Analía C. Paggi

Taxonomic and nontaxonomic responses to ecological changes in an urban lowland stream through the use of Chironomidae (Diptera) larvae.

Biotic descriptors--both taxonomic (diversity indices, species richness, and indicator species) and nontaxonomic (biomass, oxygen consumption/production, and anatomical deformities)--are useful tools for measuring a streams ecological condition. Nontaxonomic parameters detect critical effects not reflected taxonomically. We analyzed changes in Chironomidae populations as taxonomic parameters and mentum deformities as a nontaxonomic parameter for evaluating a South-American-plains stream (Argentina). We performed samplings seasonally (March, June, September, and December; 2005) and physical and chemical measurements at three sampling sites of the stream (DC1 at river source, through DC3 downstream). The specimens collected in sediment and vegetation were analyzed to investigate mouth deformities in Chironomidae larvae. We identified a total of 9 taxa from Chironomidae and Orthocladiinae subfamilies. Shannons diversity index for Chironomidae decreased from 1.6 bits ind⁻¹ (DC1) to 0.3 bits ind⁻¹ (DC3). The total density of the Chironomidae exhibited a great increase in abundance at site DC3, especially that of Chironomus calligraphus. Chironomidae taxonomic composition also changed among the three sites despite their spatial proximity: C. calligraphus, Goeldichironomus holoprasinus, Parachironomus longistilus, and Polypedilum were present at all three; Corynoneura and Paratanytarsu at DC1 only; Cricotopus at DC1 and DC3; Apedilum elachistus notably at DC2 and DC3; and Parametriocnemus only at DC2. C. calligraphus individuals from DC1 showed no mentum deformities; only 2 from DC2 exhibited mouth-structure alterations; while specimens from DC3 presented the most abnormalities, especially during autumn and late winter. Type-II deformities (supernumerary teeth and gaps) were the most common. Anatomical deformities are sublethal effects representing an early alert to chemically caused environmental degradation. Mentum deformities in benthic-Chironomidae larvae constitute an effective biological-surveillance tool for detecting adverse conditions in sediments and evaluating sediment-quality-criteria compliance. Taxonomic (community composition) and nontaxonomic (condition of larval mouth parts) descriptors, used together, can indicate a streams ecological state.

Evaluation of zoobenthic assemblages and recovery following petroleum spill in a coastal area of Río de la Plata estuarine system, South America

The objective of this work was to analyse zoobenthic assemblages in the coastal sector of the Río de La Plata, Argentina, after a petroleum spill. Sampling stations were located in representative sites of various landscapes. Structure, composition, physico-chemical parameters and seasonal changes were recorded in order to assess taxocenosis evolution during the period 1999-2003. Recovery signs were estimated by means of biotic indices and the presence of sensitive species. Tolerant species were dominant in heavily polluted sites, with low diversity and water quality values, according to the biotic indices used. In certain zones, sediment quality remains impoverished, with a visible oil film on the surface. However, during the last sampling, some points showed an increase in biotic indices, pointing to a slight improvement in environmental conditions.

Polypedilum parthenogeneticum (Diptera: Chironomidae): a new parthenogenetic species from Eryngium L. (Apiaceae) phytotelmata

All life stages of Polypedilum parthenogeneticum sp. n. are described and figured. The larva lives in the water held in the leaf axils of Eryngium pandanifolium Chamb and Schlecht (Apiaceae). The species is considered to be parthenogenetic as only females were obtained by rearing in the laboratory. Preliminary notes on the biology of P. parthenogeneticum are given.

Life cycle of Goeldichironomus holoprasinus goeldi (Diptera: Chironomidae) in laboratory

The larvae of Chironomidae are very important due to their density and role in aquatic food webs. Goeldichironomus holoprasinus Goeldi is one of the most abundant species of Chironomidae in man-made and natural systems, being widely used in water quality assessments. Because of its tolerance to stressing environmental factors, many studies have investigated the effects of stressors on G. holoprasinus anatomy and bionomic attributes. The main aim of this work was to describe G. holoprasinus life cycle attributes in laboratory conditions. The cephalic capsule growth among instars was 1.64 in average (Dyar proportion), whereas the total size growth was continuous. The average room temperature registered was 26 degrees C (18-33 degrees C). In this conditions the D value (time from oviposition to first imago emergence) was 13 days, whereas the minimum G value (interval from the oviposition to the first progeny of the next generation) was 16 days. The emergence lasted four days, which determined that average G of 18 days. Thus, at registered temperatures G. holoprasinus has a short life cycle.

Ecological Responses to Different Degrees of Hydrologic Connectivity: Assessing Patterns in the Bionomy of Benthic Chironomids in a Large River-Floodplain System

Floodplain wetlands of the Middle Paraná River, Argentina, are regulated by their hydrologic connectivity to the main channel as well as by their position within the river network. The Chironomids are the most abundant insects that inhabit the benthos of the Paraná River floodplain habitats. In order to address whether wetlands with different degrees of connectivity (disconnected, temporarily, and permanently connected) exhibit different abundance patterns and secondary production of benthic chironomids, samples were collected during a year comprising high and low water phases. The disconnected wetland exhibited the highest abundance and secondary production of chironomids. Both attributes were positively correlated to the degree of connectivity for most of the predators among the connected wetlands. Differences in assemblages’ composition and secondary production were found to be in relation to the degree of connectivity, the cover of macrophytes, the detritus at the bottom, the transparency of water, the proportion of clay in bottom sediments and the location of wetlands within the floodplain. The interaction between local environmental factors mediated by lateral connectivity and regional dynamics of metapopulations established diverse patterns in the metrics of chironomids along the Paraná River floodplain wetlands. Thus, various degrees of hydrologic connectivity of wetlands should be preserved to maintain a high productivity of different chironomids in the floodplain.

A new Neotropical species of Oliveiriella Wiedenbrug & Fittkau (Diptera: Chironomidae) from Argentina, with description of all its life stages

The South American genus Oliveiriella is reported for the first time from Argentina. Description and diagnosis of all stages of a new species as well as the larva of O. almeidai are given.

Podonomus fastigians Brundin 1966 (Chironomidae: Podonominae): Redescription of the Adult Male and Female, the Pupa, and Description of the Larva

ABSTRACT: The larva of Podonomus fastigians is described for the first time, and the male and female adult and pupa are redescribed and illustrated. This is the first report of the non-biting midge P. fastigians in Argentina. Ecological remarks are included.

New record, geographic variation and redescription of Apedilum elachistus Townes (Diptera: Chironomidae: Chironominae)

Apedilum elachistus Townes 1945 is recorded from Argentina, representing the southernmost record of this species. Due to dissimilarities found between South and North American specimens a Principal Component Analysis and Minimum Spanning Tree were performed in order to determine if these differences reflect a geographic differentiation. The results show North–South variation in the number of acrostichal setae, number of dorsocentral setae, number of prealar setae, wing length, VR, length of thorax, and length of abdomen for males, and number of gonocoxite IX setae, length of thorax, number of temporal setae, length of palpomere III, wing length, BV2, length of notum, BV1, number of dorsocentral setae, length of palpomere IV, length of abdomen, VR, and length of palpomere V for females. Consequently, Apedilum elachistus is redescribed as larva, pupa, male, and female.

Zoobenthic communities in relation to slope, substrate heterogeneity and urban disturbances in Pampean hill streams (Argentina)

The pattern distribution of aquatic organisms in the three srudied streams of Sierras de Tandil System in the Pampean Biogeographic Province (Buenos Aires, Argentina) are strongly influenced by substrarum characteristics and the water flow conditions (RooRIGUES CAPfTULO et al. 200 l). The association of these factors increases the habitat diversity, resulting in a large range of microhabitats with different sediment particle size, availability of food resources (BEISEL et al. 1998), and types and distribution of hydrophytes. The majority of the creeks and streams in this area are only influenced by agriculrure. However, near small cities (Ayacucho, Pirán, Maipú), urban contamination was observed, and the changes in the macroinvertebrate communities were assessed.

The Cricotopus ( Oliveiriella ) (Diptera: Chironomidae) of the High Altitude Andean Streams, with Description of a New Species, C . ( O .) rieradevallae

The genus Oliveiriella (Chironomidae, Orthocladiinae) was erected by Wiedenbrug & Fittkau (1997). The adults have characteristic black spots on their wings and other characteristics similar to the genus Cricotopus. Pupal skins are very characteristic with strong short spines in the anal lobe instead of setae, while larvae are distinguishable by the long anal papillae and the intense blue color of their body. However, Andersen et al (2013) consider Oliveiriella as a subgenera of Cricotopus. In this paper, using the sequences of the cox1 gene, we conclude that Oliveiriella should be considered a subgenus within Cricotopus, confirming its status in Andersen et al (2013). Furthermore, we describe Cricotopus (Oliveiriella) rieradevallae Prat & Paggi sp. n. from the Saltana river (Ecuador). The adult males, females, and preimaginal stages of the two species of subgenus Oliveiriella known from South America Cricotopus (O.) almeidai n. comb. from Peru, Brazil, and Argentina and Cricotopus (O.) sanjavieri n. comb. from Argentina are compared with those of Cricotopus (O.) rieradevallae sp. n. from Ecuador. The differences allow the distinction of the three species. The cox1 gene reveals that at least three different undescribed species of the same subgenus are present in the high-altitude tropical Andes. The morphology of the available pupae and pupal exuviae reveals the presence of several morphotypes that are candidates to be described as new species. A key used to distinguish these pupal morphotypes is provided, including the three described species. Additionally, the distribution of the subgenus is discussed.