Effect of Animal Stocking Density and Habitat Enrichment on Survival and Vitality of Wild Green Shore Crabs, Carcinus maenas, Maintained in the Laboratory

Abstract

The wide geographic distribution, large size and ease of capture has led to decapod crustaceans being used extensively in laboratory experiments. Recently in the United Kingdom decapod crustaceans were listed as sentient beings, resulting in their inclusion in animal care protocols. Ironically, little is known about how captive conditions affect the survival and general condition of wild decapod crustaceans. We used the green shore crab, Carcinus maenas, to investigate the effects of stocking density and shelter on survival and vitality indices during a 6 month period in the laboratory. Neither stocking density nor the presence of shelter affected survival. Stocking density also had no effect on the vitality indices (limb loss, claw strength, BRIX, righting time, leg flare and retraction). The presence of shelter did affect the number of limbs lost and the leg retraction response, but had no effect on the other vitality indices. All vitality indices changed, and mortality increased over time, independent of treatment: this became most apparent after 8 to 11 weeks storage in the laboratory. This decline in condition may have been due to repeated handling of the crabs, rather than the stocking conditions. In support of this, untracked, non-handled (control) individuals sustained a 4% mortality rate compared with 67% mortality in experimental crabs during the 6 month period. Although simple experimental monitoring of crabs with biweekly vitality tests only produced transient short-term stress events, the repeated handling over time apparently led to a cumulative stress and a deterioration in animal health. Bringing wild crustaceans into the laboratory and holding them, even with modest experimental manipulation, may result in high mortality rates. Researchers and animal care committees need to be aware that wild captive invertebrates will respond very differently to laboratory-bred vertebrates, and plan experiments accordingly.

Towards a ‘systems’ approach for viral challenge experiments in shrimp: Reporting guidelines for publication

“…These impacts may become additive with the experimental treatment or pathogen challenge, confounding experimental findings 151 . Stress due to handling or sampling of crustaceans can result in significant shifts in physiological, metabolic, and immune responses 144,149,150 and can yield significant differences in mortality during long‐term experiments involving repeated handling 152 . Despite the lack of well‐defined stress tolerance in shrimp related to handling and sampling, subtle changes in the captive environment or treatment of the shrimp, such as handling shrimp between tanks, may be sufficient to induce a stress response 144 or elevate disease expression 52 .…”

“…151 Stress due to handling or sampling of crustaceans can result in significant shifts in physiological, metabolic, and immune responses 144,149,150 and can yield significant differences in mortality during long-term experiments involving repeated handling. 152 Despite the lack of well-defined stress tolerance in shrimp related to handling and sampling, subtle changes in the captive environment or treatment of the shrimp, such as handling shrimp between tanks, may be sufficient to induce a stress response 144 or elevate disease expression. 52 In some studies, stress due to handling and sampling of experimental animals has been attributed to the triggering of acute disease states in P. monodon from chronic infection with gill-associated virus 52 and WSSV.…”