Discovery of the Asian clam Corbicula sp. form A in Ensenada, Baja California through conventional taxonomy and innovative shell dna whole genome amplification

Ensenada, Baja California is characterized by intermittent runoff occurrences, typically limited to the rainy season, and scarce hot springs, devoid of documented native freshwater clam populations. Notably, the region encompasses the 'Emilio López Zamora' reservoir, vital for water storage and urban supply. However, an unexpected phenomenon unfolded during the dry season of 2021: a substantial accumulation of deceased freshwater clam shells was serendipitously discovered along a stretch of sandy reservoir bed. The goals of this study were to determine the identity of the clam, analyze its possible origin and consider its potential control/use. A sampling of 100 these shells was carried out to perform morphological and molecular identification. Morphological identification was carried out using conventional malacological techniques of taxonomy based on shell morphology. Molecular identification was conducted by extracting DNA from both the shell and periostracum of deceased clams, employing whole-genome amplification (WGA) in conjunction with PCR and sequencing techniques. The integration of classic malacological methods with molecular analysis unequivocally confirmed the lineage of the clam as Corbicula sp. form A. This is the first record of this invasive species in the city of Ensenada, Baja California. The WGA method demonstrated its efficacy in identifying deceased mollusks when only the shell remains, and nucleic acid availability is constrained. The origin of the clam within the reservoir remains elusive, underscoring the need for future investigations to delve into its potential for biomonitoring, bioremediation, and aquaculture applications.