2016

Regulation of Heat Exchange across the Hornbill Beak: Functional Similarities with Toucans?
  • T.M.F.N. van de Ven
  • R.O. Martin
  • T.J.F. Vink
  • A.E. McKechnie
  • S.J. Cunningham
PLOS One, 2016
@article{10.1371/journal.pone.0154768,
    author = {van de Ven, T. M. F. N. AND Martin, R. O. AND Vink, T. J. F. AND McKechnie, A. E. AND Cunningham, S. J.},
    journal = {PLoS ONE},
    publisher = {Public Library of Science},
    title = {Regulation of Heat Exchange across the Hornbill Beak: Functional Similarities with Toucans?},
    year = {2016},
    month = {05},
    volume = {11},
    url = {http://dx.doi.org/10.1371%2Fjournal.pone.0154768},
    pages = {1-14},
    abstract = {<p>Beaks are increasingly recognised as important contributors to avian thermoregulation. Several studies supporting Allen?s rule demonstrate how beak size is under strong selection related to latitude and/or air temperature (T<sub>a</sub>). Moreover, active regulation of heat transfer from the beak has recently been demonstrated in a toucan (<italic>Ramphastos toco</italic>, Ramphastidae), with the large beak acting as an important contributor to heat dissipation. We hypothesised that hornbills (Bucerotidae) likewise use their large beaks for non-evaporative heat dissipation, and used thermal imaging to quantify heat exchange over a range of air temperatures in eighteen desert-living Southern Yellow-billed Hornbills (<italic>Tockus leucomelas</italic>). We found that hornbills dissipate heat via the beak at air temperatures between 30.7°C and 41.4°C. The difference between beak surface and environmental temperatures abruptly increased when air temperature was within ~10°C below body temperature, indicating active regulation of heat loss. Maximum observed heat loss via the beak was 19.9% of total non-evaporative heat loss across the body surface. Heat loss per unit surface area via the beak more than doubled at T<sub>a</sub> &gt; 30.7°C compared to T<sub>a</sub> &lt; 30.7°C and at its peak dissipated 25.1 W m<sup>-2</sup>. Maximum heat flux rate across the beak of toucans under comparable convective conditions was calculated to be as high as 61.4 W m<sup>-2</sup>. The threshold air temperature at which toucans vasodilated their beak was lower than that of the hornbills, and thus had a larger potential for heat loss at lower air temperatures. Respiratory cooling (panting) thresholds were also lower in toucans compared to hornbills. Both beak vasodilation and panting threshold temperatures are potentially explained by differences in acclimation to environmental conditions and in the efficiency of evaporative cooling under differing environmental conditions. We speculate that non-evaporative heat dissipation may be a particularly important mechanism for animals inhabiting humid regions, such as toucans, and less critical for animals residing in more arid conditions, such as Southern Yellow-billed Hornbills. Alternatively, differences in beak morphology and hardness enforced by different diets may affect the capacity of birds to use the beak for non-evaporative heat loss.</p>},
    number = {5},
    doi = {10.1371/journal.pone.0154768}
}

2015

Spawning and nest guarding of the river goby (Glossogobius callidus) from the Eastern Cape province of South Africa
  • Ryan J. Wasserman
  • Tim J.F. Vink
  • Darragh J. Woodford
  • and P William Froneman
African Journal of Ecology, 2015
@article {AJE:AJE12228,
author = {Wasserman, Ryan J. and Vink, Tim J. F. and Woodford, Darragh J. and Froneman, P. William},
title = {Spawning and nest guarding of the river goby (Glossogobius callidus) from the Eastern Cape province of South Africa},
journal = {African Journal of Ecology},
volume = {53},
number = {4},
issn = {1365-2028},
url = {http://dx.doi.org/10.1111/aje.12228},
doi = {10.1111/aje.12228},
pages = {609--612},
year = {2015},
}
Fish predation regimes modify benthic diatom community structures: Experimental evidence from an in situ mesocosm study
  • R.J. Wasserman
  • T.J.F. Vink
  • T. Dalu
  • P.W. Froneman
Austral Ecology, 2015
@article{wasserman2015fish,
  title={Fish predation regimes modify benthic diatom community structures: Experimental evidence from an in situ mesocosm study},
  author={Wasserman, RJ and Vink, TJF and Dalu, T and Froneman, PW},
  journal={Austral Ecology},
  volume={40},
  number={7},
  pages={806--815},
  year={2015}
}
Preliminary Evidence for the Organisation of a Bacterial Community by Zooplanktivores at the Top of an Estuarine Planktonic Food Web
  • R.J. Wasserman
  • G.F. Matcher
  • T.J.F. Vink
  • P.W. Froneman
Microbial Ecology, 2015
@Article{Wasserman2015,
author="Wasserman, R. J.
and Matcher, G. F.
and Vink, T. J. F.
and Froneman, P. W.",
title="Preliminary Evidence for the Organisation of a Bacterial Community by Zooplanktivores at the Top of an Estuarine Planktonic Food Web",
journal="Microbial Ecology",
year="2015",
volume="69",
number="2",
pages="245--253",
abstract="As part of a larger investigation, the effect of apex predation on estuarine bacterial community structure, through trophic cascading, was investigated using experimental in situ mesocosms. Through either the removal (filtration) or addition of specific size classes of planktonic groups, four different trophic scenarios were established using estuarine water and its associated plankton. One such treatment represented a ``natural'' scenario in which stable apex predatory pressure was qualified. Water samples were collected over time from each of the treatments for bacterial community evaluation. These samples were assessed through pyrosequencing of the variable regions 4 and 5 of the bacterial 16S rRNA gene and analysed at the species operational taxonomic unit (OTU) level using a community procedure. The blue-green group dominated the samples, followed by Proteobacteria and Bacteroidetes. Samples were the most similar among treatments at the commencement of the experiment. While the bacterial communities sampled within each treatment changed over time, the deviation from initial appeared to be linked to the treatment trophic scenarios. The least temporal deviation-from-initial in bacterial community was found within the stable apex predatory pressure treatment. These findings are consistent with trophic cascade theory, whereby predators mediate interactions at multiple lower trophic levels with consequent repercussions for diversity.",
issn="1432-184X",
doi="10.1007/s00248-014-0505-3",
url="http://dx.doi.org/10.1007/s00248-014-0505-3"
}
Utilization of mangrove crab-burrow micro-habitats by the goby Redigobius dewaali: Evidence for dominance hierarchy
  • R. Kramer
  • C.D. McQuaid
  • T.J.F. Vink
  • B.P. Mostert
  • R.J. Wasserman
Journal of Experimental Marine Biology and Ecology, 2015
@article{Kramer20151,
title = "Utilization of mangrove crab-burrow micro-habitats by the goby Redigobius dewaali: Evidence for dominance hierarchy ",
journal = "Journal of Experimental Marine Biology and Ecology ",
volume = "462",
number = "",
pages = "1 - 7",
year = "2015",
note = "",
issn = "0022-0981",
doi = "http://dx.doi.org/10.1016/j.jembe.2014.10.012",
url = "http://www.sciencedirect.com/science/article/pii/S0022098114002731",
author = "R. Kramer and C.D. McQuaid and T.J.F. Vink and B.P. Mostert and R.J. Wasserman",
keywords = "Estuary",
keywords = "Gobiidae",
keywords = "Niche overlap",
keywords = "Ontogeny",
keywords = "Scylla serrata burrows",
keywords = "Size-class ",
abstract = "Abstract When a range of life-history groups within a population exploit similar niches, hierarchies are often established whereby optimal resources are capitalized by dominant individuals. The present study investigates the feeding and movement of a size structured population of gobies residing in crab burrow micro-habitats, within this context. All life-history stages of the goby Redigobius dewaali were found to utilize burrow-pools formed by the crab Scylla serrata in the mangrove intertidal zone of an estuary at low tide. Gut content analysis was therefore conducted to test for feeding overlap and potential intraspecific competition among various sizes of fish residing in these habitats. In addition, an exclosure experiment was conducted to determine whether these fish leave the burrow-pools at high tide to forage over the intertidal flats. While ontogenetic dietary shifts across size-classes occurred, copepods and amphipods comprised the most important components of the diet for most size-classes, resulting in a large degree of dietary overlap. Of the adult R. dewaali sampled from pools, a single large mature male was sampled from each burrow, suggesting territoriality, a trait well observed in males of many goby species. The experimental component of the study highlighted the movement of smaller individuals, but not larger individuals, from the burrow-pools at high tide. As all life-history stages occur in the same microhabitats, and forage on much of the same prey, we suggest that the existence of a competitive hierarchy resulted in the need for the smaller individuals to find alternate feeding areas, consistent with dominance hierarchy theory. "
}

2014

Conspecific alarm cue sensitivity by the estuarine calanoid copepod, Paracartia longipatella
  • Ryan J. Wasserman
  • Rachel Kramer
  • Tim J. F. Vink
  • P. William Froneman
Austral Ecology, 2014
@article{wasserman2014conspecific,
  title={Conspecific alarm cue sensitivity by the estuarine calanoid copepod, Paracartia longipatella},
  author={Wasserman, Ryan J and Kramer, Rachel and Vink, Tim JF and Froneman, P William},
  journal={Austral Ecology},
  volume={39},
  number={6},
  pages={732--738},
  year={2014}
}
Effect of mate-guarding on the swimming behaviour of female Euterpina acutifrons (Copepoda, Harpacticoida)
  • R. J. Wasserman
  • T. J. F. Vink.
Journal of Plankton Research, 2014
@article{wasserman2014effect,
  title={Effect of mate guarding on the swimming behaviour of female Euterpina acutifrons (Copepoda, Harpacticoida)},
  author={Wasserman, RJ and Vink, TJF},
  journal={Journal of Plankton Research},
  volume={36},
  number={5},
  pages={1385--1390},
  year={2014},
  publisher={Oxford University Press}
}

2013

Hyperbenthic and pelagic predators regulate alternate key planktonic copepods in shallow temperate estuaries
  • R. J. Wasserman
  • T. J. F. Vink
  • R. Kramer
  • P. W. Froneman
Marine & Freshwater Research, 2013
@article{wasserman2013hyperbenthic,
  title={Hyperbenthic and pelagic predators regulate alternate key planktonic copepods in shallow temperate estuaries},
  author={Wasserman, RJ and Vink, TJF and Kramer, R and Froneman, PW},
  journal={Marine \& Freshwater Research},
  year={2013},
  publisher={CSIRO}
}