Natural and Experimental Evidence Drives Marmosets for Research on Psychiatric Disorders Related to Stress

Knowledge of the behavioral ecology of marmosets carried out in their natural habitat associated with the advent of a non-invasive technique for measuring steroid hormones in feces has made a significant contribution to understanding their social relationships and sexual strategies. These studies showed that they are mainly monogamous, live in relatively stable social groups according to a social hierarchy in which females compete and males cooperate, and form social bonds similar to humans, which makes this species a potential animal model to study disorders related to social stress. In addition, laboratory studies observed the expression of behaviors similar to those in nature and deepened the descriptions of their social and reproductive strategies. They also characterized their responses to the challenge using behavioral, cognitive, physiological, and genetic approaches that were sexually dimorphic and influenced by age and social context. These findings, added to some advantages which indicate good adaptation to captivity and the benefits of the birth of twins, small size, and life cycle in comparison to primates of the Old World, led to their use as animal models for validating psychiatric diseases such as major depression. Juvenile marmosets have recently been used to develop a depression model and to test a psychedelic brew called Ayahuasca from the Amazon rainforest as an alternative treatment for major depression, for which positive results have been found which encourage further studies in adolescents. Therefore, we will review the experimental evidence obtained so far and discuss the extension of the marmoset as an animal model for depression.

Transcriptomic Assessment of Dietary Fish Meal Partial Replacement By Soybean Meal and Prebiotic Inclusion In The Liver of Juvenile Pacific Yellowtail (Seriola Lalandi)

Seriola lalandi is an important species for aquaculture, due to its rapid growth, adaptation to captivity and formulated diets, and high commercial value. Due to the rise in fish meal (FM) price, efforts are made to replace it partially or entirely with vegetable meals in diets for carnivorous fish. The use of prebiotics when feeding vegetable meals has improved fish health. In this study, four experimental diets were assessed in juveniles, the control diet consisted of FM as the main protein source, the second diet included 2% GroBiotic®-A (FM-P), the third included FM with 25% replacement by soybean meal (SM25), and the fourth consisted in SM25 with 2% of GroBiotic®-A (SM25-P). RNA-seq of the liver tissue was performed, followed by differential expression analysis and functional annotation to identify genes affected by the diets. Growth was not affected by this level of FM replacement, but it was improved by the prebiotic. Annotation was achieved for 78,826 transcripts, of which 135 were up-regulated and 78 down-regulated among all treatments compared to the control. Transcriptomic profiles of control samples were clustered with those from fishes fed SM25 and SM25-P diets, and the most differentiated group was that one fed the FM-P diet. SM25-P showed the least amount of differentially expressed genes, maintaining general transcriptomic profiles of control diet in the liver, therefore this diet is a potential economic alternative to the FM diet, for S. lalandi juveniles. Assessment of the effects of this diet along the digestive tract is recommended.

Characterization of the different behaviours exhibited by juvenile grey mullet (Mugil cephalus) under rearing conditions

This research described the common behaviour of grey mullet (Mugil cephalus) under rearing conditions. The different behaviours exhibited by mullets were videorecorded with submersible cameras installed inside of three tanks. A total of 690 minutes per day (07:30 - 18:30 hours) were recorded per tank during a week. Afterwards, an ethogram was elaborated to organize the different behaviours exhibited by juvenile M. cephalus, with two general categories: a) locomotion, including three different observed behaviours (resting, swimming and fast swimming) b) feeding, including three behaviours (surface feeding, bottom feeding and rubbing). The video recordings showed that M. cephalus is a species with a constant locomotion associated to feeding, since they showed constantly movement during most of day light period the opposite to dark periods. Mullets were observed to be a non-aggressive fish species, due to the absence of dominance and aggression towards conspecifics, resulting in a high predisposition for adaptation to captivity. Finally, behavioural frequencies of grey mullet’s juveniles were not significantly different among the three tanks for most of the behavioural variables analysed (p>0.05) except for the variable bottom feeding (p=0.02). Results from this study could be of interest to the aquaculture industry to implement protocols and to optimize rearing techniques for the production of grey mullet.

Whole-genome Resequencing Provides Insights into the Population Structure and Domestication Signatures of Ducks in Eastern China

Background: Ducks are an ancient domesticated animal with high economic value, uesd for its meat, eggs, and feathers. However, the origin of indigenous Chines ducks remains elusive. To address this question, we performed whole-genome resequencing to explore the genetic relationships among the domestic ducks and wild ducks in eastern China and to identify the genomic differences shaped by artificial selections. Results: The whole genomes of 60 ducks from eastern China were sequenced, with an average effective sequencing depth of ~6× per individual. The results of population and demographic analysis indicate that all individuals from the same breed gather together, and domestic ducks form a cluster separating from wild ducks. By applying selective sweep analysis, we identified that several candidate genes, important pathways and GO categories associated with artificial selection were functionally related to cellular adhesion, type 2 diabetes, lipid metabolism, the cell cycle, liver cell proliferation, and muscle functioning in domestic ducks.Conclusion: Genetic structure analysis showed that the domesticated ducks were not direct descendants of the mallard or Spot-billed duck and probably originated from an unknown population. During the long history of artificial selection, domesticated ducks have developed a complex biological adaptation to captivity.

Family variation in surface feeding behavior of steelhead fry predicts growth rate under hatchery conditions

Hatchery reared salmonid fish often have lower fitness than their natural-origin counterparts when spawning in the wild. Although this difference appears to result from rapid adaptation to captivity, it is not known what traits are under selection. We hypothesize that variation in traits that confer a growth rate advantage to some individuals in the novel hatchery environment are under strong selection because survival at sea is correlated with size at release. Here we show that full sibling families of steelhead trout (Oncorhynchus mykiss) show substantial variation in propensity to feed at the surface as fry, and that the more surface-oriented families grew faster under hatchery conditions. We hypothesize that surface-oriented fry gain an initial growth advantage that persists through size at release. Because surface orientation is a correlate of generalized boldness, hatcheries may inadvertently select for that phenotype, which could explain the fitness differences observed between hatchery and natural-origin fish in the wild.

Description of the Annual Reproductive Cycle of Wreckfish Polyprion americanus in Captivity

Successful spontaneous reproduction and the production of viable offspring of wild fish in captivity can take some years of adaptation, and may also involve different environmental conditions, sex ratios and densities compared to natural populations. We followed the reproductive cycle of wreckfish Polyprion americanus—a late maturing, deep-sea benthic species—in captivity in three different broodstocks in Spain under natural photoperiod and temperature, and one broodstock in Greece under a constant temperature of 16 °C for two consecutive years, to describe the reproductive cycle of the species and the associated sex steroid hormone profiles. Oogenesis begun in the fall and post-vitellogenic oocytes of 1250 μm were present between March and June. Males were in spermiation condition and produced good-quality sperm throughout the year, regardless of the temperature profile to which they were exposed. Some females completed oogenesis, underwent oocyte maturation, and spawned spontaneously under both constant and fluctuating temperatures. The sex steroid hormones of both males and females followed the already-known profiles during fish gametogenesis, except for 17,20β-dihydroxy-progesterone, which did not seem to be related to either female or male maturation. The female reproductive dysfunctions that were identified included (a) the arrest of oogenesis at the cortical alveoli stage in certain females; (b) the failure to undergo oocyte maturation in others; and (c) the production of large percentages of unfertilized eggs from the females that spawned spontaneously. Our study suggests that reproduction in captivity is possible in wreckfish maintained under typical marine aquaculture conditions, but that reliable spawning and production of high-quality eggs may require some years of adaptation to captivity, before the reproductive dysfunctions will be overcome.