OLFACTO E REPRODUÇÃO: A INFLUÊNCIA DA COMUNICAÇÃO QUÍMICA NA PUBERDADE EM PEIXES

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Publications

Social organization and endocrine profiles of Australoheros facetus, an exotic freshwater fish in southern Portugal

Publication . Baduy, F.; Silva, FBV; Guerreiro, Pedro M; Canario, A.V.M.; L. Saraiva, João

Australoheros facetus is a neotropical cichlid and an exotic species in the Guadiana and Odelouca basins (Southern Portugal). In this research, we aimed to characterize the main behavioural patterns and circulating hormones, 17 beta-estradiol (E-2) for females, and testosterone, 11-ketotestosterone (11KT) and cortisol for both sexes, during the formation of social groups, a crucial step in the life-history of A. facetus. A pair-breeding strategy with territorial behaviour and aggressive interactions was found, with a positive correlation between dominance and size for both sexes. There were no significant differences between non-territorial and territorial individuals in the baseline levels of hormones, but 11KT was higher in males when they became territorial, as E-2 for territorial females, while there was no clear pattern for testosterone. In contrast, cortisol was higher in non-territorial males and correlated negatively with social dominance. These results suggest that size is the main driver for social dominance and that formation of stable hierarchies result in higher circulating 11KT and lowers stress in territorial males. Related to A. facetus' behaviour, aggressiveness and biparental care may be an advantage during the invasion process of A. facetus, facilitating colonization of new habitats.

2017-10Journal article

Restricted access

Taxonomic re-evaluation of the non-native cichlid in Portuguese drainages

Publication . Carecho, João; Baduy, F.; Silva, FBV; Guerreiro, Pedro; Saraiva, João L.; Ribeiro, Filipe; Veríssimo, Ana

A non-native cichlid fish firstly reported in Portugal in 1940 was originally identified as Cichlasoma facetum (Jenyns 1842) based on specimens reported from “Praia de Mira” (Vouga drainage, northwestern Portugal). Currently, the species is known only from three southern Portuguese river drainages, namely Sado, Arade and Guadiana, and no other record has been made from Praia de Mira or the Vouga drainage since the original record. The genus Cichlasoma has since suffered major taxonomic revisions: C. facetum has been considered a species-complex and proposed as the new genus Australoheros, including many species. Given the current taxonomic re-arrangement of the C. facetum species group, we performed a taxonomic re-evaluation of species identity of this non-native cichlid in Portuguese drainages using morphological and molecular analyses. Morphological data collected on specimens sampled in the Sado river drainages confirmed the identification as Australoheros facetus. Moreover, nucleotide sequences of the cytochrome b gene obtained from specimens from Sado, Arade and Guadiana showed the existence of a single haplotype across drainages, which was 100% identical to A. facetus specimens collected in native Argentinean waters (i.e. Uruguay River). The current non-native distribution range of the species in Portugal results from human-mediated introductions across the southern drainages.

2018Journal article

Open access

Chemical diplomacy in male tilapia: urinary signal increases sex hormone and decreases aggression

Publication . Saraiva, João; Keller-Costa, Tina; Hubbard, Peter; Rato, Ana; Canario, Adelino

Androgens, namely 11-ketotestosterone (11KT), have a central role in male fish reproductive physiology and are thought to be involved in both aggression and social signalling. Aggressive encounters occur frequently in social species, and fights may cause energy depletion, injury and loss of social status. Signalling for social dominance and fighting ability in an agonistic context can minimize these costs. Here, we test the hypothesis of a 'chemical diplomacy' mechanism through urinary signals that avoids aggression and evokes an androgen response in receiver males of Mozambique tilapia (Oreochromis mossambicus). We show a decoupling between aggression and the androgen response; males fighting their mirror image experience an unresolved interaction and a severe drop in urinary 11KT. However, if concurrently exposed to dominant male urine, aggression drops but urinary 11KT levels remain high. Furthermore, 11KT increases in males exposed to dominant male urine in the absence of a visual stimulus. The use of a urinary signal to lower aggression may be an adaptive mechanism to resolve disputes and avoid the costs of fighting. As dominance is linked to nest building and mating with females, the 11KT response of subordinate males suggests chemical eavesdropping, possibly in preparation for parasitic fertilizations.

2017-08Journal article

Open access

Distribution and risk assessment of potential invasiveness of Australoheros facetus (Jenyns, 1842) in Portugal

Publication . Baduy, Flavia; Saraiva, João; Ribeiro, Filipe; Canario, Adelino; Guerreiro, Pedro

Invasive species are recognized as a major cause of biodiversity decline. Legal regulations relating to the prevention, control, or eradication of invasive species should always be up-to-date, as the failure to recognize the problem, lack of adequate scientific information, or long legal intervals required to prepare the legislation may result in irreversible, possibly catastrophic, outcomes. This implies constant monitoring of the species distribution and levels of establishment, as well as detailed knowledge about its biology to predict dissemination and viability under changing environmental conditions. Pre-screening kits for potential invasive species are valuable tools for policy makers, as they provide information about if and how management measures should be taken. The Freshwater Fish Invasiveness Scoring Kit (FISK) and the Aquatic Species Invasiveness Screening Kit (AS-ISK) have been suggested as reliable tools to assess the potential risk of a species becoming invasive. The present study highlights the spread of the non-native chameleon cichlid Australoheros facetus in several streams of the major river drainages in southern Portugal and compares the fish assemblages and ecological indices in two selected sites in the Vascão and Odelouca rivers. We reviewed the current knowledge on the distribution, physiology, and behavior of A. facetus, and applied the toolkits FISK v2 and AS-ISK to this species to evaluate whether the species should be classified as invasive in Portugal. Field data show high abundance of the species in most streams and dominance in specific hotspots. The scores reached by the kits (FISK v2: 23; AS-ISK: 37) places A. facetus as a species with high potential of invasiveness and support the recent inclusion of this species in the invasive species list in Portugal (Decree-Law 92/2019), but, most of all, highlights the importance of frequent updates in both the field monitoring and the legal regulation and watch lists of invasive organisms.

2019-12-27Journal article

Open access

Maternal thyroid hormones are essential for neural development in Zebrafish

Publication . Campinho, Marco António; Saraiva, João; Florindo, Claudia; Power, Deborah M.

Teleost eggs contain an abundant store of maternal thyroid hormones (THs), and early in zebrafish embryonic development, all the genes necessary for TH signaling are expressed. Nonetheless the function of THs in embryonic development remains elusive. To test the hypothesis that THs are fundamental for zebrafish embryonic development, an monocarboxilic transporter 8 (Mct8) knockdown strategy was deployed to prevent maternal TH uptake. Absence of maternal THs did not affect early specification of the neural epithelia but profoundly modified later dorsal specification of the brain and spinal cord as well as specific neuron differentiation. Maternal THs acted upstream of pax2a, pax7, and pax8 genes but downstream of shha and fgf8a signaling. The lack of inhibitory spinal cord interneurons and increased motoneurons in the mct8 morphants is consistent with their stiff axial body and impaired mobility. The mct8 mutations are associated with X-linked mental retardation in humans, and the cellular and molecular consequences of MCT8 knockdown during embryonic development in zebrafish provides new insight into the potential role of THs in this condition.

2014-07Journal article

Open access