Anti-oesophageal cancer activity in extracts of deep-water Marion Island sponges
- Davies-Coleman, Michael T, Froneman, P William, Keyzers, Robert A, Whibley, Catherine, Hendricks, Denver T, Samaai, Toufiek, McQuaid, Christopher D
- Authors: Davies-Coleman, Michael T , Froneman, P William , Keyzers, Robert A , Whibley, Catherine , Hendricks, Denver T , Samaai, Toufiek , McQuaid, Christopher D
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6569 , http://hdl.handle.net/10962/d1004132
- Description: Oesophageal cancer is one of the most common causes of cancer-related deaths in South African black males. The limited efficacy of chemotherapeutic agents to treat this disease has prompted a search for potential new chemical entities with anticancer properties. We report here on the evidence for anti-oesophageal cancer activity in the methanolic extracts of five species of sponges dredged from a depth of approximately 100 m in the vicinity of Marion Island in the Southern Ocean during the autumn of 2004.
- Full Text:
- Authors: Davies-Coleman, Michael T , Froneman, P William , Keyzers, Robert A , Whibley, Catherine , Hendricks, Denver T , Samaai, Toufiek , McQuaid, Christopher D
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6569 , http://hdl.handle.net/10962/d1004132
- Description: Oesophageal cancer is one of the most common causes of cancer-related deaths in South African black males. The limited efficacy of chemotherapeutic agents to treat this disease has prompted a search for potential new chemical entities with anticancer properties. We report here on the evidence for anti-oesophageal cancer activity in the methanolic extracts of five species of sponges dredged from a depth of approximately 100 m in the vicinity of Marion Island in the Southern Ocean during the autumn of 2004.
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Contrasting spatial heterogeneity of sessile organisms within mussel (Perna perna L.) beds in relation to topographic variability
- Erlandsson, J, McQuaid, Christopher D, Kostylev, V E
- Authors: Erlandsson, J , McQuaid, Christopher D , Kostylev, V E
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6949 , http://hdl.handle.net/10962/d1011979
- Description: We examined the spatial heterogeneity in three sessile rocky shore organisms, the mussel Perna perna, the barnacle Octomeris angulosa (Sowerby) and the red alga Gelidium pristoides (Turn.) at a range of continuous local scales along horizontal transects within mid- and upper mussel beds of South African shores. We also examined the relationships between variability of organisms and topographic features (rock depressions, slope, aspect), and between mussel, barnacle and algal variability over the same scales. To estimate spatial heterogeneity, we analyzed scaling properties of semivariograms using a fractal approach. Relationships between different variables at the different scales were examined by cross-semivariograms. Spatial dependence of P. perna variability increased with spatial dependence of topographic variability, so that scaling regions of mussel and topographic distributions corresponded well. This relationship often improved with larger local scales (mussel cover increased with depressions, steeper slope and aspect towards waves), while at smaller spatial scales, variability in mussel cover was less well explained by variability in topography. The variability of the barnacle O. angulosa exhibited spatial dependence, even on topographically unstructured shores. In contrast, the distribution of the alga G. pristoides revealed high fractal dimensions, showing spatial independence on topographically unstructured shores. Algae also showed a very strong negative relationship with mussels at most local scales, and a negative relationship with barnacles in upper zones, especially at larger local scales. Barnacles may show clear spatial dependence because of hydrodynamics (at larger local scales) and the need to find a future mate in close proximity (at smaller local scales), while algae may show a strong negative relationship with mussels because of competition for space.
- Full Text:
- Authors: Erlandsson, J , McQuaid, Christopher D , Kostylev, V E
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6949 , http://hdl.handle.net/10962/d1011979
- Description: We examined the spatial heterogeneity in three sessile rocky shore organisms, the mussel Perna perna, the barnacle Octomeris angulosa (Sowerby) and the red alga Gelidium pristoides (Turn.) at a range of continuous local scales along horizontal transects within mid- and upper mussel beds of South African shores. We also examined the relationships between variability of organisms and topographic features (rock depressions, slope, aspect), and between mussel, barnacle and algal variability over the same scales. To estimate spatial heterogeneity, we analyzed scaling properties of semivariograms using a fractal approach. Relationships between different variables at the different scales were examined by cross-semivariograms. Spatial dependence of P. perna variability increased with spatial dependence of topographic variability, so that scaling regions of mussel and topographic distributions corresponded well. This relationship often improved with larger local scales (mussel cover increased with depressions, steeper slope and aspect towards waves), while at smaller spatial scales, variability in mussel cover was less well explained by variability in topography. The variability of the barnacle O. angulosa exhibited spatial dependence, even on topographically unstructured shores. In contrast, the distribution of the alga G. pristoides revealed high fractal dimensions, showing spatial independence on topographically unstructured shores. Algae also showed a very strong negative relationship with mussels at most local scales, and a negative relationship with barnacles in upper zones, especially at larger local scales. Barnacles may show clear spatial dependence because of hydrodynamics (at larger local scales) and the need to find a future mate in close proximity (at smaller local scales), while algae may show a strong negative relationship with mussels because of competition for space.
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Interacting effects of wave exposure, tidal height and substratum on spatial variation in densities of mussel Perna perna plantigrades
- McQuaid, Christopher D, Lindsay, Justin R
- Authors: McQuaid, Christopher D , Lindsay, Justin R
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6879 , http://hdl.handle.net/10962/d1011635
- Description: A fine time-scale study was undertaken on the effects of wave exposure, tidal height and substratum type on mussel recruit densities on the south coast of South Africa. Prior to sampling, an exposed and a sheltered shore were identified at each of 2 sites (Diaz Cross and High Rocks) 7 km apart. Each shore was divided into 3 shore levels (termed zones) within which 3 substrata (adult mussels, coralline and non-coralline macroalgae) were sampled. Destructive sampling of early (<1 mm) and late (1 to 5 mm) plantigrades was performed daily over 30 d during a period of comparatively high recruitment. Recruitment was synchronised among substrata within zones, but not among zones or between sites. This suggests that larvae will settle on all substrata within a zone, but will prefer some substrata over others. They will not, however, search among zones for favoured substrata. Densities of early (but not late) plantigrades were consistently greater at Diaz Cross than High Rocks, indicating important differences in post-settlement mortality between sites. At both sites, densities of both recruit classes were greater on the low and mid shore than on the high shore. Generally (18 out of 20 comparisons), plantigrade densities within each zone were greater on algae than on adult mussels. Approximately 45% of all recruits collected were found on the foliose coralline alga Corallina, 37% on adult mussels and 18% on the rhodophyte Gelidium pristoides. Without secondary relocation from macroalgae to adult mussel beds, juveniles recruiting onto algae are likely to be lost. On low shore algae, densities of both early and late plantigrades were greater for exposed shores. Densities of plantigrades on the mussel bed and on algae on the mid and high shore were not correlated with exposure. Thus, site, substratum and zone all had significant and interacting effects on the density of recruits on both exposed and sheltered shores. The effect of wave exposure on recruitment, at least on the low shore, suggests that spatial subsidies not only in the form of food supply, but also in the form of larval transport, have a role in structuring mussel populations.
- Full Text:
- Authors: McQuaid, Christopher D , Lindsay, Justin R
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6879 , http://hdl.handle.net/10962/d1011635
- Description: A fine time-scale study was undertaken on the effects of wave exposure, tidal height and substratum type on mussel recruit densities on the south coast of South Africa. Prior to sampling, an exposed and a sheltered shore were identified at each of 2 sites (Diaz Cross and High Rocks) 7 km apart. Each shore was divided into 3 shore levels (termed zones) within which 3 substrata (adult mussels, coralline and non-coralline macroalgae) were sampled. Destructive sampling of early (<1 mm) and late (1 to 5 mm) plantigrades was performed daily over 30 d during a period of comparatively high recruitment. Recruitment was synchronised among substrata within zones, but not among zones or between sites. This suggests that larvae will settle on all substrata within a zone, but will prefer some substrata over others. They will not, however, search among zones for favoured substrata. Densities of early (but not late) plantigrades were consistently greater at Diaz Cross than High Rocks, indicating important differences in post-settlement mortality between sites. At both sites, densities of both recruit classes were greater on the low and mid shore than on the high shore. Generally (18 out of 20 comparisons), plantigrade densities within each zone were greater on algae than on adult mussels. Approximately 45% of all recruits collected were found on the foliose coralline alga Corallina, 37% on adult mussels and 18% on the rhodophyte Gelidium pristoides. Without secondary relocation from macroalgae to adult mussel beds, juveniles recruiting onto algae are likely to be lost. On low shore algae, densities of both early and late plantigrades were greater for exposed shores. Densities of plantigrades on the mussel bed and on algae on the mid and high shore were not correlated with exposure. Thus, site, substratum and zone all had significant and interacting effects on the density of recruits on both exposed and sheltered shores. The effect of wave exposure on recruitment, at least on the low shore, suggests that spatial subsidies not only in the form of food supply, but also in the form of larval transport, have a role in structuring mussel populations.
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Supply-side ecology of the brown mussel, Perna perna: an investigation of spatial and temporal variation in, and coupling between, gamete release and larval supply
- McQuaid, Christopher D, Lawrie, S M
- Authors: McQuaid, Christopher D , Lawrie, S M
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6954 , http://hdl.handle.net/10962/d1011987
- Description: Sampling of recruitment-associated variables of Perna perna was done approximately monthly for 14 months at intertidal locations 500 m apart, nested within sites 25 km apart. Paired with intertidal locations were nearshore locations, 600 m to sea. Sampling assessed spawning, densities of larvae in the water column and densities of late plantigrades and juveniles on the shore. Major events in each variable were synchronous over larger scales (10s of kilometres) while subsidiary events were synchronised at smaller scales, varying within sites (100s of metres) or even within locations (metres). This suggests that the processes driving major events operated over large scales while processes operating at much more local scales drove less intense, more localised events. A major spawning event occurred at all locations in May–June 1998. Weaker spawning events occurred at different times in different locations. Larvae were found on 80% of sampling occasions, densities peaking in January–March 1998 and 1999 at all locations. Plantigrades and juveniles showed less clear patterns, with considerable residual variation. There was no sign of strong coupling among variables with few significant direct or cross correlations. The major sources of variability shifted from time to space as one progressed from spawning, to plantigrade density to juvenile density. For spawning, time was the most important source (58%) of heterogeneity and space accounted for little (8%) of the total variance. For larvae and late plantigrades, time was still the most important source of variability (41% and 33%, respectively), but space was a much more substantial component. For juveniles, small-scale (residual) spatial variability dominated total variability (75%). This strongly suggests the importance of hydrography and its effects on variation in delivery of larvae to the intertidal from offshore. These findings also indicate greater spatial heterogeneity as recruits age, reflecting small-scale variations in larval delivery and the increasing importance of post-settlement mortality.
- Full Text:
- Authors: McQuaid, Christopher D , Lawrie, S M
- Date: 2005
- Language: English
- Type: Article
- Identifier: vital:6954 , http://hdl.handle.net/10962/d1011987
- Description: Sampling of recruitment-associated variables of Perna perna was done approximately monthly for 14 months at intertidal locations 500 m apart, nested within sites 25 km apart. Paired with intertidal locations were nearshore locations, 600 m to sea. Sampling assessed spawning, densities of larvae in the water column and densities of late plantigrades and juveniles on the shore. Major events in each variable were synchronous over larger scales (10s of kilometres) while subsidiary events were synchronised at smaller scales, varying within sites (100s of metres) or even within locations (metres). This suggests that the processes driving major events operated over large scales while processes operating at much more local scales drove less intense, more localised events. A major spawning event occurred at all locations in May–June 1998. Weaker spawning events occurred at different times in different locations. Larvae were found on 80% of sampling occasions, densities peaking in January–March 1998 and 1999 at all locations. Plantigrades and juveniles showed less clear patterns, with considerable residual variation. There was no sign of strong coupling among variables with few significant direct or cross correlations. The major sources of variability shifted from time to space as one progressed from spawning, to plantigrade density to juvenile density. For spawning, time was the most important source (58%) of heterogeneity and space accounted for little (8%) of the total variance. For larvae and late plantigrades, time was still the most important source of variability (41% and 33%, respectively), but space was a much more substantial component. For juveniles, small-scale (residual) spatial variability dominated total variability (75%). This strongly suggests the importance of hydrography and its effects on variation in delivery of larvae to the intertidal from offshore. These findings also indicate greater spatial heterogeneity as recruits age, reflecting small-scale variations in larval delivery and the increasing importance of post-settlement mortality.
- Full Text:
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