ICAH. In conclusion, it is suggested that salamander larvae gill MRC take part in the adaptation of the larvae to changing H+ concentrations of their milieu rather than in their adaptation to changes in its osmolality.

Aging↗
PubMed1982

Collagens from the skin and cartilage of the larval salamander Ambystoma tigrinum.

The major collagens of larval salamander (Ambystoma tigrinum) skin and cartilage were purified and characterized by CM-cellulose chromatography and amino acid analysis of the component alpha chains. The collagens are similar to type I (skin) and type II (cartilage) collagens of birds and mammals. The type I molecule has the chain composition (alpha 1)2 alpha 2, and the type II molecule is an (alpha 1)3 molecule. Both collagens have lower levels of proline hydroxylation than the collagens isolated from homoiotherms, and generally higher serine contents. The type II collagen molecule has about half of its lysine residues hydroxylated, as in cartilage collagens of other species. Cyanogen bromide digestion of the component alpha chains followed by CM-cellulose chromatography or SDS gel electrophoresis of the peptides confirms that each chain is a different gene product and allows identification of the collagens in this species. Similar collagens were isolated from newt (Notophthalmus viridescens) tissues by pepsin extraction and fractional salt precipitation. These data will allow more effective utilization of the regeneration salamander limb for studies of collagen metabolism during regeneration.

Ambystoma↗
PubMed1987

Heat shock protein induction and induced thermal tolerance are independent in adult salamanders.

Ectothermic vertebrates become thermally tolerant (heat hardened) after exposure to heat shock. Eukaryotic cells show a similar response. Cellular thermal tolerance is correlated with the induction of heat shock proteins (hsps). We have investigated the relationship between heat hardening in salamanders and the induction of hsps in the tissues of these organisms. Although the synthesis of hsps can be induced in these animals by sublethal heat shocks, conditions required for hsp induction and heat hardening often do not coincide. We conclude that induced thermal tolerance in adult salamanders is independent of hsp induction in their tissues.

Acclimatization↗
PubMed2001

Homology and evolutionary novelty in the deployment of extracellular matrix molecules during pigment pattern formation in the salamanders Taricha torosa and T. rivularis (Salamandridae).

Salamander larvae exhibit a diverse array of pigment patterns shortly after hatching. Previous studies have identified roles for the extracellular matrix and lateral line sensory system in promoting the development of a phylogenetically common pattern of horizontal melanophore stripes. In contrast, salamanders in the genus Taricha exhibit evolutionarily derived pigment patterns and pattern-forming mechanisms. Taricha torosa larvae exhibit compact melanophore stripes that develop via redundant, lateral line-independent mechanisms, whereas T. rivularis larvae lack stripes and instead have melanophores uniformly distributed over the flank. In this study, I test roles for candidate patterning molecules of the extracellular matrix in promoting the development of species-specific pigment patterns in Taricha. I show that tenascin deposition is negatively correlated with melanophore distributions both intraspecifically and interspecifically: this matrix molecule is present where melanophores do not localize in T. torosa and is absent from these same regions where melanophores are abundant in T. rivularis. Embryological manipulations further indicate that transient expression of tenascin in a prospective interstripe region of T. torosa reflects a phylogenetically conserved effect of lateral line development. Finally, anti-laminin immunoreactivity is negatively correlated with melanophore distributions in T. torosa, and this species exhibits a general retardation of extracellular matrix development that may allow persistent, evolutionarily novel melanophore motility in this species. Together these findings identify tenascin and laminin, or molecules co-regulated with these matrix components, as candidates for promoting early larval pigment pattern development in Taricha.

Animals↗
PubMed2005

Olfactory metamorphosis in the Coastal Giant Salamander (Dicamptodon tenebrosus).

This study examined the gross morphology and ultrastructure of the olfactory organ of larvae, neotenic adults, and terrestrial adults of the Coastal Giant Salamander (Dicamptodon tenebrosus). The olfactory organ of all aquatic animals (larvae and neotenes) is similar in structure, forming a tube extending from the external naris to the choana. A nonsensory vestibule leads into the main olfactory cavity. The epithelium of the main olfactory cavity is thrown into a series of transverse valleys and ridges, with at least six dorsal and nine ventral valleys lined with olfactory epithelium, and separated by ridges of respiratory epithelium. The ridges enlarge with growth, forming large flaps extending into the lumen in neotenes. The vomeronasal organ is a diverticulum off the ventrolateral side of the main olfactory cavity. In terrestrial animals, by contrast, the vestibule has been lost. The main olfactory cavity has become much broader and dorsoventrally compressed. The prominent transverse ridges are lost, although small diagonal ridges of respiratory epithelium are found in the lateral region of the ventral olfactory epithelium. The posterior and posteromedial wall of the main olfactory cavity is composed of respiratory epithelium, in contrast to the olfactory epithelium found here in aquatic forms. The vomeronasal organ remains similar to that in large larvae, but is now connected to the mouth by a groove that extends back through the choana onto the palate. Bowman's glands are present in the main olfactory cavity at all stages, but are most abundant and best developed in terrestrial adults. They are lacking in the lateral olfactory epithelium of the main olfactory cavity. At the ultrastructural level, in aquatic animals receptor cells of the main olfactory cavity can have cilia, short microvilli, a mix of the two, or long microvilli. Supporting cells are of two types: secretory supporting cells with small, electron-dense secretory granules, and ciliated supporting cells. Receptor cells of the vomeronasal organ are exclusively microvillar, but supporting cells are secretory or ciliated, as in the main olfactory cavity. After metamorphosis two distinct types of sensory epithelium occur in the main olfactory cavity. The predominant epithelium, covering most of the roof and the medial part of the floor, is characterized by supporting cells with large, electron-lucent vesicles. The epithelium on the lateral floor of the main olfactory cavity, by contrast, resembles that of aquatic animals. Both types have both microvillar and ciliated receptor cells. No important changes are noted in cell types of the vomeronasal organ after metamorphosis. A literature survey suggests that some features of the metamorphic changes described here are characteristic of all salamanders, while others appear unique to D. tenebrosus.

Animals↗
PubMed1976

Tongue evolution in the lungless salamanders, family plethodontidae. I. Introduction, theory and a general model of dynamics.

Plethodontid salamanders capture prey by projecting the tongue from the mouth. An analysis of theoretical mechanics of the hyobranchial skeleton is used to formulate a working hypothesis of tongue movements. Predictions that the skeletal elements of the tongue are included in the projectile and that the hyobranchial skeleton is folded during projection are central to the analysis. When decapitated in a particular way, salamanders project the tongue, and it is not retracted. When these heads are fixed and sectioned, examination confirms the predications. In turn, these observations are used to refine the working hypothesis and to generate a general model of tongue dynamics for plethodontids. Muscles performing the major roles of projection (subarcualis rectus I) and retraction (rectus cervicis profundus) are identified. The skeleton is folded passively along a morphological track having the form of a tractrix. Predictions concerning the shape of the track and the exact configuration of the folded skeleton are confirmed by study of sectioned material. The skeleton unfolds along the track during retraction and is spread into the resting state. The model developed herein will be used as a basis for predictions concerning selection patterns in the family and for analytical purposes in comparative and evolutionary studies.

Animals↗
PubMed1983

Miniaturization and its effects on cranial morphology in plethodontid salamanders, genus Thorius (Amphibia, Plethodontidae): II. The fate of the brain and sense organs and their role in skull morphogenesis and evolution.

Relative size and arrangement of the brain and paired sense organs are examined in three species of Thorius, a genus of minute, terrestrial salamanders that are among the smallest extant tailed tetrapods. Analogous measurements of representative species of three related genera of larger tropical (Pseudoeurycea, Chiropterotriton) and temperate (Plethodon) salamanders are used to identify changes in gross morphology of the brain and sense organs that have accompanied the evolution of decreased head size in Thorius and their relation to associated changes in skull morphology. In adult Thorius, relative size (area measured in frontal plane, and length) of the eyes, otic capsules, and brain each is greater than in adults of all of the larger genera; relative size of the nasal capsules is unchanged or slightly smaller. Interspecific scaling phenomena--negative allometry of otic capsule, eye and brain size, isometry or slight positive allometry of nasal capsule size, all with respect to skull length--also are characteristic of intraspecific (ontogenetic) comparisons in both T. narisovalis and Pseudoeurycea goebeli. Predominance of the brain and eyes in Thorius results in greater contact and overlap among these structures and the nasal capsules in the anterior portion of the head. This is associated with anterior displacement of both the eyes and nasal capsules, which now protrude anterior to the skull proper; a change in eye shape; and medial deformation of anterior braincase walls. Posteriorly, predominance of the otic capsules has effected a reorientation of the jaw suspensorium to a fully vertical position that is correlated with the novel presence of a posteriorly directed squamosal process and shift in origin of the quadropectoralis muscle. Many of these changes in cranial morphology may be explained simply as results of mechanical (physical) interactions among the skeletal, nervous, and sensory components during head development at reduced size. This provides further evidence of the role of nervous, sensory, and other "soft" tissues in cranial skeletal morphogenesis, and reinforces the need to consider these tissues in analyses of skull evolution.

Animals↗
PubMed1983

Tongue evolution in lungless salamanders, family plethodontidae. III. Patterns of peripheral innervation.

Innervation of the tongue and associated musculature in plethodontid salamanders was studied using Palmgren stained sectioned materials, fresh dissection, and whole mounts of experimental specimens treated with horseradish peroxidase (HRP). Species studied were chosen to represent modes of tongue projection recognized by Lombard and Wake ('77). Special attention was given to species of the genera Plethodon, Batrachoseps, Pseudoeurycea, and Hydromantes, but representatives of other genera were investigated. As expected we found that cranial nerves IX and X and spinal nerve 1 supplied the muscles involved in tongue movement. The peripheral courses of the nerves were traced, and both functionally related and phylogenetically determined routes were found. As relative projection length increases, the nerves supplying the tongue tip also increase in length. When the tongue is at rest the long nerves are stored in coils. The coil of ramus lingualis lies between the ceratobranchials, but that of ramus hypoglossus is more variable, although constant within a species. Ramus hypoglossus bifurcates into separate branches to tongue and anterior musculature of the floor of the mouth. In generalized, presumably primitive, modes the bifurcation and coiling are far anterior. In most of the tongue projection modes bifurcation is relatively posterior, but in one, bifurcation is anterior, but coiling is relatively posterior in position. The most unusual condition is in Hydromantes, in which bifurcation is relatively posterior and a coiled ramus hypoglossus joins a coiled ramus lingualis to form a unique, coiled common ramus to the tongue tip. Hydromantes has the greatest projection distance of any salamander.

Anatomy, Comparative↗
PubMed1993

Spermathecal cytology of Ambystoma opacum (Amphibia: Ambystomatidae) and the phylogeny of sperm storage organs in female salamanders.

Sperm storage glands, spermathecae, were examined from mated female Ambystoma opacum during the breeding season. No differences occur in the spermathecal ultrastructure of individuals sacrificed prior to oviposition and those sacrificed within 3 days of removal from tended clutches of recently oviposited eggs. The simple tubuloalveolar glands produce two types of secretory vacuoles. Apical secretory vacuoles contain glycosaminoglycans for export into the lumen to bathe stored sperm, perhaps providing the chemical/osmotic environment necessary for sperm quiescence. The other type of secretory vacuole contains an unsaturated lipid that is produced for export into the connective tissue surrounding the spermathecae. The role of this secretion may involve the contraction of myoepithelial cells, resulting in sperm expulsion. Some sperm undergo degradation in the spermathecal epithelium, and an interepithelial leukocyte was observed in one specimen. Apical secretory vacuoles and sperm are absent from the spermathecae of a specimen sacrificed 62 days after removal from a tended egg clutch. This is the first report on the spermathecal cytology of a salamander from the Ambystomatidase, and comparisons with salamanders from other families provide a morphological basis for considering spermathecae polyphyletic within the Caudata.

Ambystoma↗