ABSTRACT
The vertical distribution of meiofauna within subtidal sediments was studied in four stations pertaining to mangrove or muddy flats habitats. In 2003, replicated samples were taken in dry (February) and wet (July) seasons at the Bacunagua Inlet, southwestern coast of Cuba. The abundance and number of meiofaunal taxa exhibited a vertical gradient possibly due to changes in the concentrations of oxygen and hydrogen sulphide, rather than food availability along this gradient. Nematodes are capable of distributing themselves throughout the whole sediment column due to their ability to tolerate reducing conditions; however depletion of communities along depth was evident. Their presence in deeper sediments (6 - 10 cm) suggests that certain species are adequately adapted to spend their entire life cycle in these harsh environments (where soluble tannins and decomposing organic matter predominate). Copepods showed a strong limitation to vertical distribution (concentrating in the top 2 cm), possibly in response to a sharp vertical decline in oxygenation within these organically enriched sediments. Rev. Biol. Trop. 56 (3): 1127-1134. Epub 2008 September 30.
Se estudió la distribución vertical de la meiofauna dentro de los sedimentos en cuatro estaciones ubicadas en manglares y planos fangosos. En el año 2003, tomamos muestras (con repetición) en época de seca (febrero) y de lluvia (julio) en la ensenada de Bacunagua, costa suroccidental de Cuba. La abundancia y el número de táxones de la meiofauna mostraron un gradiente vertical debido posiblemente a cambios en las concentraciones de oxígeno y sulfuro de hidrógeno, más que a la disponibilidad de alimento a lo largo del gradiente. Los nemátodos son capaces de distribuirse a través de la columna de sedimento debido a su habilidad para tolerar condiciones reducidas; sin embargo, fue evidente la reducción de las comunidades con la profundidad. Su presencia en los sedimentos profundos (6-10 cm) sugiere que ciertas especies están adecuadamente adaptadas a permanecer todo su ciclo de vida en un ambiente adverso (donde predominan los taninos solubles y la descomposición de la materia orgánica). Los copépodos mostraron una fuerte limitación en su distribución vertical (concentrándose en los 2 cm superficiales) posiblemente como respuesta a un gradiente marcado en la oxigenación dentro de estos sedimentos enriquecidos orgánicamente.
Subject(s)
Animals , Avicennia/classification , Combretaceae/classification , Ecosystem , Invertebrates/classification , Rhizophoraceae/classification , Cuba , Geologic Sediments , Population Density , Population Dynamics , Seasons , SeawaterABSTRACT
The vertical distribution of meiofauna within subtidal sediments was studied in four stations pertaining to mangrove or muddy flats habitats. In 2003, replicated samples were taken in dry (February) and wet (July) seasons at the Bacunagua Inlet, southwestern coast of Cuba. The abundance and number of meiofaunal taxa exhibited a vertical gradient possibly due to changes in the concentrations of oxygen and hydrogen sulphide, rather than food availability along this gradient. Nematodes are capable of distributing themselves throughout the whole sediment column due to their ability to tolerate reducing conditions; however depletion of communities along depth was evident. Their presence in deeper sediments (6 - 10 cm) suggests that certain species are adequately adapted to spend their entire life cycle in these harsh environments (where soluble tannins and decomposing organic matter predominate). Copepods showed a strong limitation to vertical distribution (concentrating in the top 2 cm), possibly in response to a sharp vertical decline in oxygenation within these organically enriched sediments.
Subject(s)
Avicennia/classification , Combretaceae/classification , Ecosystem , Invertebrates/classification , Rhizophoraceae/classification , Animals , Cuba , Geologic Sediments , Population Density , Population Dynamics , Seasons , SeawaterABSTRACT
The effect of sodium diethyldithiocarbamate (DDC) and S-2-aminoethyl-isothiouronicadenosin-5-triphosphate (adeturon) in the induction of Escherichia coli SOS response promoted by gamma-irradiation was studied by measuring the induction of sulA gene and the induction of lambda prophage. Furthermore, as a way of measure the exonuclease activity in gamma-irradiated cells in the presence or absence of both compounds, the DNA degradation was determined. Adeturon did not affected DNA degradation, but inhibited the induction of the SOS functions studied. On the contrary, DDC inhibited DNA degradation as well as the induction of the sulA gene, but enhanced lambda induction in E. coli lysogenic strains. These results indicate that both compounds diminish the DNA damage produced by gamma-irradiation and also suggest that the mechanisms of radioprotection must be different. Thus, radioprotection mediated by DDC should involve free hydroxyl radical scavenging and a minor activity of exonuclease. The enhancement of phage induction in E. coli cells that DDC produces could be attributed to its quelant effect and this would not be not probably directly related to radioprotection. Adeturon, as thiols, may serve also as scavenging agent of free hydroxyl radicals, diminishing indirectly the DNA damage level. In addition, adeturon must interact with DNA in the same form that other aminothiol compounds do it. This interaction, mediated by amino groups of adeturon, may serve to concentrate these compounds near of the DNA damage site, increasing the potential for the thiol portion of the molecule to donate hydrogen, decreasing the damage level on DNA molecule. However, adeturon do not modify the exonuclease activity. Some topic about the possible clinical application of both compounds are discussed.
