Nile tilapia ( Oreochromis niloticus ) is an African freshwater fish that displays a genetic sex determination system (XX|XY) where high temperatures (above 32°C to 36.5°C) induce masculinization. In Nile tilapia, the thermosensitive period was reported from 10 to 30 days post fertilization. In their natural environment, juveniles may encounter high temperatures that are above the optimal temperature for growth (27–30°C). The relevance of the thermal sex reversal mechanism in a natural context remains unclear. The main objective of our study is to determine whether sexually undifferentiated juveniles spontaneously prefer higher, unfavorable temperatures and whether this choice skews the sex ratio toward males. Five full-sib progenies (from 100% XX crosses) were subjected to (1) a horizontal three-compartment thermal step gradient (thermal continuum 28°C– 32°C– 36.5°C) during the thermosensitive period, (2) a control continuum (28°C– 28°C– 28°C) and (3) a thermal control tank (36.5°C). During the first days of the treatment, up to an average of 20% of the population preferred the masculinizing compartment of the thermal continuum (36.5°C) compared to the control continuum. During the second part of the treatment, juveniles preferred the lower, nonmasculinizing 32°C temperature. This short exposure to higher temperatures was sufficient to significantly skew the sex ratio toward males, compared to congeners raised at 28°C (from 5.0 ± 6.7% to 15.6 ± 16.5% of males). The proportion of males was significantly different in the thermal continuum, thermal control tank and control continuum, and it was positively correlated among populations. Our study shows for the first time that Nile tilapia juveniles can choose a masculinizing temperature during a short period of time. This preference is sufficient to induce sex reversal to males within a population. For the first time, behavior is reported as a potential player in the sex determination mechanism of this species.

Abstract. Water supply sectors are facing higher uncertainty in both resource availability and consumer demand. Future conservation programs require a full understanding of underlying factors of residential water consumption. However, previous studies have only considered one or several groups of factors without putting them all together in a bigger picture. This study was developed to provide a comprehensive view on these determinants and their relationships, as well as to discuss current gaps and possible directions. Determinants are categorized into six groups: (1) Economic; (2) Socio-demographic; (3) Physical properties; (4) Technological; (5) Climatic; and (6) Spatial drivers. All these determinants produce a very complex picture with many possible interrelationships. This nature, in one hand, poses challenges in selecting suitable technique to avoid autocorrelation, but on the other hand, provides chances to substitute unavailable important data with proxy variables. We have emphasized the lack of regional and cultural diversity in current studies, as most of them were carried out in developed and arid areas. Hence, a wider range of country specific and local-based studies is needed to better reflect the determinants and their relationships in diverse contexts. In future studies, a broader assessment scope taking into account effects such as feedback loop, spillover, and rebound should also be considered. In addition, these studies must deal with modern issues such as balancing between smart monitoring device utilization and consumer privacy.

The COVID-19 pandemic has led to many countries closing their borders, and numerous people spending their holidays at home instead of traveling abroad. This sudden reduction in travel activities, and other ‘new normals’, might have influenced people’s water usage. Hence, using Liège as a case study, this study aims to address the potential effect of outbound tourism on water consumption and how the current situation might affect the total water demand. Statistical models were developed and validated using the total daily volume of 23 municipalities in the Liège conurbation, the monthly total number of outbound trips, and other meteorological data. Results suggest significantly lower water demand in the months with high numbers of outbound travel activities. Though the projected risk of increased water needs due to fewer people traveling is moderate, the threat becomes much higher during long periods of dry and hot weather.

Persistent organic pollutants (POPs) are posing major environmental and health threats due to their stability, ubiquity, and bioaccumulation. Most of the numerous studies of these compounds deal with single chemicals, although real exposures always consist of mixtures. Thus, using different tests, we screened the effects on zebrafish larvae caused by exposure to an environmentally relevant POP mixture. Our mixture consisted of 29 chemicals as found in the blood of a Scandinavian human population. Larvae exposed to this POP mix at realistic concentrations, or sub-mixtures thereof, presented growth retardation, edemas, retarded swim bladder inflation, hyperactive swimming behavior, and other striking malformations such as microphthalmia. The most deleterious compounds in the mixture belong to the per- and polyfluorinated acids class, although chlorinated and brominated compounds modulated the effects. Analyzing the changes in transcriptome caused by POP exposure, we observed an increase of insulin signaling and identified genes involved in brain and eye development, leading us to propose that the impaired function of the condensin I complex caused the observed eye defect. Our findings contribute to the understanding of POP mixtures, their consequences, and potential threats to human and animal populations, indicating that more mechanistic, monitoring, and long-term studies are imperative.

Studies on residential water determinants often considered a limited number of possible factors due to lacking data, especially at micro-levels. This study aims to address the simultaneous effects of (1) household characteristics, (2) alternative sources of water, (3) dwelling properties, (4) water appliances, (5) attitudes, and (6) urban form on household water use in Wallonia (Belgium). Results emphasize the importance of household characteristics, use of alternative water sources, and dwelling properties. When compared to these variables, the influence of urban density appears very limited. Accordingly, the often-observed location factors are mainly related to the shared household characteristics, such as composition, income, lot area, or the practice of using rainwater.