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Sexual Differences in Appendages of a Fossorial Narrow-Mouth Frog, Kaloula rugifera (Anura, Microhylidae)
by
, ,
Wenyi Zhang
1,2,
Xianzheng Wang
3,
Jin Huang
3,
Xiuping Wang
1,2,
Bin Wang
2
,
Jianping Jiang
2
,
Bingjun Dong
1,* and
Meihua Zhang
2,* 1
College of Life Sciences, Shenyang Normal University, Shenyang 110034, China
2
Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610213, China
3
Shengda Hydropower Co., Ltd., Sinohydro Group Ltd., Leshan 614000, China
*
Authors to whom correspondence should be addressed.
Animals 2025, 15(17), 2566; https://doi.org/10.3390/ani15172566
Submission received: 20 July 2025
/
Revised: 20 August 2025
/
Accepted: 28 August 2025
/
Published: 31 August 2025
(This article belongs to the Section Herpetology)
Simple Summary
The appendicular skeletons are of great importance in vertebrate adaptation and evolution. However, the research on sexual differences mainly focuses on the external morphological traits and muscle mass of appendages. This study presents the first comprehensive and detailed investigations into the appendicular skeletons of a fossorial anuran species using 3D geometric morphometrics. The results show that there are obvious sexual shape differences in the coracoids, pubis-ischium regions, and humerus. These findings facilitate our understanding of sex-specific behaviors, reproductive strategies, and ecological adaptations.
Abstract
Skeletons serve as the body’s fundamental structure and perform multiple vital functions, and thus even subtle modifications can lead to functional changes. However, studies on sexual shape dimorphism in the appendicular skeletons of anurans remain scarce, especially for fossorial species. Herein, we investigated the sexual differences in the external morphology and internal skeletal shape of girdles and limbs of fossorial Kaloula rugifera during the breeding season. The results reveal the following: (1) Males exhibit significantly longer forelimbs and hindlimbs, suggesting advantages in male‒male competition and amplexus. (2) Males possess more curved and dilated coracoids and broader pubis-ischium regions, which may enhance forelimb contraction efficiency and hindlimb locomotor performance. (3) Males feature a more developed crista ventralis, likely enhancing forelimb flexion for tightly grasping females during mating. In contrast, females display a torsioned femur and robust hindlimb morphology, suggesting adaptations for digging and load-bearing. These findings provide insights into how anurans optimize reproductive fitness and ecological adaptations through morphological specialization. To our knowledge, this study presents the first examination of sexual shape dimorphism in anuran appendicular skeletons utilizing three-dimensional geometric morphometrics.
