Morphological comparison between Doryteuthis pleii and D. sanpaulensis (Cephalopoda, Myopsida, Loliginidae) from Brazil

Abstract

The distinction of squid species in the genus Doryteuthis is not easy due to their morphological similarity, lack of conspicuous specific characters, and overlap geographical occurrence. This difficulty has leading to an almost exclusive molecular approach, and a premature neglect of the morpho-anatomy. To emphasize that the squid phenotypic features can be useful to identify, as well as to perform any comparative analyses (such as taxonomy and phylogeny), two close species were selected as outset. Doryteuthis pleii and D. sanpaulensis are common sympatric squids in Brazilian waters, commonly used in fisheries, not so difficult to distinguish by external features of the adult specimens. The samples were analyzed from biometric data to dissections, and the found most expressive characters to distinguish them are the mantle-fin ratio; morphology of the tentacle club, its ratio compared to the mantle length; hectocotylus morphology and nidamental gland morphology.