A phylogenetic comparative analysis on the evolution of sequential hermaphroditism in seabreams (Teleostei : Sparidae)

The Sparids are an ideal group of fish in which to study the evolution of sexual systems since they exhibit a great sexual diversity, from gonochorism (separate sexes) to protandrous (male-first) and protogynous (female-first) sequential hermaphroditism (sex-change). According to the size-advantage model (SAM), selection should favour sex change when the second sex achieves greater reproductive success at a larger body size than the first sex. Using phylogenetic comparative methods and a sample of 68 sparid species, we show that protogyny and protandry evolve from gonochorism but evolutionary transitions between these two forms of sequential hermaphroditism are unlikely to happen. Using male gonadosomatic index (GSI) as a measure of investment in gametes and proxy for sperm competition, we find that, while gonochoristic and protogynous species support the predictions of SAM, protandrous species do not, as they exhibit higher GSI values than expected even after considering mating systems and spawning modes. We suggest that small males of protandrous species have to invest disproportionally more in sperm production than predicted not only when spawning in aggregations with high levels of sperm competition, but also when spawning in pairs due to the need to fertilize highly fecund females, much larger than themselves. We propose that this compensatory mechanism, together with Bateman’s principles in sequential hermaphrodites, should be formally incorporated in the SAM

Heat-induced masculinization in domesticated zebrafish is family-specific and yields a set of different gonadal transcriptomes

Understanding environmental influences on sex ratios is important for the study of the evolution of sex-determining mechanisms and for evaluating the effects of global warming and chemical pollution. Fishes exhibit sexual plasticity, but the underlying mechanisms of environmental effects on their reproduction are unclear even in the well-established teleost research model, the zebrafish. Here we established the conditions to study the effects of elevated temperature on zebrafish sex. We showed that sex ratio response to elevated temperature is family-specific and typically leads to masculinization (female-to-male sex reversal), resulting in neomales. These results uncovered genotype-by-environment interactions that support a polygenic sex determination system in domesticated (laboratory) zebrafish. We found that some heat-treated fish had gene expression profiles similar to untreated controls of the same sex, indicating that they were resistant to thermal effects. Further, most neomales had gonadal transcriptomes similar to that of regular males. Strikingly, we discovered heat-treated females that displayed a normal ovarian phenotype but with a “male-like” gonadal transcriptome. Such major transcriptomic reprogramming with preserved organ structure has never been reported. Juveniles were also found to have a male-like transcriptome shortly after exposure to heat. These findings were validated by analyzing the expression of genes and signaling pathways associated with sex differentiation. Our results revealed a lasting thermal effect on zebrafish gonads, suggesting new avenues for detection of functional consequences of elevated temperature in natural fish populations in a global warming scenario

Switches, stability and reversals in the evolutionary history of sexual systems in fish

Sexual systems are highly diverse and have profound consequences for population dynamics and resilience. Yet, little is known about how they evolved. Using phylogenetic Bayesian modelling and a sample of 4614 species, we show that gonochorism is the likely ancestral condition in teleost fish. While all hermaphroditic forms revert quickly to gonochorism, protogyny and simultaneous hermaphroditism are evolutionarily more stable than protandry. In line with theoretical expectations, simultaneous hermaphroditism does not evolve directly from gonochorism but can evolve slowly from sequential hermaphroditism, particularly protandry. We find support for the predictions from life history theory that protogynous, but not protandrous, species live longer than gonochoristic species and invest the least in male gonad mass. The distribution of teleosts’ sexual systems on the tree of life does not seem to reflect just adaptive predictions, suggesting that adaptations alone may not fully explain why some sexual forms evolve in some taxa but not others (Williams’ paradox). We propose that future studies should incorporate mating systems, spawning behaviours, and the diversity of sex determining mechanisms. Some of the latter might constrain the evolution of hermaphroditism, while the non-duality of the embryological origin of teleost gonads might explain why protogyny predominates over protandry in teleosts

Information impact on consumers' perceptions towards aquaculture : Dismantling the myth about feeds for farmed fish

Altres ajuts: Acord transformatiu CRUE-CSICAquaculture products are commonplace in markets around the world. However, despite efforts to minimize the negative perceptions towards aquaculture, several misbeliefs or myths still persist, and thus globally consumers tend to value wild fish more highly than farmed fish. The lack of information has been shown to be one of the most important causes of this preference, driving buying decisions to be more emotional than rational. The aim of this study was to determine whether scientific-supported information contrasting one myth could contribute to a better perception of farmed products. To that end, consensus on a series of aquaculture-related issues among different scientists, external experts, and aquaculture societies was used to build up the scientific information. This information was provided to 300 Spanish consumers using two different communication tools (150 consumers each tool): an interactive web documentary and a written and printed document, to detect possible differences in the change of consumers' perception. Consumers were asked for their degree of agreement on a set of 14 statements before and after providing the scientific information. A variable collecting the assessment of each of the statements was calculated as the Overall-perception. Possible significant differences between the scores before and after providing the information and for the 'overall perception' were analysed separately for each communication tool as well as for the combined sample. Possible relationship between the consumers' perception with the sociodemographic factors, the consumers' knowledge and the fish consumption habits were also assessed. Results show that consumer's perception of aquaculture before the query were moderate (5.6 average in a 0 to 10 scale) but that it increased slightly but significantly and regardless of the communication tool used. Among sociodemographic factors, age and gender were the ones that most influenced consumer's perceptions, being older people those who exhibited a generally more positive opinion towards aquaculture. The effects of consumption habits and knowledge about aquaculture were also the two most explicative factors for change in perception. Importantly, the opinion of consumers with less knowledge about seafood products in general and production methods or consuming only wild fish products, improved after being exposed to the information. These results demonstrate the utility of science- and fact-based communication campaigns to improve the societal perception of aquaculture practices and products, regardless of the tool used to transmit this information

Crecimiento y desarrollo gonadal de rodaballos (Scophthalmus maximus L.) triploides hasta los 18 meses de edad

El objetivo de este trabajo fue determinar los efectos de la triploidía sobre el crecimiento, proporción de sexos y desarrollo gonadal de los rodaballos (Scophthalmus maximus L.) hasta los 18 meses de edad. Los resultados obtenidos demostraron una proporción significativamente mayor de hembras en el grupo triploide respecto del control diploide, un crecimiento significativamente superior, en el mismo grupo, y un desarrollo gonadal significativamente inferior en los triploides, especialmente en las hembra