The Application of DNA Barcodes for the Identification of Marine Crustaceans from the North Sea and Adjacent Regions

During the last years DNA barcoding has become a popular method of choice for molecular specimen identification. Here we present a comprehensive DNA barcode library of various crustacean taxa found in the North Sea, one of the most extensively studied marine regions of the world. Our data set includes 1,332 barcodes covering 205 species, including taxa of the Amphipoda, Copepoda, Decapoda, Isopoda, Thecostraca, and others. This dataset represents the most extensive DNA barcode library of the Crustacea in terms of species number to date. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for 198 (96.6%) of the analyzed species. Six species were characterized by two BINs (2.9%), and three BINs were found for the amphipod species Gammarus salinus Spooner, 1947 (0.4%). Intraspecific distances with values higher than 2.2% were revealed for 13 species (6.3%). Exceptionally high distances of up to 14.87% between two distinct but monophyletic clusters were found for the parasitic copepod Caligus elongatus Nordmann, 1832, supporting the results of previous studies that indicated the existence of an overlooked sea louse species. In contrast to these high distances, haplotype-sharing was observed for two decapod spider crab species, Macropodia parva Van Noort & Adema, 1985 and Macropodia rostrata (Linnaeus, 1761), underlining the need for a taxonomic revision of both species. Summarizing the results, our study confirms the application of DNA barcodes as highly effective identification system for the analyzed marine crustaceans of the North Sea and represents an important milestone for modern biodiversity assessment studies using barcode sequence

Empirically adjusted ray amplitudes in the vicinity of the critical region

Se desarrolla un método para corregir empíricamente las amplitudes de las ondas P producidas a partir de la teoría geométrica de rayos en la vecindad de la distancia critica xc, donde es bien sabido que la teoría produce amplitudes erróneas. Se encuentra que simplemente mediante un suavizamiento de las amplitudes dentro de una zona definida como "zona critica" con un polinomio de tercer grado, las curvas de AVO generadas mediante la teoría de rayos se ajustan muy bien a los resultados exactos. El método toma en consideración implícitamente las variaciones de amplitud vs. offset, frecuencia, altura de la fuente y receptor por encima de las interfaces y de los parámetros físicos del modelo geológico