Crayfish chimneys function as burrow-ventilation structures

Most crayfish species are capable of constructing underground burrows. Burrow construction provides crayfishes the potential to actively engineer microhabitat and optimize local environmental conditions. Little attention, however, has been paid to quantifying the environmental outcomes of burrow morphology. We examined the potential of chimneys to ventilate burrows via wind-assisted buoyancy ventilation. We first conducted proof-of-concept trials in the field using smoke tracers. We then used a wind tunnel to quantify effects of wind velocity, chimney height, burrow orientation, and tunnel angle on model burrow ventilation rates. We developed a predictive model to predict burrow airflow based on endogenous and exogenous factors, and proofed the model with field measurements from a natural burrow. Proof-of-concept trials showed that during breezy conditions (i.e., 8–16 km−h wind gusts), smoke generated near a natural burrow was rapidly drawn into the non-chimney entry, through the burrow, and out the chimney. Wind-tunnel trials revealed significant effects of chimney height and wind velocity on burrow airflow, but no significant effects of burrow orientation towards the prevailing wind direction, nor of the angle of the burrow beneath the chimney. A model developed from wind-tunnel trials predicted air velocities exiting a theoretical chimney that were within 85% of observed velocities exiting natural chimney-burrow complexes. We conclude that crayfish chimneys can serve as passive ventilation systems for crayfish burrows, with chimney height and wind velocity exerting particularly strong effects on airflow. Costs and benefits associated with chimney construction and ventilation are still speculative but should comprise a productive line of research for future studies focused on burrowing crayfish ecology and conservation.

Erratum to Burrow morphology of three species of fiddler crab (Uca) along the coast of Pakistan

This is a Erratum without an abstract.

Burrow Morphology of Genus Ocypode (Brachyura: Decapoda: Ocypodidae) Along the Coast of Karachi

Burrow morphology of Ocypode rotundata and O. ceratophthalma was studied on the sandy beach of Karachi with the aim of identifying their significance and relationship to the shore environment. The small sized burrows found at low tide level and large sized burrows found at the high tide level up to dry or splash zone. The burrow count during the winter season was lower as compared summer season. Only single burrow opening was observed in O. rotundata and O. ceratophthalma oriented towards the sea. The burrow depth was between 460 to 1300 mm and 490 to 760 mm in O. rotundata and O. ceratophthalma respectively. Strong correlation (r2=81.2 and 89.2%) was observed between carapace length and burrow diameter of the O. rotundata and O. ceratophthalma respectively. For the grain size analysis, maximum amount of grain resulted with fine sand 57.04% (2.5Φ, 3.0Φ). For anthropogenic analysis, data showed no any significant difference (P value =0.128 and 0.671) from two sites but number of burrow counts decreases as the number of human activity increasing day by day at the selected beaches.