Sepiolid paralarval diversity in a regional upwelling area of the NE Atlantic

Sepiolid paralarvae are poorly studied, at least in part, because of the difficulty of accurate identification using morphological analysis. To unravel the biodiversity of sepiolid paralarvae collected in the Ría de Vigo during the upwelling season (2012–2014), and to overcome the difficulties of traditional identification, sepiolid paralarvae were identified by amplifying the barcoding gene cytochrome c oxidase subunit I (COI). In addition, morphometric analysis (Generalised Lineal Models, GLM and Discriminant Analysis, DA) was used to identify morphometric patterns useful for paralarval species identification. Genetic barcoding successfully identified 34 Sepiola pfefferi, 31 Rondeletiola minor, 30 Sepiola tridens, 4 Sepiola atlantica, 2 Sepietta neglecta and 1 Sepiola ligulata. COI analysis also allowed us to infer that the paralarvae of the three most abundant species belonged to the same populations independently of the year sampled. GLM suggested that total length (statistically different among the three species) and tentacle length (statistically larger in S. pfefferi from the other two species) were good variables to distinguish among species. DA succeeded in separating S. pfefferi from S. tridens, but R. minor overlapped along the first axes with both species, decreasing the accurate classification rate to 67%.