Morphological and Genetic Differentiation of Loliolus (Nipponololigo) beka (Cephalopoda: Loliginidae) in Coastal China

Abstract

The population genetic structure of 211 samples of Loliolus (Nipponololigo) beka, which were selected from across seven geographic localities—in the Bohai Sea, the Yellow Sea and the East China Sea—were analyzed using mitochondrial COI and 16S rRNA gene markers. Phylogenetic trees and a haplotype network both showed that the L. (N.) beka localities were genetically distinct, forming two homogeneous lineages: Lineage A and Lineage B. The results of an AMOVA showed that the genetic variation in the L. (N.) beka populations was dominated by the genetic variation between the two lineages, and both the genetic distance and genetic differentiation indices indicated that the genetic differentiation between the two lineages of L. (N.) beka in Chinese waters had reached the level of species divergence. To further confirm the differences between the two lineages shown in the molecular results, we performed a detailed analysis based on morphometric observations and a multivariate statistical analysis to compare the morphology characteristics of Lineage A and Lineage B. The results showed that there were significant differences (p < 0.05) in the ventral mantle length (VML); the mantle width index (MWI); the fin width index (FWI); the head length index (HLI); the left Arm IV length index (LALI4), the right Arm III length index (RALI3), the right Arm IV length index (RALI4), and the hectocotylized proportion of the left Arm IV length (HcL%) between the two lineages. The differences between the two lineages were also supported by the analysis results for the number of sucker ring teeth. Accordingly, the results of the morphological analysis further confirmed the molecular analysis and provided additional evidence for the presence of the cryptic species of L. (N.) beka in the coastal areas of China.