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

Understanding the aging process of gastropods offers valuable insights into comprehending their life cycles and reproductive strategies. In this research, morphological changes of known-aged whelks (Neptunea cumingii) at 3 (n = 43), 6 (n = 46), 9 (n = 22), and 12 (n = 24) mo were analyzed using morphological measurements and geometric morphometry methods. The results were also cross-validated with randomly selected gastropods. Distinct patterns in shell length distribution were detected at each developmental stage, with measurements of 8.16 ± 2.48, 11.76 ± 2.63, 21.43 ± 7.64, and 32.08 ± 4.89 mm, respectively. The Neptune whelk Neptunea cumingii exhibited specific morphological characteristics at each stage, primarily in the number of spiral whorls and the shape of the shell apex. The individual development trajectories displayed unique growth patterns in shell size and shape, indicating allometric growth. Analysis of variance showed that there was a significant difference in the shell size of Neptunea cumingii at different months of age (P < 0.01). The growth curve, based on shell length, confirmed an accelerating growth rate of Neptunea cumingii before 12 mo of age. The results indicate that the use of geometric morphometry can enable nondestructive age assessment of Neptunea cumingii in Dalian, providing valuable insights for resource management and aquaculture. The preliminary findings of this study will be extended to age determination within wild populations, geographical distinct groups, and populations subject to various aquaculture practices in the future.