Locomotor activity rhythm in the Japanese eel Anguilla japonica elvers

Under artificial LD cycles （6, 12, 18 L）, the elvers of Japanese eel, Anguilla japonica, showed a 24 h cycle of locomotor activity rhythm being most active at light transitions ： the eels＇ activity rose to a primary peak after lights-off, followed by a quiescent period during which they buried into the shelters or lying motionlessly on sand for most of the time, and then reached a secondary peak before lights-on. Elvers could resynchronize their activity rhythm with a new photo cycle within 4 d. Moreover, their activity level at dark phase significantly increased as the light period was prolonged ： higher activity levels during shorter dark period. However, the elvers did not display clearly the existence of a circadian rhythm under constant light or dark conditions. The timing of daily activity rhythm evidenced in the Japanese eels may occur through the action of the LD cycles with a weak participation of an endogenous circadian system. In all the LD cycles, over 99% of the activity occurred in the dark phase, indicating that the eels were always nocturnally active no matter what time of day it might be. Under 12 L conditions, the eels＇ activity level and the time outside sand were significantly elevated both at light and dark phases as temperature increased from 10 - 15 to 20 - 25 ℃. The activity rhythm pattern （ i. e. , two peaks occurring around light transitions） did not apparently change among temperatures. However, in contrast with the primary activity peaks immediately after lights-off at 20 and 25 ℃, the timing of the primary peaks at 10 and 15 ℃ showed a latency of a few hours following lights-off, indicating the inhibiting effect of low temperature on the eels＇ activity.

Could Ambient Vibrations Be Related to <i>Cerithidea decollate</i>Migration?

Physiological and behavioral systems exist to reduce the stress that the intertidal fauna may face during the unsuitable tidal phase. Cerithidea decollata is a common western Indian Ocean mangrove gastropod. It feeds on the ground at low tide, and climbs the trees two-three hours before the water arrival to avoid submersion. Moreover, it regularly settles on the trunk roughly 40 centimeters above the level that the water will reach, in spite of the irregular East African tidal pattern. Migration usually takes place about twice a day unless at Neap Tide, when snails may remain on the dry ground. Biological clock cannot account for water level foreseeing while direct visual cues or chemical information from the water itself or from previous migrations have already been experimentally discarded. Indirect cues could be hypothesize related to the effect of the oceanic wave reaching the coast and the barrier reef (seismic noise), or alternatively related to changes in ground resistivity (self potential) caused by the sea water moving close. To verify these hypotheses a seismic noise and self potential survey was carried out at Mida Creek (Kenya). This paper presents the first results of the seismic noise measurements. A significant correlation between the time evolution (mean value) of the low frequency seismic signal, tides, and snails movements has been identified.

Circadian clock in plants:Linking timing to fitness

Endogenous circadian clock integrates cyclic signals of environment and daily and seasonal behaviors of organisms to achieve spatiotemporal synchronization,which greatly improves genetic diversity and fitness of species.This review addresses recent studies on the plant circadian system in the field of chronobiology,covering topics on molecular mechanisms,internal and external Zeitgebers,and hierarchical regulation of physiological outputs.The architecture of the circadian clock involves the autoregulatory transcriptional feedback loops,post-translational modifications of core oscillators,and epigenetic modifications of DNA and histones.Here,light,temperature,humidity,and internal elemental nutrients are summarized to illustrate the sensitivity of the circadian clock to timing cues.In addition,the circadian clock runs cell-autonomously,driving independent circadian rhythms in various tissues.The core oscillators responds to each other with biochemical factors including calcium ions,mineral nutrients,photosynthetic products,and hormones.We describe clock components sequentially expressed during a 24-h day that regulate rhythmic growth,aging,immune response,and resistance to biotic and abiotic stresses.Notably,more data have suggested the circadian clock links chrono-culture to key agronomic traits in crops.