Cortisol in Correlation to Other Indicators of Fish Welfare

Cortisol is the major corticosteroid in teleost fish, secreted and released by interrenal cells of the head kidney during activation of the hypothalamic-pituitary-interrenal (HPI) axis. Although cortisol is universally recognized as a key mediator of stress-associated responses, other hormones are also involved in the stress response, e.g., arginine vasotocin (AVT), isotocin (IT), urotensins, dopamine, serotonin or β-endorphin. Cortisol affects AVT and IT secretion from nerve endings in gilthead sea bream (Sparus aurata) and round goby (Neogobius melanostomus). Moreover, it is pointed out that different mechanisms are involved in the regulation of AVT and IT release from the hypothalamic-pituitary complex in round goby. In the case of AVT, both genomic and nongenomic pathways are mediating the effect of cortisol while in the case of IT, it is only the nongenomic pathway. In turn, urotensin I instead of corticotropin-releasing factor (CRF) may contribute to the regulation of HPI axis and regulate AVT in Sparus aurata. In this species, urotensin II together with AVT and IT may control stress response to different salinities. Therefore, AVT, IT and urotensins, and their interactions with cortisol, seem to be significant in response to stress in fish

Adaptation to salinity in Atlantic cod from different regions of the Baltic Sea

Highlights: • The stress response to salinity in subpopulations of the Baltic cod was examined. • Two different profiles of response to salinity were observed. • Changes in response profiles may be a functional adaptation to variable salinity. • Adaptation protects cod against stress during vertical and long-distance migrations. • Salinity is a barrier maintaining the genetic and physiological separations of cod. Abstract: Atlantic cod (Gadus morhua) occur in marine water of different salinities: from oceanic waters at salinity of 35 to Baltic Sea waters where the lowest level of salinity reaches 5–6. The stress response to different salinities in the eastern and western Baltic cod populations was examined. Two genes of Na +, K + -ATPase 1a (atp1a) and heat shock protein 70 (hsp70) expression, plasma cortisol and osmolality were used as markers of osmotic stress to characterize the reaction profiles of two populations of G. morhua from the western and eastern parts of the Baltic Sea. Atlantic cod were sampled in November 2012 from western Kiel Bight (KIEL, salinity of 18) and eastern Gdańsk Bay (GDA, salinity of 8). Live fish were transported to the Marine Station of the University of Gdańsk in Hel and were settled in tanks (3500 L). Cod were kept at 10 °C in recirculated water, which simulated the natural salinities of the geographic source region of the fish. Results showed that in the reduced and elevated salinity water of the KIEL group, we observed no change in expression of atp1a and slightly increased expression of hsp70. In the GDA group, there were no significant changes of hsp70 expression but the level of atp1a was significantly increased in both salinities. In both groups, concentration of cortisol increased after exposure to elevated salinity, while in fish exposed to reduced salinity, a significantly higher concentration of cortisol was observed after 72 h. The high expression of atp1a that observed in the eastern group (GDA) supports the thesis of a genetic background to the adaptation to variable salinity. This adaptation may protect this species against an osmotic stress caused by daily vertical migrations and long-distance migration to spawning areas. At the same life-time, salinity is a barrier maintaining the genetic and physiological separations between G. morhua stocks and affecting the structure of this fish subpopulation in the Baltic Sea

Critical comment on the paper „Five years of difficult experiences with the Act of the protection of animals used for scientific or educational purposes dated of January 15, 2015”

The authors criticize the claims relating to the functioning of the National Committee on Ethical Review of Animal Research made in the paper „Five years of difficult experiences with the Act of the protection of animals used for scientific or educational purposes dated of January 15, 2015” published in „Nauka” (3/2020) relating to the functioning of the National Ethics Committee on Animal Experimentation. The comment proves many statements of that paper blatantly false given either statistical data or legal regulations. It includes the duties of the National Ethics Committee, right of non-governmental organizations to participate in administrative proceedings, conflict of interest, and the approach of the National Ethics Committee to appeals from the decisions made by local committees. The authors prove that the paper’s suggestions of the alleged misconduct by the National Ethics Committee on Animal Experimentation are ill-founded and result from the poorly understood legal situation as well as lack of reference to relevant empirical data

Brain nonapeptide and gonadal steroid responses to deprivation of heterosexual contact in the black molly

Fish may respond to different social situations with changes in both physiology and behaviour. A unique feature of fish is that social interactions between males and females strongly affect the sexual characteristics of individuals. Here we provide the first insight into the endocrine background of two phenomena that occur in mono-sex groups of the black molly (Poecilia sphenops): masculinization in females and same-sex sexual behaviour, manifested by gonopodial displays towards same-sex tank mates and copulation attempts in males. In socially controlled situations, brain neurohormones impact phenotypic sex determination and sexual behaviour. Among these hormones are the nonapeptides arginine vasotocin (AVT) and isotocin (IT), counterparts of the well-known mammalian arginine vasopressin and oxytocin, respectively. To reveal potential hormone interactions, we measured the concentrations of bioactive AVT and IT in the brain, along with those of the sex steroids 17β-estradiol and 11-ketotestosterone in the gonads, of females, masculinized females, males displaying same-sex sexual behaviour and those who did not. These data were supplemented by morphological and histological analyses of the gonads. Correlations between brain nonapeptides and gonadal steroids strongly suggest a cross talk between hormonal systems. In the black molly, the masculinization process was associated with the production of brain AVT and gonadal steroids, whereas same-sex sexual behaviour involves both brain nonapeptides, but neither of the sex steroids. This study extends current knowledge of endocrine control of phenotypic sex and sexual behaviour in fish and for the first time links brain nonapeptides with the occurrence of male-male sexual behaviour in lower vertebrates

How does oestradiol influence the AVT/IT system in female round gobies during different reproductive phases?

In this in vitro gradient perfusion study, we determined whether there is a functional relationship between oestradiol and the arginine vasotocin/isotocin (AVT/IT) system in the female round goby (Neogobius melanostomus). Brain explants were perfused in medium supplemented with 17β-oestradiol (E2) at doses mimicking the plasma levels of this hormone in nature during the spawning-capable phase and regressing phase. We aimed to establish which pathway, genomic or non-genomic, is involved in this mechanism in different reproductive phases. For this purpose, brain explants were perfused in medium supplemented with Fulvestrant (ICI 182.780) or Actinomycin D (Act D) separately or in combination with E2. The contents of AVT and IT in the perfusion media were determined using high-performance liquid chromatography (HPLC) with fluorescence and UV detection. During the spawning-capable phase, the effect of E2 on AVT release is mediated through oestrogen receptors (ERs) via both genomic and non-genomic pathways, while IT release is mediated through ERs via a genomic pathway only. In the regressing phase, release of both nonapeptides is mediated through ERs via a genomic pathway. This is the first study to present a feasible mechanism of oestradiol action on the AVT/IT system in female fish during different phases of the reproductive cycle

Agonistic interactions elicit rapid changes in brain nonapeptide levels in zebrafish

The teleost fish nonapeptides, arginine vasotocin (AVT) and isotocin (IT), have been implicated in the regulation of social behavior. These peptides are expected to be involved in acute and transient changes in social context, in order to be efficient in modulating the expression of social behavior according to changes in the social environment. Here we tested the hypothesis that short-term social interactions are related to changes in the level of both nonapeptides across different brain regions. For this purpose we exposed male zebrafish to two types of social interactions: (1) real opponent interactions, from which a Winner and a Loser emerged; and (2) mirror-elicited interactions, that produced individuals that did not experience a change in social status despite expressing similar levels of aggressive behavior to those of participants in real-opponent fights. Non-interacting individuals were used as a reference group. Each social phenotype (i.e. Winners, Losers, Mirror-fighters) presented a specific brain profile of nonapeptides when compared to the reference group. Moreover, the comparison between the different social phenotypes allowed to address the specific aspects of the interaction (e.g. assessment of opponent aggressive behavior vs. self-assessment of expressed aggressive behavior) that are linked with neuropeptide responses. Overall, agonistic interactions seem to be more associated with the changes in brain AVT than IT, which highlights the preferential role of AVT in the regulation of aggressive behavior already described for other species.Fundação para a Ciência e a Tecnologia (FCT); Institute of Oceanology PAN – Polan

Region specific changes in nonapeptide levels during client fish interactions with allopatric and sympatric cleaner fish

<div><p>Social relationships are crucially dependent on individual ability to learn and remember ecologically relevant cues. However, the way animals recognize cues before engaging in any social interaction and how their response is regulated by brain neuromodulators remains unclear. We examined the putative involvement of arginine vasotocin (AVT) and isotocin (IT), acting at different brain regions, during fish decision-making in the context of cooperation, by trying to identify how fish distinguish and recognize the value of other social partners or species. We hypothesized that the behavioural responses of cleaner fish clients to different social contexts would be underlain by changes in brain AVT and IT levels. We have found that changes in AVT at the level of forebrain and optic tectum are linked with a response to allopatric cleaners (novel or unfamiliar stimuli) while those at cerebellum are associated with the willingness to be cleaned (in response to sympatric cleaners). On the other hand, higher brain IT levels that were solely found in the diencephalon, also in response to allopatric cleaners. Our results are the first to implicate these nonapeptides, AVT in particular, in the assessment of social cues which enable fish to engage in mutualistic activities.</p></div

Frequency of observed behavioural measures for each experimental treatment.

<p>These include: a) the frequency of cleaning interactions, b) mean inspection duration, c) proportion of interactions in which tactile stimulation was applied to clients, d) frequency of jolts per 100 s of inspection, e) frequency of chases, f) duration of chases and g) frequency of bites given by focal individual. Mean ± Standard Error (SEM) are provided for each behavioural measure.</p

Levels of arginine vasotocin (AVT) in different brain macro-areas: Forebrain, diencephalon, optic tectum, cerebellum and brain stem in clients (<i>Naso elegans</i>).

<p>Four treatment groups: a) sympatric cleaner (<i>Labroides dimidiatus</i>), b) allopatric cleaner (<i>Elacatinus evelynae</i>), c) conspecific (<i>N</i>. <i>elegans</i>) and d) ball, expressed as AVT (pmol/mg). Medians (full lines) and interquartile range are presented in boxes.</p