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PubMed2007

Cranial musculature in the larva of the caecilian, Ichthyophis kohtaoensis (Lissamphibia: Gymnophiona).

Within the Gymnophiona (caecilians) oviparous species with biphasic life-cycles possess a free living semi-aquatic larval stage that feeds in aquatic habitats. The larvae pass through a metamorphosis to a purely terrestrial adult stage. It is likely that the cranial morphology of caecilian larvae has specializations for aquatic feeding. However, little is known about the cranial morphology, and the cranial musculature is especially neglected in the literature. This study provides a detailed description of the jaw and hyobranchial musculature in larval stages of a caecilian. We studied late embryonic and early larval specimens of Ichthyophis kohtaoensis. Furthermore, we compared and homologized the cranial muscles found in larval I. kohtaoensis with the muscles described for adult caecilians. Most cranial muscles of larval I. kohtaoensis are also present in the adult, except for the m. levator mandibulae externus and the m. subarcualis obliquus II. Our results were compared with the data available for larval frogs and salamanders in order to hypothesize the cranial musculature in the larva of the most recent common ancestor of the Lissamphibia. Larval caecilians, frog tadpoles, and salamander larvae share many characters in their cranial musculature, which, consequently, can be assigned to the lissamphibian ground pattern. However, the m. pterygoideus and the m. levator quadrati are unique to the Gymnophiona.

Aging↗
PubMed1986

Comparative morphology of the amphibian opercularis system: I. General design features and functional interpretation.

The morphology of the opercularis system of anuran and caudate amphibians suggests that it acts to produce motion of the operculum that in turn produces fluid motion within the inner ear. The operculum and opercularis muscle form a lever system, with a narrow connection between the operculum and otic capsule acting as a fulcrum about which the operculum moves in response to forces applied via the muscle. The opercula of many species possess a muscular process on which the muscle inserts, thereby increasing the moment arm through which the muscle acts. The tonicity of the opercularis muscle allows tensile forces produced by substrate vibration or other mechanical energy applied to the forelimb to be effectively transmitted to the operculum; the elasticity of the connective tissue holding the operculum in place should act to return the operculum to its original position. The opercularis systems of frogs and non-plethodontid salamanders are similar structurally and functionally; that of plethodontid salamanders is structurally distinct but also functions as a lever system. Fluid motion produced by opercular motion could stimulate various end organs of the inner ear; the saccule, lagena, and amphibian papilla are in close approximation and wave energy could directly affect their otoconial or tectorial structures. In those anurans with a tympanic ear, the stapedial footplate and operculum articulate, but this articulation allows both to move independently. The stapes-tympanum complex and opercularis system therefore appear to be independent functional systems, and it is unlikely that the opercularis system modulates middle ear responsiveness. The general design of the opercularis system is consistent with a function in reception of substrate vibrations.

Animals↗
PubMed1995

Embryonic origin of amphibian taste buds.

Despite numerous descriptive studies, the embryonic origin of vertebrate taste buds has never been experimentally determined. A number of different alternatives have been suggested for taste bud origins, including epibranchial placodes, the neural crest, and the local epithelium of the oropharyngeal cavity. The role of a series of epibranchial placodes and the cephalic neural crest, which together give rise to the cranial nerves innervating taste buds, was examined with regard to the development of oropharyngeal taste buds in an ambystomatid salamander, the axolotl. When pigmented placodal ectoderm or neural folds were grafted isotopically and isochronically into nonpigmented host embryos, known derivatives of each tissue contained pigmented cells, but labeled taste buds were never encountered. Thus, neither epibranchial placodes nor neural crest contribute cells to taste buds during embryogenesis. The majority of the oropharyngeal cavity of ambystomatid salamanders is lined by an endodermal epithelium. In order to demonstrate conclusively that taste buds arise from this local epithelium, the presumptive cephalic endoderm of early axolotl gastrulae was microinjected with the lipophilic dye, DiI. In the oropharyngeal epithelium of all larvae examined, both taste buds and general epithelial cells were labeled with DiI, indicating their common endodermal origin. Our findings are novel in that this is the first experimental demonstration of the endodermal origin of a vertebrate sensory receptor cell class.

Ambystoma↗
PubMed2000

Effects of spray-irrigated wastewater effluent on temporary pond-breeding amphibians.

Comparison was made of abiotic conditions, amphibian reproductive outputs, and the survival of embryonic and larval amphibians in wastewater effluent-irrigated and natural temporary ponds in an area in Centre County, Pennsylvania that has been spray-irrigated with secondarily treated, chlorinated wastewater effluent from The Pennsylvania State University for approximately 14 years. Three species of temporary pond-breeding amphibians were studied: wood frogs (Rana sylvatica LeConte), Jefferson salamanders (Ambystoma jeffersonianum Green), and spotted salamanders (A. maculatum Gravenhorst). Comparisons of physico-chemical parameters in 10 wastewater-irrigated and 10 natural temporary ponds over 19 weeks in 1997 indicated that wastewater -irrigated ponds had significantly higher median conductance, pH, ¿Na, ¿K, ¿Ca, ¿Mg, and ¿N-NO(3) and lower ¿dissolved oxygen. Many of the wastewater-irrigated ponds supported large mats of duckweed (Lemna spp.) that completely blanketed the pond's surface by mid-May. There were significantly fewer egg masses of all three species in wastewater-irrigated ponds than in natural ponds in both 1997 and 1998. In situ egg hatching success and larval survival (over a 6-day period) of all species was lower in wastewater-irrigated ponds than in natural ponds. Cumulatively, these studies suggest that wastewater effluent irrigation may impact amphibian populations by reducing the survival of amphibian eggs and larvae.

Ambystoma↗
PubMed1997

Purification and structural characterization of insulin from the lesser siren, Siren intermedia (Amphibia: Caudata).

Insulin has been isolated from an extract of the pancreas of a salamander, the lesser siren Siren intermedia, and its primary structure was established as: A-chain, Gly-Ile-Val- Glu-Gln-Cys-Cys-His-Asn-Thr10-Cys-Ser-Leu-Tyr-Gln-Leu-Glu-Asn-Tyr- Cys20-Asn, and B-chain, Val-Pro-Asn-Lys-Pro- Leu-Cys-Gly-Ala-His10-Leu-Val-Glu-Val-Met-Tyr-Phe-Val- Cys-Gly20-Asp-Arg-Gly-Phe-Phe-Tyr-Pro-Ser-Ser-Thr 30. Although those amino acid residues considered to constitute the receptor-binding region of insulin have been retained, siren insulin contains several substitutions (Gln-->Lys at B4, Ser-->Ala at B9, Ala-->Val at B14, Leu-->Met at B15, Leu-->Phe at B17, Pro-->Ser at B28, and Lys-->Ser at B29) of amino acid residues that are conserved in insulins from species of other amphibian orders. The biological activity of siren insulin was not investigated in this study but the substitutions at B28 (involved in dimer formation) and at B14 and B17 (involved in hexamer formation) may be expected to influence conformation and therefore biological potency. The data are consistent with the view that the Sirenoidea represent an early divergence from the ancestral stock of salamanders.

Amino Acid Sequence↗
PubMed2000

Pharmacological adrenalectomy with mitotane.

The potential of mitotane (ortho, para'-DDD, commonly used to treat adrenal carcinomas in humans and dogs) was investigated as an alternative to surgical adrenalectomy in birds, salamanders, and lizards. House sparrows (Passer domesticus) were injected twice daily with vehicle or one of two doses of mitotane (225 or 450 mg/kg), and basal and stress-induced levels of corticosterone (CORT) were measured 3 and 5 days after injections. Mitotane reduced basal CORT levels to nondetectable and abolished stress-induced CORT increases by the 3rd day of treatment. In another study, a single injection of mitotane was effective in lowering endogenous CORT levels 36 h later, but levels had apparently recovered by 10 days after the injection. Mitotane did not effect testicular weights and had no detectable effect on testosterone levels. In contrast to its effects on house sparrows, mitotane did not lower endogenous CORT levels in either tiger salamanders (Ambystoma tigrinum) or tree lizards (Urosaurus ornatus), even at doses much higher than those used in house sparrows.

Adrenalectomy↗
PubMed1984

Electrophysiology and anatomy of direction-specific pretectal units in Salamandra salamandra.

Pretectal cells of the European fire salamander were recorded extracellularly during binocular and monocular horizontal optokinetic stimulations. The locations of the individual units within the pretectal nucleus were verified with Alcian blue injections. The particular anatomical properties of single cells were demonstrated after single-unit recordings by means of horseradish peroxidase preparations. Direction selective pretectal cells were found to be predominantly (2/3) sensitive to temporo-nasal movements in the visual field of the contralateral eye. They usually possessed large receptive fields centered on the visual equator with restricted diameters in the dorso-ventral axis. Their resting discharge was low, and in some cells no spontaneous discharges were observed. The cells preferred low stimulus velocities, most of them being optimally stimulated with velocities of 1 to 10 deg/s. A group of units was exclusively sensitive to accelerated movements. A subclass of them was transiently responsive when the stimulus stopped. In the anterior and most dorsal part of the pretectal nucleus, binocularly influenced units were found. These cells responded best with binocular optokinetic stimulations and less vigorously or with less pronounced direction selectivity if only the contralateral eye was stimulated. With ipsilateral stimulations alone no response could be elicited. This response type could be explained by inhibitory inputs from the ipsilateral eye via direct ipsilateral projections or crossing pretectal fibers. The responses of these cells are well correlated to behavioral results showing that OKN performance in salamanders, as in some other vertebrates, is different with binocular as compared to monocular stimulations. The direction-sensitive pretectal cells usually possess extensive dendritic arborizations within the ipsilateral pretectal neuropil. Most of the cell bodies were scattered in the white substance or in the superficial layers of the periventricular gray. In the cases where the efferent fiber of a particular cell could be clearly recognized, the axon projected to the basal optic neuropil of the accessory optic system, the contralateral pretectum or, in two cases, to the medulla oblongata into a region which might be homologous to the inferior olive of higher vertebrates.

Animals↗
PubMed1976

Olfactory epithelium of Necturus maculosus and Ambystoma tigrinum.

The morphological study presented here provides a general description of the elements of the olfactory epithelium in the mud puppy and tiger salamander,, and gives evidence about their dynamic activity and interrelationships. There are morphological indications of local bursts of reduplication and a continual line of differentiation of receptor cells from basal cell progenitors through stages of mature development to senescence (indicated by the accumulation of pigment granules) and cell death and disposal (by expulsion of pycnotic cell nuclei and by phagocytosis by macrophages). The supporting cells probably play several roles: a secretory role which supplements the activity of Bowman's glands, a minor insulating role in which some dendrites are shielded from the surrounding milieu, and a skeletal role in which they facilitate the efficient displacement of dendrites. The dendrites are regularly arranged in organized relationships with one another and are for the most part in direct apposition, separated only by a 200 A intercellular gap, thus suggesting the possibility of functional interrelationships. This study emphasizes the fact that efficient planning of experimental investigations must include knowledge and consideration of the thickness of the particular olfactory epithelium under study. It also suggests that because of the large receptor-cell size, the mud puppy and/or tiger salamander would make good model systems for single cell recording. Further, the olfactory epithelia of these species are suggested as favorable targets for studies of the aging process in nerve cells.

Ambystoma↗
PubMed1983

Evidence for orthogonal arrays of particles in the plasma membranes of olfactory and vomeronasal sensory neurons of vertebrates.

Plasma membranes of sensory neurons from the olfactory and vomeronasal neuroepithelia of the male rat and olfactory neuroepithelium of the tiger salamander (Ambystoma tigrinum) have been examined, using the freeze-fracture technique, for the presence and morphology of orthogonal arrays of particles (OAP). Numerous OAP were scattered on the P-face of plasma membranes of the dendrites and cell bodies from rat vomeronasal sensory neurons. The OAP were 720 +/- 200 nm2 in area and they consisted of 4 to 20 particles whose centre-to-centre distance was about 7 nm. On the E-face, complementary orthogonal arrays of pits were observed. No OAP were detected in the olfactory sensory neurons of the rat. In the dendritic and perikaryal plasma membranes of the tiger salamander olfactory sensory neurons, OAP 2230 +/- 970 nm2 in area were observed on the P-face. The OAP consisted of 12 to 36 particles. The centre-to-centre distance of the particles was about 7 nm. In the olfactory receptor cell plasma membranes of this species, OAP formed complexes of 2 to 28 individual OAP, the longitudinal axes of which were usually arranged in parallel. Complementary complexes of orthogonal arrays of pits were observed on the E-face.

Ambystoma↗
PubMed1998

Effects of boron and nitrate on hatching success of amphibian eggs.

As part of a land-application wastewater disposal system in central Pennsylvania, vernal ponds are commonly exposed to wastewater effluent containing high levels of boron and nitrate. We examined the individual effects of these compounds on the eggs of amphibians breeding in these ponds. Wood frog (Rana sylvatica), Jefferson salamander (Ambystoma jeffersonianum), spotted salamander (A. maculatum), and American toad (Bufo americanus) eggs were exposed to boron (0, 50, and 100 mg L-1) and nitrate (0, 10, 25, and 40 mg L-1) under laboratory conditions. There was no difference in the hatching success or proportion of deformed larvae among the four nitrate levels in any of the species. High boron concentrations reduced the hatching success of B. americanus and produced more deformed offspring in R. sylvatica, A. jeffersonianum, and A. maculatum. Deformed R. sylvatica and A. jeffersonianum hatchlings displayed a "curling defect" in which the larvae had a crescent body shape and expressed difficulty in swimming. A. maculatum larvae from high boron treatments displayed a different abnormality, possibly because of longer times to hatching, characterized by a swelling of the thoracic region and altered gill morphology. Although the concentrations of boron and nitrate tested were within the range measured in wastewater effluent, maximum levels of boron and nitrate in breeding ponds were only 1.5 mg L-1 and 26.7 mg L-1 respectively, likely due to rainwater dilution and biological and chemical processes reducing the levels of these compounds in vernal ponds. Nonetheless, these studies are the first to examine the effects of boron and nitrate on amphibian egg hatching success, and to demonstrate that elevated boron concentrations can detrimentally affect the development of amphibian embryos.

Amphibians↗
PubMed2004

Discrimination of conspecific sex and reproductive condition using chemical cues in axolotls ( Ambystoma mexicanum).

Chemosensory cues play an important role in the daily lives of salamanders, mediating foraging, conspecific recognition, and territorial advertising. We investigated the behavioral effects of conspecific whole-body odorants in axolotls, Ambystoma mexicanum, a salamander species that is fully aquatic. We found that males increased general activity when exposed to female odorants, but that activity levels in females were not affected by conspecific odorants. Although males showed no difference in courtship displays across testing conditions, females performed courtship displays only in response to male odorants. We also found that electro-olfactogram responses from the olfactory and vomeronasal epithelia were larger in response to whole-body odorants from the opposite sex than from the same sex. In males, odorants from gravid and recently spawned females evoked different electro-olfactogram responses at some locations in the olfactory and vomeronasal epithelia; in general, however, few consistent differences between the olfactory and vomeronasal epithelia were observed. Finally, post hoc analyses indicate that experience with opposite-sex conspecifics affects some behavioral and electrophysiological responses. Overall, our data indicate that chemical cues from conspecifics affect general activity and courtship behavior in axolotls, and that both the olfactory and vomeronasal systems may be involved in discriminating the sex and reproductive condition of conspecifics.

Action Potentials↗
PubMed2004

Hatching asynchrony, survival, and the fitness of alternative adult morphs in Ambystoma talpoideum.

The mole salamander, Ambystoma talpoideum, exhibits both aquatic (gilled) and terrestrial (metamorphosed) adult morphologies. Previous studies have shown the existence of body-size advantages associated with the terrestrial morph in A. talpoideum and other polymorphic salamanders (e.g., A. tigrinum). However, aquatic adult A. talpoideum mature at a younger age and often breed earlier than terrestrial adults. We tested the hypothesis that early maturation and reproduction in aquatic adults increase fitness (irrespective of body size). We reared larval A. talpoideum in mesocosms and varied the timing of hatching, with early-hatching larvae representing the offspring from early-breeding aquatic adults, and late-hatching larvae representing the offspring of later-breeding terrestrial adults. Our results demonstrate significantly higher survival rates among early-hatchlings relative to late-hatching conspecifics, supporting the hypothesis that early reproduction may be an important mechanism mediating the polymorphism in A. talpoideum. We discuss our results within the context of size-based models of the fitness of alternative life-cycles.

Ambystoma↗
PubMed2006

Predator defense along a permanence gradient: roles of case structure, behavior, and developmental phenology in caddisflies.

Species replacements along freshwater permanence gradients are well documented, but underlying mechanisms are poorly understood for most taxa. In subalpine wetlands in Colorado, the relative abundance of caddisfly larvae shifts from temporary to permanent basins. Predators on caddisflies also shift along this gradient; salamanders (Ambystoma tigrinum nebulosum) in permanent ponds are replaced by predaceous diving beetles (Dytiscus dauricus) in temporary habitats. We conducted laboratory and field experiments to determine the effectiveness of caddisfly cases in reducing vulnerability to these predators. We found that larvae of a temporary-habitat caddisfly (Asynarchus nigriculus) were the most vulnerable to salamanders. Two relatively invulnerable species (Limnephilus externus, L. picturatus) exhibited behaviors that reduced the likelihood of detection and attack, whereas the least vulnerable species (Agrypnia deflata) was frequently detected and attacked, but rarely captured because cases provided an effective refuge. Vulnerability to beetle predation was also affected by cases. The stout cases of L. externus larvae frequently deterred beetle larvae, whereas the tubular cases of the other species were relatively ineffective. Two of these vulnerable species (A. nigriculus and L. picturatus) often co-occur with beetles; thus, case construction alone is insufficient to explain patterns of caddisfly coexistence along the permanence gradient. One explanation for the coexistence of these two species with beetles is that they develop rapidly during early summer and pupate before beetle larvae become abundant. One species (L. picturatus) pupates by burying into soft substrates that serve as a refuge. The other (A. nigriculus) builds stone pupal cases, which in field experiments, more than doubles survival compared to organic pupal cases. The combined results of these experiments suggest that caddisfly distributions along permanence gradients depend on a suite of primary and secondary predator defenses that include larval and pupal case structure, predator-specific escape behaviors, and the phenology of larval development.

Ambystoma↗
PubMed1986

Amphibian terminal nerve: distribution revealed by LHRH and AChE markers.

Immunocytochemical and histochemical studies in the tiger salamander and bullfrog demonstrated the presence of luteinizing hormone-releasing hormone-like immunoreactive (LHRH-ir) material and acetylcholinesterase (AChE) in the terminal nerve (TN). Immunoreactive perikarya and processes were found within the olfactory, vomeronasal and trigeminal nerves and in the nasal epithelium. Central TN projections consisted of fibers terminating in the olfactory bulb and bundles that projected to another group of LHRH-ir perikarya in the preoptic region. Up to 4 weeks following hypophysectomy, the labeling intensity and number of TN-immunoreactive neurons were not altered. Acetylcholinesterase histochemistry in the salamander revealed two distinct groups of neurons associated with the TN: a lightly labeled group of fusiform perikarya was located in the olfactory nerve proper and a more heavily labeled group of larger oval perikarya was found within AChE-positive trigeminal fascicles in the ventral mucosa. This study has demonstrated that the amphibian TN follows olfactory, vomeronasal and trigeminal nerves to reach peripheral targets in the nasal mucosa. The projection of TN fibers to discrete olfactory bulb glomeruli, especially evident in the bullfrog, suggests that the TN functions in odor processing. The TN projection to the preoptic region in both of these amphibians implicates the TN in reproductive processes.

Acetylcholinesterase↗
PubMed1987

Evidence of an alpha 2-macroglobulin-like molecule in plasma of Salamandra salamandra. Structural and functional similarity with human alpha 2-macroglobulin.

A high-Mr (Mr 750,000) alpha 1-macroglobulin, obtained from Salamandra salamandra, is described. Salamander alpha 1-macroglobulin is composed of two monomers of equal Mr, which are composed of two polypeptide chains, each of Mr 180,000, linked by disulfide bonds. The molecular parameters of this protein, its binding to trypsin and inactivation by methylamine suggest that salamander alpha 1-macroglobulin is closely related to human alpha 2-macroglobulin and to other related proteins described in the animal kingdom.

Animals↗
PubMed1986

Multiple forms of gonadotropin-releasing hormone in amphibian brains.

Several forms of gonadotropin-releasing hormone (GnRH)-like molecules were found in brains of both anurans (frogs) and urodeles (salamanders). The presence of the mammalian-like GnRH molecule was confirmed by HPLC and cross-reactivity studies. Small amounts of salmonid-like GnRH molecules in the brains of frogs (Rana pipiens, Hyla regilla) and salamanders (Taricha granulosa, Ambystoma gracile) were detected by comparing the HPLC chromatographic pattern and immunological reactivity of the brain extracts with native trout and synthetic salmon GnRH. This nonmammalian form of GnRH in the amphibian brain is similar and perhaps identical, at least by indirect evidence, to a form of GnRH reported earlier to be in sympathetic ganglion, retina, chromaffin tissue, and tadpole brain. If two of the amphibian GnRH molecules prove to be mammalian and salmon GnRH, then it is likely that two separate genes in amphibians code for the distinct primary structures of the molecules. The most parsimonious interpretation of the presence of both mammalian- and salmon-like GnRH in anurans and urodeles is that a common phylogenetic ancestor also possessed the two forms of GnRH. Thus the mammalian form of GnRH may well have been present in labyrinthodont amphibians. Independent of evolutionary origin, the functions of the different GnRH molecules in amphibians are unknown.

Ambystoma↗
PubMed1987

Further classification of skin alkaloids from neotropical poison frogs (Dendrobatidae), with a general survey of toxic/noxious substances in the amphibia.

Cutaneous granular glands are a shared character of adult amphibians, including caecilians, and are thought to be the source of most biologically active compounds in amphibian skin. Data are available from one or more species in over 100 of nearly 400 genera comprising the three living orders of Amphibia. Many species contain unidentified substances judged to be noxious based on predator aversion or human taste. Additionally, there is a great diversity of known compounds, some highly toxic as well as noxious, which can be tabulated under four broad categories: biogenic amines, peptides, bufodienolides (bufogenins) and alkaloids. The last category includes alkaloids derived from biogenic amines, water-soluble alkaloids (tetrodotoxins) and lipophilic alkaloids. Most compounds are known only from skin of adult amphibians, but the toxic and noxious properties of eggs and larvae of certain salamanders and toads can be attributed to tetrodotoxins and bufodienolides, which occur also in adult tissues other than skin. Predator aversion and various antipredator behaviors and aposematic colorations clearly prove the defensive value of these diverse metabolites, whether or not they are elaborated primarily (e.g. alkaloids) or secondarily (e.g. some peptides and biogenic amines) for this function. Lipophilic alkaloids include the samandarine alkaloids, known definitely only from an Old World genus of salamanders, and the more than 200 dendrobatid alkaloids. Nearly all the latter are unique to neotropical poison frogs of the genera Dendrobates and Phyllobates (Dendrobatidae), except for seemingly homoplastic occurrences of a few such alkaloids in small brightly colored anurans of several other families. Owing to recent discoveries and new structural information, the dendrobatid alkaloids are here partitioned among the following major and minor classes: batrachotoxins, histrionicotoxins, indolizidines, pumiliotoxin-A class and its allopumiliotoxin and homopumiliotoxin subclasses, decahydroquinolines, gephyrotoxins, 2,6-disubstituted piperidines, 2,5-disubstituted pyrrolidines, pyridyl-piperidines, indole alkaloids, azatricyclododecenes and amidine alkaloids. Except for the steroidal batrachotoxins, and the minor classes of pyrrolidine alkaloids, indole alkaloids and amidine alkaloids, all the above contain a piperidine ring. A large number of piperidine-based alkaloids occur mainly as trace compounds in Dendrobates and remain unclassified; the only water-soluble toxin so far discovered in a dendrobatid (Colostethus) is structurally unknown, but conceivably an alkaloid.

Alkaloids↗
PubMed1984

Collateralization in the spinothalamic tract: new methodology to support or deny phylogenetic theories.

Components of the spinothalamic system that ascend in the anterolateral funiculus are reviewed. The presence of collateralization in this system in mammals is discussed with regard to theories of the phylogenetic development of pathways. The major theory investigated suggested that collateralization is an intermediate stage between a multisynaptic pathway and a direct non-collateralized lemniscus. The evidence and theories are reviewed. Methods for confirming or rejecting this theory are discussed. The literature reporting ascending spinal projections for non-mammalian vertebrates is reviewed. Certain reptiles have projections analogous to both the mammalian neospinothalamic and paleospinothalamic tracts. The presence of spinothalamic projections in elasmobranchs and amphibians is still controversial. Confirmation of earlier reports of projections in salamander and dogfish shark based on degeneration techniques have not been done. In addition, results from too few species of these classes have been reported. However, it is possible that paleospinothalamic connections are present in some species (e.g. salamander, nurse shark) and not in others (e.g. frog, dogfish shark) of the same class. Spinothalamic projections have not been reported for teleosts. A plea for new research in this area is made.

Animals↗