An assessment of the factors determining rotifer assemblage in river-lake systems: the effects of seasonality and habitat

Zooplankton exhibit several trends of variation in space and time, and these trends can be more evident in natural environments without anthropic perturbations. Examples of anthropic factors are climate change, eutrophication and construction of reservoirs. This study evaluated the influence of three factors – seasonality, type of environment and the presence of aquatic macrophytes – on various ecological attributes of rotifers in a river-lake system located in the Paraná River floodplain. Monthly samplings were conducted during 1993 and 1994. The mean species richness per sample was 60 species. The seasonality and the type of environment influenced the ecological attributes of rotifer assemblages, while the presence or absence of aquatic macrophytes did not. Species richness was highest in the lake system and during the months when water levels were low. Multivariate analysis indicates a small group of species associated with the low water-level phase. In contrast, many species were associated with high water levels or increasing water levels. The seasonal variation of hydrological cycle and the type of environment are the most important factors for rotifer structure in natural conditions

Vocal repertoire and group-specific signature in the Smooth-billed Ani, Crotophaga ani Linnaeus, 1758 (Cuculiformes, Aves)

Vocal plasticity reflects the ability of animals to vary vocalizations according to context (vocal repertoire) as well as to develop vocal convergence (vocal group signature) in the interaction of members in social groups. This feature has been largely reported for oscine, psittacine and trochilid birds, but little has been investigated in birds that present innate vocalization. The smooth-billed ani (Crotophaga ani) is a social bird that lives in groups between two and twenty individuals, and which presents innate vocalization. Here we analyzed the vocal repertoire of this species during group activities, and further investigated the existence of a vocal group signature. The study was conducted in the Southeast of Brazil between May 2017 and April 2018. Two groups of smooth-billed anis were followed, Guararema and Charqueada groups, and their vocalizations were recorded and contextualized as to the performed behavior. The vocal repertoire was analyzed for its composition, context and acoustic variables. The acoustic parameters maximum peak frequency, maximum fundamental frequency, minimum frequency, maximum frequency and duration were analyzed. To verify the vocal signature of the group, we tested whether there was variation in the acoustic parameters between the monitored groups. We recorded ten vocalizations that constituted the vocal repertoire of the Smooth-billed Ani, five of which (“Ahnee”, “Whine”, “Pre-flight”, “Flight” and “Vigil”) were issued by the two groups and five exclusive to the Charqueada group. There were significant differences in the acoustic parameters for “Flight” and “Vigil” vocalizations between the groups, suggesting vocal group signature for these sounds. We established that the Smooth-billed Ani has a diverse vocal repertoire, with variations also occurring between groups of the same population. Moreover, we found evidence of vocal group signature in vocalizations used in the context of cohesion, defense and territory maintenance

New Diaptomidae records (Crustacea: Copepoda: Calanoida: Diaptomidae) in the Neotropical region

TIn this study we present 208 new diaptomids records, including 36 species from 10 genera. They are the result of new samplings as well as of the revision of samples from previous surveys from various localities in the Neotropical Region. In an attempt to clear elucidate about the species ranges we gathered all biogeographically important data and present them here, with comments about the relevance of each record to the understanding of the distribution of the group. © 2013 Check List and Authors

Similaridade do micro-zooplâncton e relações com variáveis ambientais em um estuário subtropical

The spatial and seasonal variations of the micro-zooplankton abundance in a subtropical estuary were studied during a year. Five sampling sites were monthly sampled in Guaratuba Bay, Paraná State, from September 2004 to July 2005. The microzooplankton was sampled in the water subsurface with suction pump and filtered in 64μm plankton net. The environmental variables was gotten with a multiparameter Horiba U10 (salinity, dissolved oxygen, temperature and pH), and Secchi disk (transparency). The cluster similarity analysis grouped zooplankton in freshwater, summer meroplanktonic organisms and holoplanktonic contend different ontogenetic stages. The distinct groups among stations sampling occurred for the high proximity of the tributaries discharges or in function of the linking of the estuary with the ocean. Between the months, the seasons had been separate. The canonical correlation analysis (81% of explanation) complemented the results of the analysis of grouping, separating seasonally and spatially the main groups and its abundance. The results suggest clear space and seasonal variations for the micro-zooplankton in the Guaratuba Bay, with peaks of abundance in the summer due to meroplankton contribution associated to the highest water temperatures. Copepoda had dominated numerically under other groups, mainly the immature forms, sufficiently showed in reason of the small opening mesh of the employed net.Foram estudadas as variações espaciais e temporais da abundância do micro-zooplâncton em um estuário subtropical, com auxílio de análises multivariadas. Utilizou-se análise de agrupamento por similaridade com índice de Bray Curtis sobre a abundância dos grupos zooplanctônicos, pontos e meses; e análise de correlação canônica - ACC da abundância com variáveis ambientais mensuradas. Mensalmente, de setembro/04 a julho/05, foram amostrados cinco pontos na baía de Guaratuba, Paraná. Na sub-superfície da água o zooplâncton foi coletado com moto-bomba, filtrado em rede cônica de 64μm, e as variáveis ambientais obtidas com uma sonda Horiba U10 (salinidade, oxigênio dissolvido, temperatura e pH), e com imersão do disco de Secchi (transparência). A análise de similaridade agrupou o zooplâncton em organismos límnicos, meroplanctônicos especialmente de verão e holoplanctônicos contendo diferentes estágios ontogênicos. A formação de distintos agrupamentos entre os pontos de coleta ocorreu pela maior proximidade das descargas dos tributários ou em função da ligação do estuário com o oceano. Entre os meses, as estações do ano foram separadas. A ACC (91% de explicação) complementou os resultados da análise de agrupamento, separando espaço temporalmente os principais grupos quanto à abundância. Os resultados sugerem nítidas variações espaciais e temporais para o micro-zooplâncton na baía de Guaratuba, com picos de abundância no verão devido à contribuição do meroplâncton associado às maiores temperaturas da água. Os copépodes dominaram numericamente sob os demais grupos estuarinos, principalmente as formas imaturas, bastante amostradas em razão da pequena abertura de malha da rede empregada

Variação espaço-temporal de Rotifera em um reservatório eutrofizado no sul do Brasil

We analyzed the spatial and temporal variation of rotifers in a small, shallow and eutrophic reservoir, with intense Cyanobacteria blooms, in seven sampling stations during 17 months (March/2002 to July/2003). Fifty-two taxa were identified, comprising 16 families. Brachionidae, Conochilidae, Synchaetidae, Lecanidae, Collothecidae, Trichocercidae, and Gastropodidae were the most commonly found. Collotheca sp. Was abundant in the winter (dry period), while numbers of Conochilus coenobasis and Keratella cochlearis were low. The abundance of Brachionus mirus var. reductus, Filinia longiseta and Keratella lenzi peaked in the summer (rainy season), while for Kellicottia bostonensis, Ploesoma truncatum, Polyarthra remata, Polyarthra vulgaris and Ptygura sp., abundance was highest in the winter, mainly associated with atypical rainfall. Significant differences in the number of taxa and abundance of rotifers were observed during the sampling period. The canonical correspondence analysis explained 46% of the relationship between rotifer abundance and environmental variables, positively correlated with rainfall, nitrite, water temperature, organic nitrogen, nitrate and air temperature. Variations in rotifer abundance were observed a month after changes in the phytoplankton community. Taxa, such as Filinia longiseta, Keratella lenzi and Keratella cochlearis, showed a temporal variation similar to that of other eutrophic reservoirs, while the heterogeneous distribution pattern observed in most taxa could be due to the hydrodynamics of the recently built reservoir and the adverse climatic conditions