Morphological differences between the Patagonian squid Loligo gahi populations from the Pacific and Atlantic oceans

A total of 243 specimens of the loliginid squid Loligo gahi was examined.The samples comprised 82 specimens (34 males and 48 females) from Peruvian waters and 94 (78 males and 16 females) from Southern Chilean waters in the Pacific Ocean, and 58 (35 males and 23 females) from waters around the Falkland Islands in the Atlantic Ocean.Size of the specimens ranged from 83 to 201 mm dorsal mantle length (ML).After defrosting at room temperature, sex, maturity stage, 23 morphometric and five meristic characters from each individual were recorded.Measurements and counts were obtained by the same sampler and under similar conditions.In order to test potential differences between these three populations a Discriminant Analysis was undertaken using morphometric characters.Meristic characters were analyzed using the U Mann-Whitney nonparametric test.Males and females from Falkland Islands population differed in all morphometric characters examined showing higher sexual dimorphism than those from Peruvian and Southern Chilean waters.Significant differences between sexes also occurred in Peruvian population attached to gladius width, gladius rachis length and lower hood length.However, no significant differences between sexes were found in the Chilean population.Significant differences between the three populations, comparing males and females separately, were found.All morphometric characters, except fin length and gladius width, and the number of teeth in the largest sucker of the third arm and the number of gill lamellae accounted for these differences.Hard structures (gladius, beaks and statoliths) proved to be more accurate than soft body parts to separate between populations.Systematics and evolutive implications of the differences found are discussed.