Nocturnal Mosquitoes of Pará State in the Brazilian Amazon: Species Composition, Habitat Segregation, and Seasonal Variation

2020 ◽  
Vol 57 (6) ◽  
pp. 1913-1919
Author(s):  
Walter Santos de Araújo ◽  
Thallyta Maria Vieira ◽  
Guilherme Antunes de Souza ◽  
Isaque Clementino Bezerra ◽  
Paulo Henrique Costa Corgosinho ◽  
...  
Keyword(s):  
Culex Quinquefasciatus ◽  
Disease Transmission ◽  
Rainy Season ◽  
Mosquito Species ◽  
Species Abundance ◽  
Abundant Species ◽  
Dry Season ◽  
Habitat Segregation ◽  
Vector Species ◽  
High Degree

Abstract Mosquitoes (Diptera: Culicidae) are one of the most important disease vector species in the world. Many species have a high degree of anthropophilia and are often found in human habitations. In the present study, we have inventoried the nocturnal mosquito assemblage in intra-, peri-, and extradomicile environments in four municipalities in Pará, Brazil. At each municipality, a residence was selected and the mosquitoes were sampled using the protected human attraction capture and Shannon trap methods in April (rainy season) and August 2018 (dry season). We have collected a total of 696 mosquito specimens belonging to 8 genera and 17 species. The most abundant species were Mansonia (Mansonoides) titillans (Walker) (366/696, 52.6%), Anopheles (Nyssorhynchus) albitarsis Lynch-Arribálzaga (97/696, 13.9%), and Culex (Culex) quinquefasciatus Say (93/696, 13.4%). Mosquito richness, abundance, and composition did not differ between intra-, peri-, and extradomicile environments suggesting limited habitat segregation among the different species. However, mosquito species richness and mosquito species abundance were significantly higher during the rainy season than during the dry season, suggesting increased mosquito activity during the rainy season. We detected several important vector species of human diseases including Aedes (Stegomyia) aegypti (Linnaeus), Anopheles (Nyssorhynchus) darlingi Root, Haemagogus (Conopostegus) leucocelaenus (Dyar and Shannon), Coquillettidia (Coquillettidia) venezuelensis (Theobald), and Culex (Culex) quinquefasciatus which are the main transmitters of dengue, malaria, yellow fever, mayaro, and oropouche fever, respectively. As inventories of disease-carrying mosquitoes in the region are very scarce, mainly in residential environments, our results suggest high potential for mosquito-borne disease transmission in Pará State.

scholarly journals Peces de la Laguna Cormorán, Parque Nacional Sangay, Ecuador

2017 ◽  
Vol 9 (15) ◽  
Author(s):  
Fernando Anaguano-Yancha
Keyword(s):  
Aquatic Ecosystem ◽  
Rainy Season ◽  
Transition Period ◽  
Species Abundance ◽  
Abundant Species ◽  
Dry Season ◽  
Fish Diversity ◽  
Astyanax Fasciatus ◽  
The Family ◽  
Rhamdia Quelen

AbstractI conducted a fish inventory at the Cormoran Lagoon, in the icthyogeographic area Upano–Zamora, during October 2011 (dry season), February 2012 (transition period), and May 2012 (rainy season). Fish were sampled using four trammels (20 m length, 1.5 m height), 40 fishing lines, and a hand net. A total of 599 individuals of 16 species and six families were captured. The order Characiformes was the most abundant and diverse, and Lebiasina elongata (Lebiasinidae) and Astyanax fasciatus (Characidae) were the most abundant species. Species abundance gradually decreased as the rainy season arrived. Elevational ranges of the genus Chaetostoma (Chaetostoma microps) and of the family Heptapteridae (Rhamdia quelen) are increased to 1783 m in Ecuador. Fish diversity at Cormoran Lagoon still needs more studies. It is necessary to carry out taxonomic, ecological, and biogeographic studies that contribute to the knowledge of fish diversity in this tropical aquatic ecosystem. It is posible that some species are endemic, specially in the genera Astroblepus and Bryconamericus.  ResumenSe realizó un inventario de peces en la laguna Cormorán, en la zona ictiogeográfica Upano–Zamora, durante octubre 2011 (época de seca), febrero 2012 (época de transición) y mayo 2012 (época de lluvias). Los peces fueron muestreados usando cuatro trasmallos (20 m de largo, 1,5 m de alto), 40 anzuelos y una red de mano. Un total de 599 individuos de 16 especies y seis familias fueron capturados. El orden Characiformes fue el más abundante y diverso, y Lebiasina elongara (Lebiasinidae) y Astyanax fasciatus (Characidae) fueron las especies más abundantes. La abundancia de especies disminuyó paulatinamente conforme llegaba la época de lluvias. Se extienden los rangos altitudinales del género Chaetostoma (Chaetostoma microps) y de la familia Heptapteridae (Rhamdia quelen) hasta 1783 m en Ecuador. La ictiofauna de la laguna Cormorán todavía necesita mayores de estudios. Es necesario realizar estudios taxómicos, ecológicos y biogeográficos que contribuyan al conocimiento de la diversidad de peces de este ecosistema acuático tropical. Es posible que algunas especies encontradas en este estudio sean endémicas, especialmente en los géneros Astroblepus y Bryconamericus. 

New Mosquito Collection Records for Southern Georgia

2001 ◽  
Vol 36 (2) ◽  
pp. 114-121 ◽  
Author(s):  
John P. Smith ◽  
Thomas G. Floore
Keyword(s):  
Culex Quinquefasciatus ◽  
Species Abundance ◽  
Abundant Species ◽  
Light Traps ◽  
Aedes Vexans ◽  
Detailed Report ◽  
Mosquito Collection ◽  
Abundance And Diversity ◽  
Southern Georgia

Twenty-nine species representing eight genera, numerous new county records and one state record, Mansonia titillans (Walker), were collected in a surveillance project conducted in 20 southern Georgia counties during the summer of 1997. A detailed report of species abundance and diversity is presented. Overall, as sampled by CO2 light traps, Culex quinquefasciatus Say was the most widely distributed species and Aedes vexans (Meigen) was the most abundant species followed closely by Aedes atlanticus Dyer and Knab.

scholarly journals The Abundance and Biting Patterns of Culex quinquefasciatus Say (Culicidae) in the Coastal Region of Nigeria

ISRN Zoology ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Emmanuel C. Uttah ◽  
Gloria N. Wokem ◽  
Christiana Okonofua
Keyword(s):  
Culex Quinquefasciatus ◽  
Rainy Season ◽  
Coastal Region ◽  
Dry Season ◽  
Human Landing Catch ◽  
Light Traps ◽  
Transmission Potential ◽  
Human Landing ◽  
The Mean

This study was aimed at determining the abundance and biting patterns of Culex quinquefasciatus in the coastal region of Nigeria. Collections were done by human landing catch and by CDC miniature light traps from September 2005 to August 2006. A total of 3798 C. quinquefasciatus females were collected. The highest number of females was caught in the month of August and it represented nearly a quarter (24.0%) of the total females collected. In all, 38.8% of females dissected were parous. The abundance of C. quinquefasciatus followed the pattern of rainfall with the population starting to expand at the onset of the rains. The highest increase was found after the temperature had peaked. The mean of biting was 3.2 times more in the rainy season than in the dry season, whereas the transmission potential was higher in the dry season. C. quinquefasciatus is presently regarded as a biting nuisance having no significant epidemiological importance yet. Efforts at its control should be intensified before it is too late.

scholarly journals Effets saisonniers sur les relations poids-longueurs et coefficients de condition pour 16 espèces de poissons de la Lagune Mvassa, basse Guinée, République du Congo

2020 ◽  
Vol 44.1 ◽  
pp. 7540-7552
Author(s):  
Hélène Dembe Louvinguila Tenda ◽  
Armel Ibala Zamba ◽  
Joseph Goma-Tchimbakala ◽  
Lérège Batiabo Mikembi ◽  
Honest Freedom Poaty Ngot ◽  
...  
Keyword(s):  
Rainy Season ◽  
Condition Factor ◽  
Abundant Species ◽  
Common Species ◽  
Dry Season ◽  
Mugil Cephalus ◽  
Seasonal Effects ◽  
Length Relationship ◽  
Fish Samples ◽  
Sarotherodon Melanotheron

Objectifs : La présente étude a été initiée pour établir les relations poids-longueur et les facteurs de condition de Ethmalosa fimbriata, Sardinella maderensis, Coptodon guinensis, Oreochromis schwebischi, Neochelon falcipinnis, Mugil cephalus, Parachelon grandisquamis, Eucinostomus melanopterus, Hemichromis elongatus, Pomadasys jubelini, Eleotris daganensis, Bathygobius soporator, Trachinotus teraia, Lutjanus goreensis, Mugil banannensis, et Sarotherodon melanotheron, 16 espèces les plus abondantes de la lagune Mvassa en République du Congo. Méthodologie et résultats : Les échantillonnages des poissons ont été réalisés sur 9 stations à l’aide des filets maillants de 8, 10, 20 et 30 mm de côté de la maille. Les relations poidslongueur ont été réalisées en utilisant l’équation P = aLSb et leurs coefficients de condition en utilisant l’équation K = 100*(P ⁄ LSb ). Au total, 1566 spécimens, réparties en 5 ordres, 8 familles, 16 espèces dont 10 ont été capturées en saison sèche, 14 en saison des pluies et 8 espèces communes pour les deux saisons ont été utilisés dans le cadre de cette étude. Le coefficient de détermination r 2 était significatif pour les deux saisons et variait de 0,91 pour Neochelon falcipinnis et 0,99 pour Pomadasys jubelini avec une moyenne de 0,97 ± 0,02. En saison sèche, le coefficient d’allométrie b de la relation poids-longueur variait de 2,04 pour Mugil cephalus à 3,48 Sardinella maderensis avec une moyenne de 2,79 ± 0,03. Le facteur de condition variait en moyenne de 0,66 ± 0,06 pour Sardinella maderensis à 12,22± 0,28 pour Mugil cephalus. En saison des pluies, le coefficient d’allométrie b variait de 2,41 pour Eucinostomus melanopterus à 3,94 pour Sardinella maderensis, avec une moyenne de 3,01 ± 0,05. Le facteur de condition variait de 0,02± 0,002 pour Parachelon grandisquamis à 6,73 ± 0,41 pour Eucinostomus malanopterus. Pour les huit espèces communes, le coefficient d’allométrie b était plus élevé en saison de pluie qu’en saison sèche pour la plupart des espèces (63 %). Conclusion et application des résultats : Ces résultats rapportent des informations relatives à la biologie des poissons rencontrés dans la lagune Mvassa, mais aussi sur l’influence de la saison sur les relations poids-longueur et les coefficients de condition. Dembe Louvinguila et al., 2020 Journal of Animal & Plant Sciences (J.Anim.Plant Sci. ISSN 2071-7024) Vol.44 (1) : 7540-7552 https://doi.org/10.35759/JAnmPlSci.v44-1.1 7541 Seasonal effects on weight-length relationships and condition factors for 16 fish species from the Mvassa Lagoon, Lower Guinea, Republic of the Congo ABSTRACT Objectives: This study was initiated to establish weight-length relationships and condition factors of Ethmalosa fimbriata, Sardinella maderensis, Coptodon guinensis, Oreochromis schwebischi, Neochelon falcipinnis, Mugil cephalus, Parachelon grandisquamis, Eucinostomus melanopterus, Hemichromis elongatus, Pomadasys jubelini, Eleotris daganensis, Bathygobius soporator, Trachinotus teraia, Lutjanus goreensis, Mugil banannensis, et Sarotherodon melanotheron, 16 most abundant species of the Mvassa lagoon in the Republic of Congo. Methodology and results: Fish samples were taken at 9 stations utilizing 8, 10, 20 and 30 mm mesh gillnets. The weight-length relationships were performed using equation P = aLSb and their condition coefficients using equation K = 100*(P/LSb ). A total of 1566 specimens, divided into 5 orders, 8 families, 16 species of which 10 were caught in the dry season, 14 in the rainy season and 8 common species for both seasons were used in this study. The correlation coefficient r 2 was significant for both seasons and ranged from 0.91 for Neochelon falcipinnis and 0.99 for Pomadasys jubelini with an average of 0.97 ± 0.02. In the dry season, the allometry coefficient b of the weight-length relationship ranged from 2.04 for Mugil cephalus to 3.48 Sardinella maderensis with an average of 2.79 ± 0.03. The condition factor ranged on average from 0.66 ± 0.06 for Sardinella maderensis to 12.22 ± 0.28 for Mugil cephalus. In the rainy season, the allometry coefficient b ranged from 2.41 for Eucinostomus melanopterus to 3.940 for Sardinella maderensis, with an average of 3.014 ± 0.05. The condition factor ranged from 0.02 ± 0.002 for Parachelon grandisquamis to 6.73 ± 0.41 for Eucinostomus malanopterus. For the eight common species, the allometry coefficient b was higher in the rainy season than in the dry season for most species (63%). Conclusion and application of the results: These results report information on the biology of the fish encountered in the Mvassa lagoon, but also on the influence of the season on weight- length relationships and condition coefficients

scholarly journals Keragaman Spesies Vektor Japanese encephalitis di Sekitar Kandang Babi Kabupaten Tangerang

2020 ◽  
Vol 12 (1) ◽  
pp. 37-44
Author(s):  
Muhammad Umar Riandi ◽  
Tri Wahono ◽  
Mara Ipa ◽  
Joni Hendri ◽  
Subangkit Subangkit
Keyword(s):  
Japanese Encephalitis ◽  
Culex Quinquefasciatus ◽  
Rna Virus ◽  
Mosquito Species ◽  
Abundant Species ◽  
Cross Sectional Study ◽  
Rt Pcr ◽  
Cross Sectional ◽  
Mosquito Abundance ◽  
Outdoor Resting

Abstract. Japanese encephalitis is a mosquito-borne zoonotic disease that has pigs as the amplifying host. It is important to study the diversity of mosquito species around pig populations to determine the potential of Japanese encephalitis vectors in the region. This study is a cross-sectional study with a single sampling method for adult mosquitoes around pigpen in Tangerang Regency. The capture of adult mosquitoes is carried out by the outdoor resting mosquitoes collection at 18:00 - 24:00 using aspirators and light traps. Female mosquitoes were identified and subsequently tested RT-PCR for JEV. Catching results obtained 223 mosquitoes from the genus Culex, Armigeres, Aedes, Anopheles, and Mansonia with a total of 10 species. Species diversity in the pigpen area is classified as moderate (H = 1.0875 – 1.292) with Culex vishnui and Culex quinquefasciatus as the most abundant species. RT-PCR test found there’s no mosquito’s samples with positive JE RNA virus. Several species of mosquitoes found around pigpens in Tangerang District have the potential to become JEV vectors, so that control to the mosquito abundance and health of pigs is needed as a preventative measure.  Keywords: Diversity, Japanese encephalitis, pig, vector   Abstrak. Japanese encephalitis merupakan penyakit zoonosis yang ditularkan oleh nyamuk dan babi sebagai inang penguat. Studi keanekaragaman jenis nyamuk di sekitar populasi babi penting dilakukan untuk mengetahui potensi vektor Japanese encephalitis pada wilayah tersebut. Desain penelitian ini adalah potong lintang dengan metode sampling tunggal terhadap nyamuk dewasa sekitar kandang babi di Kabupaten Tangerang. Penangkapan nyamuk dewasa dilakukan dengan metode koleksi outdoor resting pada malam hari pukul 18.00 – 24.00 menggunakan aspirator dan perangkap cahaya. Nyamuk betina diidentifikasi  dan selanjutnya diuji RT-PCR virus JE. Hasil penangkapan didapatkan 700 ekor nyamuk dari genus Culex, Armigeres, Aedes, Anopheles, dan Mansonia dengan total 10 spesies. Keanekaragaman spesies pada seluruh wilayah penelitian tergolong sedang (H=1,0875 – 1,292) dengan Culex vishnui dan Culex quinquefasciatus sebagai spesies paling melimpah. Uji RT-PCR tidak menemukan adanya sampel nyamuk positif RNA virus JE. Beberapa spesies nyamuk yang ditemukan di sekitar kandang babi di Kecamatan Panongan memiliki potensi sebagai vektor JEV sehingga diperlukan pengendalian kepadatan nyamuk dan kesehatan ternak babi terhadap JEV sebagai upaya pencegahan.  Kata Kunci: Keanekaragaman, Japanese encephalitis, babi, vektor

scholarly journals On the relation amongst limnological factors and fish abundance in reservoirs at semiarid region

2015 ◽  
Vol 27 (1) ◽  
pp. 24-38 ◽  
Author(s):  
Ronaldo César Gurgel-Lourenço ◽  
Carlos Alberto de Sousa Rodrigues-Filho ◽  
Ronaldo Angelini ◽  
Danielle Sequeira Garcez ◽  
Jorge Iván Sánchez-Botero
Keyword(s):  
Dissolved Oxygen ◽  
Chlorophyll A ◽  
Rainy Season ◽  
Activity Patterns ◽  
Species Abundance ◽  
Temporal Patterns ◽  
Abundant Species ◽  
Fish Abundance ◽  
Semiarid Region ◽  
Predator Species

Aim:To evaluate possible nycthemeral and seasonal temporal patterns in fish assemblage associated with limnological aspects and biotic factors in two reservoirs in semarid Northeastern Brazil.MethodsFish were sampled with gillnets in nycthemeral cycles throughout the dry and rainy season in two reservoirs (Paulo Sarasate/PS and Edson Queiroz/EQ). The stomach contents of the predator species were surveyed. The limnological variables were submitted to principal components analysis, while their relation to fish abundance was determined by canonical correspondence analysis. Temporal patterns in relative fish species abundance were detected with nMDS.ResultsTemperature and dissolved oxygen levels segregated the reservoirs physico-chemically. Turbidity and chlorophyll-a levels differed between seasons, and the relative abundance of species differed between the reservoirs. Predators were more abundant in PS, while detritivores were more abundant in EQ. Triportheus signatusand Plagioscion squamosissimus were the most abundant species in both reservoirs. In general, predator abundance was positively associated with high temperature and dissolved oxygen (PS>EQ) and negatively associated with turbidity. The activity patterns of P. squamosissimus could not be explained by fluctuations in environmental variables. Non-predators tended to cluster around the vectors chlorophyll-a, pH and turbidity. Predators had a more diversified diet in PS in accordance with food availability, while predators in EQ ate only fish and shrimp. Nycthemeral patterns varied for the same species depending on the reservoir. Generally, in PS predators were more active during daylight hours while non-predators were more active after dark. However, in EQ predators and non-predators displayed similar nycthemeral activity patterns. Regardless of the reservoir, predators were more abundant in the rainy season. No seasonal trend was observed for non-predators.ConclusionsLimnological differences between PS and EQ influenced temporal species abundance patterns. The species distribution was determined by predation conditions and physiological attributes.

scholarly journals Temporal variation in the phytoplankton community of Acapulco Bay, Mexico

2012 ◽  
Vol 3 (1) ◽  
pp. 4 ◽  
Author(s):  
Agustín A. Rojas-Herrera ◽  
Juan Violante Gonzalez ◽  
Sergio García-Ibáñez ◽  
Víctor M.G. Sevilla-Torres ◽  
Jaime S. Gil-Guerrero ◽  
...  
Keyword(s):  
Species Composition ◽  
Temporal Variation ◽  
Rainy Season ◽  
Phytoplankton Community ◽  
Species Abundance ◽  
Sampling Period ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Diatom Species ◽  
Oceanic Environments

<p>Species composition and abundance of the phytoplankton community in Acapulco Bay, Mexico, were studied from May to December 2009. Samples were collected at 5 stations (4 coastal and 1 oceanic) at 3 depths (1, 5 and 10 m). Eighty-seven species were identified: 54 dinoflagellates, 32 diatoms and 1 silicoflagellate. The community was structured mainly by adiaphoric species, that is, species adapted to both neritic and oceanic environments. Species abundance and composition varied significantly during the sampling period due to increased nutrient concentrations in the rainy season. Dinoflagellate species were more abundant during the dry season, and diatom species dominated numerically during the rainy season.</p>

scholarly journals Diversity, Co-Occurrence, and Nestedness Patterns of Sand Fly Species (Diptera: Psychodidae) in Two Rural Areas of Western Panamá

Insects ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 113
Author(s):  
Chystrie A. Rigg ◽  
Milixa Perea ◽  
Kadir González ◽  
Azael Saldaña ◽  
José E. Calzada ◽  
...  
Keyword(s):  
Land Use ◽  
Species Richness ◽  
Rural Areas ◽  
Rainy Season ◽  
Land Use Changes ◽  
Species Abundance ◽  
Abundant Species ◽  
Sand Fly ◽  
Sand Flies ◽  
Seasonal Weather

Cutaneous Leishmaniasis transmission in the New World is observed in areas with rich sand fly species’ faunas. The diversity and composition of sand fly species can change in response to seasonal weather and land use changes. Here, we present results from a two-year-long study where we collected, using Centers for Disease Control (CDC) light traps, sand flies from two rural areas, Las Pavas (LP) and Trinidad de las Minas (T) in western Panamá. Over 710 trap-nights, we collected 16,156 sand flies from 15 genera and 35 species. We identified 34 species in T, and the most abundant species collected was Nyssomyia trapidoi (Fairchild and Hertig, 1952) (n = 2278, 37%), followed by Psychodopygus panamensis (Shannon, 1926) (n = 1112, 18%), and Trichopygomyia triramula (Fairchild and Hertig, 1952) (n = 1063, 17%). In LP, we identified 26 species, and the most abundant species collected were Ty. triramula (n = 4729, 48%), and Ps. panamensis (n = 3444, 35%). We estimated a higher species’ richness in T (Chao2 ± S.E.: 36.58 ± 3.84) than in LP (27.49 ± 2.28). In T, species’ richness was significantly higher in the rainy season, but no seasonal differences were observed in LP. Species’ assemblages were nested in the two areas. Phlebotomine sand fly species’ abundance increased at the two sites during the rainy season. Our data suggest that seasonality is more important than land use as a factor driving sand fly species’ diversity at the studied sites.

scholarly journals Myxomycete diversity in a humid montane forest on the eastern slopes of the Peruvian Andes

2020 ◽  
Vol 153 (3) ◽  
pp. 390-398
Author(s):  
Italo F. Treviño-Zevallos ◽  
Carlos Lado
Keyword(s):  
Species Turnover ◽  
Species Abundance ◽  
Alpha Diversity ◽  
Abundant Species ◽  
Montane Forest ◽  
Dry Season ◽  
Wet Season ◽  
Montane Forests ◽  
Peruvian Andes ◽  
Species Richness And Abundance

Background – The humid montane forests on the eastern slopes of the Peruvian Andes are known for their high biodiversity and natural resources. While their incredibly rich plant and animal communities are still in the process of being discovered, the diversity of smaller organisms such as the Myxomycetes are even more scarcely known. In this work, we document the Myxomycete diversity in these montane forests and evaluate species abundance, occurrence by substrates, distribution, and seasonality, thus documenting population status and species ecology.Material and methods – The study was carried out at the Wayqecha Biological Station located in the Cusco region of Peru. Two sampling campaigns took place in late January (wet season) and early May (dry season) of 2018. We performed a species inventory and evaluated alpha diversity, assemblage similarity, and abundance of Myxomycetes within six 100 m2 plots. We documented variations of species richness and abundance between seasons as well as between substrates. Results – We recorded a total of 81 taxa of Myxomycetes. The order Physarales was the most diverse, and the most abundant species were Didymium squamulosum and Diderma deplanatum during the wet and dry season, respectively. The substrate with highest diversity overall was dead leaves. Diversity was similar in both seasons but with a notable species turnover. Conclusion – The humid montane forest on the eastern slopes of the Andes in Peru revealed an unexpected richness in Myxomycetes. Based on our results, we conclude that this type of forest harbours one of the greatest Myxomycetes diversities in the Peruvian territory, also due to the important seasonal species turnover.

scholarly journals Short-term variability of copepod abundance in Jurumirim Reservoir, São Paulo, Brazil

2001 ◽  
Vol 61 (4) ◽  
pp. 577-598 ◽  
Author(s):  
E. A. PANARELLI ◽  
M. G. NOGUEIRA ◽  
R. HENRY
Keyword(s):  
Rainy Season ◽  
Sampling Period ◽  
Abundant Species ◽  
Sao Paulo ◽  
Dry Season ◽  
Dispersion Pattern ◽  
São Paulo ◽  
Short Term ◽  
Copepod Abundance ◽  
Short Term Variability

Short-term variability in composition and abundance of copepod populations were studied during the dry (winter) and rainy (summer) seasons, at the dam region of Jurumirim Reservoir, São Paulo, Brazil. An intensive sampling program was carried out during 30 days in each period of the year. Samples and measurements were taken every other day at 0, 5, 10, 15, 20 and 25 m depths. The relationship between variability of the populations and some environmental factors was analyzed. The main species were: Argyrodiaptomus furcatus (Sars), Notodiaptomus iheringi (Wright), Mesocyclops longisetus (Thiébaud), Thermocyclops decipiens (Fischer), and T. minutus (Lowndes). Thermocyclops minutus was the most abundant species in dry season and its abundance varied significantly between sampling days. A large increase in abundance of calanoids occurred during the rainy season. This increase was correlated with higher temperature values. At that time, Notodiaptomus iheringi was dominant. This species showed significant short-term variations in abundance in both dry and rainy seasons. Significant variation in density of populations within the same sampling period might result from either the dispersion pattern of the populations or continuous substitution of the water masses. Significant correlation was observed between copepod abundance and temperature, especially for species of calanoids and there was also some correlations between densities of particular species of copepods and some phytoplankton taxa, mainly during the dry season. As for vertical distribution, most organisms were found between the surface and 15 m deep. During the rainy season, there was some evidence of the occurrence of spatial segregation between species of cyclopoids and calanoids, with the cyclopoids in a deeper position within the water column.

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