Interacting effects of predation risk and resource level on escape speed of amphibian larvae along a latitudinal gradient

Fast‐growing genotypes living in time‐constrained environments are often more prone to predation, suggesting that growth‐predation risk trade‐offs are important factors maintaining variation in growth along climatic gradients. However, the mechanisms underlying how fast growth increases predation‐mediated mortality are not well understood. Here, we investigated if slow‐growing, low‐latitude individuals have faster escape swimming speed than fast‐growing high‐latitude individuals using common frog (Rana temporaria) tadpoles from eight populations collected along a 1500 km latitudinal gradient. We measured escape speed in terms of burst and endurance speeds in tadpoles raised in the laboratory at two food levels and in the presence and absence of a predator (Aeshna dragonfly larvae). We did not find any latitudinal trend in escape speed performance. In low food treatments, burst speed was higher in tadpoles reared with predators but did not differ between high‐food treatments. Endurance speed, on the contrary, was lower in high‐food tadpoles reared with predators and did not differ between treatments at low food levels. Tadpoles reared with predators showed inducible morphology (increased relative body size and tail depth), which had positive effects on speed endurance at low but not at high food levels. Burst speed was positively affected by tail length and tail muscle size in the absence of predators. Our results suggest that escape speed does not trade‐off with fast growth along the latitudinal gradient in R. temporaria tadpoles. Instead, escape speed is a plastic trait and strongly influenced by the interaction between resource level and predation risk.     

Specific induced responses to different predator species in anuran larvae

Models of defence against multiple enemies predict that specialized responses to each enemy should evolve only under restrictive conditions. Nevertheless, tadpoles of Rana temporaria can differentiate among several predator species. Small tadpoles used a refuge when Notonecta backswimmers were in the pond, but showed a weaker hiding response to adult Triturus alpestris newts and no response to aeshnid dragonfly larvae (Aeshna and Anax). All predators caused a decline in feeding and swimming activity. Large tadpoles reserved the strongest behavioural response for dragonflies, while Triturus caused no response. The shift during development suggests that tadpoles distinguished among predators, rather than exhibiting a graded dosage response to a single cue associated with predation. Information on habitat distributions of predators suggests that they are regularly encountered, which would facilitate evolution of adaptive behavioural responses. Morphological responses to all predators were similar, perhaps because similar morphologies defend against all four predators. The evolutionary maintenance of specialized responses to multiple predators may be possible because adaptive responses do not conflict and the predators themselves do not interact strongly.     

鄱阳湖滨藕塘生境中白鹤取食行为研究

2016年12月—2017年2月和2017年12月—2018年1月,采用焦点动物法对鄱阳湖滨藕塘生境中白鹤(Grus leucogeranus)的取食行为进行观察,共记录921只次成鹤和547只次幼鹤的取食行为。结果表明,白鹤栖息水深为(17.29±8.75)cm(n=1468),取食水深为(18.84±10.32)cm(n=600),单次取食持续时间为(3.10±1.69)s(n=600),取食频次为(12.24±3.89)次/min(n=1012),取食成功频次为(1.78±1.59)次/min(n=1468),取食成功率为(16.26±14.41)%(n=1012)。成鹤取食成功频次(SymbolcA@~2=70.797,df=1,P=0.000)和取食成功率(SymbolcA@~2=5.356,df=1,P=0.020)均显著高于幼鹤,表明成鹤取食能力较幼鹤强,成鹤可以获得更多的能量。成鹤除维持自身能量支出外,还需要花费较多的能量用于辅食和警戒行为。成幼鹤的取食频次和单次取食持续时间无显著差异,这与成幼鹤的体型大小、能量需求和体内氧气储存量类似有关,也与多数研究认为幼鹤觅食经验不足,觅食成功率低,需要靠多次取食来补偿能量的观点不同。成鹤取食水深极显著高于幼鹤(SymbolcA@~2=50.945,df=1,P0.0001),这可能与体型和取食经验有关。不同栖息水深下白鹤的取食成功率(SymbolcA@~2=15.297,df=4,P=0.004)和取食成功频次(SymbolcA@~2=23.155,df=4,P0.0001)均存在极显著差异。不同时段的取食频次、取食成功频次和取食成功率均无显著差异,这可能与藕塘生境中白鹤采取触觉取食有关。此外,白鹤昼间取食行为无明显节律性,因此昼间能量需求相似,取食参数没有显著差异。     

Temporal pattern in foraging behaviour of the Indian pond heron,Ardeola grayii at Ratanpur,Chhattisgarh, India

In avian population, the biological clock is synchronized with the photoperiod as a significant time cue. However, information on feeding behaviour of the Indian Pond Heron, Ardeola grayii at Ratanpur, Chhattisgarh, India is not available. In present study we examined the effect of ‘time of the day’ and ‘photoperiod’ on daytime feeding behaviour of A. grayii at Ratanpur (85º17’E longitude and 22º3’N latitude), Chhattisgarh, India. The different feeding techniques of A. grayii, were recorded for two consecutive days each during long days (May and June 2014) and during short days (December 2014 and January 2015). One-way ANOVA (using SPSS 16.0) was applied to find out the effects of ‘photoperiod’ and ‘time of the day’ on daytime feeding activity with respect to frequency of feeding techniques. The rhythms in daytime feeding activity were evaluated using the Cosinor rhythmometry at 24 h and 12 h. The present study revealed that the A. grayii adopted three major techniques viz., slowly walking, probing and striking on which the slowly walking and striking was popularly used feeding technique as compared to the probing technique during the feeding. Moreover, the A. grayii is found to be bimodal viz., morning and evening type during both of long and short days. Furthermore, bird was more active during short day as compared to the long day.     

广州地区冬季鱼塘水温特征及其预测预报

冬季水温对耐寒性较差的热带、亚热带鱼类的安全越冬有重要影响。本文根据鱼塘水温和附近气象站气温观测资料 ,研究了广州地区冬季鱼塘水温特征及其预测模型。结果表明 ,与气温相比 ,鱼塘水温日振幅较小 ,日最高温度出现时间滞后 ,这种特征在逐时温度和日平均温度上表现得都非常明显 ;晴天条件下水温的日变化远大于阴天 ;随水层深度的增加 ,水温日振幅逐渐减小 ,位相滞后也愈加明显。水温与气温的交叉相关分析表明 ,水温与当日、前一日、前二日、前三日的气温有显著的相关关系 ,与前四日、前五日的关系已不明显。利用逐步回归分析 ,建立了以气温为自变量的各水层水温预报模型。各模型的回归效果都达到了显著水平 ,平均绝对误差均在 0 5℃以内 ,平均相对误差均在 1 0 %以内 ,具有较高的精度 ,可用于冬季鱼塘水温的预报。     

Reproductive dynamics of three amphibian species in Mediterranean wetlands: the role of local precipitation and hydrological regimes

1. Although the influence of water availability and precipitation regimes on amphibians has been studied at large scales, whether and how interannual rainfall and hydrological variations affect amphibians dynamics at a local scale have rarely been addressed. In this respect, accounting for variations in species detectability in space and time has also been overlooked. 2. We assessed the effects of rainfall and hydrological variations on the breeding dynamics of three amphibian taxa: Pelodytes punctatus, Hyla meridionalis and Pelophylax spp. in 20 ponds of the Camargue region (southern France) over a 7‐year study period. 3. We used multiple season occupancy models to test the effect of winter–spring rainfall and interannual variations in hydroperiod, mean water depth and drought events on tadpole presence in spring (March–June), a proxy for breeding dynamics. 4. We used an independent survey with spatial replicates (dipnet sweeps) to disentangle the relative contributions of phenology and detectability to the absence of records in a given month. For the three taxa considered, the probability of missing a species when that species was actually present in a pond was most often negligible. Hence, we could consider that multiseason models properly tracked changes in species phenology. 5. Pelodytes punctatus was first detected in March, while the two other taxa appeared later in April. Hyla meridionalis appeared as a mid‐season species with much more synchronous pond occupancy than Pelodytes punctatus. The detection peak of Pelophylax spp. was short and unexpectedly early for this taxon. 6. Seasonal winter–spring rainfall was associated with a decrease in extinction rates and even more strongly with an increase in colonisation rates at individual ponds. 7. Colonisation rate increased following an annual drought and was best modelled as a negative quadratic effect of the variance of pond hydroperiod. Extinction probability was best modelled by a negative quadratic effect of mean water level. Hence, breeding was more stochastic (i) in unpredictable and shallow ponds because of yearly drying up and (ii) in highly predictable and deep ponds, possibly due to the presence of predators such as fish and crayfish. 8. Overall, we show that ponds with intermediate rather than extreme variations in environmental conditions currently correspond to optimal breeding sites. Our study demonstrates that amphibian monitoring coupled with fine‐scale analysis of environmental conditions is necessary to understand species dynamics in the long run and to inform conservation efforts for these species.     

Wandering behaviour and pupariation in tsetse larvae

Abstract .Following parturition, the third instar larva of Glossina morsitans morsitans West begins a wandering period in which it crawls to the site of pupariation. The duration of wandering can be drastically shortened by pinching or by denying the larva physical contact with the substrate. Contact with water increases the wandering period. Duration of subsequent activities appears to be rigidly fixed. At the end of the wandering period, the larva quickly progresses through a stereotypic sequence of behaviours that include immobilization and excretion of a liquid from the anus, retraction of the anterior segments, cuticular shrinkage, and tanning. Muscular activity and mechanical changes in the cuticle are reflected in changes of haemocoelic pressure. Muscular contractions produce pressure pulses that gradually increase in frequency and intensity, reaching a peak during retraction of the anterior segments. Changes in the mechanical properties of the cuticle cause a more gradual elevation of baseline pressure as the cuticle shrinks and loses its plasticity. As tanning begins, muscular activity ceases and haemocoelic pressure gradually decreases. In spite of its unusual early development within the confines of the female's uterus, the free-living larva shows the full behavioural repertoire observed in other cyclor-rhaphous Diptera at pupariation.     

Differences in feeding behaviour among Chironomus species revealed by measurements of sulphur stable isotopes and cadmium in larvae

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A marine dinoflagellate, Amphidinium eilatiensis n. sp., from the benthos of a mariculture sedimentation pond in Eilat, Israel

A species of Amphidinium bloomed in a mariculture sedimentation pond that was used to grow bivalves near the Gulf of Eilat, Israel. Its overall length averaged 13 microm, the hypocone was 11 microm, and its width was 8 microm. It has a ventral ridge. The sulcus begins at the longitudinal flagellar pore and does not project forward in the apex toward the transverse flagellar pore and left margin of the cingulum. The sulcus is a very shallow groove that projects variably about a third of the body length toward the antapex. The cingulum is a deep groove as it circles the cell from the left ventral side to the dorsal side and then becomes very shallow on the right ventral side as it arches posterior toward the longitudinal flagellar pore. Using a modified method for studying dinoflagellate chromosomes in the SEM, we observed 31 chromosomes. The plastid is dorsal and peripheral with 6 ventrally projecting peripheral digital lobes that wrap around the sides of the ventral and posterior nucleus. Amphidinium eilatiensis n. sp. is morphologically closest to Amphidinium carterae and Amphidinium rhynchocephalum, but it does not have the obvious thecal plates or polygonal units described for the former species. Instead, it has a series of spicules, bumps, and ridges on its surface. It differs from A. rhynchocephalum by two morphological characters: surface morphology and gross plastid architecture. The amplified fragments of the rDNA from A. eilatiensis n. sp. isolated from 2 separate sedimentation ponds in Eilat include the 3'- end of the SSU rDNA (about 100 nt), the whole ITS region (ITS1 + 5.8S + ITS2) and the 5'-end of the LSU rDNA (about 900 nts). The total length of the sequences ranged from 1,460 nt. (A. eilatiensis isolate #1) to 1,461 nts. (A. eilatiensis isolate #2). The latter sequences are identical, the difference in length being due to three insertions. Amphidinium eilatiensis is genetically more closely related to A. carterae than to A. klebsii, with respectively 2.36% and 6.93% of sequence divergence.     

Cross‐scale effects of structural and functional connectivity in pond networks on amphibian distribution in agricultural landscapes

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Variation in anti-parasite behaviour and infection among larval amphibian species

Along with immune defences, many animals exhibit effective anti-parasite behaviours such as parasite avoidance and removal that influence their susceptibility to infection. Host ecology and life history influence investment into comparatively fixed defences such as innate immunity but may affect the strength of anti-parasite behaviours as well. We investigated activity levels in five different species of larval amphibian with varying life histories and ecology in control, novel food stimulus, and trematode parasite (Echinoparyphium sp.) threat conditions. There was a significant interaction of species and treatment given that American toad (Bufo americanus), wood frog (Lithobates sylvaticus), and bullfrog (Lithobates catesbeianus) tadpoles generally increased their activity when parasite infectious stages were present while grey tree frogs (Hyla versicolor) and northern leopard frogs (Lithobates pipiens) did not, even though activity was negatively related to infection. In addition, there was considerable variation among species in their susceptibility to parasitism, with infection prevalence ranging from 17 % in bullfrog tadpoles to 70 % in wood frogs. However, amphibian life history (larval and adult traits) was not related to parasitism or level of anti-parasite behaviour at the species level. Consequently, we suggest that future investigations include more species with a range of life history traits and also consider host ecology, particularly if conspicuous anti-parasite behaviours are more likely in amphibian species that experience a relatively low risk of predation.     

Upper thermal tolerance plasticity in tropical amphibian species from contrasting habitats: Implications for warming impact prediction

Tropical ectothermic species are currently depicted as more vulnerable to increasing temperatures because of the proximity between their upper thermal limits and environmental temperatures. Yet, the acclimatory capacity of thermal limits has rarely been measured in tropical species, even though they are generally predicted to be smaller than in temperate species. We compared critical thermal maximum (CT_max) and warming tolerance (WT: the difference between CT_max and maximum temperature, T_max), as well as CT_max acclimatory capacity of toad species from the Atlantic forest (AF) and the Brazilian Caatinga (CAA), a semi-arid habitat with high temperatures. Acclimation temperatures represented the mean temperatures of AF and CAA habitats, making estimates of CT_max and WT more ecologically realistic. CAA species mean CT_max was higher compared to AF species in both acclimation treatments. Clutches within species, as well as between AF and CAA species, differed in CT_max plasticity and we discuss the potential biological meaning of these findings. We did not find a trade-off between absolute CT_max and CT_max plasticity, indicating that species can have both high CT_max and high CT_max plasticity. Although CT_max was highly correlated to T_max, CT_max plasticity was not related to T_max or T_max coefficients of variation. CAA species mean WT was lower than for AF species, but still very high for all species, diverging from other studies with tropical species. This might be partially related to over-estimation of vulnerability due to under-appreciation of realistic acclimation treatments in CT_max estimation. Thus, some tropical species might not be as vulnerable to warming as previously predicted if CT_max is considered as a shifting population parameter.     

Exploratory behaviour of barnacle larvae in field conditions

The aim of this work was to develop techniques for the real time filming of Semibalanus balanoides cyprid larvae in the field in order to describe the exploratory behaviour of S. balanoides cyprids under natural field conditions. The underwater camera system consisted of a high resolution, remotely controlled colour camera attached to a cradle which could be deployed from a pier. A light utilising a battery of far‐red light‐emitting diodes (λ_min = 615 nm) was used for filming at night. Transparent acrylic treated with barnacle settlement factor and smooth green polyester tiles were used as targets. From the films the tracks of the exploring cyprids were digitised from the 30 min trials. During five, 30 min trials a total of 1014 cyprids explored the surface. The numbers of cyprids exploring the surface varied from 49 to 522 cyprids per trial, and a Monte‐Carlo randomisation model showed that larval supply was random or aggregated. The mean exploration time spent on the target was 163 s with a mean distance travelled on the target of 8.5 cm. Exploratory track length was related to water current velocity by a negative curvilinear regression (R² = 0.92, F = 45.65, p < 0.05). There were significant differences in exploratory behaviour between day and night for total distance travelled (p < 0.001), straight line distance (p < 0.001) and velocity (p < 0.001) and the mean heading angle of the exploratory track (p < 0.01). The results are discussed in relation to settlement patterns and the screening of antifouling surfaces.     

Habitat selection in the larvae of two species of Zygoptera (Odonata): biotic interactions and abiotic limitation

Field and laboratory experiments were set up to obtain data on the reasons for different habitat selection of Enallagma cyathigerum and Platycnemis pennipes. (1) Rearing of larvae in two different ponds showed that while P. pennipes was not able to survive conditions of low oxygen content, 50% of the E. cyathigerum larvae survived. (2) In field predation experiments with sticklebacks and dragonflies as predators, we found that E. cyathigerum suffered highest predation by the fish. In P. pennipes, mortality was highest with Anax imperator. (3) Experiments regarding larval behaviour showed that E. cyathigerum was generally more active and had higher foraging success than P. pennipes. Both species reduced activity in the presence of fish, but E. cyathigerum did so to a minor extent. In contrast to P. pennipes, E. cyathigerum showed escaping behaviour. (4) In the laboratory, the growth of E. cyathigerum was faster than that of P. pennipes.     

Variation in the hormonal stress response among larvae of three amphibian species

In a series of studies, we examined how larval corticosterone treatment for several species of amphibians can impact fitness parameters both during exposure and after metamorphosis. We completed confinement stress series on larvae of three species in natural/semi-natural conditions: wood frogs (Rana sylvatica), Jefferson salamanders (Ambystoma jeffersonianum), and Eastern spadefoot toads (Scaphiopus holbrooki). Two of the species had a typical vertebrate response of increasing corticosterone with confinement. However, Eastern spadefoot toads, which have a very short developmental period before metamorphosis, did not show any increase in corticosterone in response to confinement. In a second study, we treated the three species with a low and a high concentration of corticosterone (0.001 and 0.01?μM dissolved in tank water) in the laboratory and examined effects on growth. Although we were successful in raising baseline corticosterone levels with our high corticosterone concentrations, this did not translate into changes in mean larval growth for any of the three species. The larval treatments also did not appear to translate into differences in the juvenile response to confinement stress after metamorphosis. Although juvenile wood frogs did respond to confinement with increasing corticosterone, there was no variation based on larval treatment. As with the larval responses, the juvenile Eastern spadefoot toads did not have a hormonal response to confinement. In summary, while our larval corticosterone exposures did elevate baseline corticosterone levels, we did not see effects of exposure on growth or any latent effects of larval exposure on juvenile responses to confinement.     

Agonistic behaviour in final-instar larvae of Austrolestes colensonis (Odonata: Lestidae)

Abstract

The agonistic displays of Austrolestes colensonis larvae are described. A terminology is developed to classify larval agonistic displays in the family Lestidae.     

Growth behaviour of Azolla pinnata at various salinity levels and induction of high salt tolerance

Azolla pinnata is an extremely NaCl-sensitive plant and cannot tolerate an external NaCl concentration beyond 30 mM. Preincubation of plants in 20 mM NaCl for 18 days, followed by stepwise transfer (10 mM NaCl per day) made them able to grow at an otherwise lethal NaCl concentration of 60 mM at rates comparable to the growth of unadapted plants in 20 mM NaCl. Plants, not preincubated in 20 mM NaCl or preincubated for a duration shorter than 18 days were unable to survive and did not grow in 60 mM external NaCl. Na+, K+ and Ca2+ concentrations in the control, NaCl-stressed and adapted plants differed significantly indicating that adaptation involved the development of a capability in the plants to regulate ion concentration.     

Complex behaviour in four species food-web model

A four-dimensional food-web system consisting of a bottom prey, two middle predators and a generalist predator has been developed with modified functional response. The system is well posed and dissipative. Some results on uniform persistence have been developed. The dynamics of the system is found to be chaotic for certain choice of parameters. The coexistence of all four species is possible in the form of periodic orbits/strange attractors for suitably chosen set of parameters.     

Evolution of resting behaviour in polymorphic 'industrial melanic' moth species

The behaviour of individually marked melanic and typical forms of Allophyes oxyacanthae was followed in four successive tests in an apparatus comprising bark of three different reflectances. In samples of wild populations, melanics showed a moderate preference for dark bark, while typicals did not seem to prefer or avoid this substrate. However, in four of the eight families of known parentage tested, both melanics and typicals preferred to rest on dark bark. These four families were the progeny of dark typicals which had shown a preference for dark bark and were the families containing the darkest typicals. In A. oxyacanthae the variation in resting behaviour is not therefore closely associated with the melanic allele but may be linked to a 'dark typical' allele which, together with other loci, produces polygenic darkening of the normal phenotype. The results with A. oxyacanthae are compared with those obtained with Biston betularia and other moth species.