ABSTRACT
Atherinella blackburni is a silverside species whose occurrence on the Brazilian coast was not properly registered until recently. So far, records of its distribution along the Brazilian shore were limited to Itaparica Island, Bahia State, and Porto Inhaúma, Rio de Janeiro State. In a recent survey of the ichthyofauna of Itamambuca Beach, Ubatuba, São Paulo State, 100 specimens of this species were collected, yielding a considerable source of information regarding its ecology and a new southern limit of its distribution. A detailed survey of an ichthyological collection revealed lots of this species from regions of the Brazilian Northeast, resulting in a northward expansion of the occurrence of A. blackburni in Brazilian waters. Besides the populations found on the Brazilian coast, the species also occurs discontinuously in the Atlantic coasts of Costa Rica, Panama and Venezuela. Meristic and morphometric analysis showed overlapped values between Brazilian populations and the ones closer to the Caribbean. An ecological study of A. blackburni at Itamambuca Beach revealed that it is a predominantly diurnal species with preference for warm and salty waters, often occurring in sandy-bottom environments. It was more abundant in Summer and Winter, when individuals with smaller values of length and weight also occurred.
Subject(s)
Ecosystem , Fishes/classification , Animals , Brazil , Fishes/anatomy & histology , Fishes/physiology , Population Dynamics , Seasons , SeawaterABSTRACT
Atherinella blackburni is a silverside species whose occurrence on the Brazilian coast was not properly registered until recently. So far, records of its distribution along the Brazilian shore were limited to Itaparica Island, Bahia State, and Porto Inhaúma, Rio de Janeiro State. In a recent survey of the ichthyofauna of Itamambuca Beach, Ubatuba, São Paulo State, 100 specimens of this species were collected, yielding a considerable source of information regarding its ecology and a new southern limit of its distribution. A detailed survey of an ichthyological collection revealed lots of this species from regions of the Brazilian Northeast, resulting in a northward expansion of the occurrence of A. blackburni in Brazilian waters. Besides the populations found on the Brazilian coast, the species also occurs discontinuously in the Atlantic coasts of Costa Rica, Panama and Venezuela. Meristic and morphometric analysis showed overlapped values between Brazilian populations and the ones closer to the Caribbean. An ecological study of A. blackburni at Itamambuca Beach revealed that it is a predominantly diurnal species with preference for warm and salty waters, often occurring in sandy-bottom environments. It was more abundant in Summer and Winter, when individuals with smaller values of length and weight also occurred.
Atherinella blackburni é uma espécie de peixe-rei cuja ocorrência na costa brasileira não havia sido precisamente registrada até recentemente. Ainda assim, sua distribuição no litoral brasileiro estava restrita à Ilha de Itaparica, Bahia e Porto Inhaúma, Rio de Janeiro. Em um recente levantamento da ictiofauna da Praia de Itamambuca, Ubatuba, São Paulo, foram coletados 100 espécimes desta espécie, originando uma fonte considerável de informações no tocante à sua ecologia e a um novo limite sul de sua distribuição. Um estudo detalhado revelou lotes desta espécie em regiões do nordeste brasileiro em coleção ictiológica, resultando na expansão para o norte da ocorrência de A. blackburni em águas brasileiras. Além das populações encontradas na costa brasileira, a espécie também ocorre descontinuamente na costa Atlântica da Costa Rica, Panamá e Venezuela. Análise merística e morfométrica revelou valores sobrepostos entre populações brasileiras e aquelas mais próximas ao Caribe. O estudo ecológico de A. blackburni na Praia de Itamambuca evidenciou que é uma espécie predominantemente diurna com preferência por águas quentes e salgadas, freqüente em ambientes com fundo arenoso. Foi mais abundante no verão e inverno, quando indivíduos com menores valores de comprimento e peso também ocorreram.
Subject(s)
Animals , Ecosystem , Fishes/classification , Brazil , Fishes/anatomy & histology , Fishes/physiology , Population Dynamics , Seasons , SeawaterABSTRACT
An in vitro system developed for the site-specific mutagenesis of 16S RNA of Escherichia coli ribosomes (Krzyzosiak et al., Biochemistry 26, 2353-2364, 1987) was used to make 10 single base changes around C1400, the residue known to be at the decoding site. C1400 was replaced by U, A, or G, 5 single base deletions at and to either side of C1400 were made, and C or U was inserted next to C1400. Another mutant possessed 7 additional nucleotides at the 3' end of the 16S RNA such that a stem and loop involving the anti-Shine-Dalgarno sequence could form. Another series of 8 mutants tested hypothetical base-pairing between C1404, G1405 and C1496, G1497. The activity of these 19 mutants in A and P site binding, and in initiation-dependent and initiation-independent peptide synthesis was determined. None of the base substitutions of C1400 were strongly inhibitory. The insertions and deletions completely blocked initiation-dependent peptide synthesis but markedly stimulated the initiation-independent reaction. The effects of tRNA binding were variable. The only alteration to block all ribosomal function was the deletion of G1401. The extra stem and loop at the 3'-end blocked initiation-dependent peptide synthesis, but all other assays were normal. The mutants which break and reform the hypothetical base-pairs had a functional pattern that suggest the contiguous base-pairs do exist and are functionally important.