Amazonian Chironomidae (Diptera, Chironomidae): A contribution to chironomid research in the Neotropics

FABRICIUS described the first two South American Chironomidae in 1805, without naming where they were found. A few years earlier, in 1803, MEIGEN had established the first two genera of today's Diptera family Chironomidae, Tanypus and Chironomus. One hundred years were to go by before Emílio GOELDI discovered the first Chironomidae in the Amazon region and described two species in all their phases of development. Real chironomid research in Brazil, and in particular in Amazonia, did not start until 50 years later. The most comprehensive collection of Amazonian Chironomidae until now was presented at the beginning of the 60s and 70s by the Instituto Nacional de Pesquisas da Amazônia in cooperation with the Max-Planck-lnstitute for Limnology, Plön. This collection is now in the State Zoological Collection in Munich. At present, approximately 650 existing species are known from Central and South America. Only a third of these, 190 species, from tropical South America have been described, the majority using material from the Munich collection. How inadequate our knowledge still is concerning Amazonian Chironomidae is proven by studies of pupal exuviae from the surface drift of a woodland stream in Central Amazonia, which can be assigned to at least 200 chironomid species. We can expect a total far exceeding 1000 chironomid species in Amazonia alone, the occrrence of which appears to be limited to the Neotropics or which belong to endemic South American genera. Information on dispersal patterns for the individual species or their ecological integration in Amazonian waterways is inadequate at present

Crocodiles and the nutrient metabolism of Amazonian waters

The example of the Central Amazonian rain forest is used to illustrate an ecological principle which determines the structure of a tropical ecosystem with a low, but balanced supply of nutrients. This principle implies that the stability of the biocenosis of such a system increases with the abundance and diversity of its species of biota, that is, the degree of differentiation and the size of its biomass. Higher abundance and diversity enable the system to take up the available allochthonous nutrients, to conserve them, and to continuously hold them in shortened nutrient cycles as effìciently as possible. In the Central Amazonian rain forest, we have an extremely large and diverse plant biomass (fresh weight), which assimilates the allochthonous nutrients supplied in the rain. The same principle may also be recognized in the aquatic ecosystems, where the geochemical impoverishment of the Central Amazonian "terra firme" (that land which is not inundated by the annual floods of the main river system) is expressed even more severely than in the terrestrial realm. The low levels of electrolytes in the waters of such systems scarcely permit any primary production, so that here, the food chain is based directly or indirectly on allochthonous organic material. Formation of a strongly differentiated and relatively large biomass, which is mostly due to animals in macroscopic size classes, occurs only where the supply of organic material is relatively great, i.e., in the narrow upper reaches of the streams. A large number of invertebrate animals, especially insect larvae, live on bacteria and fungi. These decompose the materials such as leaves and wood, which are poor in nutrients and not directly available to the fauna. The fishes, which make up most of the biomass act partly as direct filters for the allochthonous materials richer in nutrients, such as insects, flowers, fruit. etc. which are also contributed to the aquatic systems by the forest. As the supply of allochthonous organic material decreases relative to surface area and volume along the courses of the streams, the aquatic biocenosis becomes qualitatively and quantitatively poorer. A new ecological situation arises in the lower reaches, which are annually backed up to form lakes. The main difference is the immigration of brooding fishes from the bordering waters of the main river system, which have high levels of nutrients and primary production. This introduces allochthonous nutrients and permits the existence of a much larger biomass. The "filters" for this periodical supply of nutrients are primarily the caimans, in addition to large piscivorous fishes, turtles, otters and dolphins. In "river-mouth lakes" which have not been disturbed by man, these predators must constitute a large proportion of the biomass. In the Central Amazonian "river lakes", local settlers believe that the fish crops have declined following extermination of the caimans. The ecological interactions which must have existed between caimans and fishes were presented in a previous study. The present work is an attempt to determine whether the amounts of nutrients transferred by the caimans from their largely allochthonous prey, during periods of rapid growth or in longer periods of starvation, are sufficient to influence the ecosystem. The experiments showed that medium-sized caimans daily eat an amount equal to about 0.6 to 0.8 % of their body weight. The total amounts of N, P, Ca, Mg, Na and K released daily under such feeding conditions are about 0.20 to o.27 % of their weight; when the animals are starving, this fraction is reduced to 0.08 to 0.10 % of the body weight. Based on the situation of an hypothetical (but realistic) lake with a surface area of 5 km² and a mean depth of 5 m at medium high water, the following amounts would be released over a 10-day period (in γ/l): a) with good nourishment: N-34, P-9.6, Ca-1.5, Mg-0.1, Na-0.1, K 5..0; b) during starvation: N-17, P-1.5, Ca-0.9, Mg-0.7, Na-0.5, K-1.5. Over the same period the lake would receive in the rain among other materials, (y/l): N-14.9, P-0.4, Ca-5.4, Mg-4.5. The groups of nutrients added by caimans and rain complement each other in the biologically important elements, those which are present in limiting amounts in river water. (River water concentrations in y/l : N-280; P-7, Ca-0, Mg- less than 20). These values show that caimans daily add nutrients (mostly of allochthonous origin) in quantities that are sufficient to enable an elevation of primary production and thereby an enlargement of the autochthonous food chain based on it. With their ability to undergo long periods of starvation, during which accumulated nutrients are continuously released, the animals are especially well adapted to the ecologically extreme environment of the river-lake

Síolimgía amazoníca n. gen. n. spec., eine flugfähige Chironomide fDiptera) mit einem Hypopygium inversum

Siolimlia amazonica n. gen. n. spec. ist die bisher einzige voll flugfahige Chironomide mit einem Hypopygium inversum. Die Metamorphose weist eine nahe phylogenetische Verwandtschaft mit Goeldichironomus au{. Siolim2ia scheint haufig in produktionsreichen stehenden Gewässern der Tropen Amerikas zu sein und hier oft zur Massenentwicklung zu kommen. In den elektrolytarmen Gewässern Zeniralamazoniens dürfte die neue Art fehlen

Response of littoral chironomid community and organic matter to late glacial lake level and environmental changes at Lago dell'Accesa (Tuscany, Italy).

International audienceThis study focuses on the response of lacustrine littoral chironomid communities to late glacial changes in limnological, environmental and climate conditions in the Mediterranean context. Late glacial chironomid (Diptera: Chironomidae) assemblages, organic petrography and geochemistry were analysed in a sediment core from the littoral zone of Lago dell'Accesa (Tuscany, Italy), where the lake-level fluctuations and the vegetation history have been previously reconstructed. Comparison of the chironomid stratigraphy to other proxies (pollen assemblages, organic petrography and geochemistry, lake-level) and regional climate reconstruction suggested the predominant influence of lake-level changes on the littoral chironomid fauna. The main lowering events that occurred during the Oldest and the Younger Dryas were followed by higher proportions of taxa typical of littoral habitats. A complementary study of organic matter suggested the indirect impact of lake-level on the chironomids through changes in humic status and habitat characteristics, such as the type of substrate and aquatic macrophyte development. Several chironomid taxa, such as Glyptotendipes, Microtendipes and Cricotopus type patens, were identified as possible indicators of low lake-level in the late glacial records. Nevertheless, this study suggested that parallel analyses of organic matter and chironomid assemblages may be needed to circumvent misinterpretation of littoral chironomid assemblage stratigraphy. There was a weak response of the chironomid assemblages to small lake-level lowerings that corresponded to the Older Dryas and Preboreal oscillations. A higher level of determination, e.g. to the species group level, may be necessary to increase the sensibility of the indicators to lake-level changes

Five new species of Ectobiidae (Blattodea) collected in the Reserva Ducke, Amazonas, Brazil

Herein we describe five new species of the Ectobiidae subfamilies Pseudophyllodromiinae (Amazonina spiculata sp. nov., Amazonina spinostylata sp. nov., Cariblatta duckeniana sp. nov., Cariblatta manauensis sp. nov.) and Nyctiborinae (Nyctibora nigra sp. nov.), collected in the Reserva Ducke, Manaus, state of Amazonas. The specimens were collected from litter, fallen logs, branches, and foliage. We illustrate the male genitalia of the new species