Patterns of Sexual and Spatial Morphometric Variation in Parasesarma eumolpe (De Man, 1895): Insights from A Tropical Delta Environment
DOI:
https://doi.org/10.48048/tis.2026.12381Keywords:
Carapace, Claw, Gamma–log regression, Morphometrics, Parasesarma eumolpeAbstract
This is the first fundamental morphometric study of Parasesarma eumolpe conducted in Vietnam. The study aimed to determine and compare key morphometric characteristics of P. eumolpe collected from two mangrove forest sites in the Mekong Delta, including Can Tho and Ca Mau. A total of 203 specimens (115 from Can Tho and 88 from Ca Mau) were collected monthly from August to October 2025. Six morphometric parameters, carapace width (CWLR, CWRL), smallest and biggest manus width (MW2, MW3), pollex width (PW5), and dactyl width (DW7), were analyzed using generalized linear mixed models (GLMM) and Gamma–log regression. The results revealed significant differences in morphometric traits by sex and site (p < 0.05), with males exhibiting larger carapace and claw dimensions than females. Geographic variation was also evident: CW and MW2 were higher in Can Tho, whereas MW3 and PW5 were greater in Ca Mau. Regression analyses showed strong positive correlations between carapace width and claw dimensions (R² > 0.60), particularly between MW2, MW3, PW5, and DW7, reflecting the integrated development of claw structures. The The Principal Component Analysis further supported these patterns by illustrating clear clustering trends by sex and sampling site. These findings provide fundamental morphometric data for taxonomy, sexual dimorphism, and ecological adaptation studies of P. eumolpe and contribute to a better understanding of morphological variation among sesarmid crabs inhabiting the Mekong Delta mangrove ecosystem.
HIGHLIGHTS
- Morphometric variation of Parasesarma eumolpe was examined across two mangrove sites within a tropical delta environment.
- Generalized Linear Mixed Models (GLMM) and Gamma–log regression were applied to assess the effects of sex and locality on six morphometric traits.
- Male crabs exhibited significantly larger carapace and claw dimensions than females, indicating evident sexual dimorphism.
- Morphometric differences between sites suggest local ecological influences on body and claw development.
- Strong correlations (R² > 0.60) among claw dimensions reflect coordinated allometric growth relevant to taxonomy and functional morphology.
GRAPHICAL ABSTRACT
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