Covariation among behavioral traits and hatching time in zebrafish.

Individuals of the same population differ in several ways. For instance, in fish populations, individuals who hatch earlier show more active behavior and are more explorative than those that hatch later, which is a characteristic of the behavioral personality type. One of the aspects relevant to this theory is the consistency of behavioral differences between contexts and over time. Thus, the present study evaluated the relationship between hatching time and behavioral consistency in two ontogenetic stages: juvenile and adult, and different contexts in zebrafish (Danio rerio). For this, the animals were separated according to hatching time into early-hatching (EH) and late-hatching (LH) fish and tested in an anxiety-like context (black-white paradigm) at the 30th-day post fertilization (dpf) and the 120th dpf. The animals were also tested in a novel tank paradigm and novel object paradigm to access explorativeness and boldness, respectively. In the black-white test, EH animals presented shorter latency to enter the white area and stayed longer in the black area than LH animals. The EH individuals were more explorative and bold in the novel tank and novel object tests and showed less anxiety-like behavior than the LH. In general, the results obtained suggest that hatching time may indicate consistent differences for zebrafish behavioral profiles.

Erythroxylum pungens Tropane Alkaloids: GC-MS Analysis and the Bioactive Potential of 3-(2-methylbutyryloxy)tropan-6,7-diol in Zebrafish (Danio rerio).

Tropane alkaloids are specialized plant metabolites mostly found in the Erythroxylaceae and Solanaceae families. Although tropane alkaloids have a high degree of structural similarity because of the tropane ring, their pharmacological actions are quite distinct. Brazil is one of the main hotspots of Erythroxylum spp. diversity with 123 species (almost 66% of the species catalogued in tropical America). Erythroxylum pungens occurs in the Caatinga, a promising biome that provides bioactive compounds, including tropane alkaloids. As part of our efforts to investigate this species, 15 alkaloids in specimens harvested under different environmental conditions are presented herein. The occurrence of 3-(2-methylbutyryloxy)tropan-6,7-diol in the stem bark of plants growing in their natural habitat, greenhouse controlled conditions, and after a period of water restriction, suggests that it is a potential chemical marker for the species. This alkaloid was evaluated for several parameters in zebrafish (Danio rerio) as a model organism. Regarding toxicity, teratogenic effects were observed at 19.5 µM and the lethal dose for embryos was 18.4 µM. No mortality was observed in adults, but a behavioral screen showed psychostimulatory action at 116.7 µM. Overall, the alkaloid was able to cause zebrafish behavioral changes, prompting further investigation of its potential as a new molecule in the treatment of depression-like symptoms. In silico, targets involved in antidepressant pathways were identified by docking.

Behavioral Screening of Alcohol Effects and Individual Differences in Zebrafish (Danio rerio).

AIM: To better understand the individual differences that make up a population, this study aimed to evaluate the effects of different alcoholic concentrations on the behavioral profiles of zebrafish (Danio rerio). METHODS: For this purpose, adult animals were separated into two behavioral profiles: bold and shy, according to the emergence order. Bold and shy fish were individually tested for exploration after exposure to the drug. Acute exposure treatments were alcohol 0.00, 0.10, 0.25 and 0.50%. The behavioral parameters evaluated were speed while moving, maximum speed, total distance traveled and distance from the bottom of the tank. RESULTS: For the groups that did not receive alcohol, bold animals showed higher speed while moving. Shy 0.00% and shy 0.10% had the highest maximum speed compared with other concentrations and profiles. For the distance from the bottom tank, our results showed that the increase induced by the low acute dose (0.10%) was observed for both profiles. CONCLUSIONS: Our results corroborate with previous findings that alcohol affects the behavioral profiles of zebrafish differently, with bold animals apparently more resistant to these changes.

Individual Differences in Hatching Time Predict Alcohol Response in Zebrafish.

There are significant individual differences in response to alcohol: some people seem to exhibit higher alcohol sensitivity, while others are more resistant. These differences are related to alcohol metabolism, inherited traits, environmental/social pressure, personal habits and other indeterminate causes. In order to test how individual differences in hatching time are related to behavioral response to different alcohol concentrations, we separated zebrafish larvae into two categories according to egg emergence time: eggs hatched between 48 and 72 hours post-fertilization (hpf) were considered early emerging (EE), while those hatched from 72 to 96 hpf were considered late emerging (LE). On the 30th day post fertilization, EE and LE fish were exposed to four alcohol concentrations: 0.00% (control), 0.10%, 0.25% and 0.50%, and behavior was recorded for 60 min. We observed average and maximum swimming speed, distance traveled, and freezing time (immobility that indicates state of anxiety). For EE fish, 0.10% alcohol did not change behavior, while 0.25% and 0.50% increased freezing and decreased locomotion. By contrast, LE fish increased locomotion when exposed to both 0.10 and 0.25% alcohol, and increased freezing time at 0.50% alcohol. These results show that zebrafish behavioral profiles exhibit different sensitivities to alcohol, likely due to traits that can be tracked from early life stages and may indicate individuals' predisposition to alcohol tolerance and dependence.