Arbuscular mycorrhizas amplify the risk of heavy metal transfer to human food chain from fly ash ameliorated agricultural soils

Soil contaminants threaten global food security by posing threats to food safety through food chain pollution. Fly ash is a potential agent of soil contamination that contains heavy metals and hazardous pollutants. However, being rich in macro- and micronutrients that have direct beneficial effects on plant growth, fly ash has been recommended as a low-cost soil ameliorant in agriculture in countries of the Global South. Arbuscular mycorrhizal fungi (AMF), ubiquitous in agricultural soils, enhance efficiency of plant nutrient uptake from soils but can equally increase uptake of toxic pollutants from fly ash ameliorated soils to edible crop tissues. We investigated AMF-mediated amplification of nutrient and heavy metal uptake from fly ash amended soils to shoots, roots and grains of barley. We used a microcosm-based experiment to analyse the impacts of fly ash amendments to soil in concentrations of 0 (control), 15, 30 or 50% respectively, on root colonization by AMF Rhizophagus irregularis and AMF-mediated transfer of N, P and heavy metals: Ni, Co, Pb and Cr to barley tissues. These concentrations of fly ash are equivalent to 0, 137, 275 and 458 t ha−1 respectively, in soil. Root AMF colonization correlated negatively with fly ash concentration and was not detected at 50% fly ash amendment. Shoots, roots and grains of mycorrhizal barley grown with 15, 30 and 50% fly ash amendments had significantly higher concentrations of Ni, Co, Pb and Cr compared to the control and their respective non-mycorrhizal counterparts. Presence of heavy metals in barley plants grown with fly ash amended soil and their increased AMF-mediated translocation to edible grains may significantly enhance the volume of heavy metals entering the human food chain. We recommend careful assessment of manipulation of agricultural soils with fly ash as heavy metal accumulation in agricultural soils and human tissues may cause irreversible damage

Male and Female Stridulation in an Indian Weta (Orthoptera: Anostostomatidae)

We present the first description of the calls and stridulatory structures of males and females of an Indian weta species from the Western Ghats of Southern India. Calls of males and females produced by femoro-abdominal stridulation were recorded and call features such as chirp duration, chirp period, syllable period and syllable duration were characterised. The calls of males were highly stereotyped with regular chirp periods and durations whereas chirp rates in the female calls were more variable. The number of syllables per chirp was constant for males and females and the fine temporal features such as syllable periods and syllable durations showed low inter-individual variation in both males and females. The arrangement of femoral stridulatory structures was different from the previously described anostostomatid species. The high stereotypy of calls of males and females indicates that the signal could serve for identification of species and sex

Vertical stratification in an acoustically communicating ensiferan assemblage of a tropical evergreen forest in southern India

This study provides the first quantitative description of vertical stratification in calling heights of ensiferan species constituting most of the dry-season nocturnal acoustic community of an evergreen forest in Kudremukh National Park in south-west India. Calling heights of an average of 26 individuals of each of the 20 ensiferan species were measured and subjected to an analysis of variance to test for differences in mean calling height between species and a cluster analysis to check for the presence of discontinuous calling height layers. There were significant differences in mean calling heights between species. Calling heights of different gryllid and tettigoniid species ranged from the ground to the canopy. More gryllid than tettigoniid species occupied the ground and herb layer. Our study revealed vertical stratification of calling heights, with discrete layers corresponding to the canopy, understorey and the ground layer. These clusters emerged from the raw data of calling heights of individuals without a priori distinction of layers. We found no significant correlation between the calling heights of species and call features, including mean dominant frequency of narrow band calls, mean syllable rate and mean duty cycle

Singers in the grass: call description of conehead katydids (family: Tettigoniidae) and observations on avoidance of acoustic overlap

<p>The sub-family Conocephalinae constitutes one of the richest groups of katydids in terms of diversity and distribution. Tropical katydids especially in India have largely escaped academic attention. Here, we record and describe call patterns for six conehead katydids from India: <i>Conocephalus melanus, Conocephalus sp X, Euconocephalus indicus, Euconocephalus mucro, and Euconocephalus sp Y</i> from North-Eastern Himalayas and <i>Euconocephalus pallidus</i> from the Western Ghats. All the species showed broadband frequency spectra (10.5–42.4 kHz), and three of the six species showed high rates of calling (289–453 syllables/s). We observed that the co-occurring call types never called at the same time or from the same location. We hypothesized this partitioning between call types is due to similarity in their calls; we used non-metric multi-dimensional scaling (NMDS) to investigate patterns of temporal or habitat-partitioning that some of the co-occurring call types exhibited during the course of study. The co-occurring <i>Euconocephalus sp Y and E. mucro</i> with high degree of overlap and similarity in their calls exhibited partitioning on a spatial scale. <i>Conocephalus sp. X</i> and <i>C. melanus</i> with distinct calling activity peaks formed separate clusters based on temporal call structures. As females rely heavily on spectral qualities, we speculate partitioning on temporal scale to avoid heterospecific interference due to similar spectral properties between the two call types.</p

Delineating the calling pattern of Oecanthus indicus from native and non-native plant species

The study attempted to understand the effect of the host plants on the call parameters of native tree cricket, Oecanthus indicus (Order: Orthoptera, Sub-order: Ensifera, Family: Gryllidae) while calling from native (Justicia adhatoda) and non-native host plant species (Lantana camara and Hyptis suaveolens). The study was conducted at four locations across India. Calls of O. indicus were recorded on these host plants in the field and spectral and temporal parameters of calls were analysed. The results suggested that the peak frequency varied among the two non-native plant species while the difference in temporal pattern between the native and non-native host plants was observed only in the syllable period. The study also quantified the choice of calling positions of insects from the three-host species. The native O. indicus chose non-native H. suaveolens leaves extensively as a preferable site to baffle (37%). Differences in the call parameters and choice of the host plant by insects may ultimately affect the preference and performance of insects on invasive plants. The study would aid in exploring the underlying evolutionary and ecological processes of adaptive success of insects on non-native plants

A rain forest dusk chorus: cacophony or sounds of silence?

A rain forest dusk chorus consists of a large number of individuals of acoustically communicating species signaling at the same time. How different species achieve effective intra-specific communication in this complex and noisy acoustic environment is not well understood. In this study we examined acoustic masking interference in an assemblage of rain forest crickets and katydids. We used signal structures and spacing of signalers to estimate temporal, spectral and active space overlap between species. We then examined these overlaps for evidence of strategies of masking avoidance in the assemblage: we asked whether species whose signals have high temporal or spectral overlap avoid calling together. Whereas we found evidence that species with high temporal overlap may avoid calling together, there was no relation between spectral overlap and calling activity. There was also no correlation between the spectral and temporal overlaps of the signals of different species. In addition, we found little evidence that species calling in the understorey actively use spacing to minimize acoustic overlap. Increasing call intensity and tuning receivers however emerged as powerful strategies to minimize acoustic overlap. Effective acoustic overlaps were on average close to zero for most individuals in natural, multispecies choruses, even in the absence of behavioral avoidance mechanisms such as inhibition of calling or active spacing. Thus, call temporal structure, intensity and frequency together provide sufficient parameter space for several species to call together yet communicate effectively with little interference in the apparent cacophony of a rain forest dusk chorus