Development of the tectum in Gymnophiones,with comparison to other amphibians

Tectal development in a number of caecilian (Gymnophiona: Amphibia) species was examined and compared with that in frogs and salamanders. The caecilian optic tectum develops along the same rostrocaudal and lateromedial gradients as those of frogs and salamanders. However, differences exist in the time course of development. Our data suggest that, as in salamanders, simplification of morphological complexity in caecilians is due to a retardation or loss of late developmental stages. Differences in the time course of development (heterochrony) among different caecilian species are correlated with phylogenetic history as well as with variation in life histories. The most pronounced differences in development occur between the directly developing Hypogeophis rostratus and all other species examined. In this species, the increase in the degree of morphological complexity is greatly accelerated. J. Morphol. 236:233–246, 1998. © 1998 Wiley-Liss, Inc.     

Connection of the auditory cortex secondary zones with the auditory subcortical cerebral centers in the cat

As it has been demonstrated microscopically, the corticofugal fibers in the AII and Ep zones of the auditory cortex in all the auditory subcortical centers (medial geniculate body, posterior colliculi of the tectum mesencephali and the superior olive nuclei) terminate by means of single axodendritic synapses, having an asymmetrically active zone, and mixed (by their form) synaptic vesicles. Small and middle dendrites make their postsynaptic part. A comparison has been carried out on distribution and form of synapses, completing the projection fibers from the zone of the primary acoustic responses (AI) and of the primary acoustic zone (AIV). Basing on the morphological data, concerning distribution and form of the synaptic terminals, a suggestion is made that physiological influence of each acoustic cortex zone is different for the medial geniculate body and posterior colliculi of the tectum mesencephali, but it is unitypical for the superior olive level.     

Phylogenetic implications of the morphology of the braincase of caecilian amphibians (Gymnophiona)

Caecilian morphology is strongly modified in association with their fossorial mode of life. Currently phylogenetic analyses of characters drawn from the morphology of caecilians lack resolution, as well as complementarity, with results of phylogenetic analyses that employ molecular data. Stemming from the hypothesis derived from the mammal literature that the braincase has the greatest potential (in comparison to other cranial units) to yield phylogenetic information, the braincase and intimately associated stapes of 27 species (23 genera) of extant caecilians were examined using images assembled via microcomputed tomography. Thirty‐four new morphological characters pertaining to the braincase and stapes were identified and tested for congruence with previously recognized morphological characters. The results reveal that when added to previous character matrices, characters of the braincase and stapes resolve generic‐level relationships in a way that is largely congruent with the results of molecular analyses. Analysis of a combined data set of molecular and morphological data provides a framework for conducting ancestral character state reconstructions, which resulted in the identification of 95 new synapomorphies for various clades and taxa, 27 of which appear to be unique for the taxa that possess them. Together these data demonstrate the utility of the application of characters of the braincase and stapes for resolving phylogenetic relationships for a group whose morphology is largely confounded by functional modifications. In addition this study provides evidence of the utility of the braincase in resolving problematic morphology‐based phylogeny outside of Amniota, in an amphibian group. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 160–201.     

Relationship between arginine vasotocin-like and natriuretic peptide-like immunoreactive structures in the brain of the toad Bufo marinus

The distribution of natriuretic peptide-like immunoreactivity was investigated in the brain of Bufo marinus and compared with arginine vasotocin-like immunoreactivity using fluorescence immunohistochemistry. The antisera used were rabbit anti-porcine brain natriuretic peptide, which recognises the three main structural forms of natriuretic peptides, and guinea-pig antivasopressin, which recognises arginine vasotocin. Natriuretic peptide-like immunoreactive fibres were observed in many regions of the brain, being densest in the preoptic/hypothalamic region of the diencephalon and the interpeduncular nucleus of the mesencephalon. Natriuretic peptide-like immunoreactive cell bodies were observed in the dorsal and medial pallium, the medial amygdala, the preoptic nucleus, the ventral hypothalamus, the nucleus posterodorsalis tegmenti mesencephali, and the interpeduncular nucleus. No natriuretic peptide-like immunoreactivity was seen in the pituitary gland. The distribution of arginine vasotocin-like immunoreactivity was similar to that described previously for other amphibian species. Numerous immunoreactive cell bodies were present in the preoptic nucleus whilst immunoreactive fibres were observed in the preoptic/hypothalamic region as well as in extrahypothalamic regions such as the medial amygdala and the medial pallium. Double-labelling immunohistochemistry revealed no colocalisation of arginine vasotocin-like and natriuretic peptide-like immunoreactivities in the same neural elements. The results suggest that natriuretic peptides and arginine vasotocin have distinct distributions in the brain but that natriuretic peptide-like immunoreactive fibres in the hypothalamus could influence the activity of arginine vasotocin-like immunoreactive cell bodies.     

Dynamic changes in the gene expression of zebrafish Reelin receptors during embryogenesis and hatching period

The brain morphology of vertebrates exhibits huge evolutionary diversity, but one of the shared morphological features unique to vertebrate brain is laminar organization of neurons. Because the Reelin signal plays important roles in the development of the laminar structures in mammalian brain, investigation of Reelin signal in lower vertebrates will give some insights into evolution of vertebrate brain morphogenesis. Although zebrafish homologues of Reelin, the ligand, and Dab1, a cytoplasmic component of the signaling pathway, have been reported, the Reelin receptor molecules of zebrafish are not reported yet. Here, we sought cDNA sequence of zebrafish homologue of the receptors, vldlr and apoer2, and examined their expression patterns by in situ hybridization. Developmental gene expression pattern of reelin, dab1, vldlr, and apoer2 in the central nervous system of zebrafish was compared, and their remarkable expression was detected in the developing laminar structures, such as the tectum and the cerebellum, and also non-laminated structures, such as the pallium. The Reelin receptors exhibited different spatial and temporal gene expression. These results suggest a possibility that duplication and subsequent functional diversity of Reelin receptors contributed to the morphological and functional evolution of vertebrate brain.     

Linear dimensions of the lamina of the tectum mesencephali during human ontogenesis]

The dynamics of the establishment of linear dimensions of the lamina of tectum mesencephali in ontogenesis was studied in 145 preparations of human brain. The investigation was performed with by the M. M. Sauliak-Savitskaja apparatus (1953). The obtained data were processed by the method of mathematical analysis. The relief of the superior colliculi was found to be formed earlier than that of the inferior colliculi. The linear dimensions of both colliculi are practically equal to those of adult men during the third year of life. No correlative relationship between the sex of the objects under study and the linear dimensions of the lamina of tectum mesencephali was found as well as between thr right and left parts of the lamina tecti. The linear dimensions of it in all age groups are very variable.     

Discovery of a new family of amphibians from northeast India with ancient links to Africa

The limbless, primarily soil-dwelling and tropical caecilian amphibians (Gymnophiona) comprise the least known order of tetrapods. On the basis of unprecedented extensive fieldwork, we report the discovery of a previously overlooked, ancient lineage and radiation of caecilians from threatened habitats in the underexplored states of northeast India. Molecular phylogenetic analyses of mitogenomic and nuclear DNA sequences, and comparative cranial anatomy indicate an unexpected sister-group relationship with the exclusively African family Herpelidae. Relaxed molecular clock analyses indicate that these lineages diverged in the Early Cretaceous, about 140 Ma. The discovery adds a major branch to the amphibian tree of life and sheds light on both the evolution and biogeography of caecilians and the biotic history of northeast India-an area generally interpreted as a gateway between biodiversity hotspots rather than a distinct biogeographic unit with its own ancient endemics. Because of its distinctive morphology, inferred age and phylogenetic relationships, we recognize the newly discovered caecilian radiation as a new family of modern amphibians.     

A field guide to the caecilians of the Western Ghats, India

Caecilians are legless amphibians quite characteristic of the Western Ghats. Fourteen out of 16 Indian species occur in the Western Ghats and all are endemic. The present paper deals with the biology of caecilians with reference to external morphology and general breeding behaviour. It consolidates information on 26 morphological parameters which are used in caecilian identification. Metric multidimensional scaling of 16 species of caecilians using pair-wise euclidian distances calculated on the basis of 11 important morphometric parameters clearly depicts morphological distances between different species and more so the genera, thereby validating the classification. A field guide has been developed for the identification of caecilians based on a survey made all over the Western Ghats, observation of holotypes at the Natural History Museum, London and review of the literature. The study also reveals the microhabitat requirements of the caecilians. Further, the localities of caecilian distribution in the Western Ghats are mapped. The taxonomy of Indian caecilians is discussed.     

两栖类半圆丘和深核向顶盖投射及其细胞形态

将辣根过氧化物酶晶体植入两栖类顶盖,借助其逆行运输揭示出顶盖接受半圆丘和中脑深核输入,并证明两侧顶盖之间不存在相互投射。     

Organization of histamine-containing neurons in the brain of the crested newt,Triturus carnifex

The distribution of immunoreactivity for histamine was studied in the brain of the urodele Triturus carnifex using the indirect immunofluorescence method. Histamine-immunoreactive cell bodies were localized in the caudal hypothalamus within the dorsolateral walls of the infundibular recesses. These immunoreactive cell bodies were pear-shaped, bipolar and frequently of the cerebrospinal-fluid-contacting type. Histaminergic nerve fibers were detected in almost all parts of the brain. Dense innervation was seen in the telencephalic medial pallium and ventral striatum, the neuropil of the preoptic area, the septum, the paraventricular organ, the posterior commissure, the caudal hypothalamus, the ventral and lateral mesencephalic tegmentum. Medium density innervation was observed in the lateral mesencephalic tegmentum and optic tectum. Poor innervation was present in the telencephalic dorsal pallium and in the central gray of the medulla oblongata. Few fibers occurred in the olfactory bulbs and in the telencephalic lateral pallium. Double immunofluorescence staining, using an antibody against tyrosine hydroxylase, showed that histamine-immunostained somata and those containing tyrosine-hydroxylase-like immunoreactivity were co-distributed in the tuberal hypothalamus. No co-occurrence of histamine-like and tyrosine hydroxylase-like immunostaining was seen in the same neuron. The pattern of histamine-immunoreactive neurons in the newt was similar to that described in other vertebrates. Our observations, carried out on the apparently simplified brain of the newt confirm that the basic histaminergic system is well conserved throughout vertebrates.     

蛤蚧豆状核的结构及其与顶盖前端的纤维联系

运用Nissl法和辣根过氧化物酶(horseradish peroxidase,HRP)追踪标记技术,研究蛤蚧(Gekko gecko)豆状核的结构及其与顶盖前端的纤维联系。Nissl染色显示,蛤蚧豆状核细胞大小没有明显差别,由背内侧细胞密集部和腹外侧细胞稀疏部组成。将HRP注射于顶盖前端,结果豆状核背内侧部和腹外侧部分别接受同侧顶盖前端脑室内、外侧纤维的传入,核内标记有浓密的神经丛和大量纤维末梢,并在该核腹外侧部及其邻近区域发现少量大胞体标记细胞。推测豆状核腹外侧部的大胞体细胞及其邻近区域的大胞体细胞可能具有相同的功能,且该核可能形成离顶盖通路和副视系统相联系的交通要道。     

THE CENTRAL NERVOUS SYSTEM OF CHAMELEON VULGARIS

An analysis of the brain of Chameleon has given evidence of a number of modifications in the general plan of the reptilian nervous system. The telencephalon shows a reduced olfactory mechanism and suggests the presence of the true motor cortex. The ventral peduncle of the lateral forebrain bundle is unusually large with the majority of its fibres terminating in two new nuclear masses in the hypothalamus, the nucleus entopeduncularis, and a few in the nucleus ruber. A high degree of effective response to optic stimuli is indicated by the extensive correlation between the optic tectum and the nuclear masses of the midbrain and the diencephalon. The wide range of eye movements is probably correlated with the development of the basal optic root ganglion and its numerous secondary connections and the elaborate relationship of the geniculate complex. The usually highly developed tecto-bulbar system is partly replaced by a large tegmento-bulbar system that relays the tectal impulses caudally. An interesting mesencephalic nucleus is a large nucleus profundus mesencephali that receives a great variety of impulses and appears to be an important correlation center. Ascending visceral mechanisms were described bringing the hypothalamus into relationship with the lower centers. The great excursion of the tongue is associated with a highly differentiated hypoglossal nucleus. Components of the medial lemniscus from the spinal cord and the medulla to the vicinity of the thalamus were demonstrated.     

The Neuroanatomical Organization of Projection Neurons Associated with Different Olfactory Bulb Pathways in the Sea Lamprey,Petromyzon marinus

Although there is abundant evidence for segregated processing in the olfactory system across vertebrate taxa, the spatial relationship between the second order projection neurons (PNs) of olfactory subsystems connecting sensory input to higher brain structures is less clear. In the sea lamprey, there is tight coupling between olfaction and locomotion via PNs extending to the posterior tuberculum from the medial region of the olfactory bulb. This medial region receives peripheral input predominantly from the accessory olfactory organ. However, the axons from olfactory sensory neurons residing in the main olfactory epithelium extend to non-medial regions of the olfactory bulb, and the non-medial bulbar PNs extend their axons to the lateral pallium. It is not known if the receptive fields of the PNs in the two output pathways overlap; nor has the morphology of these PNs been investigated. In this study, retrograde labelling was utilized to investigate the PNs belonging to medial and non-medial projections. The dendrites and somata of the medial PNs were confined to medial glomerular neuropil, and dendrites of non-medial PNs did not enter this territory. The cell bodies and dendrites of the non-medial PNs were predominantly located below the glomeruli (frequently deeper in the olfactory bulb). While PNs in both locations contained single or multiple primary dendrites, the somal size was greater for medial than for non-medial PNs. When considered with the evidence-to-date, this study shows different neuroanatomical organization for medial olfactory bulb PNs extending to locomotor control centers and non-medial PNs extending to the lateral pallium in this vertebrate.     

Morphology of the temporal skull region in tetrapods: research history,functional explanations,and a new comprehensive classification scheme

The morphology of the temporal region in the tetrapod skull traditionally has been a widely discussed feature of vertebrate anatomy. The evolution of different temporal openings in Amniota (mammals, birds, and reptiles), Lissamphibia (frogs, salamanders, and caecilians), and several extinct tetrapod groups has sparked debates on the phylogenetic, developmental, and functional background of this region in the tetrapod skull. This led most famously to the erection of different amniote taxa based on the number and position of temporal fenestrae in their skulls. However, most of these taxa are no longer recognised to represent natural groupings and the morphology of the temporal region is not necessarily an adequate trait for use in the reconstruction of amniote phylogenies. Yet, new fossil finds, most notably of parareptiles and stem-turtles, as well as modern embryological and biomechanical studies continue to provide new insights into the morphological diversity of the temporal region. Here, we introduce a novel comprehensive classification scheme for the various temporal morphotypes in all Tetrapoda that is independent of phylogeny and previous terminology and may facilitate morphological comparisons in future studies. We then review the history of research on the temporal region in the tetrapod skull. We document how, from the early 19th century with the first recognition of differences in the temporal region to the first proposals of phylogenetic relationships and their assessment over the centuries, the phylogenetic perspective on the temporal region has developed, and we highlight the controversies that still remain. We also compare the different functional and developmental drivers proposed for the observed morphological diversity and how the effects of internal and external factors on the structure of the tetrapod skull have been interpreted.     

The lateral line mechanoreceptive mesencephalic,diencephalic, and telencephalic regions in the thornback ray,Platyrhinoidis triseriata (Elasmobranchii)

Central lateral line pathways were mapped in the thronback ray, Platyrhinoidis triseriata, by analyzing depth profiles of averaged evoked potentials (AEPs), multiunit activity (MUA), and single unit recordings. Neural activity evoked by contra- or ipsilateral posterior lateral line nerve (pLLN) shock is restricted to the tectum mesencephali, the dorsomedial nucleus (DMN) and anterior nucleus (AN) of the mesencephalic nuclear complex, the posterior central thalamic nucleus (PCT), the lateral tuberal nucleus of the hypothalamus, and the deep medial pallium of the telencephalon (Figs. 2, 3, 4, 6, 7). Neural responses (AEPs and MUA) recorded in different lateral line areas differ with respect to shape, dynamic response properties, and/or latencies (Figs. 9, 10 and Table 1). Ipsilaterally recorded mesencephalic and diencephalic AEPs are less pronounced and of longer latency than their contralateral counterpart (Fig. 9 and Table 1). In contrast, AEP recorded in the telencephalon show a weak ipsilateral preference. If stimulated with a low amplitude water wave most DMN, AN, and tectal lateral line units respond in the frequency range 6.5 Hz to 200 Hz. Best frequencies (in terms of least displacement) are 75-150 Hz with a peak-to-peak water displacement of 0.04 micron sufficient to evoke a response in the most sensitive units (Fig. 11A, B, C). DMN and AN lateral line units have small excitatory receptive fields (RFs). Anterior, middle, and posterior body surfaces map onto the rostral, middle, and posterior brain surfaces of the contralateral DMN (Fig. 12). Some units recorded in the PCT are bimodal; they respond to a hydrodynamic flow field--generated with a ruler approaching the fish--only if the light is on and the eye facing the ruler is left uncovered (Fig. 13).     

Ontophylogenetic studies of Paleozoic ammonoides

In this work the main directions of study of ontogeny and phylogeny of Paleozoic ammonoids are discussed, and the results of studies of the Permian families of this subclass are presented. It is shown that the morphogenetic evolution of taxa of different rank is caused by manifestation of major phylogenetic moduses and their various combinations. Thus, development can proceed in the direction of morphological complexity and in the direction of simplification. The conclusion about the role of family in the evolutionary history of ammonoids, which depends on the complexity of its structure, was made: the more complex it is, the greater the perspective taxon can be for formation of new groups of the supraspecific rank.     

Patterns of cellular proliferation and migration in the developing tectum mesencephali of the frog Rana temporaria and the salamander Pleurodeles waltl

The development of the tectum mesencephali was studied in the frog Rana temporaria and the salamander Pleurodeles waltl by means of nuclear staining and by labeling of cells with bromodeoxyuridine (BrdU). The general spatial and temporal pattern of cell proliferation and cell migration is the same in both species, despite drastic differences in overall tectal morphology. However, the salamander species differs from the frog species by (1) a generally lower cell proliferation rate, (2) a reduction in the activity of the lateral proliferation zone, and (3) a reduction in the formation of superficial cellular layers. Because point (3) affects processes that occur late in ontogeny, our experiments provide evidence that the simple morphology of the tectum of Pleurodeles waltl, compared with the multilayered tectum of Rana, is a consequence of a paedomorphic alteration of the ancestral developmental pattern of the amphibian tectum.     

Differences in brain morphology of brown trout across stream,lake, and hatchery environments

It has been suggested that a trade‐off between cognitive capacity and developmental costs may drive brain size and morphology across fish species, but this pattern is less well explored at the intraspecific level. Physical habitat complexity has been proposed as a key selection pressure on cognitive capacity that shapes brain morphology of fishes. In this study, we compared brain morphology of brown trout, Salmo trutta, from stream, lake, and hatchery environments, which generally differ in physical complexity ranging from low habitat complexity in the hatchery to high habitat complexity in streams and intermediate complexity in lakes. We found that brain size, and the size of optic tectum and telencephalon differed across the three habitats, both being largest in lake fish with a tendency to be smaller in the stream compared to hatchery fish. Therefore, our findings do not support the hypothesis that in brown trout the volume of brain and its regions important for navigation and decision‐making increases in physically complex habitats. We suggest that the observed differences in brain size might be associated with diet quality and habitat‐specific behavioral adaptations rather than physical habitat complexity.     

Comparison of the mammalian and avian telencephalon from the perspective of gene expression data.

Pallial and subpallial morphological subdivisions of the mouse and chicken telencephalon were examined from the new perspective given by gene markers expressed in these territories during development. The rationale of this approach is that common gene expression patterns may underlie similar histogenetic specification and, consequently, comparable morphological nature. The nested expression domains of the genes Dlx-2 and Nkx-2.1 are characteristic for the subpallium (lateral and medial ganglionic eminences). Similar expression of these markers in parts of the mouse septum and amygdala suggests that such parts may be considered subpallial. The genes Pax-6, Tbr-1 and Emx-1 are expressed in the pallium. Complementary areas of the septum and amygdala shared expression of these genes, suggesting these are the pallial parts of these units. Differences in the relative topography of pallial marker genes also define different regions of the pallium, which can be partially traced into the amygdala. Importantly, there is evidence of a novel "ventral pallium" subdivision, which is a molecularly distinct pallial territory intercalated between the striatum and the lateral pallium. Its derivatives in the mouse apparently belong to the claustroamygdaloid complex. Chicken genes homologous sequence-wise to these mouse developmental genes are expressed in topologically comparable patterns during development. The avian subpallium -the paleostriatum- expresses Dlx-2 and Nkx-2.1; expression extends as well into the septum and anterior and medial parts of the archistriatum. The avian pallium expresses Pax-6, Tbr-1 and Emx-1 and also contains a distinct ventral pallium, formed by the neostriatum and ventral intermediate parts of the archistriatum. The lateral pallium comprises the hyperstriatum ventrale, overlying temporo-parieto-occipital corticoid layer and piriform cortex, plus dorsal intermediate and posterior archistriatum. The dorsal pallium includes the dorsal, intercalated and accessory hyperstriatum, plus the dorsolateral corticoid area. The medial pallium contains the hippocampus and parahippocampal area. A dorsal part of the septum shares pallial molecular markers. Gene markers thus suggest common sets of molecular developmental determinants in either pallial or subpallial domains of the mouse and chicken telencephalon, extending all the way from the posterior pole (amygdala) to the septum. Ventral pallial derivatives identified as claustroamygdaloid in the mouse correlate with avian neostriatum and parts of the archistriatum.     

Sperm morphology of salamandrids (Amphibia, Urodela): implications for phylogeny and fertilization biology

Mature spermatozoa belonging to four salamander species, Salamandrina terdigitata, Triturus alpestris, Triturus carnifex and Triturus vulgaris, have been investigated by electron microscopy. The sperm ultrastructure of these species was compared with that of previously examined urodeles (36 species and 20 genera) and with that of anurans and caecilians. Many phylogenetic considerations may be inferred as a consequence of comparative spermatology. Urodela appears to be a monophyletic order characterized by three sperm synapomorphies: the acrosomal barb, nuclear ridge and marginal filament. Cryptobranchoidea are confirmed to form a monophyletic suborder having two synapomorphic characters: absence of mitochondria in the tail, and cylindrical shape of the tail axial rod. Within the family Salamandridae, sperm morphology confirms the phylogenetic distance between Salamandrina and Triturus, as already pointed out on the basis of molecular and morphological characters. The very complex ultrastructure of spermatozoa confirms a previous opinion that internal fertilization is the ancestral condition of the Amphibia.