Digging in Deep: Size and Site-Specific Variation in Burrow Morphology and Behaviour of the Mud Shrimp, Trypaea australiensis Dana, 1852

Abstract

The importance of habitats, particularly burrows, for intertidal crustaceans is multifaceted. These habitats provide crucial shelter, food sources, and reproductive advantages that are essential for enhancing survival and fitness. However, maintaining these habitats can be costly, influencing whether individuals adapt to or relocate under changing environments. Burrowing mud shrimp present challenges when it comes to studying their behaviours and burrow morphology, owing to their cryptic lifestyle. In this study, we investigated burrow morphology and burrowing behaviour in the mud shrimp, Trypaea australiensis, to better understand the importance of burrows for these organisms. Firstly, we quantified burrow morphology in situ using resin casts and 3D imagery at two locations. Secondly, we examined shrimp burrowing behaviour in custom-made aquarium cuvettes in the laboratory. Resin casts showed that burrows at Shoalhaven Heads exhibited larger burrows with greater variation in the length of burrow measurements compared to burrows at Port Hacking. Laboratory observations of burrowing behaviour demonstrated that shrimp dedicate a large proportion of time to maintaining the structure of their burrows, irrespective of time of day or shrimp sex. Differences were observed between size categories, where smaller individuals were observed sitting significantly more and ventilating significantly less compared to larger individuals. Overall, our study provides a quantitative insight into the importance of burrow habitats and provides the first insights into burrowing behaviour and burrow structure for this endemic ecosystem engineer.