Significant biomagnification of methylmercury in songbird nestlings through a rice-based food web: Insights from stable mercury isotopes.

To elucidate the sources and transfer of mercury (Hg) in terrestrial food chains, particularly in heavily Hg-contaminated rice paddy ecosystems, we collected rice leaves, invertebrates, and Russet Sparrow nestlings from a clear food chain and analyzed the dietary compositions and potential Hg sources using stable Hg isotopes coupled with a Bayesian isotope mixing model (BIMM). Our findings indicated that MeHg exposure is dominant through the dietary route, with caterpillars, grasshoppers, and katydids being the main prey items, while the less provisioned spiders, dragonflies, and mantises contributed the most of the Hg to nestlings. We found minimal MIF but certain MDF in this terrestrial food chain and identified two distinct MeHg sources of dietary exposure and maternal transfer. We firstly found that the dietary route contributed substantially (almost tenfold) more MeHg to the nestlings than maternal transfer. These findings offer new insights into the integration of Hg from the dietary route and maternal transfers, enhancing our understanding of fluctuating Hg exposure risk during the nestling stage. Our study suggested that Hg isotopes combined with BIMM is an effective approach for tracing Hg sources in birds and for gaining in-depth insight into the trophic transfers and biomagnification of MeHg in food chains.

A new species of Nidirana (Anura, Ranidae) from northern Guangxi, China.

A new species of music frog, Nidiranaguibeiensis sp. nov., is described from northern Guangxi, China. Based on two mtDNA fragments analyzed, phylogenetic trees reveal that N.guibeiensis sp. nov. is most closely related to N.leishanensis. However, the new species can be identified by conspicuous diagnostic morphological characteristics as well as bioacoustics. In contrast to the known Nidirana species, the advertisement calls of the new species can be divided into three types, calls with one, two, and three notes. In addition, the new species has nest construction behavior, which is inconsistent with N.leishanensis. Nidiranaguibeiensis sp. nov. occurs in paddy fields or still pools at 300-1300 m a.s.l.

Coevolution between Himalayan cuckoos and 2 sympatric Pycnonotidae hosts.

Selection due to cuckoo parasitism is responsible for the evolution of anti-parasitism defenses in hosts. Different host species breeding sympatrically with a single parasitic cuckoo may evolve different strategies to reduce the risk of counter cuckoo parasitism, resulting in different interactions between cuckoos and hosts in areas of sympatry. Here, we studied the coevolutionary interactions between Himalayan cuckoos Cuculus saturatus and 2 sympatric and closely related potential hosts belonging to the family Pycnonotidae, the brown-breasted bulbul Pycnonotus xanthorrhous and the collared finchbill Spizixos semitorques. We investigated parasitism rates and nest-site selection (nest height, nest cover, human disturbance, perch height, forest distance, and degree of concealment) related to parasitism risk, nest defense against a cuckoo dummy, and egg rejection against cuckoo model eggs. Bulbuls used specific nest sites that were further away from forests than those of finchbills, and they behaved more aggressively toward cuckoos than finchbills. In contrast, bulbuls possessed moderate egg rejection ability, whereas the finchbill rejected 100% of cuckoo model eggs. We suggest that selection of a nest site away from forests by the bulbul explains the absence of parasitism by Himalayan cuckoos. We suggest that these interspecific differences in nest-site selection and nest defense indicate alternative responses to selection due to cuckoos.

Passerine bird reproduction does not decline in a highly-contaminated mercury mining district of China.

Mercury (Hg) is a neurotoxic element with severe effects on humans and wildlife. Widely distributed by atmospheric deposition, it can also be localized near point sources such as mines. Mercury has been shown to reduce the reproduction of bird populations in field observations in North America and Europe, but studies are needed in Asia, where the majority of emissions now occur. We investigated the reproduction of two passerines, Japanese Tit (Parus minor) and Russet Sparrow (Passer rutilans), in a large-scale Hg mining district, and a non-mining district, both in Guizhou, southwest China. Concentrations of Hg were elevated in the mining district (blood levels of 2.54 ± 2.21 [SD] and 0.71 ± 0.40 µg/g, in adult tits and sparrows, respectively). However, we saw no evidence of decreased breeding there: metrics such as egg volume, nestling weight, hatching and fledgling success, were all similar between the different districts across two breeding seasons. Nor were there correlations at the mining district between Hg levels of adults or juveniles, and hatching or fledgling success, or nestling weight. Nest success was high even in the mining district (tit, 64.0%; sparrow: 83.1%). This lack of reproductive decline may be related to lower blood levels in nestlings (means < 0.15 µg/g for both species). Concentrations of selenium (Se), and Se-to-Hg molar ratio, were also not correlated to breeding success. Although blood levels of 3.0 µg/g have been considered as a threshold of adverse effects in birds, even leading to severe effects, we detected no population-level reproductive effects, despite ~25% of the adult tits being above this level. Future work should investigate different locations in the mining district, different life-stages of the birds, and a wider variety of species. The hypothesis that bird populations can evolve resistance to Hg in contaminated areas should also be examined further.

Mercury exposure in sedentary and migratory Charadrius plovers distributed widely across China.

Mercury pollution is a global problem and of particular concern in high emissions areas, such as China. We studied the migratory Kentish Plover, Charadrius alexandrinus, which breeds in coastal northern/central China and the inland Qinghai Lake, and the White-faced Plover C. dealbatus, a year-round resident of coastal southern China. We measured total mercury (THg) concentrations in feather and blood samples of breeding females. We expected low levels at the remote Qinghai Lake, but we found instead that feather THg concentrations were highest there (3.89 ± 1.53 [SD] µg/g DW [n = 34]; compared to 1.29 ± 0.61 µg/g of Kentish Plover elsewhere [n = 35] and 2.08 ± 1.45 µg/g for White-faced Plover [n = 56]), a result is consistent over 2 years. When including only coastal populations in the analysis, there were no differences in THg concentrations between the two species, although White-faced Plover had more variation. Feather THg concentrations for the coastal populations are similar to other studies on plovers and sandpipers globally, with most birds under the threshold of adverse effects (3 µg/g, an estimate that itself may be too low). Nevertheless, the Qinghai Kentish Plover population has mean feather concentrations above this threshold, indicating high exposure during the nonbreeding season, and some individuals have extreme values (e.g., a bird with a blood level of 7.63 µg/g DW from Zhanjiang, south China), so further research and monitoring are needed.

Heavy Metal, Arsenic, and Selenium Concentrations in Bird Feathers from a Region in Southern China Impacted by Intensive Mining of Nonferrous Metals.

Heavy metal pollution is widespread in China, particularly in its mining regions. Mercury (Hg) concentrations in birds from Guizhou Province were recently reported to be above adverse effect levels, even in nonmining areas. We sampled birds to investigate whether Hg might be a threat near lead (Pb), zinc (Zn), and tin (Sn) mines in Guangxi Zhuang Autonomous Region. We measured concentrations of 8 metals/metalloids in feathers of 627 resident birds representing 60 species sampled across 14 sites on 5 rivers. We found that Hg concentrations (mean ± standard deviation, 1.27 ± 2.02 ppm) were lower than in the recent Guizhou study. Mercury had the fewest correlations with other metals/metalloids; the mined metals (Pb, Sn, Zn) had the most such correlations. Levels of cadmium (Cd; 1.12 ± 2.64 ppm), arsenic (As; 4.78 ± 17.11 ppm), and Pb (17.18 ± 24.49 ppm) were closer to thresholds of adverse effects or relatively high compared to other studies. With the exception of a few hot spots for Hg, Cd, and As near mines, metal/metalloid levels were fairly evenly distributed among sites, consistent with the regional occurrence of mineable ore deposits. It appears that Hg is not threatening to all avian species in China, although it may be problematic for some species near Hg mines. In addition to Hg, however, other metals/metalloids may pose wildlife health hazards. Environ Toxicol Chem 2020;39:371-380. © 2019 SETAC.

The association between parental socioeconomic status (SES) and medical students' personal and professional development.

INTRODUCTION: In order to commit to their mission and placement requirements, medical education policy-makers are required to understand the background and character of students in order to admit, cultivate and support them efficiently and effectively. MATERIALS AND METHODS: This study sample consisted of 408 homogeneous medical students with the same level of education, occupation, school and societal environment. They differed mainly in their family background. Therefore, this study used part of a multidimensional "student portfolio system" database to assess the correlation between family status (indexed by parental education and occupation) and medical students' mental health status and characters. The controls were a group of 181 non-medical students in another university. RESULTS: The parents of the medical students were from a higher socioeconomic status (SES) than the parents of those in the control group. This showed the heritability of genetic and environment conditions as well as the socioeconomic forces at play in medical education. Students' personal and professional development were associated with their parents' SES. The mother's SES was associated with the student's selfreported stress, mental disturbances, attitude towards life, personality, health, discipline, internationalisation and professionalism. The fathers' SES did not show a statistically significant association with the above stress, physical and mental health factors, but showed an association with some of the personality factors. The greater the educational difference between both parents, the more stress, hopelessness and pessimism the student manifested. CONCLUSIONS: Medical educators need to be aware that socioeconomic factors have meaningful patterns of association with students' mental and physical health, and their characters relating to personal and professional development. Low maternal SES negatively influences medical students' personal and professional development, suggesting that medical education policy-makers need to initiate support mechanisms for those with latent vulnerability.