setembro 22, 2011

É preciso apenas uma fêmea grávida de "guppy" para uma invasão alienígena


How reproductive ecology contributes to 
the spread of a globally invasive fish.
Deacon AE, IW Ramnarine and AE Magurran 

It takes just one pregnant guppy for an alien invasion!
Copyright © Mich De May, Creative Commons


The well-known ability of female guppies (Poecilia reticulata) to store sperm for up to six months and give birth long after being inseminated is responsible for their runaway success as one of the world's worst invasive fish species.

In research published in a recent issue of the online journal PLoS ONE, Amy Deacon, Indar Ramnarine and Anne Magurran document the current global distribution of the guppy, producing the most complete picture of the current distribution of this invasive species to date, and show that it is contributing to the homogenisation of fish communities on a global scale. 
At the same time, they conducted experiments to test the prediction that a single pregnant female guppy is capable of routinely establishing viable populations when introduced to a new habitat.
Despite the small native range of the guppy, the authors found that its introduced range now spans every continent with the exception of Antarctica, as well as numerous oceanic islands. 
Their data show that the worldwide distribution of the guppy is considerably more extensive than previously described in the literature or in any database.
For the second part of their study, the authors carried out an experiment in which 30 plastic mesocosms were established and a single pregnant female wild-caught guppy was added. The experiment was allowed to run for two years, during which the fish were counted, measured and their performance (in activity and evasion) were recorded.
The authors found that the single female guppies were capable of establishing viable populations within the mesocosms during the study period in a large majority of the cases: 91% of mesocosm populations persisted at the end of the first year and 86% at the end of the second.
Furthermore, their studies showed that the behavioural performance of the offspring from such introductions was not impaired. Although inbreeding is very likely to take place as a result of using a single founder individual, the guppies may be employing a number of pre- and post-copulatory strategies to minimise inbreeding, surmise the authors.
The authors conclude, "Our results demonstrate how introductions consisting of a few animals, or even a single individual, can lead to thriving populations of invasive species. A highly specialised reproductive system, coupled with a remarkable adaptability is likely to have led to the phenomenal success of the guppy outside of its native range. These findings reinforce the need for caution when releasing exotic species, and show that seemingly innocuous or beneficial activities such as a child freeing a few pet fish or a concerned householder using guppies to control mosquitoes can result in a thriving population of invasive poeciliids that may then go on to compete with the indigenous freshwater fauna. They also illustrate how many small actions replicated across the globe, in the form of the accidental or deliberate release of a few fish, combined with natural adaptations in these fish for life in ephemeral habitats, can contribute to the reduction of diversity in freshwater fish assemblages worldwide."
Deacon AE, IW Ramnarine and AE Magurran (2011). How reproductive ecology contributes to the spread of a globally invasive fish. PLoS ONE 6, e24416. doi:10.1371/journal.pone.0024416

setembro 09, 2011

Sistema de Transposição de Peixes


Imagem          MEIO AMBIENTE




Época de piracema: Santo Antônio Energia monitora 
migração de peixes do rio Madeira
De: Santo Antônio Energia 
09 de Setembro de 2011

Imagem - Divulgação
Entre agosto e novembro, a equipe do Programa de Conservação da Ictiofauna marcará 4 mil peixes que serão monitorados em um estudo sobre as rotas migratórias no período de reprodução das espécies. O objetivo é verificar se os animais estão utilizando o Sistema de Transposição de Peixes (STP), estrutura construída para ajudá-los a ultrapassar a barragem da Usina na época de piracema.

Equipamentos de telemetria para obtenção e transmissão de dados a longa distância foram instalados em parte dos animais e o monitoramento será feito por antenas instaladas nas margens e em barcos ao longo do rio Madeira. A outra parte dos peixes receberá uma marcação chamada LEA, um tubo com um número que é fixado na barbatana para identificá-lo quando ele for pescado.

setembro 07, 2011

Cuidado Parental!!!! Fantástico momento!!!!

Jawfish Eggs about to Hatch

Photo and caption by Suzan Meldonian
A male Banded Jawfish (Opistognathus macrognathus), incubates it's eggs in it's mouth, assuring survival of at least this stage of their lives. Held in by it's father's teeth at some point the overgrown siblings become cumbersome, yet the devotion of survival mode is so strong that the jawfish will only poof them out for a second or two to quickly catch a morsel of food in the water column, then quickly sucking the eggs back into it's mouth. This process is also called aerating the eggs... so it serves more than one purpose... sort of like rotating the eggs in a hatchery.