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.

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.

Global warming is driving significant changes in aquatic ecosystems, where temperature fluctuations influence biological processes across multiple levels of organisation. As ectothermic organisms, fish are particularly susceptible, with even minor thermal shifts affecting their metabolism, behaviour, and overall fitness. Understanding these responses is essential for evaluating the ecological and evolutionary consequences of climate change. This study investigates the effects of acute (4-day) and chronic (21-day) exposure to three temperature regimes—18 °C (low), 26 °C (control), and 34 °C (high)—on the spatio-temporal shoaling behaviour of adult zebrafish (Danio rerio). Groups of four fish were tested for six minutes in water maintained at the same temperature as their prior acclimation. Shoaling behaviour was assessed by analysing shoal structure—encompassing shoal dimensions and cohesion—as well as spatial positioning. Parameters measured included inter-fish distance, shoal volume, shoal area, homogeneity index, distance to the centroid, and the shoal’s vertical and horizontal distribution. Results revealed complex behavioural changes influenced by both temperature and duration of exposure. At 18 °C, zebrafish showed a marked preference for the bottom zone and exhibited no significant temporal modulation in exploratory behaviour—patterns indicative of heightened anxiety-like responses. In contrast, exposure to 34 °C resulted in increased shoal cohesion, particularly under chronic conditions, and a progressive increase in environmental exploration over the six-minute test period. This enhancement in exploratory activity was especially evident when compared to the first minute of the test and was characterised by greater vertical movement—reflected in the increased use of the upper zone—and broader horizontal exploration, including more frequent occupation of peripheral areas. These findings align with previous research linking thermal variation to neurobiological and proteomic alterations in zebrafish. By elucidating how temperature modulates social behaviour in ectotherms, this study offers valuable insights into the potential behavioural impacts of climate change on aquatic ecosystems.

L’articolo analizza il ruolo della scientometria nel mondo accademico e il suo impatto sulla creatività dei giovani scienziati.

Here we list species-specific recommendations for housing, care and management of cephalopod molluscs employed for research purposes with the aim of contributing to the standardization of minimum requirements for establishments, care and accommodation of these animals in compliance with the principles stated in Directive 2010/63/EU. Maximizing their psychophysical welfare was our priority. General recommendations on water surface area, water depth and tank shape here reported represent the outcome of the combined action of the analysis of the available literature and an expertise-based consensus reached – under the aegis of the COST Action FA1301 – among researchers working with the most commonly used cephalopod species in Europe. Information on water supply and quality, environmental conditions, stocking density, feeding and handling are also provided. Through this work we wish to set the stage for a more fertile ground of evidence-based approaches on cephalopod laboratory maintenance, thus facilitating standardization and replicability of research outcomes across laboratories, at the same time maximizing the welfare of these animals.

In 2013, two papers suggested behavioural biologists to use videos available on social media as a tool for investigating animal behaviour, a methodology referred to as video mining. Here, this approach was applied to the study of specific aspects of peregrine falcon ( Falco peregrinus ) nestlings’ behaviour at critical developmental stages. Special attention was given to food begging behaviour and its development. The materials included 254 videos (from 31 nests and 51 different broods) that underwent strict selection procedures to ensure their reliability and quality. Following age estimation of the nestlings, videos were divided into four classes to study age-related differences in begging behaviour. No statistically significant differences emerged among age classes. Video mining may represent a valuable tool for qualitative analyses if wisely and rigorously applied in suitable species and for appropriate research questions. Besides, the video mining approach could also be applied in citizen-science-based studies.

More than 20 years ago, the late Robert McCleary warned experimental and physiological psychologists against using behavioural responses merely as convenient dependent variables. In spite of extensive work with neuroleptics and anxiolytics, some important treatment-behaviour interactions affecting the changes induced by these drugs are poorly understood. Drug treatment apparently steepened the habituation slope in the initial test series. In the case of neuroleptics, the use of a wheel activity test, previously habituated rats, and chronic treatments, revealed considerable residual effects of chlorpromazine and perphenazine after drug washout. The work described represents an attempt to elucidate further the nature of these interactions by studying the effects of various combinations of CS, US, and amphetamine pre-exposure on subsequent motor activity and active avoidance acquisition. The CS and US terminated simultaneously both during classical pairings in preexposure and in avoidance tests, which were carried out according to a conventional delayed procedure.

Experimental evidence suggests that environmental stress conditions can alter the expression of BDNF and that the expression of this neurotrophin influences behavioural responses in mammalian models. It has been recently demonstrated that exposure to 34 °C for 21 days alters the brain proteome and behaviour in zebrafish. The aim of this work was to investigate the role of BDNF in the nervous system of adult zebrafish under control and heat treatment conditions. For this purpose, zebrafish from three different genotypes (wild type, heterozygous BDNF+/− and knock out BDNF−/−) were kept for 21 days at 26 °C or 34 °C and then euthanized for brain molecular analyses or subjected to behavioural tests (Y-maze test, novel tank test, light and dark test, social preference test, mirror biting test) for assessing behavioural aspects such as boldness, anxiety, social preference, aggressive behaviour, interest for the novel environment and exploration. qRT-PCR analysis showed the reduction of gene expression of BDNF and its receptors after heat treatment in wild type zebrafish. Moreover, proteomic analysis and behavioural tests showed genotype- and temperature-dependent effects on brain proteome and behavioural responding. Overall, the absent expression of BDNF in KO alters (1) the brain proteome by reducing the expression of proteins involved in synapse functioning and neurotransmitter-mediated transduction; (2) the behaviour, which can be interpreted as bolder and less anxious and (3) the cellular and behavioural response to thermal treatment.

Experimental studies on new host-parasite systems involving farmed fish can contribute to our understanding of the host behavioural changes associated with parasite infections, as predicted by the host manipulation hypothesis. This has applied relevance because in offshore farms, intermediate hosts of Anisakis nematodes may come into contact with farmed species, with an actual risk of infection. It could therefore be useful to identify behavioural indicators of infection status to monitor animal health and develop adequate countermeasures. Spontaneous activity, sociability, feeding, predatory response and boldness were evaluated in the three weeks following the infection in farmed sea bass (Dicentrarchus labrax) experimentally infected by Anisakis pegreffii larvae. Infected animals displayed a significant increase in food intake that did not affect body weight gain. They also showed increased interest towards a prey model and towards food in a risky feeding situation. While supporting the hypothesis of increased energy drain from infection that promotes increased investment in foraging rather than active host manipulation, the observed changes could constitute preliminary behavioural indicators of parasite infection in farmed fish.

Fuel additive methylcyclopentadienyl manganese tricarbonyl (MMT) is counted as an organic manganese (Mn)-derived compound. The toxic effects of Mn (alone and complexed) on dopaminergic (DA) neurotransmission have been investigated in both cellular and animal models. However, the impact of environmentally relevant Mn exposure on DA neurodevelopment is rather poorly understood. In the present study, the MMT dose of 100 μM (about 5 mg Mn/L) caused up-regulation of DA-related genes in association with cell body swelling and increase in the number of DA neurons of the ventral diencephalon subpopulation DC2. Furthermore, our analysis identified significant brain Mn bioaccumulation and enhancement of total dopamine levels in association with locomotor hyperactivity. Although DA levels were restored at adulthood, we observed a deficit in the acquisition and consolidation of memory. Collectively, these findings suggest that developmental exposure to low-level MMT-derived Mn is responsible for the selective alteration of diencephalic DA neurons and with long-lasting effects on fish explorative behaviour in adulthood.

In mammalians, social life and circadian rhythms find their neurobiological basis in a network that includes the dopaminergic system. The malfunctioning of dopamine pathways can lead to various disorders such as AttentionDeficit/Hyperactivity and Obsessive/compulsive disorders. A useful research approach is to exploit animal models that carry a functional silencing of SLC6A3 gene, encoding the dopamine transporter (DAT). Hyperactivity, working memory deficits, and asocial tendencies are core features in truncated-DAT rats, for example. We investigated how inheritance and maternal caring style influence circadian rhythms and social behaviours in DAT heterozygous (HET) rats, belonging to four groups: Mat-P, Mat-M, Mix-P, and Mix-M (Mat label stands for care from wild-type dam, Mix label stands for care by heterozygous dam; M label stands for maternal wild-DAT and P label stands for paternal wild-DAT). In Experiment 1, we monitored 24/7 the spontaneous locomotor activity of peri-adolescent subjects. Hyperactivity occurred only in P-asset subjects (with maternal-origin truncated-DAT allele) at specific bins of the day. In Experiment 2, we observed social interactions of the same rats. Mix-M subjects (raised by HET dams and/or inheriting the wild-DAT allele from mothers) tend to interact with all rats; Mat-P (cared by WT dams and/or inheriting the truncated-DAT allele from mothers) seem to be ignored, when acting as stimulus subjects. Overall, results confirm complex modulations for circadian cycle and social life: flexible DAT expression in HET subjects depends on epigenetic combinations of parental inheritance and early experiential factors. Once confirmed, these data could shed light on trans-generational contributions to dopaminergic-related disorders.

The COVID-19 pandemic caused lifestyle changes, with unknown effect on pets’ quality of life (QoL). Between May and July 2020, we distributed an online survey to investigate the role of several factors on feline and canine QoL, including lockdown-related factors. We used existing scales to measure human and pets’ personalities (Reinforcement Sensitivity Theory Personality Questionnaire, RST-PQ; RST-Dog; RST-Cat) and the human–animal relationship (Lexington Attachment to Pets Scale, LAPS) and the Milan Pet Quality of Life instrument (MPQL). Overall, 235 participants reported about 242 adult pets (Ncats = 78, Ndogs = 164). Factor analysis confirmed the structure and internal reliability of the existing scales (RST-PQ, RST-Dog, RST-Cat, LAPS) and suggested a four-factor structure for the MPQL (physical, psychological, social, environmental). The results indicate that the pets’ psysical QoL was largely explained by pet-related elements (pets’ demographics and life experience, and pets’ personality). Conversely, the pets’ psychological QoL was explained mostly by owner-related elements, such as the owners’ demographics, COVID-19-related changes, and the owners’ personality. Predictably, the pets’ environmental QoL is mostly explained by environmental factors, such as the outdoor access in the home environment and the country. Finally, the pets’ social QoL was explained by the larger combination of models: pets’ characteristics and personality, environment and COVID-19-related changes, and the pet–human relationship. These findings can be explained by two non-mutually exclusive mechanisms. The reported changes may be a by-product of the COVID-19 pandemic’s psychological and lifestyle effects on the owners, which in turn alter the way the owners interact with their pets and look after them. However, the owners’ characteristics and mood may bias their answers regarding their pets.

Dopamine is essential to many functions like reward, motivation, and attention; when its neural pathways do not function properly, various disorders (e.g., anxiety, depression, hyperactivity, compulsions) can arise. Truncated-DAT rats display persistent stereotypies and aggressiveness; hence they are a new valuable animal model to study the pathogenesis of these disorders. The focus of research is often on the individual epigenetic determinants and much less on the impact of social experiences. Here, we investigate the developmental impact of the social environment on adolescent wild type (WT) rats. We divided subjects at weaning into three groups: living with another adolescent (WT Peer), with a WT adult, or with a truncated-DAT one, and we observed homecage social behavior of these pairs (play, jump, victory, and "bullying") during whole adolescence. When adult, we observed the same subjects in plus maze, forced swim, and social preference tests to measure levels of anxiety, depression, and quality of social interactions. Compared to the other groups, WT rats that had spent their adolescence with a truncated-DAT adult as companion show more anxious, depressive, hyperactive, impulsive, and compulsive behaviours. Results confirm that social interactions and healthy play (i.e., when play has behavioural, social, and psychomotor rewards that support the cognitive, emotional and physical development of the individual) are essential to neurobehavioral maturation. Conversely, anomalous interactions like poor play and "bullying" in developing rats may impact onto their dopaminergic system. Consequently, an impoverished social play could be one of the factors contributing to the appearance of putative indexes of attention deficit hyperactivity disorder (ADHD) and\or obsessive-compulsive disorder (OCD).

Since its first characterization in the early 1950s, the role of the polypeptidic nerve growth factor (NGF) in controlling behavior remained elusive. Since the mid-1980s, we undertook a series of experiments aimed at elucidating the biological role(s) played by neurotrophins, particularly NGF, in adult rodents. At the beginning, we concentrated on the submandibular salivary gland of the male mouse, which was known to store massive amount of NGF. We found that under specific stress conditions, the salivary NGF is released in the bloodstream: intermale fighting between isolated males was the first reported context in which salivary NGF was released, thus providing a physiological significance for its presence in the adult, territorial males. We also found that dominant males release less NGF than subordinates and provided a loop-type model which includes intermale social confrontation, adrenal gland size, and functional status, corticosterone release, a model resulting in likelihood to be stabilized in a "dominant" or a "subordinate" social status. A variety of social anxiety contexts of mammals, humans included, has been described since then, and further studies carried out on humans showed that NGF is released in the bloodstream of parachutists at their first skydiving experience and in the case of ranking high on the Passionate Love Scale (amour fou). Ethological data from lab rodents helped in understanding NGF function in subtly controlling social "status" of male mice: the considerations about the interplay among neurobiological, physiological, and behavioral factors in structuring the dominant vs subordinate phenotypes may well apply to other vertebrate species, specifically addressing the underlying role of neurotrophins in relating behavior and brain neuroplasticity.