The whelk Neptunea cumingii (Mollusca, Gastropoda, Caenogastropoda, Neogastropoda, Buccinidae)1 inhabits the Yellow Sea and northern Bohai Sea in China and the Sea of Japan2. This carnivorous gastropod undergoes creeping metamorphosis and primarily preys on bivalves, particularly the horse mussel Modiolus3.
Hao et al., (2020) divided the embryonic development process of N. cumingii into five stages based on oocyst and egg characteristics, highlighting its direct development within the oocyst. Nutrients in the oocyst provide nutritional support for developing embryos4. N. cumingii boasts high protein content, low fat content, and significant amino acid and fatty acid compositions in its muscle tissue5,6.
To date, studies of N. cumingii in China have been focused mainly on its biology, including
resource distribution and the effects of environmental factors on larvae7–11, the reproductive system, and genetic analysis12,13. Additionally, researchers have explored various methods for determining age of gastropods, such as statolith analysis14, oxygen isotope dating15, analysis of the operculum16, shell lip measurement17, shell composition18, and shell size frequency distribution19.
Among the currently available age determination methods, the use of statoliths offers high accuracy due to their location within the body20, which reduces environmental influences. However, statoliths are small calcium carbonate structures (300 µ), and analysis requires a microscope and a high level of expertise21. Alternatively, oxygen isotope dating provides precise age determination, but it requires sampling from numerous points, making the process costly22. Additionally, all of the aforementioned methods necessitate shell destruction to obtain data.
In contrast, using shell size frequency distribution for age measurement allows direct observation and measurement of sample characteristics without requiring special treatment, thereby avoiding damage to the sample. Consequently, it is more suitable for age assessment of protected species. However, while many mollusks have shell growth lines that can be used for age determination, production of these lines is susceptible to environmental influences, and accurate age measurement often requires prolonged observation23.
Geometric morphometric techniques have emerged as powerful tools for studying morphological differences24 thereby aiding in population identification and resource management. In this study, we applied geometric morphometric methods to analyze the morphological characteristics of different developmental stages (from larvae to adults) of N. cumingii, identify differences among individuals within each developmental stage, provide valuable insights into the ontogeny of this species, and facilitate age identification25,26.