摘要:

The living members of the clade Archosauria, crocodilians and birds, differ markedly in the morphology of their deep dorsal thigh muscles. To investigate whether this diversity is accompanied by differences in motor pattern and muscle function, the hindlimbs of representative archosaurs were studied by electromyography and cineradiography during terrestrial locomotion. In a crocodilian, Alligator, the iliofemoralis and pubo-ischio-femoralis internus part 2 are both active during the swing phase of the stride cycle. This appears to be the primitive motor pattern for archosaurs. There are four avian homologues of these muscles in the helmeted guineafowl, Numida. These are primarily active in the propulsive phase (iliotrochantericus caudalis and iliotrochantericus medius), the swing phase (iliotrochantericus cranialis) and a speed-dependent combination of the propulsive and/or swing phases (iliofemoralis externus). Differences between Alligator and Numida in the number and attachment of deep dorsal muscles are associated with dissimilar motor patterns and functions. Evolutionary modifications of neuromuscular control must be recognized when evaluating avian locomotor history, but are rarely considered by paleontologists. Even within the deep dorsal thigh muscles of Numida, developmentally and anatomically similar muscles are active out-of-phase. Therefore, although the actions of two adjacent muscles appear equivalent, their functions may differ dramatically. The diversity of deep dorsal thigh muscles in modern birds may be a good model for studying the relationship between activity pattern and peripheral morphology.

ISSN:0006-8977    

DOI:10.1159/000113619

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The nucleus of the basal optic root (nBOR) in birds is a component of the accessory optic system (AOS) which is involved in the analysis of visual flowfields normally resulting from self-motion. Using standard extracellular techniques, we recorded from 81 single-unit and multi-unit clusters in the nBOR of the northern saw-whet owl, Aegolius acadicus, an avian species that has a visual system with frontal emphasis. These cells responded best to large patterns of random dots moving either upward (52%), downward (31%) or nasal to temporal (N-T; contralateral visual field; 15%). Only 2 units (2%) preferred temporal to nasal motion. ''Up'' units were found in the dorsal portion of the nucleus whereas ''Down'' units were located more ventrally. The N-T units were found in both the lateral margin of the nucleus and ventral to the Down units in the lateral half of the nucleus. About half of the units tested (10/19) responded to stimulation of the ipsilateral as well as the contralateral eye. For all but one cell, the direction preference of both eyes was the same in visual space. When compared with previous studies of pigeons (Columba livia) and chickens (Gallus domesticus), these findings reveal that the nBOR in all three avian species have important similarities with respect to direction preference and functional compartmentalization. Furthermore, the high proportion of binocular neurons found in the nBOR of the saw-whet owl is similar to the condition generally reported in frontal eyed mammals and hence may reflect adaptation.

ISSN:0006-8977    

DOI:10.1159/000113620

出版商:S. Karger AG    

年代:1994

数据来源: Karger

ISSN:0006-8977    

DOI:10.1159/000113621

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Melatonin binding sites were identified in the brain and retina of the lizard Anolis carolinensis using in vitro autoradiography. Radioactive labeling was observed in areas which receive primary, secondary, and tertiary visual input: the superficial layers of the optic tectum, lateral geniculate nucleus, nucleus rotundus, dorsal ventricular ridge, and striatum. Other areas that demonstrated binding included the left medial habenular nucleus, the interpeduncular nucleus, medial cortex, dorsal cortex, mammillary nucleus, and septum. In the retina, melatonin binding was localized in the inner plexiform layer. Radioactive melatonin binding to the optic tectum was reduced in the presence of a non-hydrolyzable cyclic GMP analog, indicating that the melatonin receptor in the brain of this lizard is associated with a G-protein. These results suggest that melatonin receptor binding sites are widely distributed in the forebrain and midbrain of the iguanid lizard, and are prominent in areas of the nervous system that are associated with visual processing. The highest degree of melatonin binding appeared in the left medial habenular nucleus, interpeduncular nucleus, and dorsal ventricular ridge. This suggests that these brain regions may be important targets for the actions of melatonin, such as its effects on circadian rhythmicity, thermoregulation and photoperiodic reproduction.

ISSN:0006-8977    

DOI:10.1159/000113622

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

Electroreception evolved in the catfishes probably as a specialization of the mechanosensory lateral line system. Fibers of the anterior lateral line nerve in catfishes innervate electrosensory ampullary organs and mechanosensory neuromasts of the head lateral line system. The purpose of this study is to determine the projection patterns of the major principal branches of the ALLN and to investigate the topography within the various nuclei of the terminal fields of these different branches. Fibers of the superficial ophthalmic, buccal and hyomandibular branches of the anterior lateral line nerve terminate in a somato-topic fashion within medullary and cerebellar nuclei. These fibers project to, and terminate within, several discrete nuclei in the medulla and cerebellum, notably the electrosensory lateral line lobe, the medial and caudal octavolateralis nuclei, and portions of a nuclear complex in the cerebellum called the eminentia granulans. Furthermore, the dorsoventral somatotopy in the medullary electrosensory nucleus is a reversed or ''mirror'' image of that in the mechanosensory nucleus. This reversed map is similar to that observed in other electrosensory systems and suggests that there may be a common mechanism for the copying and preservation of spatial information as new systems are evolved from primitive sensory pathways.

ISSN:0006-8977    

DOI:10.1159/000113623

出版商:S. Karger AG    

年代:1994

数据来源: Karger

摘要:

The retinal structure of the goatfish Upeneus tragula was examined at various stages of the fish''s development from pre-settlement pelagic larvae to benthic juveniles. Histological investigation revealed a double layer of cone inner segments in the dorsal retina and high cone and bipolar cell densities in both dorsal and ventral retina prior to settlement. During settlement reorganisation of the dorsal retina was found to occur, with the two cone layers slotting together to form a single layer. In both the dorsal and ventral retina cone and bipolar cell densities were rapidly reduced. Visual acuity, as calculated from histological data on cone density and lens diameter, was found to increase rapidly prior to settlement to an asymptote of approximately 27 minutes of arc, which corresponded to settlement. The changes in the visual system are thought to be associated with changes in both habitat and feeding behaviour at settlement when the fish leave the surface waters and begin a benthic mode of life using sensory barbels to search for sediment dwelling prey.

ISSN:0006-8977    

DOI:10.1159/000113624

出版商:S. Karger AG    

年代:1994

数据来源: Karger