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Pit Organs (pit + organ)
Selected AbstractsPhylogenetic trends in the abundance and distribution of pit organs of elasmobranchsACTA ZOOLOGICA, Issue 4 2004M. B. Peach Abstract Pit organs (free neuromasts of the mechanosensory lateral line system) are distributed over the skin of elasmobranchs. To investigate phylogenetic trends in the distribution and abundance of pit organs, 12 relevant morphological characters were added to an existing matrix of morphological data (plus two additional end terminals), which was then re-analysed using cladistic parsimony methods (paup* 4.0b10). Character transformations were traced onto the most parsimonious phylogenetic trees. The results suggest the following interpretations. First, the distinctive overlapping denticles covering the pit organs in many sharks are a derived feature; plesiomorphic elasmobranchs have pit organs in open slits, with widely spaced accessory denticles. Second, the number of pit organs on the ventral surface of rays has been reduced during evolution, and third, spiracular pit organs have changed position or have been lost on several occasions in elasmobranch evolution. The concentrated-changes test in macclade (version 4.05) was used to investigate the association between a pelagic lifestyle and loss of spiracular pit organs (the only character transformation that occurred more than once within pelagic taxa). Depending on the choice of tree, the association was either nonsignificant at P = 0.06 or significant at P < 0.05. Future studies, using species within more restricted elasmobranch clades, are needed to resolve this issue. [source] The comparative morphology of pit organs in elasmobranchsJOURNAL OF MORPHOLOGY, Issue 6 2009M.B. Peach Abstract The pit organs of elasmobranchs (sharks, skates and rays) are free neuromasts of the mechanosensory lateral line system. Pit organs, however, appear to have some structural differences from the free neuromasts of bony fishes and amphibians. In this study, the morphology of pit organs was investigated by scanning electron microscopy in six shark and three ray species. In each species, pit organs contained typical lateral line hair cells with apical stereovilli of different lengths arranged in an "organ-pipe" configuration. Supporting cells also bore numerous apical microvilli taller than those observed in other vertebrate lateral line organs. Pit organs were either covered by overlapping denticles, located in open grooves bordered by denticles, or in grooves without associated denticles. The possible functional implications of these morphological features, including modification of water flow and sensory filtering properties, are discussed. J. Morphol. 2009. © 2009 Wiley-Liss, Inc. [source] Proteome analysis of the thermoreceptive pit membrane of the western diamondback rattlesnake Crotalus atroxPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 1 2003Hans Zischka Abstract Rattlesnakes detect their prey's temperature by means of a cavern-like structure, the pit organ. The sensory component of this organ lies within a thin membrane called the pit membrane. Proteome analysis conducted on this neurosensory tissue revealed only a relatively small number of proteins, thereby depicting its high degree of specialization. In addition to containing blood serum and structural proteins, the proteome of this membrane appears to be strikingly similar to that of isolated rattlesnake brain mitochondria. Indeed, our results show that over 80% of the detected tissue proteins are of mitochondrial origin. Fluorescence microscopy studies of these organelles indicate their dense arrangement and accumulation in structures which have been previously reported to be the terminal ends of free nerve fibers of the innervating trigeminal branches. Thus, original ultrastructural observations are paralleled by our findings at the molecular level. [source] Phylogenetic trends in the abundance and distribution of pit organs of elasmobranchsACTA ZOOLOGICA, Issue 4 2004M. B. Peach Abstract Pit organs (free neuromasts of the mechanosensory lateral line system) are distributed over the skin of elasmobranchs. To investigate phylogenetic trends in the distribution and abundance of pit organs, 12 relevant morphological characters were added to an existing matrix of morphological data (plus two additional end terminals), which was then re-analysed using cladistic parsimony methods (paup* 4.0b10). Character transformations were traced onto the most parsimonious phylogenetic trees. The results suggest the following interpretations. First, the distinctive overlapping denticles covering the pit organs in many sharks are a derived feature; plesiomorphic elasmobranchs have pit organs in open slits, with widely spaced accessory denticles. Second, the number of pit organs on the ventral surface of rays has been reduced during evolution, and third, spiracular pit organs have changed position or have been lost on several occasions in elasmobranch evolution. The concentrated-changes test in macclade (version 4.05) was used to investigate the association between a pelagic lifestyle and loss of spiracular pit organs (the only character transformation that occurred more than once within pelagic taxa). Depending on the choice of tree, the association was either nonsignificant at P = 0.06 or significant at P < 0.05. Future studies, using species within more restricted elasmobranch clades, are needed to resolve this issue. [source] On the vascularization and structure of the skin of a Korean bullhead Pseudobagrus brevicorpus (Bagridae, Teleostei) based on its entire body and appendagesJOURNAL OF APPLIED ICHTHYOLOGY, Issue 1 2010J. Y. Park Summary To investigate the vascularization and structure of the skin and its relationship to cutaneous respiration in Pseudobagrus brevicorpus, a histological study by light microscopy was carried out on 15 regions of the skin, including eight body regions, six fins and the barbel. The skin consisted of the epidermis, dermis and subcutis in all regions, except for the barbel that had a relatively thin dermis and subcutis. The epidermis was composed of the outermost layer, the middle layer and the stratum germinativum. There were two kinds of gland cells: the unicellular mucus cells and large club cells. The middle layer had a small number of fine blood capillaries accompanied by dermal collagen in all regions; the mean number of blood capillaries ranged from 0.9 to 5.9. The mean diffusion distance between the capillary endothelial cells and the surface of the epidermis ranged from 50.6 to 126.8 ,m. Based on these intra-epithelial blood capillaries, the relative surface area of the respiratory epithelium ranged from 0.1 to a maximum value of 1.2%. The dermis lacking scales had collagen bundles arranged parallel to each other, but vertical fiber bundles around the dorso-lateral regions were seen at intervals. Sensory organs such as taste buds, pit organs and lateral canals were found whereby the taste buds in particular were more abundant in the epidermis of the barbel. The vascularization of the skin may be closely related to an additional respiratory system used to deal with an extreme hypoxic condition during dry seasons. [source] The comparative morphology of pit organs in elasmobranchsJOURNAL OF MORPHOLOGY, Issue 6 2009M.B. Peach Abstract The pit organs of elasmobranchs (sharks, skates and rays) are free neuromasts of the mechanosensory lateral line system. Pit organs, however, appear to have some structural differences from the free neuromasts of bony fishes and amphibians. In this study, the morphology of pit organs was investigated by scanning electron microscopy in six shark and three ray species. In each species, pit organs contained typical lateral line hair cells with apical stereovilli of different lengths arranged in an "organ-pipe" configuration. Supporting cells also bore numerous apical microvilli taller than those observed in other vertebrate lateral line organs. Pit organs were either covered by overlapping denticles, located in open grooves bordered by denticles, or in grooves without associated denticles. The possible functional implications of these morphological features, including modification of water flow and sensory filtering properties, are discussed. J. Morphol. 2009. © 2009 Wiley-Liss, Inc. [source] Blood Flow in Snake Infrared Organs: Response-Induced Changes in Individual VesselsMICROCIRCULATION, Issue 2 2007RICHARD C. GORIS ABSTRACT Objective: In the past the microkinetics of blood flow in the infrared pit organs of pit vipers has been studied with Doppler flowmetry using various infrared stimuli such as a human hand or soldering iron at various distances, lasers of various wavelengths, etc. Quick-acting variations in blood flow were recorded, and interpreted as a cooling mechanism for avoiding afterimage in the infrared receptors. However, the Doppler measurements provided only the summation of blood flow in a number of vessels covered by the sensing probe, but did not give data on flow in individual vessels. Methods: In the present work the authors introduced into the bloodstream of Gloydius and Trimeresurus pit vipers fluorescent microspheres labeled with fluorescein isothiocyanate (FITC) contained in a solution of FITC-dextran in physiological saline. They observed the passage of the microspheres through individual pit organ vessels with a fluorescent microscope to which was attached a high-speed video camera and image intensifier. Output of the camera was recorded before, during, and after stimulus with a 810-nm diode laser. Recording was done at 250 frames/s on high-speed video apparatus and downloaded to a hard disk. Disk files were loaded into proprietary software and particles were tracked and average velocities calculated. The data were then tested for significance by ANOVA with post hoc tests. Results: A significant (p < .05) increase in blood velocity was found at the focal point of the stimulus laser, but not anywhere removed from this point. Proximal severing of the pit sensory nerves caused degeneration of the pit receptor terminals and abolished stimulus-induced blood flow changes, but did not affect normal blood flow. Conclusions: The authors conclude that the receptors themselves are directly and locally controlling the smooth muscle elements of the blood vessels, in response to heating of the receptors by infrared radiation. They speculate that the heavy vascularization constitutes a cooling system for the radiation-encoding receptors, and further that the agent of control may be a volatile neuromediator such as nitric oxide. [source] | ||||||||||