Acoustic and visual adaptations to predation risk: A predator affects communication in vocal female fish

Predation is an important ecological constraint that influences communication in animals. Fish respond to predators by adjusting their visual signalling behaviour, but the responses in calling behaviour in the presence of a visually detected predator are largely unknown. We hypothesize that fish will reduce visual and acoustic signalling including sound levels and avoid escalating fights in the presence of a predator. To test this we investigated dyadic contests in female croaking gouramis (Trichopsis vittata, Osphronemidae) in the presence and absence of a predator (Astronotus ocellatus, Cichlidae) in an adjoining tank. Agonistic behaviour in T. vittata consists of lateral (visual) displays, antiparallel circling and production of croaking sounds and may escalate to frontal displays. We analysed the number and duration of lateral display bouts, the number, duration, sound pressure level and dominant frequency of croaking sounds as well as contest outcomes. The number and duration of lateral displays decreased significantly in predator as compared to no-predator trials. Total number of sounds per contest dropped in parallel but no significant changes were observed in sound characteristics. In the presence of a predator dyadic contests were decided or terminated during lateral displays and never escalated to frontal displays. The gouramis showed approaching behaviour towards the predator between lateral displays. This is the first study supporting the hypothesis that predators reduce visual and acoustic signalling in a vocal fish. Sound properties, in contrast, did not change. Decreased signalling and the lack of escalating contests reduce the fish’s conspicuousness and thus predation threat.

PRIMER REGISTRO DE METACERCARIAS (DIGENEA) INFECTANDO ASTRONOTUS OCELLATUS (PERCIFORMES: CICHLIDAE) DE LA REGIÓN AMAZÓNICA, BRASIL

Este estudio tiene como objetivo el registro de la infestación por metacercarias de los géneros Posthodiplostomum Dubois, 1936 (Diplostomidae) y Dubois Herpetodiplostomum, 1936 (Proterodiplostomidae) en las branquias del Astronotus ocellatus Agassiz, 1831 (Cichlidae) del lago Pracuúba, en el Municipio de Pracuúba, Estado de Amapá, Brasil. De doscientos ejemplares de A. ocellatus examinados, 142 tenian las branquias infestadas por Herpetodiplostomum sp. (prevalencia = 70,3%) y por Posthodiplostomum sp. (prevalencia = 59,4%). Sin embargo 97 hospederos fueron infestados por estas dos especies de metacercarias (prevalencia = 48,0%). Del total de ejemplares de A. ocellatus examinados fueron extraidos 1.123 parasitos de Herpetodiplostomum sp. y 463 parasitos de Posthodiplostomum sp., y la media de intensidad de la infestación fue de 7,8 ± 3,9 y 11,6 ± 4,4, respectivamente. Este es el primer registro de Digenea en A. ocellatus.

Molecular Systematic Investigations of Three Fin Fish Cichlid Species of Oreochromis niloticus (Nile Tilapia), Genetically Improved Farmed Tilapia (GIFT) and Astronotus ocellatus (Oscar Cichlid)

Fisheries in India contribute significantly to the total GDP of agriculture and earn significant foreign exchange. Aquaculture is playing an important role in India and is bestowed with a huge biodiversity of aquatic organisms. India ranks second in total fish production in the world. Nile tilapia has become the world’s second most popular farmed fish, after carps. Oscars is a popular aquarium fish around the world. In the present study, efforts were made to analyze the extent of divergence or similarity among three cichlid finfishes (Nile Tilapia, GIFT Tilapia, and Oscar Cichlid) using molecular biology techniques such as Random Amplification of Polymorphic DNA (RAPD) and Restriction Fragment Length Polymorphism (RFLP). The Phylogenetic tree was constructed using PhyElph software to study the evolutionary relationship between the three cichlid finfish species. The Phylogenetic or evolutionary relationship was established for the three fishes, Nile tilapia, GIFT, and Oscar cichlid, with the Phylogenetic tree. It was found that Nile tilapia and GIFT share a recent common ancestor, while Oscar cichlid does not share any evolutionary relationship with Nile tilapia and GIFT.

A PESCA ARTESANAL NA REGIÃO DOS LAGOS: O CASO DO MUNICÍPIO DE PRACUÚBA, AMAPÁ

O estudo caracteriza o perfil socioeconômico dos pescadores e descreve a atividade pesqueira desenvolvida no município de Pracuúba, Amapá. Na ocasião, foram realizadas entrevistas e aplicação de formulários semiestruturados aos pescadores. A maioria era do sexo masculino, com idade média de 37 anos, baixo grau de escolaridade e renda média mensal declarada pela pesca de três salários mínimos. A pesca ocorre com maior frequência nos lagos Pracuúba e Cujubim, e no rio Flexal. As embarcações mais utilizadas são as canoas movidas a remo, o que limita a prática de captura nas proximidades de suas residências e a utilização do gelo como principal forma de conservação do pescado. A rede de emalhar (malhadeira), o anzol e a zagaia são os apetrechos de pesca mais empregados para capturar tucunarés (Cichla sp.) e apaiari (Astronotus ocellatus). Dentre as principais problemáticas registradas estão: a falta de uma fábrica de gelo, estruturas de desembarque, de fiscalização, estrada para escoamento da produção, ausência de uma política de apoio a atividade pesqueira e a diminuição gradativa das capturas, além dos impactos causados pela criação de bubalinos, afetando a dinâmica do ambiente e consequentemente a vida desses pescadores que possuem a pesca como principal fonte de renda familiar.