Synchronization of daily rhythms of locomotor activity and plasma glucose, cortisol and thyroid hormones to feeding in Gilthead seabream (Sparus aurata) under a light–dark cycle

The objective of this study was to determine whether the previously observed effects of photoperiod on body weight in Siberian hamsters were due to changes in the daily patterns of locomotor activity, energy expenditure, and/or feeding behavior. Adult males were monitored through a seasonal cycle using an automated comprehensive laboratory animal monitoring system (CLAMS). Exposure to a short-day photoperiod (SD; 8:16-h light-dark cycle) induced a significant decline in body weight, and oxygen consumption (V̇o2), carbon dioxide production (V̇co2), and heat production all decreased reaching a nadir by 16 wk of SD. Clear daily rhythms in locomotor activity, V̇o2, and V̇co2 were observed at the start of the study, but these all progressively diminished after prolonged exposure to SD. Rhythms in feeding behavior were also detected initially, reflecting an increase in meal frequency but not duration during the dark phase. This rhythm was lost by 8 wk of SD exposure such that food intake was relatively constant across dark and light phases. After 18 wk in SD, hamsters were transferred to a long-day photoperiod (LD; 16:8-h light-dark cycle), which induced significant weight gain. This was associated with an increase in energy intake within 2 wk, while V̇o2, V̇co2, and heat production all increased back to basal levels. Rhythmicity was reestablished within 4 wk of reexposure to long days. These results demonstrate that photoperiod impacts on body weight via complex changes in locomotor activity, energy expenditure, and feeding behavior, with a striking loss of daily rhythms during SD exposure.

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Effect of Light–Dark Cycle on Skin Mucosal Immune Activities of Gilthead Seabream (Sparus aurata) and European Sea Bass (Dicentrarchus labrax)

Fishes ◽

10.3390/fishes5010010 ◽

2020 ◽

Vol 5 (1) ◽

pp. 10

Author(s):

Diana Ceballos-Francisco ◽

Alberto Cuesta ◽

María Ángeles Esteban

Keyword(s):

Bactericidal Activity ◽

Sparus Aurata ◽

Dicentrarchus Labrax ◽

Maximum Level ◽

Sea Bass ◽

Immunoglobulin M ◽

Gilthead Seabream ◽

Dark Cycle ◽

European Sea Bass ◽

Skin Mucus

Changes in different immune activities in the skin mucus of gilthead seabream (Sparus aurata L.) and European sea bass (Dicentrarchus labrax L.) specimens exposed to a constant light–dark photoperiod (12 h L:12 h D) were studied. Samples were collected at 08:00 (light on), 14:00, 20:00 (light off), 02:00, and again at 08:00 to determine immunoglobulin M (IgM) levels, several enzymes related to the immune system, and bactericidal activity. IgM levels were higher during the day in seabream and reached a minimum value at 20:00, but it was hardly affected in sea bass. No significant variations were recorded in the levels of protease and antiprotease. Peroxidase reached its maximum level in seabream at 02:00, the same time that it reached its minimum level in sea bass. Lysozyme showed little variation in seabream, but it was significantly lower at 14:00 than during the rest of the cycle in sea bass. Finally, different interspecific variations on bactericidal activity against Vibrio harveyi were recorded. The findings demonstrate that the immune parameters present in skin mucus of these important fish species are affected by the light–dark cycle and that there are substantial interspecies differences.

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