Zebrafish (ZF) have gained increasing attention in developmental neuroscience due to their experimental tractability, favorable ethical profile, and translational value. However, the expanding use of the ZF model has also highlighted the need to consider species-specific differences in relation to early social and emotional development. This review adopts a comparative and ethological perspective to examine early social interactions in ZF and mammals, integrating evidence from non-altricial vertebrates and teleost species with parental care (cichlids). Selected illustrative ZF papers were discussed, while Cichlids fish were chosen as a complementary, translationally consistent subject for developmental behavioral studies. The analysis focuses on developmental stages that are relevant for behavioral phenotyping in models of neuropsychiatric conditions. Zebrafish offer multiple methodological advantages, including suitability for high-throughput experimentation and substantial genetic and neurobiological homologies with humans. Nevertheless, the absence of mother–offspring bonding limits the modeling of neurodevelopmental processes shaped by early caregiving, such as imprinting and reciprocal regulatory interactions, instead observed in cichlids. Accumulating evidence indicates that early interactions among age-matched ZF are measurable, developmentally regulated, and sensitive to environmental and experimental manipulations. Within a comparative approach, these early conspecific interactions could be analogs of early social bonding observed in altricial mammals. Rather than representing a critical limitation, such species-specific features can inform the investigation of fundamental mechanisms of social development and support the complementary use of ZF and mammalian models. A contextualized and integrative approach may therefore enhance the translational relevance of ZF-based research, particularly for the study of neurodevelopmental disorders involving early social dysfunction.

Torpor is a hypometabolic and hypothermic state that enables survival under extreme energetic constraints. Pharmacological induction with 5′-AMP produces a controllable torpor-like hypothermic state with hypometabolic features documented for this model, relevant to long-duration spaceflight. Such a state could mitigate the physiological hazards of deep-space missions, including cosmic radiation exposure and muscle wasting, and, by minimizing oxygen demand, preserve neural integrity and enhance radiation tolerance. However, translational application requires confirmation that induced hypometabolism does not impair cognitive or behavioral function; this is especially pressing given evidence that the state causes reversible tau hyperphosphorylation at phospho-sites also altered in Alzheimer’s disease, but without tau aggregation. We subjected C57BL/6 mice to 5′-AMP combined with a mildly reduced ambient temperature (15–18 °C) and compared them with cold-exposed and room-temperature vehicle controls using systematic neurobehavioral testing. Despite the deep hypothermia (and the hypometabolism documented for this model), Y-maze spontaneous alternation performance was unaffected. Locomotor activity fell transiently during post-arousal recovery, with concurrent increases in self-directed behaviors. These results support further evaluation of this reversible metabolic intervention for critical care medicine and future human space missions.

Temperature is a major environmental factor influencing fish behaviour and physiological function. In the present study, adult zebrafish were exposed to 18 °C for 21 days and compared with controls maintained at 26 °C to evaluate the behavioural effects of chronic low-temperature exposure. Behaviour was assessed using four individual-based paradigms—the novel tank diving test, light–dark preference test, social preference test, and mirror biting test—covering locomotion, exploration, social behaviour and anxiety-related responses. Chronic exposure to 18 °C was associated with a behavioural profile characterised by increased immobility, reduced exploratory activity, enhanced bottom-dwelling, and reduced active engagement with the mirror stimulus, whereas social preference towards conspecifics was largely preserved. Comparison with behavioural responses previously reported after 4 days of exposure to 18 °C suggests that several behavioural differences are still detectable after 21 days, indicating that the behavioural profile of fish maintained at 18 °C remained distinct from that of controls within the time window examined. These findings should be interpreted in light of the absence of independent tank-level replication. Previous studies conducted under comparable thermal conditions have reported molecular changes in the brain and in other neural-derived structures, such as the eye. Although these molecular findings were not generated in the present experiment and cannot be directly linked to individual behavioural endpoints, they provide a broader context for interpreting the behavioural effects of prolonged low-temperature exposure. Overall, the present findings show that chronic exposure to 18 °C is associated with persistent differences in locomotor, exploratory, and stimulus-directed behaviours, while social preference is comparatively preserved.

Among ground-based paradigms used to reproduce altered gravity exposure, the hindlimb unloading (HU) model is widely employed to simulate microgravity conditions by removing gravitational loading from the hindlimbs. Despite its extensive use, behavioral adjustments during suspension remain poorly characterized, although they may provide valuable indicators of animal welfare and individual susceptibility. Here, we comprehensively characterized the behavioral profile of mice during and after HU using a dedicated ethogram, with the aim of identifying behavioral markers associated with individual coping strategies. Several exploratory and postural behaviors showed marked time-dependent modulation, with baseline exploratory activity predicting a more adaptive behavioral trajectory during suspension, possibly indicative of greater resilience. In parallel, brain levels of the neurotrophins NGF and BDNF were measured to explore their relationship with behavioral outcomes. Although no significant group differences were detected, suspended mice displayed a progressive reduction in both neurotrophins over time, which paralleled behavioral adaptation. Together, these findings indicate that specific exploratory behaviors represent reliable predictors of resilience to HU, while NGF and BDNF may reflect ongoing neuroplastic processes associated with prolonged suspension.

Brain-derived neurotrophic factor (BDNF) is a key regulator of neural development, plasticity, and behaviour. Recent work has enabled the generation of a viable adult bdnf^−/− zebrafish line, which provides a unique opportunity to investigate how complete loss of bdnf affects social behaviour. Here, we examined three-dimensional shoaling behaviour in adult male and female AB wild-type and bdnf^−/− knock-out zebrafish to determine whether the extensive molecular and behavioural alterations previously observed in individual-based assays extend to collective contexts. The bdnf^−/− shoals showed no differences in group structure, as inter-fish distance, shoal volume, shoal area, distance to the centroid, and homogeneity index were comparable to wild-type groups. Vertical spatial distribution was also largely preserved, although bdnf^−/− fish shifted toward the upper regions of the tank earlier during the trial. By contrast, horizontal distribution revealed a clear genotype effect: bdnf^−/− shoals spent more time in peripheral regions and displayed a pronounced early peak in peripheral occupancy. These findings indicate that bdnf loss does not impair shoal formation or cohesion but selectively modulates specific components of spatial exploration. The results also highlight a dissociation between the vertical and horizontal axes of behaviour, as well as between individual- and group-based phenotypes, underscoring the importance of social context in shaping the behavioural consequences of BDNF deficiency.