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.     

Variation in grazing tolerance among three tallgrass prairie plant species

Three tallgrass prairie plant species, two common perennial forbs (Artemisia ludoviciana and Aster ericoides [Asteraceae]) and a dominant C(4) perennial grass (Sorghastrum nutans) were studied under field and greenhouse conditions to evaluate interspecific variation in grazing tolerance (compensatory growth capacity). Adaptation to ungulate grazing was also assessed by comparing defoliation responses of plants from populations with a 25-yr history of no grazing or moderate ungulate grazing. Under field conditions, all three species showed significant reductions in shoot relative growth rates (RGR), biomass, and reproduction with defoliation. In the two forbs, clipping resulted in negative shoot RGR and reductions in both number and length of shoot branches per ramet. Sorghastrum nutans maintained positive RGR under defoliation due to a compensatory increase in leaf production. Defoliation reduced rhizome production in A. ericoides and S. nutans, but not in A. ludoviciana. Clipping significantly reduced sexual reproductive allocation in all three species, although S. nutans showed a smaller reduction than the forbs. All three species showed similar responses to defoliation in burned and unburned sites. Under greenhouse conditions, a similar clipping regimen resulted in smaller reductions in growth and reproduction than those observed in the field. For all three species, the grazing tolerance indices calculated under natural field conditions were significantly lower than those estimated from greenhouse-grown plants, and the interspecific patterns of grazing tolerance were different. Aster ericoides exhibited the highest overall defoliation tolerance under greenhouse conditions, followed by S. nutans. Artemisia ludoviciana, the only study species that is typically not grazed by ungulates in the field, showed the lowest grazing tolerance. In the field experiment S. nutans showed the highest grazing tolerance and the two forbs had similar low tolerance indices. These patterns indicate that, despite high compensatory growth potential, limited resource availability and competition in the field significantly reduce the degree of compensation and alter interspecific differences in grazing tolerance among prairie plants. In all three species, defoliation suppressed sexual reproduction more than growth or vegetative reproduction. Significant interactions between plant responses to defoliation and site of origin (historically grazed or ungrazed sites) for some response variables (root/shoot ratios, rhizome bud initiation, and reproductive allocation) indicated some degree of population differentiation and genetic adaptation in response to a relatively short history of ungulate grazing pressure. The results of this study indicate that patterns of grazing tolerance in tallgrass prairie are both genetically based and also environmentally dependent.     

Measure of stress response induced by temperature and salinity changes on hatched larvae of three marine gastropod species

To better understand the cascade of molecular reactions leading to delayed development and mortality of early life stages of marine intertidal gastropods, in response to temperature and salinity changes associated with climate change, three biomarkers: total antioxidant capacity, lipid peroxidation and lysosomal stability were investigated on hatched larvae. Encapsulated embryos of three marine gastropod species (Bembicium nanum, Siphonaria denticulata and Dolabrifera brazieri), which have already proven responsive to thermal and osmotic variations, were exposed to six combinations of temperature (22 °C and 30 °C) and salinity (25‰, 35‰ and 45‰) until the larvae hatched. Time to hatching was affected by salinity and temperature in all three species. High salinity (45‰) generally retarded the hatching process although the response was species-specific for temperature. Total antioxidant capacity and lipid peroxidation were also highly species-specific with the general trend showing that these biomarkers were adversely affected by high temperature (30 °C) at salinities of 25‰ and 45‰. Bembicium nanum lysosomal destabilisation increased significantly with an increase in temperature and salinity (30 °C and 45‰) and this was associated with delayed development and increased mortality. Investigations on the additional biomarker, lysosomal stability, gave a clearer picture of the numerous and complex molecular and cellular mechanisms leading to mortality and underdevelopment in response to environmental stress for this species. As few differences were observed in the enzymatic biomarkers total antioxidant capacity and lipid peroxidation between hatched larvae and the previously investigated encapsulated embryo response to thermal and osmotic stress, it is suggested that further studies could be undertaken using embryos encapsulated in egg masses, as it is less time consuming than working on hatched larvae.     

Variation in response among threeAlnus spp. clones to progressive water stress

Summary Experiments to quantify the response of unnodulated, fertilizedAlnus species from disparate habitats to progressive water stress showed contrasting xerotolerance amongspp. clones, using stomatal diffusive resistance, leaf area, and height as indices of drought sensitivity. At moderate or severe levels of water stress, stomatal resistance values forA. glutinosa were consistently higher than values forA. serrulata orA. maritima. In addition, leaf area and height ofA. glutinosa were significantly reduced at moderate water stress as compared to well-watered controls, whereas control and moderately-stressedA. maritimia exhibited similar leaf area and height.Journal Article J-4612 of the Agricultural Experiment Station, Oklahoma State University, Stillwater, Oklahoma, USA     

Variation in dispersability among mainland and island populations of three wind dispersed plant species

Reduced dispersability of species living on islands relative to mainland has been documented in both plants and animals. One evolutionary scenario explains this trend by strong selection against dispersal, once the species has reached the island, to reduce dispersal out to sea. In this study, we compare the dispersal ability of three wind dispersed plant species (Cirsium arvense, Epilobium angustifolium, and E. hirsutum) from populations on mainland and three islands. Dispersal ability was estimated directly as drop time of diaspores, and indirectly using a morphological measure relating the weight of the diaspore to the size of the pappus (Cirsium) or seed hairs (Epilobium). Positive correlation between the morphological measure of dispersal ability and drop time of diaspores were found for all study species. Dispersal ability varied significantly among mainland and islands, and among species. C. arvense showed a significant reduction in dispersal ability on islands compared to mainland, whereas the reverse was found for the two Epilobium species. Overall Epilobium diaspores had a 2–4 times higher dispersability than C. arvense, indicating that degree of isolation of islands vary among study species. Significant differences in dispersability among plants within populations were detected in all species suggesting that this trait may have a genetic component.     

Differentiall behavioral and adrenocortical responses to stress among three macaque species

Behavioral and adrenocortical responses of rhesus (Macaca mulatta), bonnet (M. radiata), and crabeating (M. fascicularis) macaques were compared in their home cages, during exposure to novelty and during physical restraint. Both behavioral and adrenocortical responses differentiated species in each condition. In all conditions, post-test corticosteroid levels were highest for crabeaters and lowest for rhesus. Rhesus were the most active behaviorally, and bonnets were the most passive, while crabeaters exhibited the greatest signs of behavioral disturbance. Relationships between adrenocortical and behavioral responses varied between groups. Both adrenocortical and behavioral profiles were in accord with the behavior of these three species under more natural conditions. The role of psychophysiological responses in general behavioral dispositions toward the environment is discussed. It is concluded that behavioral dispositions, inclusive of psychophysiological responses, may vary qualitatively even among closely related primate species.     

Kin distribution of amphibian larvae in the wild

According to kin selection theory, the location of an individual with respect to its relatives can have important ramifications for its fitness. Perhaps more than any other vertebrate group, anuran amphibian larvae have been the subject of many experiments on this topic. Some anuran species have been shown in the laboratory to recognize and associate with their siblings and half-siblings. However, due to the difficulty of identifying sibships, no kinship studies with anuran larvae have been conducted in the wild. Here, we use microsatellite analysis to show that wood frog (Rana sylvatica) tadpoles were nonrandomly distributed in two ponds with respect to their relatives. In one pond, the tadpoles were significantly clumped with their siblings or half-siblings as expected from other published laboratory studies on this species. However, in another pond, the tadpoles were significantly nonrandomly dispersed from their siblings or half-siblings. This is the first example of kin repulsion of nonreproductive animals in the wild and the first time a species has been shown to display both aggregation and repulsion under different circumstances. These results suggest that kin distribution is context dependent and demonstrate the importance of testing kin selection hypotheses under natural conditions.     

Variation in withholding of information in three monkey species

Studies on tactical deception have reported that informed subordinates can withhold information from naive dominants, but they have not directly compared species'' performance. Here, we compared the performance in two withholding-of-information tasks of three monkey species differing in the strictness of their dominance hierarchy and degree of fission–fusion dynamics: spider monkeys, capuchin monkeys and long-tailed macaques. Food was hidden from the dominants'' view either inside an opaque box or in a transparent box that could only be opened by knowledgeable subordinates. All species were capable of withholding information, with subjects refraining from interacting with the box when the dominant was nearby. Spider monkeys were the most efficient at retrieving food, by timing it when the dominant was far from the box. Capuchin monkeys were also quite efficient when alone at the box, but they lost much of the food when manipulating the box with the dominant nearby. The results supported our predictions based on interspecific differences in the strictness of the dominance hierarchy and the degree of fission–fusion dynamics, with the former constraining the subjects'' tendency to approach the box and the latter affecting the subjects’ tendency to wait for the appropriate situation to retrieve the food.     

Growth and behaviour of six species of amphibian larvae in a winter pond in Israel

The effect of different ecological niches on growth and behaviour of larvae of four frogs (Bufo viridis, Hyla arborea, Pelobates syriacus, Rana ridibunda), and two salamanders (Salamandra salamandra and Triturus vittatus) found in a winter pond was studied. S. salamandra, T. vittatus, R. ridibunda and B. viridis were found most of the time on the bottom of the pond. However, H. arborea tadpoles were found throughout the pond and were usually sedentary, as compared with P. syriacus which moved up and down constantly. S. salamandra, T. vittatus, R. ridibunda and R viridis tadpoles from the bottom of the pond grew faster than the tadpoles from the surface of the pond. However, tadpoles of H. arborea and P. syriacus growing at the bottom or on the surface developed at similar rates.The invertebrate biomass increases during the summer and was higher at the bottom of the pond than at the surface. However the amount of chlorophyll a was about the same at the surface and at the bottom of the pond. S. salamandra and T. vittatus tadpoles feed on various types of of invertebrates, R. ridibunda and H. arborea and B. viridis tadpoles feed on vascular plants and algae, and P. syriacus tadpoles feed on both invertebrates and plants.     

Paraquat-induced oxidative stress response during amphibian early embryonic development

In addition to the endogenous production of reactive oxygen species (ROS) as a result of normal development, amphibian external development often forces embryos to deal with oxidative stress-producing agents present in the environment. Embryos should therefore develop protective systems to reduce ROS toxicity and achieve successful development. The present work was aimed to characterize the effects produced by the widespread-used ROS-generator pesticide Paraquat during early embryonic development in the toad Chaunus arenarum, as well as to get insights into the defense response elicited by amphibian embryos. The approach consisted in generating a sharp and brief oxidative stress condition early during embryonic development to stimulate the cellular mechanisms involved in ROS-antioxidant response. Results revealed that Paraquat-treatment reduced the ability of embryos to develop normally, leading to arrests of development and severe malformations such as tail abnormalities, abdominal edema, reduced head development and curved dorsal structures. Although Paraquat effects were morphologically evident from gastrula stage on, alterations such as chromatin condensation were observed even at blastula stage by histological examinations. Regarding detoxifying enzymes, a significant induction of Mn-superoxide dismutase activity was detected at stages beyond gastrula in embryos surviving Paraquat treatment, suggesting a major role of this enzyme in the antioxidant response during early embryonic development.     

Comparative study on the behavioral response to starvation in three species of antlion larvae (Neuroptera: Myrmeleontidae)

To clarify how pit-building antlion larvae behave during prolonged periods of low resource abundance, pit relocation rate, giving-up time, and respiration rate under starvation conditions were examined, using three species of antlion larvae. Most larvae ofMyrmeleon bore never relocated their pits before they starved to death, while larvae ofHagenomyia micans relocated more often thanMyrmeleon formicarius (average number of pit relocations 0.04 forM. bore, 0.19 forM. formicarius, and 0.62/individual/10 days forH. micans). The relative respiration rate, a ratio of respiration rate at starvation to that at satiation, was lower inM. bore andM. formicarius than in H. micans. Thus, there was an inversely proportional relationship between the pit relocation rate and the decrease in respiration rate under starvation conditions in the three species of antlion larvae.     

Variation of isozyme patterns among Arachis species

The genus Arachis contains a large number of species and undescribed taxa with patterns of genetic variation that are little understood. The objectives of this investigation were to estimate genetic diversity among species of Arachis by utilizing electrophoretic techniques and to establish the potential for use of isozymes as markers for germplasm introgression. One-hundred-and-thirteen accessions representing six of the seven sections of the genus were analyzed for isozyme variation of 17 enzymes. Section Rhizomatosae species were not included because they produce very few seeds. Seeds were macerated and the crude extract was used for starch-gel electrophoretic analyses. Although the cultivated species has few polymorphic isozymes, the diploid species are highly variable and two-to-six bands were observed for each isozyme among accessions. Because of the large number of isozyme differences between A. hypogaea and A. batizocoi (the presumed donor of the B genome), this species can no longer be considered as a progenitor of the cultivated peanut. Seed-to-seed polymorphisms within many accessions were also observed which indicate that germplasm should be maintained as bulk seed lots, representative of many individuals, or as lines from individual plants from original field collections. The area of greatest interspecific genetic diversity was in Mato Grosso, Brazil; however, the probability of finding unique alleles from those observed in A. hypogaea was greatest in north, north-central, south and southeast Brazil. The large number of polymorphic loci should be useful as genetic markers for interspecific hybridization studies.     

Variation in behavior of lycaenid larvae when attended by different ant species

Partner quality can be crucial for the outcome of a mutualistic interaction. In multi-species associations, the characteristics of potential partners can vary substantially and thus the associated benefits. As a consequence of such variation, one might expect strategies of adjusting investments to the characteristics of a partner. Lycaenid butterfly larvae often interact mutualistically with several ant species of different size and aggressiveness and thereby different ability to protect the larvae. Attending ants are rewarded with nutritious secretions. Both ant behavior and a larva's need for protection are known to influence larval investment in the relationship. This study investigates the effect of six ant species on larval behavior in the lycaenid butterfly, Glaucopsyche lygdamus. The overall level of secretion, as well as the response to varying number of attending ants, were found to be influenced by ant species. This revised version was published online in November 2006 with corrections to the Cover Date.     

Behavioral fever in anuran amphibian larvae.

Following intraperitoneal injection with killed gram-negative bacteria, $\text{Aeromonas}$$\text{hydrophila}$, tadpoles of $\text{Rana}$$\text{catesbeiana}$ and of $\text{R}$. $\text{pipiens}$ showed significant mean increases in preferred temperature of 2.6°C and 2.7°C, respectively, in an electronic thermoregulatory shuttlebox device. This “behavioral fever” is similar to elevations in preferred temperature previously demonstrated for fishes, reptiles and mammals, although both normal and febrile thermal preferenda vary among vertebrates.     

Comparison of imposex response in three Prosobranch species

A comparative study of the three gastropod species Nucella lapillus (L.), Ocenebra erinacea (L.) and Hinia (Nassarius) reticulata (L.) reveals that Nucella is the most TBT sensitive species while Hinia is the least sensitive. Of the two imposex indices VDSI and RPSI, good interspecies correlations were obtained only for VDSI. The three species can be considered as complementary not only in terms of their ecology but also for their levels of sensitivity. Indeed, Nucella and Ocenebra are useful test species at TBT concentrations below 2 ng Sn 1⁻¹ while Hinia is the more appropriate species at higher TBT levels. For the first time, two sterilised Hinia females are recorded. This sterilization does not seem to be due to proliferation of vas deferens tissue in the vaginal opening and further investigation is needed to find intermediary VDS stages between stage 4⁺ and sterilization. Studies using Nucella show that the use of narcotization in imposex analysis leads to an underestimation of RPSI compared with non-narcotization methods. Indeed, narcotization straightens the penis and increases its length when compared with non-narcotized animals, but this increase is proportionally higher in males than in females.     

Diets and resource partitioning between larvae of three anisopteran species

Analysis of resource partitioning between larvae of three Anisopteran species showed that Aeshna cyanea and Anax imperator (both Aeshnidae) tended to occupy similar ecological niches which were not shared by Libellula depressa (Libellulidae).The diets of these predators and comparisons between trophic availability and diets indicated that prey species eaten varied according to season and predator species, and that some selection of prey species occurred.     

Variation in human hair ultrastructure among three biogeographic populations

Human scalp hairs are often examined microscopically to study the variation and diversity among a range of visible morphological traits. In this study, we focused on the ultrastructure of human scalp hair within its keratinized matrix, emphasizing, the density and distribution of melanosomes, variation in cuticle thickness within populations, and the relationship of hair fiber ultrastructure with biogeographic ancestry. We used transmission electron microscopy (TEM) to visualize hair cross-sections and generate micron-scale resolution images for analysis of particle morphology and the layered hair matrix. Our results revealed considerable variation in all parameters examined, including the relationship of ultrastructure to biogeographic ancestry. Among the three metapopulations studied (European, African, and East Asian), we identified hair cross-sectional shape, cuticle dimensions, and melanosome distribution as traits that reveal statistically significant ancestry-related patterns. This study establishes trait patterns in hair morphology and ultrastructure among three biogeographically defined metapopulations to improve the current understanding of human variation in hair form and establish a foundation for future studies on the genetic and developmental bases of phenotypic variation in hair ultrastructure related to genotype.