Long-term effect of heavy-metal pollution on diversity of gastrointestinal microbial community of Bufo raddei.

Gastrointestinal (GI) microbiota plays a very important role in maintaining its host's health. However, the effects of environmental contamination on the GI microbiota homeostasis of amphibians have not yet been reported. The present study reveals the long-term effect of natural heavy-metal pollution on the GI microbial community diversity and structural changes of Bufo raddei (B. raddei). Basing on the 16S rRNA sequencing method, the GI microbiota of B. raddei from a heavily heavy-metal-polluted area (Baiyin, (BY)) and a relatively unpolluted area (Liujiaxia, (LJX)) were profiled. The results showed that heavy-metal pollution had caused significant shifts in the composition of the GI microbiota both at the phylum and genus levels. Specifically, Bacteroidetes dominated in the GI tract of B. raddei from BY, while Tenericutes was much more common in those from LJX. The ratio of Firmicutes/Bacteroidetes and the proportion of probiotics in the GI microbiota of B. raddei from BY were reduced compared to those from LJX, as well. Heavy-metal pollution also induced in a reduction of species diversity and decreased proportion of unique operational taxonomic units in the GI tract. In short, our results demonstrate that long-term heavy-metal exposure re-shaped the composition and decreased the species diversity of GI microbiota of B. raddei; our results also represent a novel approach to uncover the toxic effects of pollution on amphibians.

Zhang W ，Guo R ，Yang Y ，Ding J ，Zhang Y ... -  《-》

Variation of fitness and reproductive strategy in male Bufo raddei under environmental heavy metal pollution.

Environmental pollution is known to adversely affect amphibian reproduction and survival, however, the knowledge of environmental heavy metal pollution on fitness of male amphibian is largely unknown. The present study aimed to explore the variation in fitness of male Bufo raddei, a widespread anuran in northwest China, subjected to long-term heavy metal stress in Baiyin (BY) city. BY is heavily polluted by heavy metals mainly copper, zinc, lead and cadmium; meanwhile, Liujiaxia (LJX), a relatively unpolluted area, was chosen as control. Differences in advertisement call, larynx size, breeding glands size, as well as forearm force during courtship and amplexus in male B. raddei between the two populations were analyzed. The results revealed a competitive advantage in advertisement call in BY population, together with larger breeding glands size and forearm force, which demonstrated a relatively higher fitness. Using skeletochronological analysis, we found that more than 40% of males from BY began to breed at 2 years old, which was only 6.93% for males from LJX. Correspondingly, the average age for all males participate in breeding was younger from BY than from LJX. Not surprisingly, males from BY showed a relatively lower body condition. All these results illustrated males from BY invested more in reproduction to increase fitness at the cost of health and survival. This reproductive trade-off might ultimately influence stability of B. raddei population because of the environmental heavy metal pollution.

Guo R ，Zhang W ，Yang Y ，Ding J ，Yang W ，Zhang Y ... -  《-》

Sperm Morphology and Motility of Bufo raddei Under Long-Term Environmental Heavy Metal Stress.

Guo R ，Zhang W ，Yang Y ，Ding J ，Ai S ，Yang W ，Bai X ，Zhang Y ... -  《-》

Fluctuating asymmetry rather than oxidative stress in Bufo raddei can be an accurate indicator of environmental pollution induced by heavy metals.

Guo R ，Zhang W ，Ai S ，Ren L ，Zhang Y ... -  《-》

Long-term heavy metal pollution varied female reproduction investment in free-living anura, Bufo raddei.

Environment contamination is known to affect the growth, reproduction, and even mortality of anuran species, and hence modulate their life history traits. Although knowledge of the ability of amphibians to cope with harsh environments has gained ongoing research, the reproductive strategy of free-living amphibians subjected to long-term heavy metal pollution is largely unknown. This study aimed to explore the variation in the life history traits, including age structure, maturation age, reproductive investment, and reproduction trade-off, in female Bufo raddei, a widespread anuran in Baiyin (BY) in northwest of China, subjected to sublethal heavy metal pollution. B. raddei collected from Liujiaxia (LJX), a relatively unpolluted area, were used as control. Skeletochronological analysis revealed variation in the average breeding age of females: more than 70% of females from BY began to breed 1 year before the toads collected from LJX. Females from BY tended to prioritize reproduction over survival and invested more in their first reproductive event. Further, females in BY with a high fluctuating asymmetry index showed a relatively lower reproductive investment. For trade-off in offspring number and size, BY population optimize larger clutch sizes with smaller egg size compared with population in LJX. Changes in female reproductive investment caused by heavy metal pollution might ultimately alter the structural stability of amphibian population.

Zhang W ，Guo R ，Ai S ，Yang Y ，Ding J ，Zhang Y ... -  《-》