A multi-component pheromone in the urine of dominant male tilapia (Oreochromis mossambicus) reduces aggression in rivals

Males often use scent to communicate their domi- nance, and to mediate aggressive and breeding behaviors. In teleost fish, however, the chemical composition of male pher- omones is poorly understood. Male Mozambique tilapia, Oreochromis mossambicus, use urine that signals social status and primes females to spawn. The urinary sex pheromone di- rected at females consists of 5β-pregnane-3α,17α,20β-triol 3- glucuronate and its 20α-epimer. The concentration of these is positively correlated with male social rank. This study tested whether dominant male urine reduces aggression in receiver males, and whether the pregnanetriol 3-glucuronates also re- duce male-male aggression. Males were allowed to fight their mirror image when exposed to either: i) water control or a chemical stimulus; ii) dominant male urine (DMU); iii) C18- solid phase (C18-SPE) DMU eluate; iv) C18-SPE DMU eluate plus filtrate; v) the two pregnanetriol 3-glucuronates (P3Gs); or vi) P3Gs plus DMU filtrate. Control males mounted an increas- ingly aggressive fight against their image over time. However, DMU significantly reduced this aggressive response. The two urinary P3Gs did not replicate the effect of whole DMU. Neither did the C18-SPE DMU eluate, containing the P3Gs, alone, nor the C18-SPE DMU filtrate to which the two P3Gs were added. Only exposure to reconstituted DMU (C18-SPE eluate plus filtrate) restored the aggression-reducing effect of whole DMU. Olfactory activity was present in the eluate and the polar filtrate in electro-olfactogram studies. We conclude that P3Gs alone have no reducing effect on aggression and that the urinary signal driving off male competition is likely to be a multi-component pheromone, with components present in both the polar and non-polar urine fractions.

Aprendizagem das ciências em espaços não-formais: visita de estudo na rota das energias renováveis

Nos programas actuais defende-se um ensino contextualizado numa perspectiva CTSA - Ciência, Tecnologia, Sociedade e Ambiente, e a diversificação de estratégias e actividades é recomendada. Numa perspectiva construtivista, a aprendizagem fora da sala de aula, aprendizagem em espaços não-formais - as visitas de estudo - são consideradas como uma das estratégias com elevado potencial pedagógico. No presente estudo foram realizadas e avaliadas duas visitas de estudo no âmbito da disciplina de Física e Química do 10° ano de escolaridade, tendo a primeira sido feita como estudo-piloto ao Centro de Ciência Viva de Constância e uma segunda como estudo principal, Na Rota das Energias Renováveis, à Barragem do Alqueva, Central Solar Fotovoltaica da Amareleja, Parque de Natureza de Noudar e Herdade do Esporão. Realizou-se uma pré-visita aos locais a visitar, estabeleceram-se contactos privilegiados com as instituições visitadas, preparam-se materiais didácticos, um Roteiro e um Guia de Campo para cada local visitado, foram elaborados e apresentados aos alunos questionários sobre o seu grau de satisfação com as visitas e realizaram-se ainda entrevistas em grupo com alguns alunos para recolher as suas impressões. Os alunos realizaram trabalhos de divulgação da visita tendo sido disponibilizada, no "site" da escola, informação detalhada sobre a visita. Neste estudo analisou-se em que medida uma aprendizagem contextualizada num espaço não-formal foi promotora de um envolvimento produtivo dos alunos. As aprendizagens realizadas situaram-se no domínio cognitivo, social ou atitudinal e os materiais didácticos, como o Guia de Campo tiveram um papel relevante para essas aprendizagens. A motivação dos alunos para a disciplina melhorou durante e após a visita. A colaboração com as instituições visitadas mostrou-se importante no estabelecimento de uma interface entre o espaço formal e o não-formal. A realização de visitas de estudo é uma componente importante dos curricula e deve ser encarada com naturalidade a sua realização frequente, como parte de uma estratégia para motivar os alunos para a disciplina e aumentar a sua capacidade de aprender os conteúdos. ABSTRACT: Nowadays programs defend teaching model that follows a perspective based in Science, Technology, Society and Environment, with special focus in the diversification of strategies. Outside of classroom teaching, in non-formal spaces, as in field trips, is considered one of the strategies with the highest pedagogic potential. ln this study, two field trips were made based on the Physics and Chemistry program for the 1Oth grade, with the first one as the pilot visit to Centro de Ciência Viva de Constância, and the second one as the main study, ln the Path of Renewable Energies, to Alqueva’s dam, Amareleja's Solar Photovoltaic Center, Noudar's Nature Park and Herdade do Esporão. A pre-visit was made for each one of the places to visit, contacts were made, materials were created, an itinerary and a Field Guide for both field trips, satisfaction questionaries were made to the students and the teacher also interviewed some students for appreciations about the visit. The students created posters about the field trip, and information was also showed in the school website. With this study, the benefits of a contextualized learning in a non-formal space were demonstrated. These acquisitions of knowledge were in various domains, such as cognition, social behavior and the didactic materials had a relevant role in these acquirements. Moreover, the students' motivation for the subject in question improved significantly during and after the field trip. The cooperation with the visited institutions revealed to be important in the establishment of an interface between the formal and the non-formal spaces. Making field trips is an important component in the curricula and should be encouraged and seen as a natural part of a strategy of motivation of the students for a certain subject, increasing its ability to learn matters.