Contaminación en el Lago de Tota, Colombia: toxicidad aguda en Daphnia magna (Cladocera: Daphniidae) e Hydra attenuata (Hydroida: Hydridae) / Pollution in Lago de Tota, Colombia: acute toxicity on Daphnia magna (Cladocera: Daphniidae) and Hydra attenuata (Hydroida: Hydridae)

Resumen La cuenca del Lago de Tota ha sido modificada por diversas actividades humanas, como deforestación, piscicultura y el monocultivo de cebolla larga (Allium fistulosum) con un elevado uso de agroquímicos y gallinaza cruda, causando deterioro de las características ecológicas del sistema léntico de alta montaña más grande de Colombia. En este trabajo se implementaron pruebas de toxicidad para determinar posibles efectos deletéreos sobre H. attenuata y D. magna. Se aclimataron los organismos y validaron los ensayos de toxicidad en condiciones de laboratorio, posteriormente se realizó la evaluación de agua y sedimentos (elutriados) provenientes de afluentes de la cuenca del lago: Hato Laguna, El Tobal, Los Pozos y Agua Blanca, durante dos periodos hidroclimáticos contrastantes. Se evidenció una mayor sensibilidad con los ensayos en H. attenuata, ya que señalan que aguas y elutriados de Hato Laguna, El Tobal y Los Pozos generaron respuestas de subletalidad (Kruskal-Wallis; P < 0.05) y letalidad. Se registra presencia positiva de al menos cinco plaguicidas no cuantificados antes en la cuenca (clorotalonilo, aldrin, dieldrin, DDT y congéneres). Estos resultados indicarían una potencial influencia negativa de las actividades antropogénicas sobre organismos acuáticos nativos, con posibles consecuencias sobre la composición, estructura y función de las comunidades hidrobiológicas.(AU)

Abstract Lago de Tota basin is currently being impacted by human activities like agriculture, deforestation, large-scale fish farming and monoculture of onion long (Allium fistulosum) with high use of agrochemicals and chicken manure that contaminate runoff to aquatic systems in the largest high mountain lake in Colombia. We implemented toxicity tests to evaluate possible deleterious effects of contaminants on H. attenuata and D. magna, model organisms commonly used in aquatic contamination assessment. Firstly, the organisms were acclimated and toxicity tests were validated in laboratory conditions. Later, water and sediments (elutriates) were evaluated from tributaries of Lago de Tota basin: Hato Laguna, El Tobal, Los Pozos, and Agua Blanca stream, during two contrasting hydroclimatic periods. In addition, pesticides in sediments were evaluated with chromatography, spectrometry and ultraviolet detection techniques. Acute toxicity tests showed that H. attenuata was more sensitive than D. magna, as it showed sublethal (Kruskal-Wallis; P < 0.05) and lethal responses to exposure to waters and elutriates from Hato Laguna, El Tobal, and Los Pozos. At least five pesticides not quantified before in the basin were detected in chemical analyses (chlorothalonil, aldrin, dieldrin, DDT y congeners). These results indicate that anthropogenic activities have a potentially negative influence in aquatic communities composition, structure, and function, it´s demand attention in future research.(AU)

Degradation of textile dyes by cyanobacteria

Abstract Dyes are recalcitrant compounds that resist conventional biological treatments. The degradation of three textile dyes (Indigo, RBBR and Sulphur Black), and the dye-containing liquid effluent and solid waste from the Municipal Treatment Station, Americana, São Paulo, Brazil, by the cyanobacteria Anabaena flos-aquae UTCC64, Phormidium autumnale UTEX1580 and Synechococcus sp. PCC7942 was evaluated. The dye degradation efficiency of the cyanobacteria was compared with anaerobic and anaerobic-aerobic systems in terms of discolouration and toxicity evaluations. The discoloration was evaluated by absorption spectroscopy. Toxicity was measured using the organisms Hydra attenuata, the alga Selenastrum capricornutum and lettuce seeds. The three cyanobacteria showed the potential to remediate textile effluent by removing the colour and reducing the toxicity. However, the growth of cyanobacteria on sludge was slow and discoloration was not efficient. The cyanobacteria P. autumnale UTEX1580 was the only strain that completely degraded the indigo dye. An evaluation of the mutagenicity potential was performed by use of the micronucleus assay using Allium sp. No mutagenicity was observed after the treatment. Two metabolites were produced during the degradation, anthranilic acid and isatin, but toxicity did not increase after the treatment. The cyanobacteria showed the ability to degrade the dyes present in a textile effluent; therefore, they can be used in a tertiary treatment of effluents with recalcitrant compounds.

Development and population growth of Hydra viridissima Pallas, 1766 (Cnidaria, Hydrozoa) in the laboratory / Desenvolvimento e crescimento populacional de Hydra viridissima Pallas, 1766 (Cnidaria, Hydrozoa) em laboratório

Hydras, the most representative freshwater Cnidaria, are of common occurrence in bodies of water in every continent except Antarctica. This study was planned with the aim of maintaining a population of Hydra viridissima in laboratory culture to enable the determination of the individual and population growth-rates of this species, as well as its population doubling time and generation time, with a view to employing these common animals as test-organisms in ecotoxicological assays. The organisms were maintained in reconstituted water at 20 ± 2 °C, illuminated at 800 lux with a photoperiod of 12 hours light: 12 hours dark, and were fed on neonates of the cladoceran Ceriodaphnia silvestrii (3 or 4 neonates per hydra, 3 times a week). The individual growth-rate (k) of the species was 0.43, the maximum length of the column 2.53 mm and the generation time 6.6 ± 1.5 days on average. The hydra population showed an intrinsic growth-rate (r) of 0.0468, according to the fitted curve, and a doubling time of 14.8 ± 2.63 days. Hydra viridissima is easy to grow in the laboratory and performs well in the conditions used in this study. It is thus a promising candidate test-organism for ecotoxicological studies.

As hidras, os mais representativos Cnidaria de água doce, são organismos comuns em corpos de água doce de todos os continentes, exceto na Antártida. O objetivo do presente estudo foi manter o cultivo em laboratório da espécie Hydra viridissima, determinando-se o crescimento individual e populacional desta espécie, assim como seu tempo de duplicação da população e de geração, visando sua utilização como organismo-teste em ensaios ecotoxicológicos. Os organismos foram mantidos em água reconstituída, a uma temperatura de 20 ± 2 °C, com luminosidade de 800 lux e fotoperíodo de 12 horas luz/ 12 horas escuro, e foram alimentados com neonatas do Cladocera Ceriodaphnia silvestrii (3 a 4 neonatas por indivíduo). A taxa de crescimento individual (k) obtida foi de 0,43, o comprimento máximo da coluna das hidras foi de 2,53 mm e o tempo de geração foi, em média, de 6,6 ± 1,5 dias. A espécie apresentou uma taxa intrínseca de crescimento populacional (r) igual a 0,0468 para a curva ajustada e um tempo de duplicação da população de 14,8 ± 2,63 dias. A espécie Hydra viridissima é de fácil cultivo em laboratório e apresentou um bom desempenho nas condições testadas, sendo, portanto, um potencial organismo-teste para estudos ecotoxicológicos.

Ultraviolet irradiation initiates ectopic foot formation in regenerating hydra and promotes budding.

We have studied the effects of ultraviolet-C (UVC) and Ultraviolet-B (UVB) on growth and pattern formation in Pelmatohydra oligactis. UVC brings about a significant increase in budding in intact hydra while UVB does not exhibit such an effect. Excessive budding could be a response for survival at wavelengths that damage biological tissues. If the head or base piece of a bisected hydra is irradiated and recombined with the unirradiated missing part, regeneration proceeds normally indicating that exposure of a body part with either an intact head or foot to UVC does not influence pattern formation. Most significantly, in the middle piece, but not in the head or the base piece of a trisected hydra, UVC leads to initiation of ectopic feet formation in almost one third of the cases. Thus, UV irradiation interferes with pattern formation in regenerating hydra, possibly by changing positional values, and promotes budding in intact hydra. This is the first report on induction of ectopic feet formation by UV in regenerating hydra and opens up the possibility of using UV irradiation as a tool to understand pattern formation in the enigmatic hydra.

Hydra constitutively expresses transcripts involved in vertebrate neural differentiation.

The diploblastic Hydra is among the most primitive multicellular organisms. Using cross-hybridization with Xenopus probes, noggin-like transcripts were detected in the hypostome and basal disc of adult Hydra (Pelmatohydra oligactis), regions with properties similar to that of the amphibian organizer. This points to the possibility of a close molecular similarity between the Xenopus and Hydra organizers. The constitutive expression of a noggin-like gene in Hydra may be responsible for its regenerative capacity.

Nerve commitment during head regeneration in hydra.

Most important event in head regeneration in hydra is a wave of conversion of many interstitial cells into nerve cells. Experimental evidence lends support to the idea that the commitment of interstitial cells into nerve cells is the first morphogenetic prerequisite for emergence of head structures, when the number of nerve cells increases. This increase in nerve cells is delayed when regeneration occurs at a site lower in the body column.