A. C. Rietzler

Thermocyclops decipiens (Kiefer, 1929) (Copepoda, Cyclopoida) as indicator of water quality in the State of Minas Gerais, Brazil

The aim of this work was to study the possible utilization of Thermocyclops decipiens as indicator of the trophic degree and water quality of some watersheds of the state of Minas Gerais. From the beginning of the decade of 90, T. decipiens was recorded in several water collections of the state, including the basins of the rivers Paranaiba, Sao Francisco, Doce and Grande, within environments mainly of meso and eutrophics characteristics. Of the 28 places of occurrence of the species and according to the water quality index (WQI) used by Environmental Foundation of Minas Gerais (FEAM), 7 of these environments presented WQI good, 16 medium, 4 bad and one very bad. This classification corroborated the hypothesis that T. decipiens could be used as indicator species of eutrophic environments and of low water quality thus constituting an important tool for the biomonitoring of aquatic ecosystems.

Laboratory demonstration of morphological alterations in Ceriodaphnia cornuta Sars (1885) fa rigaudi induced by Chaoborus brasiliensis Theobald (1901).

Departamento de Biologia Geral, Instituto de Ciências Biológicas – ICB, Universidade Federal de Minas Gerais – UFMG, Avenida Antônio Carlos, 6627, CEP 31270-901, Belo Horizonte, MG, Brazil Departamento de Ecologia e Biologia Evolutiva, Universidade Federal de São Carlos – UFSCar, Rodovia Washington Luiz, Km 235, CEP 13565-905, São Carlos, SP, Brazil Departamento de Hidráulica e Transportes, Centro de Ciências Exatas e Tecnologia – CCET, Universidade Federal de Mato Grosso do Sul – UFMS, Cidade Universitária, CP 549, CEP 79070-900, Campo Grande, MS, Brazil

A review of typhloplanid flatworm ecology, with emphasis on pelagic species

Abstract The study of microturbellaria is not popular, and hence, the taxonomy and ecology of these animals are poorly known. In temperate zone ponds and lakes, the number of species may be up to 50+ per water body. The Typhloplanidae, the subject of this review, live in the littoral–benthic zone, but pelagic occurrences have been accumulating since the first case was reported in 1952. Four species are currently known to be occasionally pelagic; all live in warm–temperate or tropical lakes. Typically, one species per lake is found, but in one lake in Brazil, 2 species co-occur. One of these feeds on the other and on zooplankton, with a preference for Cladocera. Flatworms seem to trade the littoral zone for the pelagic if predation pressure in the littoral exceeds that in the open water, and if the pelagic offers better food. Most Typhloplanidae feed on arthropods, often with a preference for cladocerans, and show parallels with the cladocerans and rotifers in that 2 types of eggs (subitaneous and resting) are produced. In some flatworms, however, resting egg formation does not require amphimixis. There is also great variation between species in both the number of clutches and their composition, and within species, latitudinal differences may be important. At the cold extreme, species produce only one clutch of resting eggs; at the tropical extreme, species produce many subitaneous clutches, although resting eggs continue to be produced as well. The factors driving the life cycles of the pelagic species are discussed and include familiar variables such as temperature (circulation patterns), food, and predation. Flatworms also produce mucus and toxins that add complexity to their ecology; toxins are used for catching prey, and possibly for defense against predators (but not fish). If they become too abundant for their food supply, flatworms also seem to switch to resting egg production or block reproduction.

Constituintes químicos e efeito ecotoxicológico do óleo volátil de folhas de Eucalyptus urograndis (Mirtaceae)

The volatile oil from the leaves of E. urograndis was analyzed by GC and GC-MS. It was identified 10 compounds in which, orto-cimene (41.4%) and 1,8-cineol (25.8%) were the main constituents. The induction of deleterious effect to aquatic organisms due to the presence of volatile oil lixiviated from E. urograndis leaves was studied using Daphnia laevis and D. similis as bioindicators. Through the results of toxicological tests it was possible to show that the litterbag of E. urograndis represents a risk factor for the aquatic ecosystem of lakes and rivers that are in the surrounding area of large scale Eucalyptus plantations. The method can be used for monitor the quality of these types of aquatic environments.

High temperatures and absence of light affect the hatching of resting eggs of Daphnia in the tropics

Temperature and light are acknowledged as important factors for hatching of resting eggs. The knowledge of how they affect hatching rates of this type of egg is important for the comprehension of the consequences of warming waters in recolonization of aquatic ecosystems dependent on dormant populations. This study aimed at comparing the influence of different temperature and light conditions on hatching rates of Daphnia ambigua andDaphnia laevis resting eggs from tropical environments. The ephippia were collected in the sediment of three aquatic ecosystems, in southeastern Brazil. For each lake, the resting eggs were exposed to temperatures of 20, 24, 28 and 32 °C, under light (12 h photoperiod) and dark conditions. The results showed that the absence of light and high temperatures have a negative influence on the hatching rates. Statistical differences for hatching rates were also found when comparing the studied ecosystems (ranging from 0.6 to 31%), indicating the importance of local environmental factors for diapause and maintenance of active populations.

Arsenic toxicity to cladocerans isolated and associated with iron: implications for aquatic environments

Arsenic is an ametal ubiquitous in nature and known by its high toxicity. Many studies have tried to elucidate the arsenic metabolism in the cell and its impact to plants, animals and human health. In aqueous phase, inorganic arsenic is more common and its oxidation state (As III and As V) depends on physical and chemical environmental conditions. The aim of this study was to evaluate toxicity of arsenic to Daphnia similis and Ceriodaphnia silvestrii, isolated and associated with iron. The results showed differences in toxicity of As III and As V to both species. Effective concentration (EC50) mean values were 0.45 mg L-1 (As III) and 0.54 mg L-1 (As V) for D. similis, and 0.44 mg L-1 (As III) and 0.69 mg L-1 (As V) for C. silvestrii. However, As V IC25 mean value was 0.59 mg L-1, indicating that C. silvestrii has mechanisms to reduce arsenic toxicity. On the other hand, when associated with iron at 0.02 and 2.00 mg L-1, EC50 values decreased for D. similis (0.34 and 0.38 mg L-1) as well as C. silvestrii (0.37 and 0.37 mg L-1), showing synergistic effect of these substances.

Accelerated eutrophication and toxicity in tropical reservoir water and sediments: an ecotoxicological approach

The aim of this study was to jointly show the results of three independent ecotoxicological studies performed to investigate pollutants in three Brazilian tropical reservoirs undergoing accelerated eutrophication. In order to accomplish this goal, the full toxicity identification and evaluation procedure (TIE approach) was performed, at Pampulha (Minas Gerais State) and Salto Grande and Barra Bonita reservoirs (São Paulo State). Acute and chronic toxicity tests were performed using the cladocerans Daphnia similis and Ceriodaphnia dubia (exotic) and Daphnia laevis and Ceriodaphnia silvestrii (native) as test organisms. Results from TIE procedure stage I indicated the existence of nonpolar organic and filterable compounds in the water from Pampulha, probably cyanotoxins, and oxidants as part of the toxic agents. TIE results for sediments identified ammonia (Pampulha and Salto Grande), organic compounds (Pampulha), metals (Pampulha, Barra Bonita, and Salto Grande), and acidity (Salto Grande) as responsible for toxicity. Whole-sediment remediation experiments for Pampulha reservoir confirmed, through reproduction decrease, ammonia and organic compounds as contaminants. Such pollutants represent threats to aquatic biota and must be prevented. Higher temperatures as predicted from global climate change will severely affect tropical shallow reservoirs, accelerating eutrophication, the release of contaminants from sediments, and increasing toxicity.

Ecotoxicological evaluation of sediments applied to environmental forensic investigation

The present study aimed to evaluate the potential for using toxicity assays with sediment samples for the detection of water pollution caused by the discharge of tannery effluents into water bodies and its application to environmental forensic investigation. The study included ecotoxicological evaluation of sediments, survey of benthic organisms in the field, as well as chromium, cadmium and lead dosage which provided data for a sediment quality triad evaluation. The sediment samples showed acute and chronic toxicity to the bioindicators, low biodiversity of benthic macrofauna and high chromium concentration, reaching up to 4365 mg.Kg-1. A close relationship was observed between the separate results of ecotoxicological sediment evaluation and the sediment quality triad. The sediment ecotoxicological assessment proved to be applicable to tracking sources of contamination related to tanneries and similar activities in environmental forensics.The present study aimed to evaluate the potential for using toxicity assays with sediment samples for the detection of water pollution caused by the discharge of tannery effluents into water bodies and its application to environmental forensic investigation. The study included ecotoxicological evaluation of sediments, survey of benthic organisms in the field, as well as chromium, cadmium and lead dosage which provided data for a sediment quality triad evaluation. The sediment samples showed acute and chronic toxicity to the bioindicators, low biodiversity of benthic macrofauna and high chromium concentration, reaching up to 4365 mg.Kg-1. A close relationship was observed between the separate results of ecotoxicological sediment evaluation and the sediment quality triad. The sediment ecotoxicological assessment proved to be applicable to tracking sources of contamination related to tanneries and similar activities in environmental forensics.

On the first record of the exotic Moina macrocopa (Straus, 1820) in Minas Gerais State, Brazil

Sampling at Pampulha Reservoir in Minas Gerais State in August of 2012 found Moina macrocopa, until now reported for South America only in a temporary pond in Rio de Janeiro State, Brazil (Elmoor-Loureiro et al., 2010) and similar environments in South America (Valdivia-Villar, 1988; Elias-Gutiérrez and Zamuriano-Claros, 1994; Paggi, 1997). The most recent inventory (checklist) of cladocerans for Minas Gerais State (Santos-Wisniewski et al., 2011) did not mention this species, indicating recent appearance. Pampulha Reservoir is a eutrophic medium-sized reservoir with an area of 1.82km2 and mean depth of 5.0m (Bezerra-Neto and Pinto-Coelho, 2010), corresponding to the depth of the sampling site (Figure 1). Recent studies on this reservoir (Pinto-Coelho, 1998; Jaramillo and Pinto-Coelho, 2011) have reported Moina micrura among the Moinidae. In August of 2012, specimens of Moina macrocopa were also found in the central compartment of the reservoir, representing around 1% of the cladocerans. Samplings carried out in 2013, showed fluctuations in its numerical densities, with an increase in April (13% of total cladocerans) and reduction in May and June (0.03% in both months), suggesting an initial colonisation process for the species. The morphological features of the specimens (Figures 2-8) are similar to the ones described by Goulden (1968) for Moina macrocopa of the Old World, differing only in the number of setae on the ventral rim, from 70 to 77, close to what was described by Paggi (1997) and Elmoor-Loureiro et al. (2010). The mean female and male lengths correspond to 1.14 ± 0.06mm (1.05-1.20mm; n=10) and 0.92 ± 0.05mm (0.85-0.97mm; n=4). Ephippia were not found in females from the reservoir nor in attempts to induce their production in the laboratory. The studied environment corresponds with habitat descriptions of Moinidae, especially with regard to M. macrocopa, found mostly in temporary, shallow and/or eutrophic environments (Paggi, 1997; Thorp and Covich, 2001; Petrusek, 2002). Laboratory experiments conducted with field and culture water at 25°C have shown high reproduction and rapid turnover for this species (unpublished data). Mean fecundity of field and culture water treatments corresponded, respectively, to 37.0 ± 6.8 (26-44) and 120.6 ± 48.3 (55-203) neonates, and primiparous individuals were found within less than 3 days. This signifies very high reproductive ability, suggesting a high level of competitiveness if other pelagic cladocerans are kept in low densities. Representatives of Moinidae are considered ruderal species (Romanovsky, 1985), showing high biotic potential but with a need for high food concentrations, being preferably found in productive or disturbed environments. Maia-Barbosa and Bozelli (2006), studying a lake impacted by bauxite (Lake Batata, Pará State, Brazil), found Moina minuta in abundance, especially in periods with higher amounts of organic detritus and algae attached to bauxite tailings. On the other hand, Pampulha reservoir, besides being eutrophic, is highly contaminated by industrial effluents. Comparative sensitivity tests using NaCl conducted in the laboratory showed CE50 values of 1.0mg.L–1 and 1.7mg.L–1 for M. macrocopa and D. similis, respectively, indicating that M. macrocopa may be more sensitive than other cladocerans. Other studies related to cladocerans introduced into lakes and reservoirs have discussed the factors involved in the establishment of daphnids. Daphnia lumholtzi, introduced into lakes of North America (Work and Gophen, 1999; Dzialowski et al., 2000), as well as into lakes and reservoirs of Brazil (Zanata et al., 2003; Simões et al., 2009), has been favoured in oligo-mesotrophic environments, with higher temperatures (subtropical environments) and low densities of potential competitors. Biological invasions have been considered one of the main causes of biodiversity loss (Wittenberg and Cock, 2001; Simberloff, 2003). The presence of Moina macrocopa in the Pampulha Reservoir is of concern, not only because it is an opportunistic species but also with regard to environmental connectivity and dispersion possibilities (Rocha et al., 2005). A subject for future investigations should certainly be whether M. macrocopa establishes itself and succeeds in this and other reservoirs.

Methods for selection of Daphnia resting eggs: the influence of manual decapsulation and sodium hypoclorite solution on hatching rates

Cladocerans are able to produce resting eggs inside a protective resistant capsule, the ephippium, that difficults the visualization of the resting eggs, because of the dark pigmentation. Therefore, before hatching experiments, methods to verify viable resting eggs in ephippia must be considered. This study aimed to evaluate the number of eggs per ephippium of Daphnia from two tropical aquatic ecosystems and the efficiency of some methods for decapsulating resting eggs. To evaluate the influence of methods on hatching rates, three different conditions were tested: immersion in sodium hypochlorite, manually decapsulated resting eggs and intact ephippia. The immersion in hypochlorite solution could evaluate differences in numbers of resting eggs per ephippium between the ecosystems studied. The exposure to sodium hypochlorite at a concentration of 2% for 20 minutes was the most efficient method for visual evaluation and isolation of the resting eggs. Hatching rate experiments with resting eggs not isolated from ephippia were underestimated (11.1 ± 5.0%), showing the need of methods to quantify and isolate viable eggs. There were no differences between the hatching rate of resting eggs submitted to hypochlorite solution (47.2 ± 7.34%) and manually decapsulated (53.7 ± 13.24%). However, the immersion in hypochlorite was a more efficient technique, faster and not requiring manual ability.