Coloured and toxic nectar : feeding choices of the Madagascar giant day gecko, Phelsuma grandis

Coloured nectar is a rare phenomenon best known from islands and insular habitats. Islands are also known for lizard pollination, where coloured nectar potentially acts as a visual cue to attract pollinators, advertising the sweet reward. However, nectar may also contain secondary metabolites with toxic or deterrent effects. The aim of this study was to determine which factors are important as artificial nectar choice determinants to the Madagascar giant day gecko, Phelsuma grandis, an island pollinator: artificial nectar colour, artificial nectar colour saturation, artificial nectar conspicuousness and/or the presence of the alkaloid nicotine. Coloured artificial nectar and the darkest artificial nectar colour saturation were found to be important visual cues for the geckos, while the contrast between artificial nectar and petal colour was not. Geckos were deterred only by high nicotine concentrations (1000 lM in 0.63 M sucrose) and may even prefer low nicotine concentrations to sucroseonly solutions. Given their overall fondness for sugar solutions, Madagascar giant day geckos are likely to be important pollinators of Malagasy plant species that produce enough nectar to attract them, and plants with coloured nectar and/or secondary metabolites may have evolved those traits to attract the geckos in particular.This work was supported by the South African National Research Foundation (grant number 73671) and the University of Pretoria.http://onlinelibrary.wiley.com./journal/10.1111/(ISSN)1439-0310hb2013ab201

Summit metabolism and metabolic expansibility in Wahlberg's epauletted fruit bats (Epomophorus wahlbergi) : seasonal acclimatisation and effects of captivity

Summit metabolism (Msum), the maximum rate of resting metabolic thermogenesis, has been found to be broadly correlated with climatic variables and the use of heterothermy in some endotherms. Far less is known about Msum and metabolic expansibility [ME, the ratio of Msum to basal metabolic rate (BMR)] in bats compared with many other endotherm taxa. We measured BMR and Msum during winter and summer in captive and wild populations of a pteropodid from the southern subtropics, Wahlberg’s epauletted fruit bat (Epomophorus wahlbergi) in Pretoria, South Africa. The Msum of fruit bats ranged from 5.178±0.611 W (captive, summer) to 6.006±0.890 W (captive, winter), and did not vary significantly between seasons. In contrast, BMR decreased by 17–25% in winter. The combination of seasonally stable Msum but flexible BMR resulted in ME being significantly higher in winter than in summer, ranging from 7.24±1.49 (wild, summer) to 13.11±2.14 (captive, winter). The latter value is well above the typical mammalian range. Moreover, both Msum and ME were significantly higher in captive bats than in wild individuals; we speculate this represents a phenotypic response to a reduction in exerciseassociated heat production while in captivity. Our data for E. wahlbergi, combined with those currently available for other chiropterans, reveal that Msum in bats is highly variable compared with allometrically expected values for other mammals.National Research Foundation [IFR2008042200022 to A.E.M. and GUN64756 to N.C.B.].http://jeb.biologists.orghb201

Partitioning of evaporative water loss into respiratory and cutaneous pathways in Wahlberg’s epauletted fruit bats (Epomophorus wahlbergi)

Please read abstract in the article.National Research Foundation.http://www.journals.uchicago.edutoc/pbz/currenthb201

Seasonal metabolic adjustments and partitioning of evaporative water loss in Wahlberg’s epauletted fruit bat,Epomophorus Wahlbergi

4 Summary Seasonal metabolic adjustments and partitioning of evaporative water loss in Wahlberg’s epauletted fruit bat, Epomophorus wahlbergi Student: Ingrid A. Minnaar Supervisor: Prof. A. E. McKechnie Co-supervisors: Prof. N. C. Bennett, Prof. Christian T. Chimimba Department: Zoology and Entomology, University of Pretoria Degree: MSc: Zoology The capacity to thermoregulate over a wide range of TaS is critical for maintaining homeostasis in endotherms. Several aspects of the thermoregulatory properties of bats remain poorly studied when compared to other mammals and birds. I examined two specific aspects of thermoregulation in bats: the seasonal variation of maximum metabolic heat production and the partitioning of total evaporative water loss (TEWL) into respiratory and cutaneous components. I measured basal metabolic rate (BMR) and summit metabolism (Msum) in captive and wild Wahlberg’s epauletted fruit bats, Epomophorus wahlbergi, during summer and winter. I measured metabolic rate using flow-through respirometry, and elicited Msum by exposing bats to low temperatures in a helox (21% O2, 79% He) atmosphere. BMR decreased by 22-25% during winter in both captive and wild bats, with the BMR of captive bats 9-13% lower than the wild individuals across seasons. Msum was approximately seasonally stable in both captive and wild bats, but Msum in captive individuals was 13-18% higher than their wild conspecifics during both seasons. The ratio between Msum and BMR (i.e., metabolic expansibility) was greater in winter than during summer for both captive and wild bats. One likely explanation for the greater resting thermogenic capacity of the bats in captive individuals concerns their reduced activity levels; compared to wild, free-ranging bats, heat produced as a by-product of activity probably contributed far less to thermoregulation, apparently leading to an increase in resting heat production capacity in captive individuals. 5 At the other end of the thermal scale, knowledge of heat tolerance and the evaporative cooling mechanisms employed by bats in hot weather remains rudimentary. At high air temperatures (Ta), endotherms avoid overheating by dissipating heat via evaporative water loss. TEWL may be partitioned into cutaneous evaporative water loss (CEWL) and respiratory evaporative water loss (REWL). I quantified CEWL and REWL in E. wahlbergi at Tas of 10-40 °C using a latex mask. When Ta exceeded normothermic Tb, bats drastically increased their TEWL, metabolic rate and Tb. The relative contribution of CEWL to TEWL was the greatest at moderate Tas where it represented up to 80% of TEWL. REWL was the major route of evaporative cooling at the highest Ta: at Ta = 40 ºC, REWL represented 45% of TEWL. To avoid hyperthermia, E. wahlbergi greatly increased metabolic rate at high TaS to avoid hyperthermia, further compounding the need to cool down. REWL is thought to be less efficient as than CEWL in offloading heat at high TaS as panting increases metabolic heat, whereas CEWL occurs passively. There is a need for further studies to be conducted on the thermoregulatory capabilities of bats in varying environmental conditions, both intra- and interspecifically.Dissertation (MSc)--University of Pretoria, 2013.gm2014Zoology and Entomologyunrestricte