Cycles of activity, temporal spacing and sleep in Octopus vulgaris and Octopus macropus / eingereicht von Daniela Meisel

• VerfasserIn: Meisel, Daniela
• Place / Publishing House: 2006
• Year of Publication: 2006
• Language: English
• Classification: 42.66 - Ethologie
• Physical Description: 85 Bl.; Ill., graph. Darst.

ger: Timekeeping is crucial for the survival and fitness of any animal but might be of special importance for the short-lived octopuses.<br />The present study investigated their timekeeping through temporal organization of activity, predator avoidance and sleep in the laboratory. Octopus vulgaris and Octopus macropus that share the same habitat in the wild were exposed to a 12: 12 light-dark cycle and held under constant dim light for seven days. O. macropus showed nocturnal and light cued activity, while individual variation of activity was found in O.<br />vulgaris. Based on casual observations, O. vulgaris started out nocturnal but had switched to diurnal at the beginning of the experiment. The different activity patterns of the two species might reflect their lifestyles, the latter being more generalist.<br />In the second experiment O. vulgaris ability to actually switch activity phase was confirmed. Octopuses were each held for one week with a nocturnal and a diurnal predatory fish with visual and chemical but no physical contact in between periods of isolation. The octopuses increased the amount of their activity in the presence of the predators, but while they negatively correlated active periods with the triggerfish, they did not do so with the moray eel, and attempted attacks by both animals declined with the triggerfish. O. vulgaris might use temporal spacing of activity with facultative predators to reduce predation pressure.<br />Finally, it could be shown that O. vulgaris shows behavioural sleep.<br />Octopuses chose a preferred sleeping place, actively built a sleeping site and assumed a typical sleeping posture with immobility. Sleep was under circadian control and sleeping animals showed an elevated arousal threshold and state reversibility with intense stimulation. Rest deprivation during nighttime led to a rest rebound, while daytime rest deprivation reduced sleep time. Octopuses showed a typical skin pattern during the period of immobility, which was not matched to their environment. Sleep may be a common state in many phyla, perhaps expressed differently in different groups. The present studies provided insight in the temporal organization of activity in octopuses by testing them under controlled conditions. A further step in better understanding their life history has been done, because timekeeping must be an important aspect of the lives of these adaptable, soft-bodied and short-lived inhabitants of all the worlds oceans.