In humans, a person’s chronotype depends on environmental cues and on individual characteristics, with late chronotypes prevailing in youth. Social jetlag (SJL), the misalignment between an individual׳s biological clock and social time, is higher in late chronotypes. Strong SJL is expected in Uruguayan university students with morning class schedules and very late entertainment activities. Sleep disorders have been reported in Antarctic inhabitants, that might be a response to the extreme environment or to the strictness of Antarctic life. We evaluated, for the first time in Uruguay, the chronotypes and SJL of 17 undergraduate students of the First Uruguayan Summer School on Antarctic Research, using Munich Chronotype Questionnaire (MCTQ) and sleep logs (SL) recorded during 3 phases: pre-Antarctic, Antarctic, and post-Antarctic. The midsleep point of free days corrected for sleep debt on work days (MSFsc,) was used as proxy of individuals’ chronotype, whose values (around 6 a.m.) are the latest ever reported. We found a SJL of around 2 h in average, which correlated positively with MSFsc, confirming that late chronotypes generate a higher sleep debt during weekdays. Midsleep point and sleep duration significantly decreased between pre-Antarctic and Antarctic phases, and sleep duration rebounded to significant higher values in the post-Antarctic phase. Waking time, but not sleep onset time, significantly varied among phases. This evidence suggests that sleep schedules more likely depended on the social agenda than on the environmental light–dark shifts. High motivation of students towards Antarctic activities likely induced a subjective perception of welfare non-dependent on sleep duration.

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This study aims to advance knowledge on the effects of bottom trawling in the shelled megabenthic gastropods from Uruguayan continental shelf. Composition of by-catch, species distribution, direct shell damage and mortality, and frequency of repaired shell damage were analysed from data collected on board of the research vessel 'Aldebaran'. A total of 12 megabenthic gastropod species was registered from 35 stations surveyed, either as live specimens or empty shells. From these, the shelled gastropods Adelomelon beckii, Adelomelon ancilla, Odontocymbiola magellanica, Fusitriton magellanicus and Zidona dufresnei dominated numerically the by-catch. We observed a spatial segregation of the gastropod assemblages along a bathymetric and latitudinal gradient, with O. magellanica, F. magellanicus and A. ancilla occurring at the southern portion of the study area, whereas A. beckii and Z. dufresnei were restricted to the northern and shallower areas respectively. Direct mortality was barely observed, but shells of A. ancilla, O. magellanica and Z. dufresnei were frequently damaged during the fishing operation and capture handling. Accordingly, we found a high positive correlation between the observed frequency of recent shell damage and the presence of scars, suggestive but not conclusive evidence on the relationship between incidence of repaired shell damage and trawling disturbance.

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