World J Depress Anxiety | Volume 1, Issue 1 | Research Article | Open Access

Increasing Zebrafish (Danio rerio) Numbers in a Limited Tank Space Reduces Night-Time Fish Sleep-Like State and Induces Aggressive Behaviour

Mohammad Kutub Ali* and Hasina Lateefah Nicholson

Department of Basic Medical Sciences, University of the West Indies, Jamaica

*Correspondance to: Mohammad Kutub Ali 

Fulltext PDF


Inadequate sleep, besides decreasing consolidation of learning and memory, is also known to be associated with various major mental illnesses such as anxiety, psychotic disorders, mood, distress, anger, and paranoia. The studies of inhabitants of crowded city with limited space also showed similar increase in major mental illness. However, reports on the possibility of inadequate sleep contribution to heightening major mental illness in crowded urban areas with limited space are scarce. Using Zebrafish (Danio rerio) as the animal model, this investigation showed that sleeplike state (SLS) duration decreased linearly with increasing population in a limited fish tank space. Increase in fish numbers causes ever increased struggling for preferential sleeping space, resulting in the generation of aggressive and depressive behaviour. Isolating individuals from groups also causes increased anxiety followed by depression. Zebrafish SLS needed maintaining limited distance from one another. However, increasing fish numbers increases invasion of individuals’ space leading to shorter average and lower total SLS during night-time. Besides depending on fish numbers, duration of SLS also depends on air quantity, presence of drugs that decrease or stabilize motor-neuron coordination. Drugs such as alcohol decreased SLS while melatonin stabilized it. This investigation, therefore, clearly suggests the applicability of using Zebrafish as an animal model in understanding the increasing mental illness in limited space urban cities.


Zebrafish; Sleep; Population; Alcohol; Melatonin; Aggressive


Ali MK, Nicholson HL. Increasing Zebrafish (Danio rerio) Numbers in a Limited Tank Space Reduces NightTime Fish Sleep-Like State and Induces Aggressive Behaviour. World J Depress Anxiety. 2018; 1(1): 1003.

Subscribe to Our Newsletter