摘要:

The total number, size, topographic distribution and peak density of ganglion cells were studied in retinal wholemounts of the fur seal, Callorhinus ursinus. The cell distribution showed a distinct zone of high ganglion cell density. It was located in the temporal retinal quadrant, near the horizontal meridian, 10–12 mm (25–31°) from the optic disk. The peak cell density in this zone was 812–1332 cells/mm2 (mean 1053 cells/mm2), i.e. 125–205 cells/deg2 (mean 162 cells/deg2). These data predict a retinal resolution of 5.6.–7.1 cycle/deg. The ganglion cell soma size ranged from 10 to 50 µm. Cell size histograms were bimodal in shape with modes below and

ISSN:0006-8977    

DOI:10.1159/000114105

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

The central nervous system location of neurochemicals that are widely distributed among extant animals may give us clues to changes that occurred in the brains of these animals during evolution. We have been studying the brains of cartilaginous fishes, a heterogeneous group whose central nervous system varies considerably. Squalus acanthias, the spiny dogfish shark, was chosen to represent the squalomorphs, a group of living sharks known to possess many primitive characters. The distribution of tyrosine hydroxylase (TH+), serotonin (5-HT+), and leu-enkephalin (LENK+) positive cells within the brainstem of Squalus was determined by use of antibodies to these substances. All the major raphe groups described for mammals were found in Squalus. The 5-HT+ cells in raphe nuclei were more uniformly distributed in Squalus than in Heterodontus, the horn shark. Other nuclei that were 5-HT+ and LENK+, and that have been identified in mammals, included reticularis paragigantocellularis lateralis, a B9 cell group, and reticularis magnocellularis. The postcommissural nucleus and pretectal area contained 5-HT+ and LENK+ cells. These cells have been described in a holocephalian, in teleosts, and in reptiles but not in other elasmobranchs or in mammals. Cells that were TH+ were located in prominent A1/A2, A6 (locus coeruleus), A9 (substantia nigra), and A10 (ventral tegmental area) cell groups, and in a very small A5 group. We conclude that the variation in chondrichthian brainstems exceeds that in mammals, and we suggest that this variation is related to life-style and the long evolutionary history of these fishes.

ISSN:0006-8977    

DOI:10.1159/000114106

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Neurons in the brain that project to different levels of the spinal cord in the dogfish Scyliorhinus canicula have been identified by retrograde labelling with horseradish peroxidase. Injections have been made at four different levels, namely, cervical (segments 3-6), pectoral (segments 16–18), pelvic (segments 34–36) and caudal (segments 60-80). Labelled neurons were located in the diencephalon, mesencephalon and rhombencephalon. Twenty nuclei contained labelled cells following cervical injections. Fourteen of these contained labelled cells following pectoral injections as did nine following pelvic injections and only seven after caudal injections. Of the three diencephalic nuclei projecting to the cord only nucleus thalamus ventralis pars medialis projected further than cervical regions. From the mesencephalon, the tectospinal projection, which arises from tectal and tectotegmental regions, reaches only as far as the cervical cord. The reticulospinal system, arising from cell groups in both the mesencephalon and rhombencephalon, provides the major descending pathway and reaches the most caudal levels. From the octaval region a vestibulospinal pathway arises from nucleus octavus magnocellularis, to reach all levels of the cord, and from nucleus octavus descendens, to project only as far as the pectoral cord. Other rhombencephalic cell groups - the trigeminal nuclei and nuclei B, F and G - project at least as far as the pectoral cord. We conclude that few brainstem nuclei can directly affect the whole spinal cord, whereas many nuclei may have an impact on its most rostral regions; here we have found labelled spinal interneu-rons with long descending axons that reach the most caudal cord lev

ISSN:0006-8977    

DOI:10.1159/000114107

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

The efferent projections from the Wulst were studied in the little owl, Athene noctua, using anterograde migration of wheat-germ-agglutinin conjugated horseradish peroxidase (WGA-HRP). Wulst projections were distributed to telencephalic, diencephalic and mesencephalic targets in a general pattern similar to that previously described in other avian species. Our results on the organization of the Wulst-optic tectum pathway in the little owl reveal well defined and laminarly arranged terminal projections into the superficial tectal layers, with a distribution suggestive of topographical relationships between neurons of origin in the Wulst and termination fields in the optic tectum. In contrast to lateral-eyed birds, the little owl possesses conspicuous contralateral projections to the optic tectum. Ipsilateral and contralateral efferents are restricted to different tectal regions, i.e. ipsilateral projections to the caudo-dorsal and contralateral projections to the rostro-ventral optic tectum. In addition, the anterior and posterior Wulst differentially contribute to the ipsilateral and contralateral projections to the optic tectum. This differential organization of Wulst efferents, as well as the presence of substantial contralateral projections, might be related to the high degree of binocular overlap typical of frontal-eyed birds. At a functional level, electric potentials recorded in the optic tectum and evoked by visual stimulation showed that information from one eye can reach the ipsilateral optic tectum. After Wulst ablation, the amplitude of these potentials was significantly reduced, indicating that Wulst efferents may influence visually-evoked activity in the optic tectum.

ISSN:0006-8977    

DOI:10.1159/000114108

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Adults of two species of teleost fishes, the New Zealand sweep (Scorpis lineolatus) and the spotty (Notolabrus [formerly Pseudolabrus] celidotus), were recovered from dark, sealed sea water storage tanks after an extended period of residence (physical constraints meant that fish could only have entered the system as larvae or small juveniles). Individuals of both species had proportionately larger eyes than normal fishes of similar body size. Age estimation, based on unvalidated annual increments in otoliths indicated that fishes from the water tanks were all older (i.e. slower-growing) than normal fishes of similar size. This suggests that the increase in relative eye size in tank fishes may have been the result of maintenance of ocular growth, in the face of reduced rates of somatic growth, and raises the question as to whether eye growth in fishes generally, is a temporal function. In addition to ocular enlargement, sweeps from the water tanks also showed reduced densities of cones, rods, ganglion cells and, in some cases bipolar cells compared to normal fishes of similar body size. Cone, rod and bipolar cell densities of tank fishes were not different when compared with normal fishes of similar eye size; however, ganglion cell numbers were still lower than in normal fishes. This suggests that changes in cone, rod and bipolar cell densities in tank fishes resulted from the normal changes that occur with ocular growth, whereas low ganglion cell densities were a direct result of the abnormal photic environment. In contrast to the sweeps, most of the spotties from the water tanks did not show differences in retinal cell densities relative to normal fishes. Tank fishes of both species had cone outer segments with greater cross-sectional area than normal fishes, and the effect was independent of fish size. This may indicate that the large cones of some mid- and deep-water fishes (most of whom migrate from shallower water with ontogeny), which have previously been assumed to be specific adaptive features for low intensity photic environments, may rather be direct responses to changes in photic habitat that occur during ontogeny.

ISSN:0006-8977    

DOI:10.1159/000114109

出版商:S. Karger AG    

年代:1992

数据来源: Karger

摘要:

Praying mantids are thought to be so strictly predacious that, historically, carnivorousness has been used as a defining characteristic of the taxon Mantodea, and no data exist on other ingestive behaviors. We observed food- and water-deprived male and female Tenodera aridifolia sinensis (Sauss.) and Sphodromantis lineola (Burr.) in various situations and found that their ingestive behaviors are more variable than generally recognized. Both species regularly drink water in response to deprivation, the amount imbibed being correlated with the total (but not daily) percent of initial body weight lost. When presented with stimuli consisting of plastic beads of different reflective quality (shiny clear, opaque frosted, or matte black), lighted by a single direct light source, the shiny stimuli consistently elicited the most drinking-like behavior by the mantids. The preference was consistent, whether stimuli were presented together or singly. This suggests that visual cues can be used to identify water and are alone capable of maintaining drinking-like behavior. When S. lineola were presented with various stimuli, including diced apple and diced banana, in a five-way or a three-way choice test, mantids that chose a stimulus within the allotted time consistently ate the diced banana. When presented one of two stimuli differing only in odor (30 x 20 x 15 mm cloth bags filled with either plastic beads or banana), S. lineola did not attempt to eat the former, but 50% attempted to eat the bag of banana. Eating bouts were always preceded by antennae drumming in the direction of, or over the stimulus. These findings indicate that at least one species of mantid is a facultative omnivor and that olfaction or contact chemoreception plays a role in identifying potential food. Our findings for mantids fit currently accepted, general models of insect drinking and eating behavior. Further, facultative omnivorousness suggests a closer phylogenetic relationship to the suborder Blattodea. This supports the belief that Mantodea is correctly considered a suborder of Dictuoptera (rather than an order).

ISSN:0006-8977    

DOI:10.1159/000114110

出版商:S. Karger AG    

年代:1992

数据来源: Karger