Morphological and structural analysis of Penaeus vannamei mandibles and an attempt at real-time cannibalism monitoring based on passive acoustics

Abstract

Cannibalism is a significant factor contributing to individual disability, mortality, and reduced shrimp production in commercial culture. The primary challenge of controlling cannibalism is the real-time and efficient monitoring of its occurrence. Here, we simultaneously captured high-speed video and feeding acoustics to match sound signals to feeding behaviors in Penaeus vannamei. Building upon a feeding acoustics signal acquisition system, passive acoustic monitoring (PAM) was utilized to detect differences in the acoustic signals produced when shrimps fed on broken feed, pellet feed, and meat fragments of P. vannamei (cannibalism). The morphological and structural characteristics of P. vannamei mandibles were analyzed using micro-CT, nano-indentation, and Raman testing. The main findings were: (1) Feeding on meat fragments resulted in a distinct high-frequency impulse train signal that may serve as an effective indicator for monitoring cannibalistic behavior during culture. (2) Shrimps produced similar and stable acoustic signals while consuming pellet feed, broken feed, or meat fragments; however, there were significant differences in the numbers of generated pulses (P < 0.05), with broken feed < pellet feed < meat fragments. (3) The mandibles consisted of thin anterior incisors and flat thick posterior molar processes, both with stratified structures; the mandibles exhibited greater elastic modulus and hardness values in their outer layers than inner layers, and calcium phosphate deposits were present in both incisors and molar processes. The collisions between incisors showed patterns that were highly synchronized with the acoustic feeding signals. This study has expanded research on passive acoustics monitoring in crustaceans and provided crucial data for the development of precious feeding technology in crustaceans.