Fishers' Knowledge Reveals Ecological Interactions Between Fish and Plants in High Diverse Tropical Rivers

Ecosystems - Frugivory and seed dispersal by fish is an important mutualistic interaction in complex and species-rich tropical rivers. The local ecological knowledge (LEK) held by fishers can...     

Co-management and Spatial Features Contribute to Secure Fish Abundance and Fishing Yields in Tropical Floodplain Lakes

Empirical data are needed to show the efficacy of co-management, which is regarded as a promising approach to achieve conservation goals. In this study, we addressed the potential influence of fisheries co-management to increase fish abundance and fishing yields in the lower Tocantins River Basin (Brazilian Amazon), downstream from a large dam. We analyzed 590 fish landings (6.7 t of fish) from five fishing villages and 48 fish samples obtained using gillnets (10,378 fish from 101 species) in 12 floodplain lakes in four regions: two with incipient co-management and two unmanaged. The fish species richness did not differ among the regions, but the lakes in the regions that were co-managed had higher fish abundance (biomass and number of individuals) and a higher mean proportion of fish reproducing during the high water season. Fishers had higher catches per unit of effort in the co-managed regions than fishers in the non-managed regions. These results were also influenced by geographic factors (distance and accessibility of lakes), as fish biomass was higher in lakes that were distant from the main river and from the main city in the region. Managers should thus consider strategic selection of the geographic locations of managed sites, even in remote areas. However, the fish biomass sampled in lakes was more related to region than to the lakes’ geographical location. Therefore, co-management has at least partially contributed to increased fish abundance and fishing yields in the studied region, through the protection of an important fish habitat (lakes). We provide empirical evidence that co-management can contribute to the maintenance of fish abundance, sustainability of fisheries, and food security in large tropical rivers impacted by damming.     

The Tomato spotted wilt virus cell‐to‐cell movement protein (NSM) triggers a hypersensitive response in Sw‐5‐containing resistant tomato lines and in Nicotiana benthamiana transformed with the functional Sw‐5b resistance gene copy

Although the Sw‐5 gene cluster has been cloned, and Sw‐5b has been identified as the functional gene copy that confers resistance to Tomato spotted wilt virus (TSWV), its avirulence (Avr) determinant has not been identified to date. Nicotiana tabacum ‘SR1‘ plants transformed with a copy of the Sw‐5b gene are immune without producing a clear visual response on challenge with TSWV, whereas it is shown here that N. benthamiana transformed with Sw‐5b gives a rapid and conspicuous hypersensitive response (HR). Using these plants, from all structural and non‐structural TSWV proteins tested, the TSWV cell‐to‐cell movement protein (NS_M) was confirmed as the Avr determinant using a Potato virus X (PVX) replicon or a non‐replicative pEAQ‐HT expression vector system. HR was induced in Sw‐5b‐transgenic N. benthamiana as well as in resistant near‐isogenic tomato lines after agroinfiltration with a functional cell‐to‐cell movement protein (NS_M) from a resistance‐inducing (RI) TSWV strain (BR‐01), but not with NS_M from a Sw‐5 resistance‐breaking (RB) strain (GRAU). This is the first biological demonstration that Sw‐5‐mediated resistance is triggered by the TSWV NS_M cell‐to‐cell movement protein.     

Structural and ultrastructural alterations of Malpighian tubules of Anticarsia gemmatalis (Hübner) (Lepidoptera: Noctuidae) larvae infected with different Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) recombinant viruses

Malpighian tubules constitute the main excretion organ of insects. Infection by egt⁻ recombinant AcMNPV baculovirus in lepidopteran larvae promotes early degeneration of these structures, which has been correlated with earlier death of the host. However, no trace of viral infection has been detected in that tissue. We constructed two AgMNPV recombinants with the egfp gene under control of the hsp70 promoter, one being egt⁻, and used another two recombinants (one egt⁻) containing the lacZ gene. Morphological alterations in the tubules were analyzed by light and electron microscopies. Bioassays were conducted to compare the pathogenicity of recombinants. Results showed progressive presence of marker proteins and tissue degeneration without signals of infection in the tissue. Morphological and bioassay results showed increased pathogenicity for lacZ-containing recombinants compared to the egfp ones; as for egt⁻ viruses, we noted higher intensity and earlier onset of alterations. The absence of infection led us to believe that Malpighian tubules degeneration is provoked initially by the death of tracheal cells attached to the tubules and later, by the death of Malpighian tubule cells themselves. Tubule cell death might be due to oncosis and apoptosis, which may be activated by depletion of energy reserves and by accumulation of marker proteins, respectively. Absence of the egt gene may be leading to a higher energetic expense due to molting, thus aggravating tubule cell death, resulting in faster death of host.