Fish they have chronotypes like humans, but what are its causes and consequences? This question has led researchers to analyze the behavior of the raor (Xyrichthys razor), a species that is giving birth to a multitude of ecological processes until now little understood and that have a very large socioeconomic impact on the Balearic Islands.
“As a result of previous work, we know that there are individuals who wake up according to their internal clock at 7:15 a.m., coinciding with sunrise, and others that get up at 11 a.m., and this they do so consistently over time. In other words, there are different chronotypes that reflect the same thing that has been observed in people ”, explains Josep Alós, Ramón y Cajal researcher at IMEDEA (CSIC-UIB) and head of the CLOCKS project, which will last three years.
Alós, together with other researchers from the Fish Ecology Group of the Mediterranean Institute for Advanced Studies, the Neurophysiology of Sleep and Biological Rhythms Group of the Balearic University (UIB) and the Marine Research and Aquaculture Laboratory (LIMIA ) of the Balearic Government want to respond with state-of-the-art technology to why some marine fish wake up earlier and others later.
These variations of your circadian biological rhythm, called chronotypes, have consequences, as in the case of people. Getting up earlier or later has implications for our health, work, relationships, or even the economy. In fish, scientists have found that they influence the functioning of the ocean and, for example, which fish are caught and end up on our plates, affecting sustainable fishing.
“From systems such as those used in mobile devices, we will be able to know in depth how animal societies work and to study phenomena such as the transmission of social information or the spread of a disease in human societies ”, points out Alós.
Scientists will do experiments with many individuals in a homogeneous environment such as the sand of the Bahía de Palma Marine Reserve. “When the raor retires to sleep, it buries itself under the sand and this allows us to differentiate it very well. In addition, it is a representative species of many others, since It is coastal, it is exploited for fishing and it has a relevant socio-economic importance“Says the project leader.
Furthermore, this species has a complex social structure thanks to which it is possible to understand not only the consequences of the different chronotypes in fish societies, but also how animal societies function, including our species. “These characteristics make the raor a species ideal for its study ”, highlights Alós.
Cod, sea bream or lobsters
In addition to the raor, the project aims to also study the global character of chronotypes, that is to say, these differences between individuals at bedtime and getting up that have implications in the ecology and the functioning of the marine environment.
To this end, scientists will use the global database European Aquatic Animal Tracking Network and collect data on social interactions and chronotypes of many species, such as cod, sea bream or lobsters, to replicate the study of raors and see if chronotypes are a global characteristic of fish populations.
“In order to understand its circadian rhythm, the first step is to eliminate environmental and social factors, and carry out studies under laboratory conditions,” says Alós. There, researchers will analyze the behavior of adult individuals to see if they are met. the three norms of the circadian rhythm: the day-night rhythm must be adjusted to an external factor, in this case light; the rhythm must be adjusted or synchronized when the lighting conditions are continuous; and, finally, the rhythms must be compensatory for the temperature, that is, the temperature must not affect them.
The scientists will also create a captive-breeding protocol for the raor and will study the behavior and circadian rhythms of marine fish larvae for the first time. In addition, they will carry out a melatonin manipulation experiment, a hormone linked to the internal clock of all living beings and that is behind the biological rhythms of all animals.
“Melatonin generates the sleep-watch cycle, in addition to affecting the rate of cell division, and influences the secretion of growth hormone,” says Alós. The CLOCKS project will also allow study the genetic basis of chronotypes, since there is scientific evidence in different species such as birds that chronotypes are defined by small variations in the DNA sequence.