Morfologia larval e sua importância para a sistemática e taxonomia de anfíbios anuros

Os anfíbios anuros formam um grupo comprovadamente monofilético e apresentam várias características em comum que estão relacionadas, principalmente, a adaptação das espécies à ambientes úmidos, aonde estas se desenvolvem e reproduzem. Apesar da restrição do ambiente de reprodução, as espécies de anfíbios anuros apresentam grande diversidade morfológica, como também a maior diversidade de modos reprodutivos relatados para todos os grupos de tretápodas atuais. O Brasil é o país com maior riqueza de anfíbios anuros com, aproximadamente, 950 espécies descritas até o momento. A maioria das espécies do território brasileiro apresentam uma fase larval que, na maioria dos casos, se desenvolve no ambiente aquático e não apresenta qualquer semelhança com a sua forma adulta, seja na sua morfologia ou no nicho ecológico que ocupa. As larvas de anfíbios anuros são comumente utilizadas em estudos taxonômicos e fornecem informações importantes que auxiliam na classificação das espécies. Além disso, a identificação das espécies baseadas na forma larvária facilitam estudos de ecologia de populações e comunidades, como também, tornam mais precisos inventários faunísticos. Apesar disso, aproximadamente 50% dos girinos das espécies de anuro que ocorrem no território brasileiro não são conhecidas e existem poucos trabalhos com foco na variação dos caracteres larvais ao longo de várias populações, o que dificulta a avaliação da sua utilidade em estudos taxonômicos e pode contribuir, por exemplo, para a existência de espécies crípticas. Além disso, existem poucos trabalhos que descrevem a diversidade morfológica larval com enfoque em regiões específicas e, no Brasil, exsitem, apenas, três chaves de identificação de espécies com base nos caracteres larvais. A falta de descrições afeta diretamente trabalhos sobre anurofauna no país, e dificultam o desenvolvimento de trabalhos experimentais ou de interações ecológicas, por exemplo. Logo, descrições de girinos são necessários para tornar mais completo o conhecimento sobre a anurofauna das espécies que ocorrem no território brasileiro. Com isso, este trabalho teve como objetivo fornecer dados que complementam o conhecimento existente sobre as formas larvais no território brasileiro, com foco na anurofauna da região sudeste do Estado do Rio Grande do Norte. Neste trabalho, são descritos os girinos de cinco espécies cuja forma larval ainda não era conhecida, como também, elaboro uma chave de identificação dicotômica baseada em caracteres larvais para a região sudeste do Estado do Rio Grande do Norte e comento sobre a utilidade dos caracteres larvais para a taxonomia e sistemática dos diversos grupos de anfíbios anuros abordados neste trabalho. Além disso, uma nova espécie do gênero Pseudopaludicola é descrita e os caracteres larvais auxiliaram em sua diagnose e na diferenciação de congeneros. Os resultados gerados aqui poderão ser úteis ou auxiliar em trabalhos futuros que necessitem da identificação das formas larvais de anfíbios anuros, principalmente, no Estado do Rio Grande do Norte.

Preferência e competição alimentar em um grupo de Sapajus flavius em fragmento de Mata Atlântica em Caaporã – Paraíba – Brasil

Feeding is the primary selective pressure in all forms of animals. Nutritional ecological models predict consequences of preferred and non-preferred food consumption on behavioural, physiological and morphological adaptations. At same time, socioecological models infer socio-organizarion patterns based on feeding competition faced by animals. A list of preferred foods, and inferences regarding the intensity of feeding competition and its behavioural consequences are information of much importance for management of populations in fragments. In this work we observed the feeding behavior and spatial positioning of a group of more than 100 blond capuchin monkeys (Sapajus flavius) that inhabit a fragment of Atlantic forest, surrounded by sugarcane plantation. We compared the consumption of different food items with their monthly availability in the area to define the preferred and fallback food items. We recorded the vocalizations of aggression and the inter-individual distance (area of Minimum Convex Polygon/n individuals) to infer the type of food competition experienced by animals. In the year studied the fruit feeding time correlated with top consumed fruit productivity, indicating preference for fruits. Our data indicate that the species Elaeis sp., Cecropia palmata, Inga spp. and Simarouba amara are the preferred food items in the diet. Available all year round and uniformly distributed, sugarcane was a regular item in the diet and its was characterized as a staple fallback food for this group. Although fruits are preferential food items, direct competition rate did not correlate to fruit productivity in the area, maintaining the high rates throughout the year (2.45 events/ hour). The inter-individual distance index positively correlated with rain fall indicating scramble food competition. The number of neighbours of females carrying infants was smaller when fruit productivity is low, indicating that females carrying infants are suffering increased indirect competition. Our data indicates that blond capuchins in this fragment make use of sugar cane as a staple fallback food, which evidence the importance of sugar cane landscape for the survival of this critically endangered capuchin species in fragmented habitats in Northeast Brazil. A preliminary list of preferred and important foods is offered, and can assist in the choice of trees for reforestation, better fragments to be preserved and areas of release and translocation of animals. We did not observe an increase of contest competition while using preferred foods, but when using staple FBF. This may be due the altered environment, which results in high competition food throughout the year. Both the food preference as the social and behavioral consequences of high food competition experienced by animals in this fragment must be accompanied over the years to ensure the survival of this population.

Preferência e competição alimentar em um grupo de Sapajus flavius em fragmento de Mata Atlântica em Caaporã – Paraíba – Brasil

Feeding is the primary selective pressure in all forms of animals. Nutritional ecological models predict consequences of preferred and non-preferred food consumption on behavioural, physiological and morphological adaptations. At same time, socioecological models infer socio-organizarion patterns based on feeding competition faced by animals. A list of preferred foods, and inferences regarding the intensity of feeding competition and its behavioural consequences are information of much importance for management of populations in fragments. In this work we observed the feeding behavior and spatial positioning of a group of more than 100 blond capuchin monkeys (Sapajus flavius) that inhabit a fragment of Atlantic forest, surrounded by sugarcane plantation. We compared the consumption of different food items with their monthly availability in the area to define the preferred and fallback food items. We recorded the vocalizations of aggression and the inter-individual distance (area of Minimum Convex Polygon/n individuals) to infer the type of food competition experienced by animals. In the year studied the fruit feeding time correlated with top consumed fruit productivity, indicating preference for fruits. Our data indicate that the species Elaeis sp., Cecropia palmata, Inga spp. and Simarouba amara are the preferred food items in the diet. Available all year round and uniformly distributed, sugarcane was a regular item in the diet and its was characterized as a staple fallback food for this group. Although fruits are preferential food items, direct competition rate did not correlate to fruit productivity in the area, maintaining the high rates throughout the year (2.45 events/ hour). The inter-individual distance index positively correlated with rain fall indicating scramble food competition. The number of neighbours of females carrying infants was smaller when fruit productivity is low, indicating that females carrying infants are suffering increased indirect competition. Our data indicates that blond capuchins in this fragment make use of sugar cane as a staple fallback food, which evidence the importance of sugar cane landscape for the survival of this critically endangered capuchin species in fragmented habitats in Northeast Brazil. A preliminary list of preferred and important foods is offered, and can assist in the choice of trees for reforestation, better fragments to be preserved and areas of release and translocation of animals. We did not observe an increase of contest competition while using preferred foods, but when using staple FBF. This may be due the altered environment, which results in high competition food throughout the year. Both the food preference as the social and behavioral consequences of high food competition experienced by animals in this fragment must be accompanied over the years to ensure the survival of this population.

Descrição do ciclo gametogênico do ouriço-branco, Tripneustes ventricosus (Lamarck, 1816), no Arquipélago de Fernando de Noronha PE, Brasil

Sea urchins are common benthic organisms on coastal ecosystems of tropical and temperate shallow waters. The impact of sea urchins populations in shore communities is density-dependent, and therefore, knowledge of the life history of these animals is important to understand these interactions. Between 2000 and 2005 a population boom of Tripneustes ventricosus was observed in the Fernando de Noronha Archipelago. In 2004 a research program was started to monitor the population dynamics of T. ventricosus in the archipelago, when it noted a lack of basic information on the biology and reproduction of this species, despite its broad geographic distribution and economic importance in parts of its occurrence. In this context, this work focuses on the reproductive biology of T. ventricosus with emphasis on the description of the gametogenic stages. Between December 2006 and July 2007, ten urchins were collected by snorkeling in two sites of the archipelago, totaling 120 individuals. Gametogenic stages were described for both sexes through microscopic analysis, and were defined as: Recovery, Growing, Premature, Mature and Spawning. Results showed increasing in Gonad index throughout of months of sampling and suggest that the reproductive cycle of the species in the archipelago is annual

Estrutura da população de Coleodactylus natalensis Freire, 1999 (Squamata: Sphaerodactylidae) no Parque Estadual Dunas de Natal, Rio Grande do Norte, Brasil

Coleodactylus natalensis Freire, 1999, an endemic species of Atlantic Forest fragments around the Natal municipality, Rio Grande do Norte State, Brazil, has as type locality the Parque Estadual Dunas de Natal (05º48 S to 05º53 S and 35º09 W to 35º12 W), one of the largest restinga (herb and shrub association on sand dunes along the Brazilian coastline) associate fragment, surrounded by urban zone, placed on setentrional Atlantic Forest limits. We made estimates on populational density, spatial distribution, habitat and microhabitat preferences and feeding ecological aspects like sazonal and sexual variations on diet, prey electivities and niche breadth. We randomly sampled ninety-six 50m2 quadrants in each of the four habitats identified in the study area. Were collected 49 specimens and their stomach contents were analyzed; prey items found were correlated with leaf-litter invertebrates from habitat samples. We found a 98,5 ± 75,5 individuals/ha density, in grouped distribution pattern on densest habitats and random distribution on others habitats. This species lives mostly on leaf-litter in forest habitats, in higher humidity points, with lower temperatures, deeper leaf litter and lower sea level elevations than the randomly chosen points in the study area. Isopoda and Aranae were the most important prey categories in numeric, frequency and volumetric terms. Niche breadth has an intermediate value and was variable in sexual and in habitat terms. There was no correlation between morfometric measures and prey size on diet. The C. natalensis population studied seems to be diet opportunist, although selects larger prey items. The Parque Estadual das Dunas do Natal has several indications of anthropic pressure from the surrounding urban area that may affects the local C. natalensis population. Thus, the fragility of this species calls for urgent conservation efforts

A rede de marcação e recaptura: o caso de borboletas do gênero heliconius

(The Mark and Recapture Network: a Heliconius case study). The current pace of habitat destruction, especially in tropical landscapes, has increased the need for understanding minimum patch requirements and patch distance as tools for conserving species in forest remnants. Mark recapture and tagging studies have been instrumental in providing parameters for functional models. Because of their popularity, ease of manipulation and well known biology, butterflies have become model in studies of spatial structure. Yet, most studies on butterflies movement have focused on temperate species that live in open habitats, in which forest patches are barrier to movement. This study aimed to view and review data from mark-recapture as a network in two species of butterfly (Heliconius erato and Heliconius melpomene). A work of marking and recapture of the species was carried out in an Atlantic forest reserve located about 20km from the city of Natal (RN). Mark recapture studies were conducted in 3 weekly visits during January-February and July-August in 2007 and 2008. Captures were more common in two sections of the dirt road, with minimal collection in the forest trail. The spatial spread of captures was similar in the two species. Yet, distances between recaptures seem to be greater for Heliconius erato than for Heliconius melpomene. In addition, the erato network is more disconnected, suggesting that this specie has shorter traveling patches. Moving on to the network, both species have similar number of links (N) and unweighed vertices (L). However, melpomene has a weighed network 50% more connections than erato. These network metrics suggest that erato has more compartmentalized network and restricted movement than melpomene. Thus, erato has a larger number of disconnected components, nC, in the network, and a smaller network diameter. The frequency distribution of network connectivity for both species was better explained by a Power-law than by a random, Poissom distribution, showing that the Power-law provides a better fit than the Poisson for both species. Moreover, the Powerlaw erato is much better adjusted than in melpomene, which should be linked to the small movements that erato makes in the network

Estudo comparativo de dois tipos de cultivo: monocultivo (camarões) versus cultivo integrado (algas/camarões)

The integrated culture of seaweed and aquatic animals is an ancient practice in Asian countries. The expansion of this practice to western countries is consequence of the recognition of this system as a sustainable alternative that allows economical diversification and mitigation of environmental impacts generated by effluents of aquaculture. This study evaluated the growth of the seaweed Gracilaria caudata and of the shrimp Litopenaeus vannamei in monoculture (shrimps) and integrated culture (shrimps and algae) systems, and accessed the effect of the seaweed in the water quality. There were two treatments in the experiment: monoculture (shrimps) and integrated culture (shrimps/ algae). The organisms were cultured in 6 aquaria (10L) filled with seawater (35.0±0.0 PSU and 28.1±0.4°C) for 28 days. The nutrients of water (PO43-, NH4+, NO2-, NO3- and DIN), the biomass and the relative growth rate (RGR, % day-1) of seaweed and shrimps were measured weekly. The parameters pH, temperature, salinity and dissolved oxygen were measured daily. The concentration of NH4+ in integrated culture (62.8±25.2µM) was lower (Mann-Whitney p<0.001) than in monoculture (85.6±24.3µM). The mean of PO4- in monoculture (10.4±4.6µM) was markedly higher (Mann-Whitney; p=0.024) than that in integrated culture (8.7±4.1µM). The level of dissolved oxygen in integrated culture (6.0±0.6mg/L) was higher (t-Student; P=0.014) than that in shrimp monoculture (5.8±0.6mg/L). The mean values of the parameters pH, NO2-, NO3- and DIN were 7.5±0.2, 10.1±12.2µM, 24.5±3.2µM and 120.17±30.76µM in monoculture, and 7.5±0.2, 10.5±13.2µM, 27.4±3.5µM and 100.76±49.59µM in integrated culture. There were not differences in these parameters between treatments. The biomass and RGR of seaweed reached 15.0±1.9g and 7.4±2.8% day-1 at the end of the experiment. The performance of shrimp was favorable in monoculture (1.5±0.8g; 5.7±1.6% dia-1) and in integrated culture (1.5±0.7g; 5.2±1.2% dia-1), and the rate of survival was 100% in both treatments. The tolerance and favorable performance of Gracilaria caudata suggest that this seaweed might be integrated into shrimp (Litopenaeus vannamei) culture systems

Influência da profundidade e dos parâmetros ambientais sobre o desenvolvimento de Gracilaria birdiae (Rhodophyta, Gracilariales) em viveiro de camarão

This study evaluates the influence of depth and environmental parameters on the development of Gracilaria birdiae Plastino & Oliveira (Gracilariaceae Rhodophyta) in an organic shrimp pound (Litopenaeus vannamei) under euthrophical conditions. PVC structures (module) witch four ropes laden with 150 g of macroalgae each, were kept during 35 days at three different depths (surface, 10 and 20 cm depth). Wet biomass weighing and environmental parameters (temperature, salinity, turbidity, pH, transparence, precipitation, evaporation, insolation, accumulated solar radiation, nitrite, nitrate, ammonium and orthophosphate) were measured weekly. At all three proposed depths, the macroalgae displayed a higher biomass at the end of experiment than at the initial inoculations. The module kept at a 10 cm depth presented the greatest average biomass (186,3), followed by that kept at 20 cm (180,4 g) and the surface module (169,9 g). Biomass variations showed algae to suffer the direct effects of depths. Biomass loss was associated with the factors that influence light penetration, such as sediment deposits above the thallus, rate of evaporation and precipitation. The smallest loses occurred in the algae kept on surface (0,16%), followed by the algae kept at 20 cm (0,20%) and 10 cm (0,22%). The specific growth rate (SGR) of G. birdiae showed no significant difference between the three depths nor the sample periods. Nevertheless, the modules kept at 10 and 20 cm depths presented similar growth evolution, both growing 0,38%·per day-1, while the module kept on surface had an average SGR of 0,36%·day-1. The models related to growth rate demonstrated temperature, salinity, pH, orthophosphate, ammonium, precipitation and turbidity as the principal environmental parameters influencing the development of G. birdiae

Dieta do ouriço-branco, Tripneustes ventricosus (Lamarck, 1816), no Arquipélago de Fernando de Noronha, PE

Sea urchins are benthic macroinvertebrates that inhabit shallow coastal waters in tropical and temperate zones. Urchins are usually classified as generalists or omnivores as they can adjust their diet according to the food resources available in the environment. Due to the strong grazing pressure they may exert, urchins have an important role in marine ecosystems, occupying different trophic levels and stimulating the intensification of the dynamics of communities where they occur. In 2004, a monitoring program focused on the population dynamics of the white sea urchin, Tripneustes ventricosus, has been initiated in the Fernando de Noronha Archipelago. At the same time, a surprisingly lack of information on the species biology has been noted, despite their wide geographical distribution and economic importance in many parts of its range. Hence, this work was developed to provide information on the feeding habits of T. ventricosus in the archipelago. Ten specimens were collected between December 2006 and July 2007 at two sites of the archipelago, Air France and Sueste Bay for biometrics and analysis of gut contents. Test diameters ranged from 9.19 cm (± 1.1) to 10.08 cm (± 0.58). Calculated stomach repletion index (IRE) was higher (p <0.05) in the Air France site and also during January and July. The IRE was not correlated to the gonad index. Fifteen different species of algae were detected in a total of 120 stomachs examined: 4 Chlorophytas, 4 Phaeophytas and 6 Rhodophytas. Food diversity (p <0.05) was higher in December 2006 and January 2007. Although several items had a high frequency of occurrence, they were low represented in terms of weight, and consequently, had a low level of relative importance. The brown algae Dictyopteris spp and Dictyota spp, followed by the green algae Caulerpa verticillata accounted for the greatest importance in T. ventricosus diet, comprising about 90% of the consumed items

Análise do comportamento e crescimento do camarão branco Litopenaeus vannamei (Boone, 1931) em diferentes substratos inconsolidados

The aim of this study was to test the sediment preference of L. vannamei shrimp. It was observed shrimp visit frequency, swimming and burying behaviour at different sediment compositions for 24h. Juvenile (0.93 ± 0.29g) and sub-adult shrimps (10.0 ± 1.18g) were obtained from the aquaculture station at Universidade Federal Rural do Semi-Árido UFERSA, and held in a plastic tank (water volume 500 L) supplied with aerated water and kept at constant temperature, pH, and salinity. Shrimp was fed by commercial shrimp dry food. The experimental substrates were composed by A: medium sand + thick sand + very thick sand + gravel; B: very fine sand + fine sand; and C: silt + clay. Thus, six different substrate combinations were tested: A, B, C, A+B, A+C, B+C. To test preference, it was used a cylindrical tank (40 l) divided into six differently substrate compartments. A single shrimp was introduced each tank and the frequency at which this shrimp visited each compartment was recorded over a 24h study period. It was tested 54 shrimp (18 sub-adult males, 18 subadult females and 18 juveniles). For each trial, sediment and water were changed to avoid pheromones and residues influence. Shrimp were weighted and sub-adults were divided by sex: males present petasma and females present thelycum. Data were collected on the experimental day at 19:30; 20:30; 00:30; 1:30; 05:30; 06:30; 13:30 and 14:30 h. At each time point, shrimp were observed for 20-min periods, in which we noted down which compartment the shrimp was occupying at 2-min intervals. Thus, for each period we had eleven observations (88 observations per day). For observations at night, it was used dim red light that did not affect shrimp behaviour. At each 20-min period, it was observed visit frequency in each substrate, if shrimp was burred or not or if it was swimming. There was not significant difference between light and dark burry activity for females. Swimming activity was significantly higher at night, mainly at 00:30 and 01:30 h. All L. vannamei shrimp showed preference for sediment B. This animal presents cyclic activity, spends the day light period buried and swims at night

Eutrofização do reservatório Engenheiro Armando Ribeiro Gonçalves, no Rio Grande do Norte: implicações para o abastecimento público e para a piscicultura intensiva em tanques-rede

This study aimed to describe the spatial and temporal patterns of variation in trophic state and its relation with the structure and dynamics of planktonic community of a large reservoir located in semi-arid tropical region of Northeast Brazil. The reservoir Armando Ribeiro Gonçalves is the biggest reservoir of the Rio Grande do Norte State and is responsible for about 53% of all surface water accumulated in the State. The samples of water and plankton were taken monthly in 10 points distributed throughout the longitudinal axis of the reservoir and over a full hydrological cycle. The samples were collected to determine concentrations of total phosphorus, total nitrogen, chlorophyll a and suspended solids (fixed and volatile) and for determining the composition and abundance of phytoplanktonic and zooplanktonic species. During the study period, the reservoir was characterized as eutrophic and there was no trend of increasing the trophic state of the reservoir in the period of drought. The concentrations of total phosphorus and suspended fixed solids decreased towards the dam while the N:P ratios increased in the same direction due to the reduction in the phosphorus concentrations and relative constancy in the nitrogen concentrations. The N:P ratios observed were indicative of greater limitation by phosphorus than by nitrogen. However, as concentrations of both nutrients were high and the water transparency was very low, with secchi depth usually lower than one meter, it seems likely that the planktonic primary production of the reservoir is more limited by the availability of light than the availability of nutrients. High nutrient concentrations coupled with low availability of light may explain the continuing dominance of filamentous cyanobacteria such as Cylindrospermopsis raciborskii in the plankton of the reservoir.These cyanobacteria are potentially toxic and pose a serious environmental problem because it compromises the water quality for public supply, recreation and fishing when present in high densities as in this study. The mesozooplankton of the reservoir was dominated by the calanoid Notodiaptomus cearensis and the cladoceran Diaphanosoma spinulosum. In general, the structure of zooplankton community seems to be particularly influenced by the spatial variation of cyanobacteria. The results of the regression analyses show that both the chlorophyll a concentrations and the cyanobacteria biovolume were more strongly correlated with the nitrogen than with phosphorus and that the water transparency was more strongly correlated with algal biomass than with other sources of turbidity. The maximum load of phosphorus to attain the maximum permissible concentration of total P in the reservoir was estimated in 63.2 tonnes P/ year. The current external P load to the reservoir is estimated in 324 tonnes P / year and must be severely reduced to improve the water quality for water supply and allow the implementation of aquaculture projects that could contribute to the socio-economic development of the region

Efeitos da tilápia do Nilo (Oreochromis niloticus) e do enriquecimento por nutrientes sobre a comunidade planctônica em um lago artificial no semi-árido brasileiro

The major aim of this study was to test the hypothesis that the introduction of the Nile tilapia (Oreochromis niloticus) and the enrichment with nutrients (N and P) interact synergistically to change the structure of plankton communities, increase phytoplankton biomass and decrease water transparency of a semi-arid tropical reservoir. One field experiment was performed during five weeks in twenty enclosures (8m3) to where four treatments were randomly allocated: with tilapia addition (T), with nutrients addition (NP), with tilapia and nutrients addition (T+NP) and a control treatment with no tilapia or nutrients addition (C). A two-way repeated measures ANOVA was done to test for time (t), tilapia (T) and nutrient (NP) effects and their interaction on water transparency, total phosphorus, total nitrogen, phytoplankton and zooplankton. The results show that there was no effect of nutrient addition on these variables but significant fish effects on the biomass of total zooplankton, nauplii, rotifers, cladocerans and calanoid copepods, on the biovolume of Bacillariophyta, Zygnemaphyceae and large algae (GALD ≥ 50 μm) and on Secchi depth. In addition, we found significant interaction effects between tilapia and nutrients on Secchi depth and rotifers. Overall, tilapia decreased the biomass of most zooplankton taxa and large algae (diatoms) and decreased the water transparency while nutrient enrichment increased the biomass of zooplankton (rotifers) but only in the absence of tilapia. In conclusion, the influence of fish on the reservoir plankton community and water transparency was greater than that of nutrient loading. This finding suggests that biomanipulation should be a greater priority in the restoration of eutrophic reservoirs in tropical semi-arid regions

Caracterização limnológica e determinação da capacidade suporte do reservatório mendubim, (Rio Grande do Norte) para o cultivo de peixes em tanques-rede

The aims of this study were: i) assessing the trophic state of the Mendubim reservoir (semi-arid, Rio Grande do Norte, Brazil; 05° 38 99,0 S 36°55 98,0 W) based on chlorophyll-a, total phosphorus and nitrogen concentrations and water transparency; ii) relating the patterns of temporal variation of zooplankton and phytoplankton to the trophic state of the reservoir and iii) investigating the carrying capacity of the reservoir for cage fish farming. The samplingwas done monthly from July 2006 to July 2007 in three stations at the reservoir: next to the dam (barrage), in the central region and in the mouth of the main tributary. The abiotic and biotic variables analyzed were: Secchi depth, volatiles and fixed suspended solids, chlorophyll-a, total phosphorus and nitrogen, TN:TP ratio and mesozooplankton and phytoplankton composition and biomass. The results showed that the reservoir can be considered as mesotrophic with mean concentrations of total nitrogen, phosphorus and chlorophyll-a equal to 1711, 1 μg.L-1, 30,8 μg.L-1 and 5,62 μg.L-1 respectively. The Cyanophyceae class was the most representative in terms of density, with the presence of potentially toxic species such as Microcystis aeruginosa, Planktothrix planctonica, Cylindrospermopsis raciborskii, Aphanizomenon sp. ,Aphanocapsa delicatissima and Pseudanabaena acicularis. Among the zooplankton, the genus Notodiaptomus presented the largest biomass values. Overall, our results show that the light limitation should explain the weak relationship between chlorophyll-a and total phosphorus and nitrogen concentrations. We concluded that the water of Mendubim reservoir is suitable for intensive fish cage aquaculture. Based on the carrying capacity calculations for this reservoir, we found that the maximum sustainable yield of tilapias in cages in the reservoir is 126 ton per year assuming a factor of food conversion of 1.5: 1.0 and a phosphorus content in the fish food of 1%

Distribuição e abundância da malacofauna epibentônica no Parracho de Maracajaú, RN, Brasil

The mollusks present a great taxon variety and life habits in coral reefs being good environmental indicators. It is important to know the distribution pattern of the mollusks and the processes that influence it, so that disturbances in sea ecosystems could be monitored. The present study aims to accomplish the inventory and distribution of epibenthic mollusks in the Parracho of Maracajaú. 23 sites in different habitats of the Parracho were settled: 11 in the reef habitat, 3 in the sandy bottom and 9 in the seagrass bed. Qualitative and quantitative samplings have been done through snorkeling and scuba diving. Three band transects (10m²) were sampled in each site and the data were obtained to each m² of the transect, where the species were counted and the environmental variables (rugosity and recovery of the substratum) were valued. The data were submitted to multivariate analyses in order to find possible distribution patterns that could be associated to the substratum variables. The diversity indexes were calculated for each reef sites and compared with each other. A number of 46 species were registered. The reef habit at should to be the richnest area while the sandy bottom was poorest one. In the reef habitat, the mollusks were associated to rugosity and recovering of frondose algae and zoanthids, while for the seagrass bed, the animals exhibited a richness variation associated to the muddy and sandy sediment. There were found 3 species economically explored, what requires an appropriate management for the maintenance and conservation of the area resources in a sustainable way

Estrutura e dinâmica do fitoplânctone bacterioplâncton em cultivos de camarão no Rio Grande do Norte-Brasil: impacto sobre o ambiente natural

This work aimed to study the structure and dynamic of Phytoplankton and Bacterioplankton in a complete cycle of shrimp cultivation (Litopenaeus vannamei) and determine the environmental factors responsible for the structural changes of these communities. The study was realized in a saltwater shrimp farm (Macaíba, RN), between September/2005 and February/2006, and in a freshwater shrimp farm (Ceará Mirim, RN), between May/2007 and September 2007. The samplings were collected weekly in saltwater farm and every fifteen days in freshwater farm. Total phosphorus, chlorophyll a and environmental parameters (pH, dissolved oxygen, salinity, temperature, depth and water transparency) were measured. Qualitative and quantitative analysis of the phytoplankton and bacterioplankton were carried out. The Shannon-Wiener ecologic indexes of diversity and the Pielou equitability indexes were calculated to the phytoplankton. Bacterial density was determined by epifluorescence microscopy. The data were statistically analyzed by Pearson correlation and t-Test. Chlorophycea were predominat in salt water and in the captation/drainage point (24 to 99%). Diatoms had higher wealth. The species Choricystis minor had the highest occurrence (100%) and dominance (90-100%), thus showing its adaptation to the high temperatures, salinity and low water transparency conditions. Filamentous Cyanobacteria like Oscillatoria sp., Pseudoanabaena sp. and Phormidium sp. had constant levels. The negative correlation between chlorophycea and water transparency, and the positive correlation between chlorophyll a and salinity, showed that the phytoplankton was well adapted to the low transparency and to the high salinity. The bacterioplankton was negatively correlated with the total phosphorus and salinity. In freshwater, Cyanobacteria were predominant (>80%), presenting some producers of toxins species like Microcystis sp., Aphanizomenon sp., Cylindrospermopsis raciborskii e Anabaena circinalis. Cyanobacterial density and total phosphorus and chlorophyll a concentrations exceeded the maximum value allowed by legislation. The means of total phosphorus varied from 264 to 627 Wg.L-1 and the means of chlorophyll a oscillated between 22 and 182 Wg.L-1. The phytoplankton species were selected by low availability of the light, high pH, temperature and high availability of total phosphorus. The bacterioplankton showed high densities (5,13 x 107 to 8,50 x107 Bac.mL-1). The studied environments (ponds and rivers) presented a high level of trophic state based on the high concentrations of chlorophyll a and total phosphorus and cyanobacteria dominance. The composition of species in the ponds and rivers was similar, as well as high concentrations of total phosphorus and chlorophyll a, highlighting the pollution caused by the discharges of the farms in natural environment