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Effects of Diazinon on bluegill sunfish, Lepomis macrochirus, gills: scanning electron microscope observations (1997)

Dutta, H. M. ; Munshi, J. S. D. ; Roy, P. K. ; [et al.]

Springer

Experimental biology online 2 (1997), S. 1-11

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ISSN: 1430-3418

Keywords: Bluegills ; Diazinon ; Gills ; Lepomis macrochirus ; Scanning electron microscopy

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Gills of bluegill sunfish, Lepomis macrochirus, exhibited varied degrees of structural damage following a 24-h exposure to sublethal concentrations (15 μg/l, 30 μg/l, 45 μg/l, 60 μg/l and 75 μg/l) of Diazinon [O,O-diethyl-O-(2-isopropyl-6-methyl-4 pyrimidinyl ester or phosphorothioate]. Exposure to 15 μg/l and 30 μg/l resulted in exocytosis of some material to the cell surface and perforations of the microridges. At higher doses (above 45 μg/l), the extrusion was reduced and the cells were swollen. Compared to control values, the thickness of the microridge on the gill arch and on the gill filament generally increased with exposure to Diazinon. Also, the distance between microridges decreased with increased exposure concentrations. At 60 μg/l, gill arch microridges fused and some ridges of gill filaments disappeared. At 75 μg/l exposure, epithelial cells of the gill arch became obscured with severe cellular extrusions and the lamellar surfaces swelled. The mucus extrusion, lamellar swelling and reduced microridges may be related to a defence mechanism which reduces the water surface around the gill and increases the barrier distance for diffusion of toxicants from outside to the blood capillaries. Although this mechanism protects the fish from toxicants, it also reduces the oxygen supply which leads to suffocation of the fish.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s00898-997-0017-4

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Microcirculation of gills and accessory respiratory organs of the walking catfish Clarias batrachus (1995)

Olson, K. R. ; Ghosh, T. K. ; Roy, P. K. ; [et al.]

New York, NY [u.a.] : Wiley-Blackwell

The @Anatomical Record 242 (1995), S. 383-399

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ISSN: 0003-276X

Keywords: Air-breathing fish ; Clarias batrachus ; Vascular shunts ; Microcirculation ; Gills ; Respiration ; Vascular corrosion replicas ; Life and Medical Sciences ; Cell & Developmental Biology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Medicine

Notes: Background: An ability to extract oxygen directly from the atmosphere enables air-breathing fish to survive otherwise debilitating hypoxic environments. Addition of accessory respiratory organs (ARO) necessitates changes in both the general circulatory system and the microcirculation of the respiratory epithelia. Understanding these modifications provides information on the efficiency of gas exchange organs as well as an indication of the evolutionary processes associated with adaptation to terrestrial habitats.Methods: Vascular organization and structure of gills and ARO of the facultative air-breathing walking catfish Clarias batrachus were examined by scanning electron microscopy of vascular replicas and fixed tissue.Results: Well-developed filaments are present on all four pairs of gill arches and they possess three vascular pathways: respiratory (arterioarterial), nutrient (arteriovenous), and interlamellar (arteriovenous), typical of teleosts. ARO, consisting of gill fans, dendritic organs on the second and fourth gill arch, and the suprabranchial epithelium are derived from gill tissue and retain structural features and arterioarterial vessels similar to gill filaments. Gill and ARO vessels are in parallel with each other, and together they are in series with the systemic circulation. Nutrient and interlamellar vessels are reduced in ARO.Conclusions: Other than the presence of multiple ventral aortas, and an additional vessel connecting the suprabranchial epithelium to the dorsal aorta, there are no vascular shunts or anatomical modifications that indicate spatial separation of flow through the heart or between gills and ARO. However, a mechanism is proposed that would prevent unsaturation of dorsal aortic blood by local myogenic vasoconstriction of gill vessels when the fish is in hypoxic water. Despite considerable differences in the gross features of ARO in Clarias and Heteropneustes fossilis: (Olson et al. 1990 J. Morphol., 203:165), there are striking similarities in vascular organization and respiratory islet structure that suggest these ARO evolved in a common silurid ancestor and were later modified into an everted arborescent organ or inverted air sac, respectively. © 1995 Wiley-Liss, Inc.

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