Ontogenetic Changes During Development of the Whelk Neptunea cumingii Determined Using a Geometric Morphometric Method

Age determination in gastropods has been challenging due to the lack of reliable methods. In this study, we assessed the morphological changes of whelk ( Neptunea cumingii ) shells at 3, 6, 9, and 12 months of development using traditional measurements and geometric morphometry, and we cross-validated the results using a different sample of whelks. We detected distinct patterns in shell length distribution at each stage, with values of 8.16 ± 2.48 mm, 11.76 ± 2.63 mm, 21.43 ± 7.64 mm, and 32.08 ± 4.89 mm, respectively. Neptunea cumingii displayed specific morphological characteristics at each stage, primarily in the number of spiral layers and the shape of the shell apex. Individual development exhibited unique growth trajectories in shell size and shape, indicating allometric growth characteristics. One-way analysis of variance demonstrated significant differences among age groups. The growth curve based on shell length revealed an accelerating growth rate of Neptunea cumingii before 12 months of age. Our results illustrated the effectiveness of using a non-destructive approach for age identification of Neptunea cumingii in China and provided valuable insights for resource management and aquaculture practices.