Morphometrics Allometry of the Endangered Tri-spine Horseshoe Crab, Tachypleus tridentatus Leach, 1819 (Xiphosura: Limulidae), and Fishers’ Perceptions from the Philippines

ASM Sc. J., 21(1), 2026

Published on March 27, 2026

https://doi.org/10.32802/asmscj.2026.0103

Author: Cristobal B. Cayetano, Sheryl M. Balbutan, Vivian U. Villanueva, John Carlo O. Macalagay, Lota A. Creencia

Abstract

The tri-spine horseshoe crab (Tachypleus tridentatus Leach, 1819) is an endangered species whose population status and human interactions remain poorly understood in the Philippines. This study aimed to integrate morphometric and allometric analyses of T. tridentatus with fishers’ perceptions to inform species conservation. A total of 118 adult specimens (63 males and 55 females) were measured for prosomal length (PL), opisthosomal length (OL), carapace length (CL), carapace width (CW), telson length (TEL), total length (TL), and body weight (BW). Statistical comparisons using analysis of variance (ANOVA) revealed significant sexual dimorphism, with females exhibiting larger body dimensions than males. Growth patterns differed by sex, with females showing isometric growth for PL and CW, while males exhibited negative allometry for BW. Principal Component Analysis (PCA) indicated strong correlations among morphometric parameters, with the first component explaining 44.7% (males) and 46.4% (females) of total variance. To assess human dimensions, 90 fishers were interviewed across different ethnic groups. Univariate analysis revealed that Visayan fishers were the most supportive of proactive conservation actions, while PCA showed education and age as major factors shaping perception. These findings highlight the ne ed for integrated biological and social approaches to strengthen conservation strategies for T. tridentatus in the Philippines.

Keywords: Bycatch Practices, local ecological knowledge, marine biology, marine conservation survey, Southeast Asia