Bioaccumulation of Trace Elements and Health Risk Predictions in Edible Tissues of the Marsh Frog

How do different concentrations of aluminum and zinc affect the survival, body size, morphology and immune system of Physalaemus cuvieri (Fitzinger, 1826) tadpole?

The assessment of amphibian responses as bioindicators of exposure to chemical pollutants is an important tool for conservation of native species. This study aimed to investigate the effects of chronic aluminum (Al) and zinc (Zn) exposure on survival, body size, morphology (malformations), and immune system (leukocyte profile) in P. cuvieri tadpoles. Ecotoxicological analyses were performed utilizing chronic toxicity tests in which 210 tadpoles at the 25th Gosner developmental stage were exposed to Al and Zn. Individuals of P. cuvieri were maintained in glass containers containing various concentrations of aluminum sulfate (0.1, 0.2, or 0.3 mg/L) and zinc sulfate (0.18, 0.27 or 0.35 mg/L), and tests were performed in triplicate. After 14 days, amphibians were weighed, measured and survival rate, malformations in the oral and intestine apparatus, leukocyte profile, and ratio between neutrophils and lymphocytes determined. The differing concentrations of Al and Zn did not produce lethality in P. cuvieri where 95% of the animals survived 326 hr following metal exposure. Individuals exposed to Zn achieved greater body growth and weight gain compared to controls. Aluminum increased weight gain compared controls. These metals also produced malformations of the oral and intestine apparatus and enhanced occurrence of hemorrhages, especially at the highest doses. Lymphocytes were the predominant cells among leukocytes, with lymphopenia and neutrophilia observed following Al and Zn treatment, as evidenced by elevated neutrophil/lymphocyte ratio, an important indicator of stress in animals. Data suggest that further studies need to be carried out, even with metal concentrations higher than those prescribed by CONAMA, to ensure the conservation of this species.

Investigation of heavy metals in tissues and habitats of three edible frogs from Türkiye

The soil, water, and organisms have been contaminated by heavy metals due to human activities and industrialization, which has produced a major environmental problem that has a deleterious effect on human health and food quality. Frogs, one of the good bioindicators for environmental pollution, are also among the alternative essential protein sources for humans. In Türkiye, three of these frogs are edible: Pelophylax ridibundus, Pelophylax bedriagae, and Pelophylax caralitanus, also known as Anatolian water frogs. Hence, to assess the possible health risks that might result from consuming frog legs in addition aquatic habitat of Anatolian water frogs, the water, sediment, and frog tissue samples (muscle and liver) were obtained from 11 different provinces covering all regions of Türkiye and analyzed to determine Cd, Cu, Cr, Zn, Pb, and As concentrations. The results revealed considerable variations in heavy metal concentrations among frog tissues, influenced by the sampling sites and species (ANOVA: p < 0.05). The Estimated Daily Intake (EDI) values, calculated based on the average serving size, were also lower than the Provisional Tolerable Daily Intake (PTDI) levels for adult consumers. Furthermore, the study computed the Target Hazard Quotient (THQ) values for heavy metals, all of which were below the critical value of 1, indicating that consuming the hind leg muscles from these frog species would not pose an adverse health risk for humans.

Numerous uncertainties in the multifaceted global trade in frogs’ legs with the EU as the major consumer

The commercial trade in frogs and their body parts is global, dynamic and occurs in extremely large volumes (in the thousands of tonnes/yr or billions of frogs/yr). The European Union (EU) remains the single largest importer of frogs’ legs, with most frogs still caught from the wild. Amongst the many drivers of species extinction or population decline (e.g. due to habitat loss, climate change, disease etc.), overexploitation is becoming increasingly more prominent. Due to global declines and extinctions, new attention is being focused on these markets, in part to try to ensure sustainability. While the trade is plagued by daunting realities of data deficiency and uncertainty and the conflicts of commercial interests associated with these data, it is clear is that EU countries are most responsible for the largest portion of the international trade in frogs’ legs of wild species. Over decades of exploitation, the EU imports have contributed to a decline in wild frog populations in an increasing number of supplying countries, such as India and Bangladesh, as well as Indonesia, Turkey and Albania more recently. However, there have been no concerted attempts by the EU and present export countries to ensure sustainability of this trade. Further work is needed to validate species identities, secure data on wild frog populations, establish reasonable monitored harvest/export quotas and disease surveillance and ensure data integrity, quality and security standards for frog farms. Herein, we call upon those countries and their representative governments to assume responsibility for the sustainability of the trade. The EU should take immediate action to channel all imports through a single centralised database and list sensitive species in the Annexes of the EU Wildlife Trade Regulation. Further, listing in CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) can enforce international trade restrictions. More joint efforts are needed to improve regional monitoring schemes before the commercial trade causes irreversible extinctions of populations and species of frogs.

First Report on the Presence of Toxic Metals and Metalloids in East Asian Bullfrog (Hoplobatrachus rugulosus) Legs

We examined the presence of As, Cr, Cd, and Pb in 42 samples of farmed East Asian bullfrog (Hoplobatrachus rugulosus) from Vietnam and Thailand by inductively coupled plasma-mass spectrometry (ICP-MS). An estimation of the dietary intake and exposure to the toxic elements analysed was also carried out. The results showed very high As levels, with mean values of 0.094 ± 0.085 mg/Kg w.w. and a maximum of 0.22 mg/Kg. No significant differences were found for As contents between areas of production (p > 0.05). No detectable Cd contents were found in all the samples examined. The Pb concentrations of the East Asian bullfrog legs samples were below the European Commission’s permitted levels. The Cr and Pb contents of the East Asian bullfrog produced in Vietnam were significantly higher than that produced in Thailand (p < 0.05). The target hazard quotient (THQ) ratio for Cr was not exceeded for all the samples analysed. In contrast, the benchmark dose lower confidence limit (BMDL) and THQ ratios for As were exceeded, indicating carcinogenic and non-carcinogenic risks for those who consume this type of food. The results of this work confirm the role of As-contaminated water absorption as an important source of arsenic for these adult organisms.

Altitude impacts body size but not age in a gecko

Animals' age and size-related life-history traits are influenced by a variety of factors. In connection with climate, the effect of altitude on demographic parameters may differ among different populations of the same species. In the present study, it was analyzed that how body size and longevity of the Asia Minor thin-toed gecko, Mediodactylus heterocercus (Blanford, 1874), vary along with an elevational gradient in Turkey. For this purpose, a total of 138 (52 males, 75 females, and 11 young) M. heterocercus specimens from 11 different populations were analyzed. Populations at inter-mediate altitude had shorter lifespans than in both low and high elevations (marginal environments). Furthermore, the adult life expectancy (ESP), which indicates the expected lifespan of individuals having sexual maturity, was higher in high altitude populations (ESP: 6.59 years) than in intermediate populations (ESP: 5.40 years) and low altitude populations (ESP: 6.01 years). The results of the study suggest that Asia Minor thin-toed geckos' body size increases with altitude, but their age does not.