ABSTRACT
BACKGROUND: In this study we examine the feeding efficiency of copepods locally found in Guatemala on first instar Aedes aegypti larvae. Copepods are a potential tool for Aedes vector control that has shown promising results in the laboratory and in community-based field trials. METHODS: Four different copepod species from different habitat types were included in the laboratory assays of this study. RESULTS: All four tested copepod species decreased the number of the first instar Aedes larvae that were inserted into the glass vessels compared with controls. However, average predation rates between the tested species were highly different, with Thermocyclops crassus and Mesocyclops longisetus achieving the highest, with 31.0% (standard deviation [SD] 18.9) and 28. 9% (SD 11.2), respectively. CONCLUSIONS: The copepod species with identified high predation rates are potential candidates for planned and other future field trials for community-based Aedes vector control with copepods in the region.
ABSTRACT
PURPOSE: A new species of the genus Ceratocolax Vervoort, 1965 is described based on specimens collected from the Tomtate grunt Haemulon aurolineatum Cuvier, caught in the coast of Angra dos Reis, off the State of Rio de Janeiro, Brazil. METHODS: One hundred specimens of H. aurolineatum were purchased from the local fish market and examined for parasitic copepods. Parasites were fixed and preserved in 80% ethanol. Morphological features of the copepods were examined and drawn using an Olympus BX51 equipped with a drawing tube. RESULTS: Ceratocolax tavaresi n. sp. can be distinguished from all congeners by the following combination of characters in the adult female: (1) second endopodal segment of leg 3 with one seta, (2) lack of stout spinules along outer margins on rami of legs 2-4, (3) genital somite without flaplike structures, (4) terminal exopodal segment of leg 4 with seven elements; and in the adult male: (1) legs 1 to 4 with 3-segmented rami (except endopod of leg 4), (2) presence of a pair of blunt processes on dorsal surface of the third pedigerous somite, (3) second endopodal segment of leg 3 with one seta. CONCLUSION: The number of species of Ceratocolax reported in the Atlantic Ocean was increased to three, including the new species. This is the forty-second species of copepod found parasitizing haemulid fish in marine waters from the Americas; however, the diversity of parasitic copepods off this continent is still underestimated.
Subject(s)
Copepoda , Parasites , Perciformes , Female , Male , Animals , Brazil/epidemiology , Perciformes/parasitology , FishesABSTRACT
INTRODUCTION: Copepods of the genus Hatschekia Poche, 1902 are parasitic on the gills of marine actinopterygians. Currently, about 151 species of this genus have been reported in marine ecosystems and only few occur in South Atlantic Ocean. METHODS: Fifty specimens of A. virginicus from Angra dos Reis, off the State of Rio de Janeiro, Brazil, were parasitized by copepods on the gills. Parasites were fixed and preserved in 70% ethanol. Morphological observations were based on light and scanning electron microscopy. RESULTS: Hatschekia nagasawai n. sp. can be distinguished from all congeners by the combination of the following characters: (1) presence of two pointed processes on the proximal (first) segment of antennule, (2) cephalothorax octagonal to ovoid, (3) absence of processes on the intercoxal sclerite of legs 1 and 2, (4) trunk without lobes at the postero-lateral margins. Other species of Hatschekia and their hosts previously collected off Brazil were analysed and discussed. CONCLUSIONS: This is the first report of a representative of the family Hatschekiidae Kabata, 1979 parasitizing a species of Anisotremus. The number of species of Hatschekia reported in the South Atlantic Ocean was increased to five, including the new species; however, the diversity of hatschekiid copepods in this oceanographic region is still underestimated, most likely being higher than what is currently known.
Subject(s)
Copepoda , Fish Diseases , Parasites , Perciformes , Animals , Brazil , Ecosystem , Fish Diseases/parasitology , Fishes , Perciformes/parasitologyABSTRACT
The zooplankton communities often exhibit daily vertical migrations to avoid natural ultraviolet radiation and/or fish predation. However there is no information on this topic in Chilean North Patagonian lakes up to date. Therefore, this study deals with a first characterization of plankton crustacean daily vertical migration in two temperate, oligotrophic lakes (Villarrica and Panguipulli lakes, 39°S) in Southern Chile. Zooplankton were collected at different depths intervals (0-10m, 10-20 m, 20-30m, 30-40m) at early morning, middle day, evening and night in the studied site. The results revealed that zooplankton species (Daphnia pulex, Ceriodaphnia dubia, Neobosmina chilensis, Mesocyclops araucanus, and Tropocyclops prasinus) are abundant in surface zones at night, early morning and evening, whereas at middle day the zooplankton abundances are high at deep zones. The results agree with observations for Argentinean and North American lakes where these daily migration patterns in crustacean zooplankton species were reported due mainly natural ultraviolet radiation exposure, whereas for northern hemisphere lakes the vertical migration is due to combined effect of natural ultraviolet radiation and fish predation exposure.(AU)
As comunidades zooplanctônicas frequentemente exibem migrações verticais diárias para evitar a radiação ultravioleta natural e/ou a predação de peixes. No entanto, não há informações sobre esse tema em lagos chilenos no norte da Patagônia até a presente data. Portanto, este estudo trata de uma primeira caracterização da migração vertical diária de crustáceo planctônico em dois lagos temperados e oligotróficos (lagos Villarrica e Panguipulli, 39º S) no sul do Chile. O zooplâncton foi coletado em diferentes profundidades (0-10 m, 10-20 m, 20-30 m e 30-40 m) no início da manhã, ao meio-dia, à tarde e à noite no local estudado. Os resultados revelaram que as espécies de zooplâncton (Daphnia pulex, Ceriodaphnia dubia, Neobosmina chilensis, Mesocyclops araucanus e Tropocyclops prasinus) são abundantes nas zonas de superfície à noite, de manhã cedo e à tarde, enquanto, ao meio-dia, as abundâncias do zooplâncton são altas nas zonas de profundidade. Os resultados expostos corroboram as observações para outros lagos argentinos e da América do Norte, onde foram reportados esses padrões de migração diária em espécies crustáceas de zooplâncton por causa, principalmente, da exposição à radiação ultravioleta natural, enquanto, para lagos do hemisfério norte, a migração vertical se dá em razão do efeito combinado da radiação ultravioleta natural e exposição à predação.(AU)
Subject(s)
Zooplankton , Animal Migration , Lakes , Ultraviolet Rays , ChileABSTRACT
Abstract The zooplankton communities often exhibit daily vertical migrations to avoid natural ultraviolet radiation and/or fish predation. However there is no information on this topic in Chilean North Patagonian lakes up to date. Therefore, this study deals with a first characterization of plankton crustacean daily vertical migration in two temperate, oligotrophic lakes (Villarrica and Panguipulli lakes, 39°S) in Southern Chile. Zooplankton were collected at different depths intervals (0-10m, 10-20 m, 20-30m, 30-40m) at early morning, middle day, evening and night in the studied site. The results revealed that zooplankton species (Daphnia pulex, Ceriodaphnia dubia, Neobosmina chilensis, Mesocyclops araucanus, and Tropocyclops prasinus) are abundant in surface zones at night, early morning and evening, whereas at middle day the zooplankton abundances are high at deep zones. The results agree with observations for Argentinean and North American lakes where these daily migration patterns in crustacean zooplankton species were reported due mainly natural ultraviolet radiation exposure, whereas for northern hemisphere lakes the vertical migration is due to combined effect of natural ultraviolet radiation and fish predation exposure.
Resumo As comunidades zooplanctônicas frequentemente exibem migrações verticais diárias para evitar a radiação ultravioleta natural e/ou a predação de peixes. No entanto, não há informações sobre esse tema em lagos chilenos no norte da Patagônia até a presente data. Portanto, este estudo trata de uma primeira caracterização da migração vertical diária de crustáceo planctônico em dois lagos temperados e oligotróficos (lagos Villarrica e Panguipulli, 39º S) no sul do Chile. O zooplâncton foi coletado em diferentes profundidades (0-10 m, 10-20 m, 20-30 m e 30-40 m) no início da manhã, ao meio-dia, à tarde e à noite no local estudado. Os resultados revelaram que as espécies de zooplâncton (Daphnia pulex, Ceriodaphnia dubia, Neobosmina chilensis, Mesocyclops araucanus e Tropocyclops prasinus) são abundantes nas zonas de superfície à noite, de manhã cedo e à tarde, enquanto, ao meio-dia, as abundâncias do zooplâncton são altas nas zonas de profundidade. Os resultados expostos corroboram as observações para outros lagos argentinos e da América do Norte, onde foram reportados esses padrões de migração diária em espécies crustáceas de zooplâncton por causa, principalmente, da exposição à radiação ultravioleta natural, enquanto, para lagos do hemisfério norte, a migração vertical se dá em razão do efeito combinado da radiação ultravioleta natural e exposição à predação.
Subject(s)
Zooplankton , Lakes , Plankton , Ultraviolet Rays , ChileABSTRACT
Cigarette butts (CBs) comprise one of the most relevant categories of marine litter worldwide. This study was structured as a case study simultaneously assessing (i) the occurrence of CBs in a highly urbanized coastal area, (ii) their partitioning in two environmental compartments (water column and sediments) by laboratory settling tests, and (iii) the toxicity produced by the CBs leachates (measured as copepod reproduction). Marine litter was sampled in beaches of the city of Santos (SW Brazil) and CBs were collected for analysis. The characterization showed that CBs were one of the most prevalent items (51.5% in summer and 34.4% in winter) and 22 cigarettes brands were identified at different stages of decomposition. Laboratory settling tests showed that CBs remain in the water column between 3 and 20 days, subsequently reaching the sediments. The toxicity results indicated that CBs the leachates extracted from a small amount of CBs was sufficient to affect copepod reproduction (0.1 and 0.01 CBs L-1). Furthermore, the approaches adopted by the present study can serve as a preliminary assessment to estimate local impacts resulting from inadequate disposal of cigarette butts in coastal areas around the world.
Subject(s)
Tobacco Products , Waste Products , Brazil , Environmental Monitoring , Seasons , Tobacco Products/toxicity , Waste Products/analysisABSTRACT
The copepod Acartia tonsa was standardized as model organism in acute toxicity bioassays due to its key position in coastal food chains and high sensitivity. Once bioassays are performed according to a protocol their results may become tools for the protection of aquatic ecosystems. However, there are divergences in bioassays methods using A. tonsa. This study aimed to investigate: (i) the need for acclimation of A. tonsa collected from the environment for use in acute toxicological bioassays; and (ii) differences in sensitivity between copepods collected from the environment and laboratory-grown copepods. Laboratory-grown copepods are more sensitive to SDS than A. tonsa from the environment. The acclimation time of 30 h helped organisms to recover from stress of collection/handling and changing environment/conditions. Therefore, laboratory-grown copepods showed to be more sensitive than organisms from environment; and for ecotoxicological bioassays acclimating A. tonsa collected from the environment for 30 h can be adopted.
Subject(s)
Copepoda , Acclimatization , Animals , Biological Assay , Ecosystem , EcotoxicologyABSTRACT
Different groups parasitize the gills of fishes, and the organisms can interact in positive, negative, or neutral ways, depending on parasitic abundance, environmental conditions, and the availability of resources. Here, we studied the distribution of ectoparasites on the gills of the mullet Mugil curema in the Cabedelo port region (Brazil), asking if (1) the gill parasites of M. curema fix on specific host gill arches and/or (2) co-occur in the same gill arches within a host individual; (3) if the abundance of one parasite taxon affects the abundance of another on the same gill arches; and (4) considering distinct major groups, if parasites present patterns of co-occurrence on hosts and gill arches different from the expected at random. We used generalized linear models, generalized linear mixed models, and models with zero inflation to define the microhabitats (arches) with the highest abundances of parasites and null models to analyze the co-occurrences of gill parasite groups. Three taxa of Monogenea (Ligophorus brasiliensis Abdallah, Azevedo & Luque, 2009, Ligophorus sp. 1 and Ligophorus sp. 2) and six species of Copepoda were recorded (Bomolochus nitidus Wilson, 1911; Caligus praetextus Bere, 1936; Ergasilus atafonensis Amado & Rocha, 1997; Ergasilus bahiensis Amado & Rocha, 1997; Ergasilus caraguatatubensis Amado & Rocha, 1997 and Ergasilus lizae Krøyer, 1863). We found that, in general, the gill parasites were more abundant/prevalent on specific arches (I and II) of the hosts, shared such preferences and co-occurred on the gill arches. The presence of one taxon influenced the occurrence of another only in the arches I and II; as a result, the infracommunities were characterized as interactive in the gills of this host species.
Subject(s)
Fish Diseases/parasitology , Gills/parasitology , Smegmamorpha/parasitology , Trematoda/isolation & purification , Trematode Infections/veterinary , Animals , Brazil , Trematoda/classification , Trematoda/genetics , Trematode Infections/parasitologyABSTRACT
Larval copepods are frequent parasites that infest fish larvae along the Chilean coast. Because these parasites develop on fish during the early development, when their bodies are fragile and in a recent stage, they can affect the fishes' early life history traits (ELHT). The goal of this study was to determine the effect of parasitic copepods on the ELHT of the larvae of the clingfish Gobiesox marmoratus (Teleostei: Gobiesocidae) using otolith microstructure analysis. Ichthyoplankton samples were collected during austral winter (July and August 2012), in the inner shelf waters off Valparaiso Bay, central Chile. A total of 95 non-parasitized larvae (NPL) and 95 parasitized (PL) with copepods were randomly selected for subsequent analyses. Parasitized larvae of G. marmoratus were larger than NPL. The right otolith tended to be larger than the left otolith in the fish larvae, but with a higher asymmetry in PL. The PL showed larger otoliths-at-size than the NPL, particularly in smaller larvae (< 8 mm of standard length, SL). Nonetheless, parasitized larvae larger than 8 mm SL showed the opposite trend that is smaller-at-size otoliths than NPL. The Gompertz models indicated that the asymptotic length of NPL doubled the length of PL; this suggests that parasitic copepods affect the maximum size attained by the PL. In conclusion, parasitic copepods negatively affect the ELHT of G. marmoratus larvae and the greater asymmetry can be attributed to parasitism.
Subject(s)
Copepoda/metabolism , Fishes/embryology , Fishes/parasitology , Animals , Chile , Life History Traits , Parasitic Diseases, Animal , SeasonsABSTRACT
Historically, pelagic Sargassum were only found in the Sargasso Sea. Since 2011, blooms were regularly observed in warmer water, further south. Their developments in Central Atlantic are associated with mass strandings on the coasts, causing important damages and potentially dispersion of new bacteria. Microbiomes associated with pelagic Sargassum were analysed at large scale in Central Atlantic and near Caribbean Islands with a focus on pathogenic bacteria. Vibrio appeared widely distributed among pelagic Sargassum microbiome of our samples with higher occurrence than previously found in Mexico Gulf. Six out the 16 Vibrio-OTUs (Operational Taxonomic Unit), representing 81.2 ± 13.1% of the sequences, felt in cluster containing pathogens. Among the four different microbial profiles of pelagic Sargassum microbiome, Vibrio attained about 2% in two profiles whereas it peaked, in the two others, at 6.5 and 26.8% respectively, largely above the concentrations found in seawater surrounding raft (0.5%). In addition to sampling and measurements, we performed backward Lagrangian modelling of trajectories of rafts, and rebuilt the sampled rafts environmental history allowing us to estimate Sargassum growth rates along raft displacements. We found that Vibrio was favoured by high Sargassum growth rate and in situ ammonium and nitrite, modelled phosphate and nitrate concentrations, whereas zooplankters, benthic copepods, and calm wind (proxy of raft buoyancy near the sea surface) were less favourable for them. Relations between Vibrio and other main bacterial groups identified a competition with Alteromonas. According to forward Lagrangian tracking, part of rafts containing Vibrio could strand on the Caribbean coasts, however the strong decreases of modelled Sargassum growth rates along this displacement suggest unfavourable environment for Vibrio. For the conditions and areas observed, the sanitary risk seemed in consequence minor, but in other areas or conditions where high Sargassum growth rate occurred near coasts, it could be more important.
Subject(s)
Microbiota , Sargassum , Vibrio , Animals , Caribbean Region , Mexico , Seawater , West IndiesABSTRACT
The sea louse (Caligus rogercresseyi) is the most relevant parasite for the farmed salmon industry in Chile, the second largest producer worldwide. Although spatial patterns of C. rogercresseyi have been addressed from data obtained from established monitoring and surveillance programs, studies on its spatial ecology are limited. A wide geographic distribution of C. rogercresseyi is presumed in Chile; however, how this species could potentially be distributed in space is unknown. Our study presents an analysis of the habitat suitability for C. rogercresseyi in the entire area occupied by marine sites of salmon farms in Chile. Habitat suitability modeling was used to explore the likelihood of species spatial occurrence based on environmental characteristics. Due to the expanding salmon industry in southern Chile, we studied C. rogercresseyi habitat suitability models for present (average of 2005-2010) and two future projections (2050 and 2100) under different climate change scenarios. Models were constructed with the maxent algorithm using a large database of spatial C. rogercresseyi occurrences from the Chilean fisheries health authority and included 23 environmental variables obtained from the Ocean Rasters for Analysis of Climate and Environment (Bio-ORACLE). Habitat suitability models indicated that water temperature, water salinity, and current velocity of waters were the most important characteristics limiting C. rogercresseyi distribution in southern Chile. Habitat suitability models for current climate indicated a heterogeneous pattern with C. rogercresseyi being present in waters with temperature range 12.12-7.08°C (sd = 0.65), salinity range 33.7-25.5 pss (sd = 1.73), and current water velocity range 0.23-0.01 m-1 (sd = 0.02). Predictions for future projections in year 2050 and year 2100 suggest new clumped dispersion of the environmental conditions for C. rogercresseyi establishment. Our results suggest complexity and a wide dispersion of the biogeographic distribution of the C. rogercresseyi habitat suitability with potential implications for control strategies and environmental issues for salmon farming in Chile. Further investigations are required into C. rogercresseyi distribution in southern Chile considering the possible effect of climate change.
ABSTRACT
Abstract The zooplankton communities often exhibit daily vertical migrations to avoid natural ultraviolet radiation and/or fish predation. However there is no information on this topic in Chilean North Patagonian lakes up to date. Therefore, this study deals with a first characterization of plankton crustacean daily vertical migration in two temperate, oligotrophic lakes (Villarrica and Panguipulli lakes, 39°S) in Southern Chile. Zooplankton were collected at different depths intervals (0-10m, 10-20 m, 20-30m, 30-40m) at early morning, middle day, evening and night in the studied site. The results revealed that zooplankton species (Daphnia pulex, Ceriodaphnia dubia, Neobosmina chilensis, Mesocyclops araucanus, and Tropocyclops prasinus) are abundant in surface zones at night, early morning and evening, whereas at middle day the zooplankton abundances are high at deep zones. The results agree with observations for Argentinean and North American lakes where these daily migration patterns in crustacean zooplankton species were reported due mainly natural ultraviolet radiation exposure, whereas for northern hemisphere lakes the vertical migration is due to combined effect of natural ultraviolet radiation and fish predation exposure.
Resumo As comunidades zooplanctônicas frequentemente exibem migrações verticais diárias para evitar a radiação ultravioleta natural e/ou a predação de peixes. No entanto, não há informações sobre esse tema em lagos chilenos no norte da Patagônia até a presente data. Portanto, este estudo trata de uma primeira caracterização da migração vertical diária de crustáceo planctônico em dois lagos temperados e oligotróficos (lagos Villarrica e Panguipulli, 39º S) no sul do Chile. O zooplâncton foi coletado em diferentes profundidades (0-10 m, 10-20 m, 20-30 m e 30-40 m) no início da manhã, ao meio-dia, à tarde e à noite no local estudado. Os resultados revelaram que as espécies de zooplâncton (Daphnia pulex, Ceriodaphnia dubia, Neobosmina chilensis, Mesocyclops araucanus e Tropocyclops prasinus) são abundantes nas zonas de superfície à noite, de manhã cedo e à tarde, enquanto, ao meio-dia, as abundâncias do zooplâncton são altas nas zonas de profundidade. Os resultados expostos corroboram as observações para outros lagos argentinos e da América do Norte, onde foram reportados esses padrões de migração diária em espécies crustáceas de zooplâncton por causa, principalmente, da exposição à radiação ultravioleta natural, enquanto, para lagos do hemisfério norte, a migração vertical se dá em razão do efeito combinado da radiação ultravioleta natural e exposição à predação.
ABSTRACT
INTRODUCTION: Copepods are common components in all types of fish assemblages, being present in fishes of all ecosystems. The Ergasilidae Burmeister, 1835 is one of the biggest families in the order Cyclopoida Burmeister, 1834, with the majority of species found on freshwater fishes. MATERIAL AND METHODS: Ergasilus tipurus n. sp. is described from the nasal fossae of Calophysus macropterus and Sorubim lima captured in the rivers Guaporé and Mamoré in the State of Rondônia, Brazil, and from the nasal fossae and the gills of Rhaphiodon vulpinus collected from floodplain lakes of the Solimões River in the State of Amazonas, Brazil. RESULTS: The new species differs from all known species of Ergasilus from Brazilian waters by: (1) antennule setal formula 3:7:3:4:2:5; (2), having three-segmented first endopod of leg I; and (3) having leg V with a single well-developed segment with one middle distal setae, two distal setae placed laterally and two basal papillae, each provided with a simple seta. DISCUSSION: From all Ergasilus species described in the neotropics, this is the first species that can be found parasitizing the gills and nasal fossae of the reported hosts.
Subject(s)
Catfishes/parasitology , Copepoda/classification , Copepoda/growth & development , Ectoparasitic Infestations/veterinary , Fish Diseases/parasitology , Animals , Brazil , Copepoda/anatomy & histology , Ectoparasitic Infestations/parasitology , Gills/parasitology , Microscopy , Nose/parasitology , RiversABSTRACT
An approach pooling geochemical analyses and ecotoxicological tests has been applied to assess the sediment quality of the Capibaribe River Estuary, Brazil. Toxicity tests were performed to compare a well-established, labor-intensive protocol using ovigerous females to a new, easier and faster protocol using nauplii of the epibenthic marine copepod Tisbe biminiensis. The endpoints of the nauplii toxicity test were comparable to those of the female test. Nauplii proved to be more sensitive than females as a biological model for indicating sediment toxicity. All sediments collected had at least one contaminant above the threshold effects level (TEL) proposed in the literature. Furthermore, more than one-third of samples exhibited contaminants above the probable effects level (PEL). The PCA revealed that nauplii mortality was associated with metals in October 2014, which was confirmed by the Spearman correlation factor. In contrast, no strong association among contaminants and toxicological endpoints in May 2015 was found.
Subject(s)
Copepoda/growth & development , Ecotoxicology/methods , Geologic Sediments/chemistry , Animals , Brazil , Ecotoxicology/instrumentation , Estuaries , Female , Models, Biological , Rivers/chemistryABSTRACT
At the mouth of the Amazon River, a widespread carbonate ecosystem exists below the river plume, generating a hard-bottom reef (â¼9500 km2) that includes mainly large sponges but also rhodolith beds. The mesozooplankton associated with the pelagic realm over the reef formation was characterized, considering the estuarine plume and oceanic influence. Vertical hauls were carried out using a standard plankton net with 200 µm mesh size during September 2014. An indicator index was applied to express species importance as ecological indicators in community. Information on functional traits was gathered for the most abundant copepod species. Overall, 179 zooplankton taxa were recorded. Copepods were the richest (92 species), most diverse and most abundant group, whereas meroplankton were rare and less abundant. Species diversity (>3.0 bits.ind-1) and evenness (>0.6) were high, indicating a complex community. Small holoplanktonic species dominated the zooplankton, and the total density varied from 107.98 ind. m-3 over the reef area to 2,609.24 ind. m-3 in the estuarine plume, with a significant difference between coastal and oceanic areas. The most abundant copepods were the coastal species ithona plumifera and Clausocalanus furcatus and early stages copepodites of Paracalanidae. The holoplanktonic Oikopleura, an important producer of mucous houses, was very abundant on the reefs. The indicator species index revealed three groups: (1) indicative of coastal waters under the influence of the estuarine plume [Euterpina acutifrons, Parvocalanus crassirostris, Oikopleura (Vexillaria) dioica and Hydromedusae]; (2) characterized coastal and oceanic conditions (Clausocalanus); (3) characterized the reef system (O. plumifera). Two major copepods functional groups were identified and sorted according to their trophic strategy and coastal-oceanic distribution. The species that dominated the coastal area and the area over the rhodolith beds are indicators of the estuarine plume and are mixed with species of the North Brazil Current. These species practically disappear offshore, where occur oceanic species commonly found in other oligotrophic tropical areas. This ecosystem shows a mixture of estuarine, coastal and oceanic communities coexisting in the waters over the Amazon reefs, with no significant differences among these areas. However, the MDS clearly separated the communities along the salinity gradient in the plume.
ABSTRACT
Top-down grazer control of cyanobacteria is a controversial topic due to conflicting reports of success and failure as well as a bias toward studies in temperate climates with large generalist grazers like Daphnia. In the tropical lowland lakes of Brazil, calanoid copepods of the Notodiaptomus complex dominate zooplankton and co-exist in high abundance with permanent blooms of toxic cyanobacteria, raising questions for grazer effects on bloom dynamics (i.e., top-down control vs. facilitation of cyanobacterial dominance). Accordingly, the effect of copepod grazing on the relative abundance of Microcystis co-cultured with a eukaryotic phytoplankton (Cryptomonas) was evaluated in a series of 6-day laboratory experiments. Grazer effects were tested in incubations where the growth of each phytoplankton in the presence or absence of the copepod Notodiaptomus iheringi was monitored in 1 L co-cultures, starting with a 6-fold initial dominance of Cryptomonas by biomass. Compared to the no grazer controls, N. iheringi reduced the growth of both phytoplankton, but Cryptomonas growth was reduced to negative values while Microcystis growth continued positively despite grazers. Hence, in a matter of 6 days selective grazing by N. iheringi increased the biomass of Microcystis relative to Cryptomonas by an order of magnitude compared to controls, and thus, facilitated the dominance of this cyanobacterium. To account for the potential effect of allelopathy, we performed a secondary experiment comparing the abundance and growth rate of Microcystis and Cryptomonas in single and mixed co-cultures in the absence of grazers. The growth rate of Microcystis was unaffected by the presence or relative abundance of Cryptomonas, and vice versa, indicating no allelopathic effects. Our results suggest that selectively grazing zooplankton may facilitate cyanobacteria blooms by grazing on their eukaryotic phytoplankton competitors in nature. Given that selective grazers predominate zooplankton biomass in warmer waters, grazer facilitation of blooms may be a common but poorly understood regulator of plankton dynamics in a warmer and more eutrophic world.
ABSTRACT
The vertical distribution of copepod assemblages, ascertained from the surface down to 1,200 m, was investigated during two sampling periods (rainy and dry seasons), at four depths, in the oligotrophic waters of the southwestern Atlantic Ocean. Total density, diversity, and richness differed among sampling depths. Copepod density decreased with depth in the two sampling periods, with a maximum at 1 m and a slight decrease at 800 m. Higher diversities were observed at 250 m and 1,200 m during the rainy season and at 1 m and 1,200 m during the dry season. The maximum number of species was found at 1,200 m during the rainy season and at 1 m during the dry season. Various copepod assemblages were delimited in the water column in the two sampling periods. The deeper copepod assemblages occupied a wider range of depths. Salinity and temperature influenced the structure of copepod assemblages and reflected the hydrographic characteristics of the water masses in the region. Candacia pachydactyla (Dana, 1849), Scolecithrix danae (Lubbock, 1856), and Agetus limbatus (Brady, 1883) were the indicator species found at 1 m. The effects of different environmental factors on the copepod assemblages suggest that these consortia occupy distinct niches in the ocean.(AU)
Subject(s)
Animals , Copepoda , Demography , Zooplankton , Biodiversity , Atlantic Ocean , Brazil , Tropical ZoneABSTRACT
The vertical distribution of copepod assemblages, ascertained from the surface down to 1,200 m, was investigated during two sampling periods (rainy and dry seasons), at four depths, in the oligotrophic waters of the southwestern Atlantic Ocean. Total density, diversity, and richness differed among sampling depths. Copepod density decreased with depth in the two sampling periods, with a maximum at 1 m and a slight decrease at 800 m. Higher diversities were observed at 250 m and 1,200 m during the rainy season and at 1 m and 1,200 m during the dry season. The maximum number of species was found at 1,200 m during the rainy season and at 1 m during the dry season. Various copepod assemblages were delimited in the water column in the two sampling periods. The deeper copepod assemblages occupied a wider range of depths. Salinity and temperature influenced the structure of copepod assemblages and reflected the hydrographic characteristics of the water masses in the region. Candacia pachydactyla (Dana, 1849), Scolecithrix danae (Lubbock, 1856), and Agetus limbatus (Brady, 1883) were the indicator species found at 1 m. The effects of different environmental factors on the copepod assemblages suggest that these consortia occupy distinct niches in the ocean.
Subject(s)
Animals , Biodiversity , Copepoda , Demography , Zooplankton , Brazil , Atlantic Ocean , Tropical ZoneABSTRACT
Recent surveys of the copepod fauna associated with the sponge Ircinia felix (Porifera, Dictyoceratida) in Brazil resulted in the discovery of a new siphonostomatoid species belonging to a recently erected genus of Asterocheridae. Setacheres portobarrensis sp. nov. possesses a 21-segmented antennule, with 3 free distal segments, after the aesthetasc. The third exopodal segment of leg 3 shows a distal seta instead of a spine as in some other congeners. The new species shows several unique features on the third endopodal segment of the antenna, the mandibular stylet, the inner lobe of the maxillule, and setules and spinules located in specific regions of legs 1 to 4. Setacheres portobarrensis sp. nov. follows the same distributional pattern as its congeners, and this is the first record of a siphonostomatoid copepod associated with Ircinia felix.
Subject(s)
Copepoda , Animals , Brazil , PoriferaABSTRACT
Copepodids of the genus Monstrilla has been registered in the mussels culture Perna perna on the coast of Santa Catarina state, southern Brazil. Between July 2010 and June 2011, 2,880 specimens of P. perna were collected from the main mussel-farming municipalities for analysis under stereomicroscope, differential contrast microscopy (DIC), scanning electron microscopy (SEM) and histopathology. The presence of copepodites and pre-adult females was observed in nodules only in the connective tissue of mussels mantle border. Solely Palhoça presented infestation (prevalence of 43.33%) during June 2010, without mortality. There was no infiltration of hemocytes in the infested tissue.(AU)
Copepoditos do gênero Monstrilla foram registrados em Perna perna cultivados no litoral do estado de Santa Catarina, Brasil. Entre julho de 2010 a junho de 2011, foram coletados 2.880 indivíduos de P. perna nos principais municípios produtores do Estado para análises ao estereomicroscópio, microscopia de contraste diferencial (DIC), microscopia eletrônica de varredura (SEM) e histopatologia. Foi registrada a presença de copepoditos e fêmeas pré-adultas em nódulos apenas no tecido conjuntivo da borda do manto dos animais, com prevalência de 43,33% nos mexilhões de Palhoça em junho de 2010, sem casos de mortalidade. Não foi observada infiltração de hemócitos no tecido infestado.(AU)