Roberto da Gama Alves

Oligochaeta (Annelida, Clitellata) of lotic environments at Parque Estadual Intervales (São Paulo, Brazil)

Studies on benthic macroinvertebrates of lotic environments usually focus on the occurrence, distribution, and richness of aquatic insects and decapod crustaceans. Only rarely these studies include the Oligochaeta. The aim of the present study was to examine the occurrence and species richness of Oligochaeta in different substrata patches of lotic environments. The studied included seven stream sites at Parque Estadual Intervales (Sao Paulo, Brazil). Stream sites differed in size and ranged from first to fourth order. In each stream, qualitative collections were made using a D-type net sampler with 0.21 mm mesh. Measures of pH, electrical conductivity, dissolved oxygen, temperature and water turbidity were taken in the studied sites during collections of Oligochaeta. Specimens of the Tubificidae (including Naidinae) and Enchytraeidae families were collected. The Tubificidae Aulodrilus limnobius, Limnodrilus neotropicus and Limnodrilus hoffmeisteri were associated with low-flow habitats containing fine organic material. The most representative species among the Naidinae, Nais communis, was predominantly associated with rocky substrates present in fast current locations. The two other Naidinae species, Pristina osborni and Amphichaeta leydigi, presented low frequency in the studied streams. The Enchytraeidae family was present in only one of the sampled habitats.

Structure and spatial distribution of the Chironomidae community in mesohabitats in a first order stream at the Poço D’Anta Municipal Biological Reserve in Brazil

Abstract The Chironomidae occupy different habitats along the lotic system with their distribution determined by different factors such as the substrate characteristics and water speed. The input of vegetable material from the riparian forest allows a higher habitat diversity and food to the benthic fauna. The main aim of this paper is to verify the structure and spatial distribution of the Chironomidae fauna in different mesohabitats in a first order stream located at a Biological Reserve in the southeast of Brazil. In the months of July, August, and September 2007, and in January, February, and March 2008, samples were collected with a hand net (250 µm) in the following mesohabitats: litter from riffles, litter from pools, and sediment from pools. The community structure of each mesohabitat was analyzed through the abundance of organisms, taxa richness, Pielous evenness, Shannons diversity, and taxa dominance. Similarity among the mesohabitats was obtained by Cluster analysis, and Chironomidae larvae distribution through the Correspondence analysis. Indicator species analysis was used to identify possible taxa preference for a determined mesohabitat. The analyzed mesohabitats showed high species richness and diversity favored by the large environmental heterogeneity. Some taxa were indicators of the type of mesohabitat. The substrate was the main factor that determined taxa distribution in relation to water flow differences (riffle and pool). Stream characteristics such as low water speed and the presence of natural mechanisms of retention may have provided a higher faunistic similarity between the areas with different flows. The results showed that the physical characteristics of each environment presented a close relationship with the structure and spatial distribution of the Chironomidae fauna in lotic systems.

Colonization by Chironomidae Larvae in Decomposition Leaves of Eichhornia azurea in a Lentic System in Southeastern Brazil

Abstract The objective of this study was to analyze the colonization of Chironomidae (Diptera) larvae during the decomposition of Eichhornia azurea (Swartz) Kunth (Commelinales: Pontederiaceae) leaves in a lake in southeastern Brazil in two seasons of the year. The experiment was conducted from September to November 2007 and February to April 2008. In each period, 21 litter bags were used, each containing 10 g of dried leaves. Three bags were removed after 2, 5, 8, 12, 25, 45, and 65 days of colonization. The decomposition rate of the E. azurea leaves was rapid in both seasons, with no significant difference between them. The Chironomidae showed higher density than the other invertebrates. Goeldichironomus, Tonytarsus, and Corynoneura were the most abundant genera of Chironomidae. The invertebrate density increased during the experiment, differing within days but not between seasons. The faunal composition differed between the decomposition phases (initial and final), but did not differ between the seasons (dry and wet). The taxa Ablabesmyia, Caladomyia, Chironomus, Goeldichironomus, and Parachironomus were the most closely related to the final days of the experiment. Litter was the main food item found in the gut contents of the organisms of all the genera analyzed, both at the beginning and end of the decomposition. We believe that the feeding activity combined with the high larval density is an important factor contributing to the rapid decomposition of the E. azurea leaves. In conclusion, the succession process along the detritus chain of E. azurea was more important in structuring the assemblage of Chironomidae larvae than seasonal variations.

Naididae (Annelida, Oligochaeta) associated with briophytes in Brotas, State of São Paulo, Brazil

Mosses and liverworts can be colonized by various invertebrates, including fresh water oligochaete worms. However, little information is available on the habits and habitats of this oligochaetes in Brazil. Therefore, the present study was undertaken to examine the occurrence of naidids in mosses, as well as to broaden the knowledge about the habitats of these oligochaetes. Sampling of bryophytes adhered to rock substrates in the rapids of the Jacare Pepira River (municipality of Brotas, Sao Paulo, Brazil) and to a vertical rock wall of a waterfall near the river revealed 191 Naididae individuals of the species Naiscommunis Piguet, 1906, Pristinellajenkinae (Stephenson, 1931) and Pristinellamenoni (Aiyer, 1929). We believe this to be the first record of naidids associated with mosses in Brazil.

Colonisation of leaf litter by aquatic invertebrates in an Atlantic Forest stream

Riparian vegetation along streams in the Atlantic Forest in Brazil contributes to the formation of a highly heterogeneous leaf litter in streambeds. To investigate the structure and composition of the aquatic invertebrate community during the process of leaf decomposition of two plant species present along the banks of the stream studied, 21 plastic mesh bags containing 2.5g (dry weight) of leaf matter from each species (Alchornea glandulosa (Vell) and Cabralea canjerana End. and Poeppig), for a total of 5.0g, were placed in the streambed. Three bags were removed after 3, 6, 9, 12, 24, 48 and 96 days. The taxonomic density was negatively correlated with the remaining weight. The high density of collector organisms, such as Chironomidae, Oligochaeta and Amphipoda, on the last day of incubation, probably occurred due to the increased amount of fine organic matter in the more advanced decomposition stages. The highest α diversity (Shannon-Wiener) values were observed for the 3rd and 96th days of the experiment, while the β diversity values showed that these days presented the highest variation in the taxonomic composition, thus presenting a different faunistic composition. This study showed that the trophic structure and composition of aquatic invertebrates changes during the decomposition of leaf litter. The faunistic abundance and diversity observed in this study indicate that the entrance of material from plants growing along streams provides favorable conditions for the colonisation and establishment of invertebrates in lower-order streams, and thus points to the need to preserve riparian vegetation.

Oligochaetes (Annelida, Clitellata) in a neotropical stream: a mesohabitat approach

This paper analyses the relationship among mesohabitat and aquatic oligochaete species in the Galharada Stream (Campos do Jordao State Park, state of Sao Paulo, Brazil). Between August 2005 and May 2006 a total of 192 samples were obtained in areas of four different mesohabitats: riffle leaf litter (RL), pool leaf litter (PL), pool sediment (PS) and interstitial sediment from rocky beds in riffle areas (IS). In the mesohabitats sampled, 2007 specimens were identified, belonging to two families (Naididae and Enchytraeidae). Among the oligochaetes identified Naididae was represented by six genera (Allonais, Chaetogaster, Nais, Pristina, Aulodrilus and Limnodrilus). Principal components analysis (PCA) revealed the first two axes explained 85.1% of the total variance of the data. Limnodrilus hoffmeisteri Claparede, 1862 and Aulodrilus limnobius Bretscher, 1899 were associated with the pool areas (PL and PS). Most species of genera Pristina and Nais demonstrated apparent affinity with the riffle mesohabitats. The Indicator Species Analysis (IndVal) revealed that Nais communis Piguet, 1906, Pristina leidyi Smith, 1896 and Pristina (Pristinella) jenkinae (Stephenson, 1931) are indicative of RL mesohabitat, while family Enchytraeidae was considered indicative of PL mesohabitat.

Oligochaeta (Annelida: Clitellata) em córregos de baixa ordem do Parque Estadual de Campos do Jordão (São Paulo - Brasil)

This study inventoried stream oligochaetes of the Campos do Jordao State Park (CJSP), Sao Paulo, Brazil. A total of 2302 individuals of three families (Naididae, Enchytraeidae, Turbificidae) were obtained. Seventeen species were inventoried: Achaeta sp., Allonais paraguayensis, Chaetogaster diastrophus, Nais communis, Nais variabilis, Pristina biserrata, Pristina leidyi, Pristina proboscidea, Pristinella jenkinae, Pristinella longidentata, Pristinella minuta, Pristinella notopora, Pristinella osborni, Pristinella sima, Aulodrilus limnobius, Bothrioneurum sp., and Limnodrilus hoffmeisteri. The total number of species found represents 24% of all oligochaetes species (70) recorded in diverse aquatic environments in Brazil, making this inventory very important given the poor knowledge of this group in Brazil.

Spatial and temporal occurrence of Rhabdostyla cf. chironomi Kahl, 1933 (Ciliophora, Peritrichia) as an epibiont on chironomid larvae in a lotic system in the neotropics

In order to show how environmental factors could influence the spatial and temporal distribution of epibiosis, we investigated the occurrence of the ciliate Rhabdostyla cf. chironomi (Ciliophora, Peritrichia) attached to Chironomidae larvae in an urban stream in southeast Brazil. Samples were collected monthly for 1-year period at five sampling stations along the stream. Among the 24 genera analyzed, the genus Chironomus was the most abundant, with 16.84% carrying R. cf. chironomi. This epibiotic relationship was only recorded in sample stations located in a heavily populated urban area of the stream. Statistical analyses demonstrated significant correlations between infestation prevalence and environmental parameters such as rainfall, bacterial density, and host abundance. The occurrence of epibionts on the larvae was spatially and temporally heterogeneous. The results are discussed in terms of possible factors related to the heterogeneous spatial and temporal occurrence. Greater understanding of the ecological factors governing the occurrence of the epibiont–host relationship is essential to establish future use of this relationship as water quality indicator in lotic systems.

The effect of temperature on the reproduction of Limnodrilus hoffmeisteri (Oligochaeta: Tubificidae)

The tubificid worm Limnodrilus hoffmeisteri Claparede, 1862 is widely used as an indicator of organic pollution in aquatic environments. Nevertheless, little is known about its biology. The present work aimed to compare the reproductive rate of L. hoffmeisteri raised at three different temperatures (15, 20 and 25°C). Seventy-five adult individuals were kept in fifteen 250 ml beakers (five individuals per beaker) containing sand and dechlorinated tap-water each. Beakers were arranged so as to form three groups of five. Each group was kept in a given temperature for 21 days. Results show that worms raised at 25°C produced a significantly larger number of eggs compared to those raised either at 15 or 20°C, as observed in the tropical tubificid Branchiura sowerbyi Beddard, 1892.

Inventory and distribution of Oligochaeta (Annelida, Clitellata) in first-order streams in preserved areas of the state of Minas Gerais, Brazil

Data resulting from species inventories shed light on the richness and distribution of various groups. In Minas Gerais, work on inventory and distribution of the oligochaetes of lotic environments in preserved areas are non-existent. Therefore, this study aimed to inventory the limnic oligochaetes fauna of first-order streams located in four preserved areas, to expand knowledge of the ecology and distribution of this group. In total, 19 taxa were inventoried, belonging to the families Naididae and Enchytraeidae and the superorder Megadrili (earthworms), with the genus Pristina having the largest number of species. The number of species found in this investigation corresponds to 22% of oligochaetes species recorded in Brazilian aquatic environments. The results obtained add important knowledge of the distribution of some oligochaetes species in Brazil, represent the first records of species for the four preserved areas studied and confirm the first occurrence of various species in the state.