Background matching in the brown shrimp Crangon crangon : adaptive camouflage and behavioural-plasticity

A combination of burrowing behaviour and very efficient background matching makes the brown shrimp Crangon crangon almost invisible to potential predators and preys. This raises questions on how shrimp succeed in concealing themselves in the heterogeneous and dynamic estuarine habitats they inhabit and what type of environmental variables and behavioural factors affect their colour change abilities. Using a series of behavioural experiments, we show that the brown shrimp is capable of repeated fast colour adaptations (20% change in dark pigment cover within one hour) and that its background matching ability is mainly influenced by illumination and sediment colour. Novel insights are provided on the occurrence of non-adaptive (possibly stress) responses to background changes after long-time exposure to a constant background colour or during unfavourable conditions for burying. Shrimp showed high levels of intra- and inter-individual variation, demonstrating a complex balance between behavioural-plasticity and environmental adaptation. As such, the study of crustacean colour changes represents a valuable opportunity to investigate colour adaptations in dynamic habitats and can help us to identify the mayor environmental and behavioural factors influencing the evolution of animal background matching

EFFECT OF ARTERIALLY INFUSED CATECHOLAMINES AND INSULIN ON PLASMA-GLUCOSE AND FREE FATTY-ACIDS IN CARP

Common carp (Cyprinus carpio L.), kept at 20 degrees C, were fitted with an indwelling PE-50 cannula in the dorsal aorta. Hormones dissolved in Ringer saline were arterially infused at a rate of 1 mu g . kg(-1). min(-1) for epinephrine (Epi), 2 mu g . kg(-1). min(-1) for norepinephrine (NE), and 1.33 mu g . kg(-1). min(-1) for insulin. Infusion of bovine insulin in carp resulted in a long lasting (24 h) decrease of plasma free fatty acids (FFA; -0.41 +/- 0.06 mM) and glucose levels (-3.14 +/- 0.25 mM) compared with preinfusion levels at t = 0. Both Epi and NE induced a marked hyperglycemia although Epi was more potent (+8.2 +/- 0.9 and +6.9 +/- 0.8 mM, respectively). Plasma FFA levels increased by 0.25 +/- 0.03 mM compared with preinfusion levels on Epi infusion. In contrast, during NE infusion, plasma FFA levels decreased significantly by -0.21 +/- 0.03 mM. Plasma insulin titers did not significantly change during infusion of NE or Epi. It is concluded that the ratio of NE to Epi is the major factor that determines the effect of catecholamines on plasma FFA levels in carp. These results may explain species-dependent different effects of hypoxia on FFA metabolism in fish