The Experts below are selected from a list of 339 Experts worldwide ranked by ideXlab platform
David H Evans - One of the best experts on this subject based on the ideXlab platform.
-
the putative mechanism of na absorption in euryhaline elasmobranchs exists in the gills of a stenohaline marine elasmobranch squalus acanthias
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2007Co-Authors: Keith P Choe, David H Evans, Susan L Edwards, James B ClaiborneAbstract:We recently cloned an NHE3 orthologue from the gills of the euryhaline Atlantic stingray (Dasyatis Sabina), and generated a stingray NHE3 antibody to unequivocally localize the exchanger to the apical side of epithelial cells that are rich with Na+/K+-ATPase (A MRC). We also demonstrated an increase in NHE3 expression when stingrays are in fresh water, suggesting that NHE3 is responsible for active Na+ absorption. However, the vast majority of elasmobranchs are only found in marine environments. In the current study, immunohistochemistry with the stingray NHE3 antibody was used to localize the exchanger in the gills of the stenohaline marine spiny dogfish shark (Squalus acanthias). NHE3 immunoreactivity was confined to the apical side of cells with basolateral Na+/K+-ATPase and was excluded from cells with high levels of vacuolar H+-ATPase. Western blots detected a single protein of 88 kDa in dogfish gills, the same size as NHE3 in stingrays and mammals. These immunological data demonstrate that the putative cell type responsible for active Na+ absorption in euryhaline elasmobranchs is also present in stenohaline marine elasmobranchs, and suggest that the inability of most elasmobranchs to survive in fresh water is not due to a lack of the gill ion transporters for Na+ absorption.
-
a putative h k atpase in the atlantic stingray Dasyatis Sabina primary sequence and expression in gills
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2004Co-Authors: Keith P Choe, Jill W Verlander, Charles S Wingo, David H EvansAbstract:In mammals, the gastric H+-K+-ATPase (HKα1) mediates acid secretion in the stomach and kidneys. Like mammals, elasmobranchs also secrete acid from their stomachs, but unlike mammals they primarily ...
-
immunochemical analysis of the vacuolar proton atpase b subunit in the gills of a euryhaline stingray Dasyatis Sabina effects of salinity and relation to na k atpase
The Journal of Experimental Biology, 2001Co-Authors: Peter M Piermarini, David H EvansAbstract:SUMMARY In the gills of freshwater teleost fishes, vacuolar proton-ATPase (V-H + -ATPase) is found on the apical membrane of pavement and chloride (Na + /K + -ATPase-rich) cells, and is an important transporter for energizing Na + uptake and H + excretion. In the gills of elasmobranch fishes, the V-H + -ATPase has not been extensively studied and its expression in freshwater individuals has not been examined. The goals of this study were to examine the effects of environmental salinity on the expression of V-H + -ATPase in the gills of an elasmobranch (the Atlantic stingray, Dasyatis Sabina ) and determine if V-H + -ATPase and Na + /K + -ATPase are expressed in the same cells. We found that gills from freshwater stingrays had the highest relative abundance of V-H + -ATPase and greatest number of V-H + -ATPase-rich cells, using immunoblotting and immunohistochemistry, respectively. When freshwater animals were acclimated to sea water for 1 week, V-H + -ATPase abundance and the number of V-H + -ATPase-rich cells decreased significantly. Atlantic stingrays from seawater environments were characterized by the lowest expression of V-H + -ATPase and least number of V-H + -ATPase-rich cells. In contrast to teleost fishes, localization of V-H + -ATPase in freshwater stingray gills was not found in pavement cells and occurred on the basolateral membrane in cells that are presumably rich in mitochondria. In freshwater stingrays acclimated to sea water and seawater stingrays, V-H + -ATPase localization appeared qualitatively to be stronger in the cytoplasm, which may suggest the transporter was stored in vesicles. Using a double-immunolabeling technique, we found that V-H + -ATPase and Na + /K + -ATPase occurred in distinct cells, which suggests there may be two types of mitochondrion-rich cells in the elasmobranch gill epithelium. Based on these findings, we propose a unique model of NaCl and acid–base regulation where the V-H + -ATPase-rich cells and Na + /K + -ATPase-rich cells are the sites of Cl – uptake/HCO 3 – excretion and Na + uptake/H + excretion, respectively.
-
effects of environmental salinity on na k atpase in the gills and rectal gland of a euryhaline elasmobranch Dasyatis Sabina
The Journal of Experimental Biology, 2000Co-Authors: Peter M Piermarini, David H EvansAbstract:Changes in Na(+)/K(+)-ATPase activity and abundance associated with environmental salinity were investigated in the gills and rectal gland of the Atlantic stingray Dasyatis Sabina. Using a ouabain-specific ATPase assay and western blotting, we found that stingrays from fresh water had the highest activity and highest relative abundance of Na(+)/K(+)-ATPase in the gills. Using immunohistochemistry, we also found that gills from freshwater stingrays had the greatest number of Na(+)/K(+)-ATPase-rich cells. When freshwater stingrays were acclimated to sea water for 1 week, the activity and abundance of Na(+)/K(+)-ATPase and the number of Na(+)/K(+)-ATPase-rich cells decreased in the gills. In seawater stingrays, the branchial activity and abundance of Na(+)/K(+)-ATPase and the number of Na(+)/K(+)-ATPase-rich cells were further reduced. In rectal glands, the activity and abundance of Na(+)/K(+)-ATPase were lower in freshwater animals than in seawater-acclimated and seawater stingrays, both of which had equivalent levels. These findings suggest that salinity-associated changes in gill and rectal gland Na(+)/K(+)-ATPase activity are due to changes in the abundance of Na(+)/K(+)-ATPase. We conclude that the gills may be important for active ion uptake in fresh water, while the rectal gland is important for active NaCl excretion in sea water. The results from this study are the first to demonstrate an effect of environmental salinity on Na(+)/K(+)-ATPase expression in the gills and rectal gland of an elasmobranch.
-
osmoregulation of the atlantic stingray Dasyatis Sabina from the freshwater lake jesup of the st johns river florida
Physiological and Biochemical Zoology, 1998Co-Authors: Peter M Piermarini, David H EvansAbstract:ABSTRACT The goals of this study were to (1) measure plasma osmolytes and rectal gland weights of a freshwater (FW) Atlantic stingray (Dasyatis Sabina) population in the St. Johns River, Florida, and (2) determine how these parameters change after acclimation to seawater (SW). We hypothesized that the FW D. Sabina may show physiological divergence from marine D. Sabina, because the FW individuals reproduce and complete their life cycle in the St. Johns River. The FW D. Sabina hyperregulate their plasma osmolality (621.4 mOsm kg−1), with plasma Na+, Cl−, and urea concentrations of 211.9, 207.8, and 195.9 mmol L−1, respectively. FW D. Sabina were exposed to 100% SW for 8 d, and their hematocrit did not change significantly compared to control animals left in FW. However, plasma osmolality increased significantly (953 mOsm kg−1), with significant increases in plasma concentrations of Na+, Cl−, and urea to 319.13, 296.1, and 329.76 mmol L−1, respectively. The plasma of the SW‐adapted D. Sabina was hypo‐osmoti...
Peter M Piermarini - One of the best experts on this subject based on the ideXlab platform.
-
the accumulation of methylamine counteracting solutes in elasmobranchs with differing levels of urea a comparison of marine and freshwater species
The Journal of Experimental Biology, 2006Co-Authors: Jason R. Treberg, Peter M Piermarini, James S. Ballantyne, Ben Speersroesch, William R. DriedzicAbstract:We compared levels of the major organic osmolytes in the muscle of elasmobranchs, including the methylamines trimethylamine oxide (TMAO), betaine and sarcosine as well as the beta-amino acids taurine and beta-alanine, and the activities of enzymes of methylamine synthesis (betaine and TMAO) in species with a wide range of urea contents. Four marine, a euryhaline in freshwater (Dasyatis Sabina), and two freshwater species, one that accumulates urea (Himantura signifer) and one that does not (Potamotrygon motoro), were analyzed. Urea contents in muscle ranged from 229-352 micromol g-1 in marine species to 2.0 micromol g-1 in P. motoro. Marine elasmobranchs preferentially accumulate methylamines, possibly to counteract urea effects on macromolecules, whereas the freshwater species with lower urea levels accumulate the beta-amino acid taurine as the major non-urea osmolyte. A strong correlation (r2=0.84, P<0.001) with a slope of 0.40 was found between muscle urea content and the combined total methylamines plus total beta-amino acids, supporting the hypothesis that ;non-urea' osmolytes are specifically maintained at an approximately 2:1 ratio with urea in the muscle of elasmobranchs. All species examined had measurable synthetic capacity for betaine in the liver but only one species had detectable TMAO synthetic capacity. We propose a phylogenetic explanation for the distribution of TMAO synthesis in elasmobranchs and suggest that activation of liver betaine aldehyde dehydrogenase, relative to choline dehydrogenase, coincides with betaine accumulation in elasmobranchs. The latter relationship may be important in maintaining methylamine levels during periods of low dietary TMAO intake for species lacking TMAO synthesis.
-
immunochemical analysis of the vacuolar proton atpase b subunit in the gills of a euryhaline stingray Dasyatis Sabina effects of salinity and relation to na k atpase
The Journal of Experimental Biology, 2001Co-Authors: Peter M Piermarini, David H EvansAbstract:SUMMARY In the gills of freshwater teleost fishes, vacuolar proton-ATPase (V-H + -ATPase) is found on the apical membrane of pavement and chloride (Na + /K + -ATPase-rich) cells, and is an important transporter for energizing Na + uptake and H + excretion. In the gills of elasmobranch fishes, the V-H + -ATPase has not been extensively studied and its expression in freshwater individuals has not been examined. The goals of this study were to examine the effects of environmental salinity on the expression of V-H + -ATPase in the gills of an elasmobranch (the Atlantic stingray, Dasyatis Sabina ) and determine if V-H + -ATPase and Na + /K + -ATPase are expressed in the same cells. We found that gills from freshwater stingrays had the highest relative abundance of V-H + -ATPase and greatest number of V-H + -ATPase-rich cells, using immunoblotting and immunohistochemistry, respectively. When freshwater animals were acclimated to sea water for 1 week, V-H + -ATPase abundance and the number of V-H + -ATPase-rich cells decreased significantly. Atlantic stingrays from seawater environments were characterized by the lowest expression of V-H + -ATPase and least number of V-H + -ATPase-rich cells. In contrast to teleost fishes, localization of V-H + -ATPase in freshwater stingray gills was not found in pavement cells and occurred on the basolateral membrane in cells that are presumably rich in mitochondria. In freshwater stingrays acclimated to sea water and seawater stingrays, V-H + -ATPase localization appeared qualitatively to be stronger in the cytoplasm, which may suggest the transporter was stored in vesicles. Using a double-immunolabeling technique, we found that V-H + -ATPase and Na + /K + -ATPase occurred in distinct cells, which suggests there may be two types of mitochondrion-rich cells in the elasmobranch gill epithelium. Based on these findings, we propose a unique model of NaCl and acid–base regulation where the V-H + -ATPase-rich cells and Na + /K + -ATPase-rich cells are the sites of Cl – uptake/HCO 3 – excretion and Na + uptake/H + excretion, respectively.
-
effects of environmental salinity on na k atpase in the gills and rectal gland of a euryhaline elasmobranch Dasyatis Sabina
The Journal of Experimental Biology, 2000Co-Authors: Peter M Piermarini, David H EvansAbstract:Changes in Na(+)/K(+)-ATPase activity and abundance associated with environmental salinity were investigated in the gills and rectal gland of the Atlantic stingray Dasyatis Sabina. Using a ouabain-specific ATPase assay and western blotting, we found that stingrays from fresh water had the highest activity and highest relative abundance of Na(+)/K(+)-ATPase in the gills. Using immunohistochemistry, we also found that gills from freshwater stingrays had the greatest number of Na(+)/K(+)-ATPase-rich cells. When freshwater stingrays were acclimated to sea water for 1 week, the activity and abundance of Na(+)/K(+)-ATPase and the number of Na(+)/K(+)-ATPase-rich cells decreased in the gills. In seawater stingrays, the branchial activity and abundance of Na(+)/K(+)-ATPase and the number of Na(+)/K(+)-ATPase-rich cells were further reduced. In rectal glands, the activity and abundance of Na(+)/K(+)-ATPase were lower in freshwater animals than in seawater-acclimated and seawater stingrays, both of which had equivalent levels. These findings suggest that salinity-associated changes in gill and rectal gland Na(+)/K(+)-ATPase activity are due to changes in the abundance of Na(+)/K(+)-ATPase. We conclude that the gills may be important for active ion uptake in fresh water, while the rectal gland is important for active NaCl excretion in sea water. The results from this study are the first to demonstrate an effect of environmental salinity on Na(+)/K(+)-ATPase expression in the gills and rectal gland of an elasmobranch.
-
osmoregulation of the atlantic stingray Dasyatis Sabina from the freshwater lake jesup of the st johns river florida
Physiological and Biochemical Zoology, 1998Co-Authors: Peter M Piermarini, David H EvansAbstract:ABSTRACT The goals of this study were to (1) measure plasma osmolytes and rectal gland weights of a freshwater (FW) Atlantic stingray (Dasyatis Sabina) population in the St. Johns River, Florida, and (2) determine how these parameters change after acclimation to seawater (SW). We hypothesized that the FW D. Sabina may show physiological divergence from marine D. Sabina, because the FW individuals reproduce and complete their life cycle in the St. Johns River. The FW D. Sabina hyperregulate their plasma osmolality (621.4 mOsm kg−1), with plasma Na+, Cl−, and urea concentrations of 211.9, 207.8, and 195.9 mmol L−1, respectively. FW D. Sabina were exposed to 100% SW for 8 d, and their hematocrit did not change significantly compared to control animals left in FW. However, plasma osmolality increased significantly (953 mOsm kg−1), with significant increases in plasma concentrations of Na+, Cl−, and urea to 319.13, 296.1, and 329.76 mmol L−1, respectively. The plasma of the SW‐adapted D. Sabina was hypo‐osmoti...
R. B. Leonard - One of the best experts on this subject based on the ideXlab platform.
-
vestibulo oculomotor connections in an elasmobranch fish the atlantic stingray Dasyatis Sabina
The Journal of Comparative Neurology, 1994Co-Authors: Richard L Puzdrowski, R. B. LeonardAbstract:In elasmobranch fishes, including the Atlantic stingray, the medial rectus muscle is innervated by the contralateral oculomotor nucleus. This is different from most vertebrates, in which the medial rectus is innervated by the ipsilateral oculomotor nucleus. This observation led to the prediction that the excitatory vestibulo-extraocular motoneuron projections connecting each semicircular canal to the appropriate muscle should use a contralateral projection from the vestibular nuclei to the motoneurons. This hypothesis was examined in the Atlantic stingray by injecting horseradish peroxidase unilaterally into the oculomotor nucleus. It was found that vestibulo-oculomotor projections arise from the ipsilateral anterior octaval nucleus and the contralateral descending octaval nucleus. The same pattern was observed when the trochlear nucleus was involved in the injection. There were no cells labeled in the region of the abducens nucleus, and no candidate for a nucleus prepositus hypoglossus was identified. The presence of compensatory eye movements, the directional sensitivity of the semicircular canals, the location of the motoneurons innervating each eye muscle, and our results indicate that the excitatory input to the extraocular motoneurons is derived from the contralateral descending octaval nucleus, and the inhibitory input is derived from the ipsilateral anterior octaval nucleus. The absence of both abducens internuclear interneurons and a nucleus prepositus hypoglossus suggests that eye movements, particularly those in the horizontal plane, are controlled differently in elasmobranchs than in other vertebrates examined to date.
-
the octavolateral systems in the stingray Dasyatis Sabina i primary projections of the octaval and lateral line nerves
The Journal of Comparative Neurology, 1993Co-Authors: Richard L Puzdrowski, R. B. LeonardAbstract:The central projections of the electrosensory, mechanosensory, and octaval nerves of the Atlantic stingray were examined by transganglionic transport of horseradish peroxidase. Particular attention was paid to the relation of the projections to cell plates C1 and C2, and to a newly described cell plate, C3. The electroreceptors in the stingray are found in three groups on the dorsal and ventral sides of the body. The electroreceptors are represented topographically on the ipsilateral dorsal nucleus. Those of the rostral part of the head and pectoral fins are represented on the rostroventral part of the nucleus, and those on the caudal part of the head and the pectoral fin on the dorsocaudal part of the nucleus. Mechanosensory lateral line afferents terminate within the ipsilateral intermediate and caudal nuclei, and the lateral granular mass of the vestibulocerebellum. Anterior lateral line afferents also project to the magnocellular octaval nucleus. A topographic representation of the mechanosensory lateral line periphery is present on the intermediate and caudal nuclei. Mechanoreceptors on the trunk are represented laterally and those on the head medially. The terminal field of the anterior lateral line afferents on the intermediate nucleus surrounds cell plates C1 and C2. The anterior lateral line afferents also project to the medial part of the lateral granular mass, whereas the posterior lateral line afferents project to the lateral portion. Sparse projections of anterior lateral line afferents to the periventricular octaval nucleus were also observed. The octaval nerve afferents terminate largely within the octaval column. Octaval nerve projections were also observed to the reticular formation, the periventricular octaval nucleus, the deep cerebellar nucleus, the vestibulocerebellum, particularly the lower lip and medial granular mass, and the intermediate nucleus. A sparse projection to cell plate C3 was found. The relation between cell plates C1 and C2 and the anterior lateral line afferents suggests that these cell plates are related to processing lateral line information. While the relationship between cell plate C3 and the octaval afferents is not strong, the sparse octaval projection C3 receives suggests that it is relaying octaval information. © 1993 Wiley-Liss, Inc.
-
variations in cerebellar morphology of the atlantic stingray Dasyatis Sabina
Neuroscience Letters, 1992Co-Authors: Richard L Puzdrowski, R. B. LeonardAbstract:The cerebellar corpus of the Atlantic stingray consists of an anterior lobe which is divided into rostral and caudal lobules, and a posterior lobe. The long axis of the posterior lobe and rostral lobule of the anterior lobe both lie along the midline, whereas the orientation of the caudal lobule varies. We examined this variation in 127 animals. In 52% the long axis of the caudal lobule lay on the right of the midline, in 21% it was on the left, and in 27% across the midline. While this distribution is not random, it is not related to size or sex. It is proposed that the observed variation is the reflection of variation in the cerebellar developmental program.
-
identification of the midbrain locomotor region and its relation to descending locomotor pathways in the atlantic stingray Dasyatis Sabina
Brain Research, 1991Co-Authors: Nicola A Bernau, Richard L Puzdrowki, R. B. LeonardAbstract:Abstract The midbrain locomotor region (MLR) in the Atlantic stingray,Dasyatis Sabina, was identified and characterized. Stimulation (50–100 μA, 60 Hz) of the midbrain in decerebrated, paralyzed animals was used to elicit locomotion monitored as alternating activity in nerves innervating an antagonist pair of elevator and depressor muscles. Effective sites for evoking locomotion in the midbrain included parts of several nuclei: the caudal portion of the interstitial nucleus of the medial longitudinal fasciculus and the caudomedial parts of the cuneiform and subcuneiform nuclei. This region did not include the red nucleus, any parts of the optic tectum or the medial or lateral mesencephalic nuclei. Electrical stimulation in the MLR evokes locomotion in either the ipsi- or contralateral pectoral fin, wheres stimulation in the medullary reticular formation evokes locomotion only in the contralateral fin. Lesion experiments were performed to identify the location of descending pathways from the midbrain to the medullary reticular formation. To abolish locomotion evoked by electrical stimulation in the MLR, the medial reticular formation in the rostral medulla had to be lesioned bilaterally, or the ipsilateral medial medullary reticular formation and fibers projecting from the MLR to the contralateral midbrain had to be disrupted. Injections of HRP into the magnocellular/gigantocellular reticular formation confirmed that this area received bilateral projections from the MLR. The MLR of the Atlantic stingray appears to be similar to the lateral component of the mammalian MLR and to the MLR in other non-mammalian vertebrates.
Keith P Choe - One of the best experts on this subject based on the ideXlab platform.
-
the putative mechanism of na absorption in euryhaline elasmobranchs exists in the gills of a stenohaline marine elasmobranch squalus acanthias
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2007Co-Authors: Keith P Choe, David H Evans, Susan L Edwards, James B ClaiborneAbstract:We recently cloned an NHE3 orthologue from the gills of the euryhaline Atlantic stingray (Dasyatis Sabina), and generated a stingray NHE3 antibody to unequivocally localize the exchanger to the apical side of epithelial cells that are rich with Na+/K+-ATPase (A MRC). We also demonstrated an increase in NHE3 expression when stingrays are in fresh water, suggesting that NHE3 is responsible for active Na+ absorption. However, the vast majority of elasmobranchs are only found in marine environments. In the current study, immunohistochemistry with the stingray NHE3 antibody was used to localize the exchanger in the gills of the stenohaline marine spiny dogfish shark (Squalus acanthias). NHE3 immunoreactivity was confined to the apical side of cells with basolateral Na+/K+-ATPase and was excluded from cells with high levels of vacuolar H+-ATPase. Western blots detected a single protein of 88 kDa in dogfish gills, the same size as NHE3 in stingrays and mammals. These immunological data demonstrate that the putative cell type responsible for active Na+ absorption in euryhaline elasmobranchs is also present in stenohaline marine elasmobranchs, and suggest that the inability of most elasmobranchs to survive in fresh water is not due to a lack of the gill ion transporters for Na+ absorption.
-
a putative h k atpase in the atlantic stingray Dasyatis Sabina primary sequence and expression in gills
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2004Co-Authors: Keith P Choe, Jill W Verlander, Charles S Wingo, David H EvansAbstract:In mammals, the gastric H+-K+-ATPase (HKα1) mediates acid secretion in the stomach and kidneys. Like mammals, elasmobranchs also secrete acid from their stomachs, but unlike mammals they primarily ...
F F Snelson - One of the best experts on this subject based on the ideXlab platform.
-
morphological changes in the clasper gland of the atlantic stingray Dasyatis Sabina associated with the seasonal reproductive cycle
Journal of Morphology, 2006Co-Authors: Andrew N Piercy, J Gelsleichter, F F SnelsonAbstract:The clasper gland of the Atlantic stingray, Dasyatis Sabina, was examined over a 1-year period, covering an entire reproductive cycle. Changes in clasper gland tissue architecture, fluid production, and cell proliferation were assessed. No changes in tissue architecture were observed. Evidence of cell proliferation in the gland epithelium was not detected using immunocytochemistry for proliferating cell nuclear antigen, a cellular marker of mitosis. Epithelial cells were not observed to undergo mitosis, and cell membranes remained intact. The lack of structural changes and epithelial cell proliferation supports the proposed merocrinal mode of fluid secretion. Rays captured in nonbreeding months had clasper glands that exhibited tubules with reduced lumens. In contrast, rays caught during the breeding season had clasper gland tubules with enlarged lumens. Clasper gland fluid production was quantified through measurements of the fluid area and tubule area calculated from digital images. Clasper gland fluid production was significantly higher during the mating period than during months not associated with copulatory activity. These data support the notion that the clasper gland is involved in stingray copulatory activity. This study adds to the limited amount of literature focused on this poorly understood component of reproduction in skates and rays. J. Morphol. © 2005 Wiley-Liss, Inc.
-
morphological changes in the clasper gland of the atlantic stingray Dasyatis Sabina associated with the seasonal reproductive cycle
Journal of Morphology, 2006Co-Authors: Andrew N Piercy, J Gelsleichter, F F SnelsonAbstract:The clasper gland of the Atlantic stingray, Dasyatis Sabina, was examined over a 1-year period, covering an entire reproductive cycle. Changes in clasper gland tissue architecture, fluid production, and cell proliferation were assessed. No changes in tissue architecture were observed. Evidence of cell proliferation in the gland epithelium was not detected using immunocytochemistry for proliferating cell nuclear antigen, a cellular marker of mitosis. Epithelial cells were not observed to undergo mitosis, and cell membranes remained intact. The lack of structural changes and epithelial cell proliferation supports the proposed merocrinal mode of fluid secretion. Rays captured in nonbreeding months had clasper glands that exhibited tubules with reduced lumens. In contrast, rays caught during the breeding season had clasper gland tubules with enlarged lumens. Clasper gland fluid production was quantified through measurements of the fluid area and tubule area calculated from digital images. Clasper gland fluid production was significantly higher during the mating period than during months not associated with copulatory activity. These data support the notion that the clasper gland is involved in stingray copulatory activity. This study adds to the limited amount of literature focused on this poorly understood component of reproduction in skates and rays.
-
morphological and histological changes in the genital ducts of the male atlantic stingray Dasyatis Sabina during the seasonal reproductive cycle
Fish Physiology and Biochemistry, 2003Co-Authors: A Piercy, J Gelsleichter, F F SnelsonAbstract:Changes inthe morphology and histologyofthe epididymis and seminal vesicle in male Atlantic stingrays (Dasyatis Sabina) were examined in relation tothe seasonal reproductive cycle. Observations onthe size and structureofthese organs were accompanied by analysisof cell proliferation in genital duct epithelia using proliferating cell nuclear antigen (PCNA) as a marker for mitotic activity. No signsof reproductive tract growth or histological alteration were apparent duringthe initial stagesof spermatogenesis. However, increased PCNA expression inthe seminal vesicle epithelium was observed during this period, suggesting that this organ begins to undergo preparatory changes at an early stage inthe reproductive cycle. During late spermatogenesis, heightened expressionof PCNA in epithelial cellsofthe epididymis and seminal vesicle was observed in conjunction with dramatic increases in size and semen contentofthese organs. Extensive changes inthe histological architectureofthe genital ducts also were evident at this time, including regressionofthe stroma and an increase in size and secretory activityofthe epithelium. Althoughthe epididymis regressed in size and structure shortly after sperm production was completed,the seminal vesicle retained its appearance and activity forthe durationofthe 7-month copulatory period. Afterwards, immune cell content increased considerably in both ducts, likely reflecting clearanceof residual spermatozoa in preparation forthe subsequent reproductive season.the present study provides a basis for future reports onthe physiological regulationof reproductive tract function in elasmobranchs, and establishes PCNA immunocytochemistry as a novel tool for such investigations.
-
reproductive life history of the atlantic stingray Dasyatis Sabina pisces dasyatidae in the freshwater st johns river florida
Bulletin of Marine Science, 1992Co-Authors: M R Johnson, F F SnelsonAbstract:A population of the Atlantic stingray, Dasyatis Sabina, resides in the freshwater St. Johns River system, Florida. The reproductive life history of the species in Lake Monroe near Sanford, Florida, was studied from November 1990 to January 1992. No major differences in reproductive timing or performance were noted between this freshwater population and marine populations studied elsewhere in Florida. Females matured at approximately 22 cm disk width (DW), and mature ovarian eggs were ovulated in early April. Embryos were obtained from pregnant females from 15 May to 17 July, and parturition occurred in late July, when embryos attained approximately 100 mm DW. Males matured at approximately 21 cm DW. Male gonadosomatic index peaked in November and declined continually through the spring, but fluid was retained in the seminal vesicles until May. This population experienced total reproductive failure during the 1991/1992 season. Extremely low conductivity in the lake during the fall and winter of 1991 is suggested as a possible stressor.
