Which frog's legs do froggies eat? The use of DNA barcoding for identification of deep frozen frog legs (Dicroglossidae, Amphibia) commercialized in France

Annemarie Ohler,Violaine Nicolas

doi:10.5852/ejt.2017.271

Abstract

Several millions frogs captured in the wild in Indonesia are sold for food yearly in French supermarkets, as deep frozen frog legs. They are commercialized as Rana macrodon, but up to 15 look-alike species might also be concerned by this trade. From December 2012 to May 2013, we bought 209 specimens of deep frozen frog legs, and identified them through a barcoding approach based on the 16S gene. Our results show that 206 out of the 209 specimens belong to Fejervarya cancrivora, two to Limnonectes macrodon and one to F. moodiei. Thus only 0.96 % of the frogs were correctly identified. Unless misclassification was intentional, it seems that Indonesian frog leg exporters are not able to discriminate between the species. The quasi absence of L. macrodon in our samples might be an indication of its rarity, confirming that its natural populations are declining rapidly, in agreement with its “vulnerable” status according to the IUCN Red List. Our results show that the genetic and morphological diversity of the frogs in trade is much higher than the genetic and morphological diversity measured so far by scientific studies. These results underline the need for large scale studies to assess the status of wild populations.

Highlights

The international traffic of wild animals is considered an important threat to many animal species and is subject to international regulations
The 16S gene was previously recognized as one of the OHLER A. & NICOLAS V., DNA barcoding for identification of frog legs
Misidentification of frogs commercialized in France Results based on the phylogentic tree and the BLAST approach (BM, Best Close Match (BCM) and All Species Barcode (ASB)) are congruent and show that 206 out of the 209 analyzed specimens belong

Summary

Introduction

The international traffic of wild animals is considered an important threat to many animal species and is subject to international regulations. The same period, between 180 million and 1 billion specimens of frogs were collected every year in the wild in Indonesia, and one eighth of these frogs were exported to Europe (Kusrini 2005; Kusrini & Alfold 2006). The main European countries that import frog legs from Indonesia are France and Belgium (Kusrini & Alfold 2006; Altherr et al 2011). In the 1970s deep freezing technology was developed, which allowed long term storage and large scale transport of frog legs, and large numbers of frogs were collected by commercial enterprises (Dubois 1983; Neveu 2004). In 1987 Indonesia became the main exporter of frogs and more than 80% of European frog leg imports come from this country (Altherr et al 2011)

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Conclusion