Many marine invertebrates present complex life cycles comprising several developmental stages which clearly differ morphologically from those finally reached by adults. This is the case of the brachyuran crustacean decapods. Most brachyuran crabs, with the exception of a few species that show direct development, pass through a planktonic larval period with two phases, zoea and megalopa, which are very different from each other and from the adult form. This represents an important drawback in the identification of the brachyuran larvae collected from plankton, which is further complicated by the fact that reliable larval descriptions are only available for a small amount of known brachyuran species, most of them based in laboratory-reared specimens. This gap in the knowledge of brachyuran larval morphology is in turn responsible of an important amount of problems encountered by researchers when studying population dynamics, recruitment events, larval dispersal and colonization, functioning of planktonic trophic webs (inter-specific interactions) and, overall, any kind of biodiversity research. The main objective of the present study is the optimization of the joint applicability of molecular techniques, DNA barcode, particularly the analysis of mitochondrial DNA sequences (16S and Cox1), and morphological analysis, in the accurate identification of Iberian brachyuran megalopae obtained directly from planktonic samples. The first step needed to achieve this objective, is the setting-up of a complete database containing the sequences of the above-mentioned markers, for the 140 bachyuran species recorded in the Iberian Peninsula. Remarks We have presently obtained the DNA barcode for more than 80% of the Iberian crabs, and identified 26 different planktonic megalopae after examination of more than 800 specimens. Sixteen of them are megalopae of species already described from laboratory cultures that have been revised in order to look for differences with respect to wild specimens. Moreover, some of them also need to be re-described, considering that previous published descriptions were inaccurate or incomplete (i.e. Rhithropanopeus harrisii, Dyspanopeus sayi, Percnon gibbesi). Nine megalopae unknown until now (Sirpus zariquieyi, Parthenope angulifrons, Polybius zariquieyi, Ergasticus clouei, Afropinnotheres monodi, between others) will be described in detail. These new descriptions, together with the formerly existing ones, will allow the creation of an illustrated identification key, as a final objective, addressed to researchers and technicians, which is intended to assist in the correct identification of this important group of planktonic organisms

This study was funded by the Spanish “Ministerio de Ciencia e Innovación, Plan Nacional I+D” and FEDER through project MEGALOPADN (CGL2009–11225)

The Crustacean Society Summer Meeting (TCSSM) - 10th Colloquium Crustacea Decapoda Mediterranea (CCDM), 3-7 June 2012, Athens, Greece

Peer Reviewed