BCOMP - Artigos em revistas internacionais
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Browsing BCOMP - Artigos em revistas internacionais by Author "Almada, Vítor Carvalho"
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- Agonistic behaviour and shoal composition of juvenile Diplodus sargus : First field observationsPublication . Gonçalves, Ana R.; Silva, Matheus Augusto Farias da; Vendrell, Catarina L.; Almada, Vítor CarvalhoBehavioural observations of juvenile Diplodus sargus in natural habitats were conducted to test whether agonistic interactions occur in natural circumstances and, if they do, in which context they happen. The level of aggression and the shoals composition were also compared between distinct natural habitats. Behavioural observations were also conducted in captivity, and the level of aggression was comparedwith the level recorded in natural conditions to investigate which factors may promote aggressive behaviours. The observations were performed at two sites in the Atlantic Portuguese shore: São Pedro do Estoril (38°41′N, 9°22′W) and Cabo Raso (38°42′N, 9°29′W) from early July to late August 2010 and from late July to early October 2011, respectively. In nature agonistic behaviours do occur, with a higher frequency in pools than in open areas. However, even the highest values observed in nature are significantly lower than those reported for captive conditions. Shoal composition also changed in different habitats, with more members and aggregates more compact in open areas.We suggested that the high levels of aggression observed in captive groups may be an artefact caused by very high densities in confined spaces and eventually by the accumulation of chemicals that are known to be released by stressed fish and can be detected by other conspecifics. The confinement imposed in captivity may also affect shoal composition limiting the number of members and inter-individual distances in each group.
- Genetic structure and historical demography of the shanny Lipophrys pholis in the Portuguese coast based on mitochondrial DNA analysisPublication . Francisco, Sara Martins; Vieira, Maria Natividade; Almada, Vítor CarvalhoInexistente
- Homing in rocky intertidal fish. Are Lipophrys pholis L. able to perform true navigation?Publication . Jorge, Paulo; Almada, Frederico José Oliveira de; Gonçalves, Ana Sofia Ribeiro; Coelho, Pedro Duarte; Almada, Vítor CarvalhoAlthough navigation is common in many animals, only a few perform true navigation, meaning that they have the ability to return to a given place by relying on indirect cues obtained at the release site (i.e., by relying on information from a ‘‘map and compass’’ mechanism). The common intertidal fish, Lipophrys pholis, is thought to have homing abilities through a mechanism that primarily makes use of familiar landmarks (i.e., piloting). Anecdotal reports that individuals return to their home pools after release at unfamiliar sites suggest that L. pholis might use cues collected at the release site to find their way back (i.e., they might use map and compass information). Using a completely artificial setup, we tested the homing abilities of L. pholis as a function of age, sex, and familiarity with the release site. The findings showed that motivation for homing is present only in the adult phase and is independent of sex and/or familiarity with the release site. Moreover, adults released at a completely unfamiliar place oriented themselves in a direction roughly similar to that of their home pools. The fact that L. pholis were tested in a complete artificial environment means that hydrodynamic cues can be excluded as playing a role in this process and restricts the candidate options (e.g., magnetic cues). The ability to perform navigation based on a ‘‘map and compass’’ mechanism raises many interesting questions about the learning process, once these individuals have restricted home ranges during their lives. In vertebrate navigation, the cues used during the navigation process are a question of debate, and L. pholis offers an outstanding model to test hypotheses and ultimately provide answers.
- Lusitanian toadfish song reflects male qualityPublication . Amorim, M. C. P.; Simoes, J. M.; Mendonca, N.; Bandarra, Narcisa M.; Almada, Vítor Carvalho; Fonseca, P. J.Lusitanian toadfish males that provide parental care rely on acoustic signals (the boatwhistle) to attract females to their nest. We test the hypothesis that male quality, namely male size and condition that are relevant for parental success, is reflected in vocal activity and boatwhistle characteristics and thus advertised to females. We recorded 22 males over a week during the peak of the breeding season. Calling rate and calling effort (percentage of time spent calling) strongly reflected male condition (lipid content of somatic muscles) and to a smaller extent sonic muscle hypertrophy and larger gonads. Males in better condition (increased body lipid and relative higher liver mass) also contracted the sonic muscles at faster rate as shown by the shorter boatwhistle pulse periods. Amplitude modulation reflected the degree of sonic muscle hypertrophy. None of the measured male quality parameters were good predictors of boatwhistle duration and dominant frequency. Altogether this study strongly suggests that Lusitanian toadfish males advertise their quality to females primarily with boatwhistle calling rate and calling effort, which mainly reflect male condition. Because pulse period had low variability, consistent with the existence of a vocal central pattern generator, we suggest that males that sustain sonic muscles contraction at a very fast rate close to their physiological limit may be honestly advertising their quality (condition). Similarly, males that produce boatwhistles with higher amplitude modulation, a feature that seems dependent on sonic muscle hypertrophy, could be more attractive to females.