According to foreign media reports, scientists have found the first nocturnal lichfish species in Lake Malawi in Africa, which provides clues to the evolution of sleep. Due to foraging strategies, social behaviors, and the desire to avoid predators, animals' sleep and activity patterns are very diverse. These freshwater fish are home to more than 3,000 species of cichlids, and they are probably one of the most abundant species of fish in the world.
Spanning 350 miles across eastern Africa, Lake Malawi is home to more than 500 species of cichlids. They evolved from a number of species that could have entered the lake 3 million years ago and now exhibit very different behaviors and inhabit well-defined ecological niches throughout the lake.
So how did so many different species coexist in this huge tropical lake? Many factors are taken into account – including the diversity of ecological resources, predators and the ability of species of the cichlid family to evolve highly specific courtship and feeding behaviors. Despite the huge differences between day and night, the way the fish uses different times of the day has not been systematically studied.
The cichlids of Lake Malawi are thought to be very active during the day, most likely to avoid predation, although this has never been scientifically studied. Researchers at Florida Atlantic University, in collaboration with the University of Massachusetts Amherst, examined changes in the circadian rhythm of the fish's activity and the duration of the rest-wake cycle, and they first discovered Tropheops, a separate nocturnal species of Malawian lily.
The study, published in the Journal of Experimental Biology, shows that Tropheops' nocturnal behavior was sustained when sheltered (but not in persistent darkness). This suggests that it is due to an acute response to light rather than an intrinsic circadian rhythm. In addition, after revising the evolutionary history, the researchers found that nocturnal activity was associated with an increase in eye size, suggesting a link between visual processing and nocturnal activity.
The activity levels and activity patterns of the Lake Marawi lids studied in the study showed continuous changes, as well as significant differences in the activities of closely related species. The results suggest that active circadian regulation may provide a mechanism for niche development in African cilicata. The researchers also identified the diversity of motor behaviors, and at the same time, the results provide a system for studying molecular and neural underlying changes in nocturnal activity.
To study the moderating effects of niches and evolutionary history on motor activity and rest, the researchers measured the motility of 11 species of fish in Lake Malawi. They made choices in terms of habitat diversity, behavioural diversity and lineage representation diversity. Prior to this study, the circadian rhythm of activity and rest in a family living in a common environment was unknown.
"Given the impressive diversity of Marawi lidds in a range of anatomical and behavioural characteristics, we predict that they may also exhibit high-intensity and sustained variations in rest-activity patterns. We believe these differences also extend to sleep and foraging behaviors, which provide a system that can be used to study complex traits that are critical for survival and development," said Lex Keene, lead author of the study, "And our finding is that the timing and duration of rest and activity vary greatly between Populations of Lake Marawi, which raises the possibility that these differences play a key role in rapid speciation in this system." ”