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Michelle R Heupel - One of the best experts on this subject based on the ideXlab platform.
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estuarine nursery areas provide a low mortality environment for young bull sharks carcharhinus Leucas
Marine Ecology Progress Series, 2011Co-Authors: Michelle R Heupel, Colin A SimpfendorferAbstract:Defining the role and impact of mortality within aquatic populations is often difficult. As a result, we still lack a clear understanding of the level of mortality in natural populations and the role habitat may play in survival. We used long-term acoustic monitoring of neonate bull sharks Carcharhinus Leucas in a south Florida estuary to determine mortality rates within this population. Estimates of natural, fishing and total mortality varied among the years examined, but not significantly, suggesting similar survival among years with the majority of individuals (77%) surviving beyond 18 mo. Compared with other juvenile sharks, mortality rates of C. Leucas were low. The results indicate that the use of mesohaline estuarine habitats by C. Leucas may provide benefits that are not present in more marine habitats where their counterparts reside. Use of estuarine regions may be a successful ecological strategy for improving survival because of reduced predation and competition.
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Habitat use and movement patterns of bull sharks Carcharhinus Leucas determined using pop-up satellite archival tags
Journal of Fish Biology, 2010Co-Authors: John K. Carlson, Christina L Conrath, Marta Ribera, Michelle R Heupel, George H BurgessAbstract:Habitat use, movement and residency of bull sharks Carcharhinus Leucas were determined using satellite pop-up archival transmitting (PAT) tags throughout coastal areas in the U.S., Gulf of Mexico and waters off the south-east U.S. From 2005 to 2007, 18 fish (mean size = 164 cm fork length, L(F)) were tagged over all seasons. Fish retained tags for up to 85 days (median = 30 days). Based on geolocation data from initial tagging location to pop-off location, C. Leucas generally travelled c. 5-6 km day(-1) and travelled an average of 143.6 km. Overall, mean proportions of time at depth revealed C. Leucas spent the majority of their time in waters
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habitat use and movement patterns of bull sharks carcharhinus Leucas determined using pop up satellite archival tags
Journal of Fish Biology, 2010Co-Authors: John K. Carlson, Christina L Conrath, Marta Ribera, Michelle R Heupel, George H BurgessAbstract:Habitat use, movement and residency of bull sharks Carcharhinus Leucas were determined using satellite pop-up archival transmitting (PAT) tags throughout coastal areas in the U.S., Gulf of Mexico and waters off the south-east U.S. From 2005 to 2007, 18 fish (mean size = 164 cm fork length, L(F)) were tagged over all seasons. Fish retained tags for up to 85 days (median = 30 days). Based on geolocation data from initial tagging location to pop-off location, C. Leucas generally travelled c. 5-6 km day(-1) and travelled an average of 143.6 km. Overall, mean proportions of time at depth revealed C. Leucas spent the majority of their time in waters <20 m. They exhibited significant differences among depths but were not found at a particular depth regardless of diurnal period. Most fish occupied temperatures c. 32 degrees C with individuals found mostly between 26 and 33 degrees C. Geolocation data for C. Leucas were generally poor and varied considerably but tracks for two individuals revealed long distance movements. One fish travelled from the south-east coast of the U.S. to coastal Texas near Galveston while another moved up the east coast of the U.S. to South Carolina. Data on C. Leucas movements indicated that they are found primarily in shallower waters and tend to remain in the same location over long periods. While some individuals made large-scale movements over open ocean areas, the results emphasize the importance of the coastal zone for this species as potential essential habitat, particularly in areas of high freshwater inflow.
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occurrence home range and movement patterns of juvenile bull carcharhinus Leucas and lemon negaprion brevirostris sharks within a florida estuary
Marine and Freshwater Research, 2008Co-Authors: Beau G Yeiser, Michelle R Heupel, Colin A SimpfendorferAbstract:The movement patterns of large juveniles are poorly known for many shark species. With increasing pressure on shark populations these data are critical for the management of large coastal species. A series of acoustic receivers were positioned in Pine Island Sound, Florida, USA, to passively track the long-term movements of large juvenile bull (Carcharhinus Leucas) and lemon (Negaprion brevirostris) sharks. Nineteen C. Leucas and five N. brevirostris were monitored during 2003 and 2004. Individual C. Leucas were present for 8 to 89 days, while N. brevirostris were present for 12 to 83 days. Weekly minimum convex polygons and kernel utilisation distributions were calculated to demonstrate the home range and core areas of use of both species. Spectral analysis demonstrated that several N. brevirostris showed repetitive diel north–south movement patterns over periods of up to 28 consecutive days. C. Leucas demonstrated regular use of backwater habitats. Long-term use of estuarine areas by these large juvenile sharks suggests that estuarine coastal lagoons provide an important habitat for this portion of their life history and as such, protection of these habitats may assist in shark management and conservation.
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distribution and habitat partitioning of immature bull sharks carcharhinus Leucas in a southwest florida estuary
Estuaries, 2005Co-Authors: Colin A Simpfendorfer, Garin G Freitas, Tonya R Wiley, Michelle R HeupelAbstract:The distribution and salinity preference of immature bull sharks (Carcharhinus Leucas) were examined based on the results of longline surveys in three adjacent estuarine habitats in southwest Florida: the Caloosahatchee River, San Carlos Bay, and Pine Island Sound. Mean sizes were significantly different between each of these areas indicating the occurrence of size-based habitat partitioning. Neonate and young-of-the-year animals occurred in the Caloosahatchee River and juveniles older than 1 year occurred in the adjacent embayments. Habitat partitioning may reduce intraspecific predation risk and increase survival of young animals. Classification tree analysis showed that both temperature and salinity were important factors in determining the occurrence and catch per unit effort (CPUE) of immatureC. Leucas. The CPUE of <1 year oldC. Leucas was highest at temperatures over 29°C and in areas with salinities between 7‰ and 17.5‰ Although they are able to osmoregulate in salinities from fresh to fully marine, youngC. Leucas may have a salinity preference. Reasons for this preference are unknown, but need to be further investigated.
Craig E. Franklin - One of the best experts on this subject based on the ideXlab platform.
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Branchial osmoregulation in the euryhaline bull shark, Carcharhinus Leucas: a molecular analysis of ion transporters.
The Journal of experimental biology, 2011Co-Authors: Beau D Reilly, Rebecca L Cramp, Jonathan M Wilson, Hamish A Campbell, Craig E. FranklinAbstract:Bull sharks, Carcharhinus Leucas, are one of only a few species of elasmobranchs that live in both marine and freshwater environments. Osmoregulation in euryhaline elasmobranchs is achieved through the control and integration of various organs (kidney, rectal gland and liver) in response to changes in environmental salinity. However, little is known regarding the mechanisms of ion transport in the gills of euryhaline elasmobranchs and how they are affected by osmoregulatory challenges. This study was conducted to gain insight into the branchial ion and acid-base regulatory mechanisms of C. Leucas by identifying putative ion transporters and determining whether their expression is influenced by environmental salinity. We hypothesised that expression levels of the Na(+)/K(+)-ATPase (NKA) pump, Na(+)/H(+) exchanger 3 (NHE3), vacuolar-type H(+)-ATPase (VHA) and anion exchanger pendrin (PDN) would be upregulated in freshwater (FW) C. Leucas. Immunohistochemistry was used to localise all four ion transporters in gills of bull sharks captured in both FW and estuarine/seawater (EST/SW) environments. NHE3 immunoreactivity occurred in the apical region of cells with basolateral NKA expression whereas PDN was apically expressed in cells that also exhibited basolateral VHA immunoreactivity. In accordance with our hypotheses, quantitative real-time PCR showed that the mRNA expression of NHE3 and NKA was significantly upregulated in gills of FW-captured C. Leucas relative to EST/SW-captured animals. These data suggest that NHE3 and NKA together may be important in mediating branchial Na(+) uptake in freshwater environments, whereas PDN and VHA might contribute to Cl(-)/HCO(3)(-) transport in marine and freshwater bull shark gills.
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plasma and erythrocyte solute properties of juvenile bull sharks carcharhinus Leucas acutely exposed to increasing environmental salinity
Journal of Experimental Marine Biology and Ecology, 2006Co-Authors: Susumu Hyodo, Richard D. Pillans, Jonathan P. Good, Yoshio Takei, Neil Hazon, Gary W Anderson, Craig E. FranklinAbstract:Plasma and erythrocyte solute properties were examined in freshwater (FW) acclimated juvenile Carcharhinus Leucas following acute transfer to 75% seawater (SW), and 100% SW. Blood samples were taken at 0, 12 and 96 h following transfer to 75% SW and 24 and 72 h after transfer to 100% SW. A control group in FW was subjected to the same sampling regime. Upon transfer of C Leucas to 75% and 100% SW, plasma Na+, Cl-, K+, Mg2+, Ca2+, urea and TMAO concentrations all increased significantly but disproportionately. Plasma Na+ and Cl- increased immediately, followed by ail increase in plasma urea. Erythrocyte urea and TMAO concentrations increased significantly following transfer to 75% and 100% SW; however, changes in erythrocyte inorganic ion concentrations were insignificant. Haematocrit, haemoglobin and mean cell haematocrit did not differ significantly after transfer to seawater; however, plasma water was slightly reduced after 24 and 72 h in 100% SW. Red blood cell (RBC) water content was elevated 24 h after transfer to 100% SW but returned to FW levels after 72 h. These results demonstrate that the transfer from 75% to 100% SW presents C. Leucas with a greater osmoregulatory challenge than transfer from FW to 75% SW, despite the larger concentration gradient in the latter. In summary, C. Leucas tolerate rapid and significant increases in salinity by rapidly increasing plasma osmolality to be hyperosmotic to the environment whilst maintaining a tight regulation of their intracellular fluid environment. (C) 2005 Elsevier B.V All rights reserved.
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Hepatic urea biosynthesis in the euryhaline elasmobranch Carcharhinus Leucas
Journal of experimental zoology. Part A Comparative experimental biology, 2005Co-Authors: W. Gary Anderson, Richard D. Pillans, Jonathan P. Good, Neil Hazon, Craig E. FranklinAbstract:Plasma urea levels and hepatic urea production in the euryhaline bull shark, Carcharhinus Leucas, acclimated to freshwater and seawater environments were measured. It was found that plasma urea concentration increased with salinity and that this increase was, in part, the result of a significant increase in hepatic production of urea. This study provides direct evidence that hepatic production of urea plays an important role in the osmoregulatory strategy of C. Leucas.
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Sequence, circulating levels, and expression of C-type natriuretic peptide in a euryhaline elasmobranch, Carcharhinus Leucas.
General and comparative endocrinology, 2005Co-Authors: W. Gary Anderson, Susumu Hyodo, Takehiro Tsukada, Lara Meischke, Richard D. Pillans, Jonathan P. Good, Yoshio Takei, Gordon Cramb, Craig E. Franklin, Neil HazonAbstract:The present study has examined expression and circulating levels of C-type natriuretic peptide (CNP) in the euryhaline bull shark, Carcharhinus Leucas. Complementary DNA and deduced amino acid sequence for CNP in C Leucas were determined by RACE methods. Homology of CNP amino acid sequence in C. Leucas was high both for proCNP and for mature CNP when compared with previously identified elasmobranch CNPs. Mature CNP sequence in C. Leucas was identical to that in Triakis seyllia and Seyliorhinus canicula. Levels of expression of CNP mRNA were significantly decreased in the atrium but did not change in either the brain or ventricle following acclimation to a SW environment. However, circulating levels of CNP significantly increased from 86.0 +/- 7.9 fmol ml(-1) in FW to 144.9 +/- 19.5 fmol ml(-1) in SW. The results presented demonstrate that changes in environmental salinity influences both synthesis of CNP from the heart and also circulating levels in C. Leucas. Potential stimulus for release and modes of action are discussed. (c) 2005 Elsevier Inc. All rights reserved.
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plasma osmolyte concentrations and rectal gland mass of bull sharks carcharhinus Leucas captured along a salinity gradient
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2004Co-Authors: Richard D. Pillans, Craig E. FranklinAbstract:Bull sharks (Carcharhinus Leucas) were captured across a salinity gradient from freshwater (FW) to seawater (SW). Across all salinities, C Leucas were hyperosmotic to the environment. Plasma osmolarity in FW-captured animals (642 +/- 7 mosM) was significantly reduced compared to SW-captured animals (1067 +/- 21 mosM). In FW animals, sodium, chloride and urea were 208 +/- 3, 203 +/- 3 and 192 +/- 2 mmol l(-1), respectively. Plasma sodium, chloride and urea in SW-captured C Leucas were 289 +/- 3, 296 +/- 6 and 370 +/- 10 mmol l(-1), respectively. The increase in plasma osmolarity between FW and SW was not linear. Between FW (3 mosM) and 24%o SW (676 mosM), plasma osmolarity increased by 22% or 0.92% per 1parts per thousand rise in salinity. Between 24%o and 33parts per thousand, plasma osmolarity increased by 33% or 4.7% per 1 parts per thousand rise in salinity, largely due to a sharp increase in plasma urea between 28parts per thousand and 33parts per thousand. C. Leucas moving between FW and SW appear to be faced with three major osmoregulatory challenges, these occur between 0-10parts per thousand, 11-20parts per thousand and 21-33parts per thousand. A comparison between C Leucas captured in FW and estuarine environments (20-28%o) in the Brisbane River revealed no difference in the mass of rectal glands between these animals. However, a comparison of rectal gland mass between FW animals captured in the Brisbane River and Rio San Juan/Lake Nicaragua showed that animals in the latter system had a significantly smaller rectal gland mass at a given length than animals in the Brisbane River. The physiological challenges and mechanisms required for C Leucas moving between FW and SW, as well as the ecological implications of these data are discussed. (C) 2004 Elsevier Inc. All rights reserved.
Nishteswar K - One of the best experts on this subject based on the ideXlab platform.
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A Review on Source Plants of Dronpushpi - Leucas cephalotes (Roth) Spreng and Leucas aspera Spreng
International Journal of Ayurvedic Medicine, 2013Co-Authors: Sachin Chavan, Nishteswar KAbstract:Dronpushpi is a classical medicinal plant attributed with certain specific indications like Vishamjwara, Kamala. Two different plant species of Leucas are taken in use in the name of Dronpushpi. Among them Leucas cephalotes (Roth) Spreng has been accepted as an official equivalent to Dronpushpi by the Central Council for Research in Ayurveda in its official formulary. It has also been mentioned in Unani Materia Medica. Leucas aspera Spreng is the most widely used substitute of Dronapushpi and is also equally important ethnobotanically. Leucas cephalotes (Roth) Spreng and Leucas aspera Spreng grow as a weed on wastelands and roadsides all over India from October to February. The plants are used as insecticides and indicated in traditional medicine for coughs, cold, painful swellings, chronic skin eruptions and rheumatism. Experimentally both the species have shown good antioxidant, hepatoprotective and antimicrobial activities. They contain β-sitosterol, triterpenoids, oleanolic acid, ursolic acid, phenolic compounds, diterpenes, glucosides as major chemical constituents. The current review revealed that Leucas cephalotes and Leucas aspera have number of potentials in therapeutic field.
David W. Sims - One of the best experts on this subject based on the ideXlab platform.
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To Madagascar and back: long‐distance, return migration across open ocean by a pregnant female bull shark Carcharhinus Leucas
Journal of fish biology, 2015Co-Authors: James S. E. Lea, Nicolas E. Humphries, Christopher R. Clarke, David W. SimsAbstract:A large, pregnant, female bull shark Carcharhinus Leucas was tracked migrating from Seychelles across open ocean to south-east Madagascar, c. 2000 km away, and back again. In Madagascar, the shark spent a prolonged period shallower than 5 m, consistent with entering estuarine habitat to pup, and upon return to Seychelles the shark was slender and no longer gravid. This represents an unprecedented return migration across the open ocean for a C. Leucas and highlights the need for international collaboration to manage the regional C. Leucas population sustainably.
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oceans apart short term movements and behaviour of adult bull sharks carcharhinus Leucas in atlantic and pacific oceans determined from pop off satellite archival tagging
Journal of Fish Biology, 2010Co-Authors: Juerg M Brunnschweiler, David W. Sims, Nuno QueirozAbstract:Adult bull sharks Carcharhinus Leucas were monitored with electronic tags to investigate horizontal and vertical movements in the Atlantic and Pacific Oceans. In both locations, C. Leucas showed some fidelity to specific coastal areas with only limited horizontal movements away from the tagging sites after tag attachment. Fish tagged in the Bahamas were detected mostly in the upper 20 m of the water column in water 25-26° C, whereas C. Leucas tagged in Fiji spent most of their time below 20 m in water usually >26° C. The results highlight the importance of coastal inshore habitats for this species.
Colin A Simpfendorfer - One of the best experts on this subject based on the ideXlab platform.
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estuarine nursery areas provide a low mortality environment for young bull sharks carcharhinus Leucas
Marine Ecology Progress Series, 2011Co-Authors: Michelle R Heupel, Colin A SimpfendorferAbstract:Defining the role and impact of mortality within aquatic populations is often difficult. As a result, we still lack a clear understanding of the level of mortality in natural populations and the role habitat may play in survival. We used long-term acoustic monitoring of neonate bull sharks Carcharhinus Leucas in a south Florida estuary to determine mortality rates within this population. Estimates of natural, fishing and total mortality varied among the years examined, but not significantly, suggesting similar survival among years with the majority of individuals (77%) surviving beyond 18 mo. Compared with other juvenile sharks, mortality rates of C. Leucas were low. The results indicate that the use of mesohaline estuarine habitats by C. Leucas may provide benefits that are not present in more marine habitats where their counterparts reside. Use of estuarine regions may be a successful ecological strategy for improving survival because of reduced predation and competition.
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occurrence home range and movement patterns of juvenile bull carcharhinus Leucas and lemon negaprion brevirostris sharks within a florida estuary
Marine and Freshwater Research, 2008Co-Authors: Beau G Yeiser, Michelle R Heupel, Colin A SimpfendorferAbstract:The movement patterns of large juveniles are poorly known for many shark species. With increasing pressure on shark populations these data are critical for the management of large coastal species. A series of acoustic receivers were positioned in Pine Island Sound, Florida, USA, to passively track the long-term movements of large juvenile bull (Carcharhinus Leucas) and lemon (Negaprion brevirostris) sharks. Nineteen C. Leucas and five N. brevirostris were monitored during 2003 and 2004. Individual C. Leucas were present for 8 to 89 days, while N. brevirostris were present for 12 to 83 days. Weekly minimum convex polygons and kernel utilisation distributions were calculated to demonstrate the home range and core areas of use of both species. Spectral analysis demonstrated that several N. brevirostris showed repetitive diel north–south movement patterns over periods of up to 28 consecutive days. C. Leucas demonstrated regular use of backwater habitats. Long-term use of estuarine areas by these large juvenile sharks suggests that estuarine coastal lagoons provide an important habitat for this portion of their life history and as such, protection of these habitats may assist in shark management and conservation.
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distribution and habitat partitioning of immature bull sharks carcharhinus Leucas in a southwest florida estuary
Estuaries, 2005Co-Authors: Colin A Simpfendorfer, Garin G Freitas, Tonya R Wiley, Michelle R HeupelAbstract:The distribution and salinity preference of immature bull sharks (Carcharhinus Leucas) were examined based on the results of longline surveys in three adjacent estuarine habitats in southwest Florida: the Caloosahatchee River, San Carlos Bay, and Pine Island Sound. Mean sizes were significantly different between each of these areas indicating the occurrence of size-based habitat partitioning. Neonate and young-of-the-year animals occurred in the Caloosahatchee River and juveniles older than 1 year occurred in the adjacent embayments. Habitat partitioning may reduce intraspecific predation risk and increase survival of young animals. Classification tree analysis showed that both temperature and salinity were important factors in determining the occurrence and catch per unit effort (CPUE) of immatureC. Leucas. The CPUE of <1 year oldC. Leucas was highest at temperatures over 29°C and in areas with salinities between 7‰ and 17.5‰ Although they are able to osmoregulate in salinities from fresh to fully marine, youngC. Leucas may have a salinity preference. Reasons for this preference are unknown, but need to be further investigated.