On the surface or down below: Field observations reveal a high degree of surface activity in a burrowing crayfish, the Little Brown Mudbug (Lacunicambarus thomai)

Abstract

Opposed to most crayfish species that inhabit permanent bodies of water, a unique burrowing lifestyle has evolved several times throughout the crayfish phylogeny. Burrowing crayfish are considered to be semi-terrestrial, as they burrow to the groundwater—creating complex burrows that occasionally reach 3 m in depth. Because burrowing crayfishes spend most of their lives within their burrow, we lack a basic understanding of the behavior and natural history of these species. However, recent work suggests that burrowing crayfishes may exhibit a higher level of surface activity than previously thought. In the current study, we conducted a behavioral study of the Little Brown Mudbug, Lacunicambarus thomai using video surveillance to determine their degree of surface activity and behavioral patterns. Throughout 664 hrs of footage, we observed a surprisingly high amount of activity at the surface of their burrows—both during the day and night. The percentage of time that individual crayfish was observed at the surface ranged from 21% to 69% per individual, with an average of 42.48% of the time spent at the surface across all crayfish. Additionally, we created an ethogram based on six observed behaviors and found that each behavior had a strong circadian effect. For example, we only observed a single observation of foraging on vegetation during the day, whereas 270 observations of this behavior were documented at night. Overall, our results suggest that burrowing crayfishes may exhibit higher levels of surface activity than previously thought. To increase our understanding of burrowing crayfish behaviors ecology, we encourage the continued use of video-recorded observations in the field and the laboratory.

Living on the edge: Crayfish as drivers to anoxification of their own shelter microenvironment

“…Primary burrowing crayfish spend most of their life in elaborate burrows disconnected from running, oxygenated waters, from which they emerge for mating and food foraging [ 17 , 57 ]. Even though these burrows contain an air/water interface, conditions inside the flooded portions of these burrows are harsh: the dissolved oxygen levels might reach as low as 0.7 mg/L and a pH below 4.5 [ 51 ].…”

Correlated evolution of conspicuous colouration and burrowing in crayfish

“…We found that conspicuous colouration in crayfish is evolutionarily correlated to a semi-terrestrial burrowing strategy. Therefore, the typical association between light environment and adaptive colouration lacks support based on the reclusive lifestyle of semi-terrestrial burrowing crayfishes because semi-terrestrial burrowing species are nocturnal and rarely interact with each other on the surface [83]. Thus, two major questions remain unresolved: why conspicuous colours would be more common in species that rarely leave their burrow and are nocturnal, and are there costs and benefits to these conspicuous colours?…”

Correlated evolution of conspicuous coloration and burrowing in crayfish

“…We found that conspicuous coloration in crayfish is evolutionary correlated to a semi-terrestrial burrowing strategy. Therefore, the typical association between light environment and adaptive coloration lacks support based on semi-terrestrial burrowing crayfish's reclusive lifestyle; because semi-terrestrial burrowing species are nocturnal and based on current knowledge, rarely interact with each other on the surface (Diehl et al, 2022). Thus, major questions remain unresolved, for example: why would conspicuous colors be more common in species that rarely leave their burrow and are nocturnal?.…”