黄海南部蟹类大眼幼体的COI条形码鉴定及形态检索表构建OA

Accurate species identification of brachyuran crab megalopa is essential for regional plankton surveys and resource monitoring.In this study,we established a reliable DNA barcoding and morphological identification system for megalopal specimens collected from the southern shelf of the Shandong Peninsula in the Yellow Sea during the spring and summer of 2021-2023.We selected 156 morphologically distinct individuals for mitochondrial cytochrome c oxidase subunit I(COI)barcoding,successfully obtaining 139 high-quality sequences(>600 bp,representing an 89.1%amplification success rate).Based on sequence comparisons with GenBank and phylogenetic analyses using Neighbor-Joining(NJ)and Maximum Likelihood(ML)methods,24 taxonomic units were identified.Among these,22 units were robustly identified to the species level,belonging to 12 families and 18 genera,while the remaining two were identified only to the family level.Varunidae(5 species),Portunidae(3 species),and Macrophthalmidae(3 species)accounted for the highest proportion of species richness.The NJ and ML trees displayed consistent topologies at species level,with all specimens forming stable monophyletic clades alongside their corresponding adult reference sequences,which strongly supported the reliability of the molecular identification.Building upon this molecular confirmation,we screened stable,externally observable diagnostic characters that can be identified without dissection,and systematically constructed the first dichotomous morphological key for brachyuran megalopa in this region.Key diagnostic features included the morphological specialization of the fifth pereiopod and its terminal setae,carapace outline,the development of frontal and dorsal spines,and the shapes of the abdominal lateral processes and telson.This study provides fundamental molecular and morphological tools for the accurate identification of brachyuran megalopa in the southern Yellow Sea.