The benthic litter-dwelling macrofauna of the Amazonian forest stream Tarumã-Mirím: patterns of colonization and their implications for community stability

Abstract

Between 1983 and 1988 a total of 928 litter-filled baskets (1.8 1 volume), exposed for various periods on a stream litterbank and in its vicinity, collected 2703 individuals of 122 macrofaunal species, excluding chironomids. Species abundance was analysed in relation to exposure time, annual inundation cycle, water depth and sample size. Long-term, average species packing and animal density proved to be relatively invariant and revealed non-random frequency patterns. Previous and present data indicate that these patterns are a function of regular, specific life cycles and of intra-specific, stereotype behaviour in relation to space and litter quality, among other possibilities not considered here. Potential competition for space in these communities is discussed, considering the assumption of individual random movement versus species maintenance as a function of genetically and neurophysiologically informed, non-random behaviour.

Omnivory and resource - sharing in nutrient - deficient Rio Negro waters: stabilization of biodiversity?

“…Cladocera and the larvae of Chironomids (including the predatory Tanypodinae) and of Ephemeroptera are the prevalent prey types, again, as argued for the case of the Odonata, because these prey organisms have the highest population densities in the benthic habitat of submerged litter (Walker 1987(Walker , 1994. Cladocera input is not the passive result of periphyton scraping, if this were the case, peripyton-feeding would be more frequent than Cladocera ingestion.…”

“…The Anisoptera occupy niches within the litter layers, and thus, have access to the small oligochaetes that colonize the surface of litter leaves, while the Zygoptera usually occupy surfaces near the open water, where oligochetes are less frequent. The prevalent prey of both Odonata species are Ephemeroptera and Chironomidae, presumably because these are the most frequent and ubiquitious insect larvae in these benthic habitats (Walker 1994(Walker , 1998. Algae ingestion is questionable, because small algae may accidentally enter the ventricle in the course of prey capture.…”

“…Ecological reality seems to be more in tune with this type of system: For the benthic fauna of the Tarumã-Mirím, there is convincing evidence that space-rather than resource-is limiting. Relative standing-stock densities between predators and prey in the benthic litter habitat are relatively stable, and potential prey individuals available per predator is usually >100 and never drops to below 50 (Walker 1994, Walker et al 1991. Indeed, space limitation may be a common feature of aquatic faunas: thus Maltchik and Pedro (2000) showed a positive relation between biodiversity and stability in the communities of shallow lakes, and Schmid-Abraya et al (2002), analysing the foodweb of an acid stream, conclude that the dense web-connectance provides alternative energy pathways for the top-predators, with a stabilizing effect on the energy flow through the system.…”

Revisão taxonômica e filogenia dos camarões de água doce da família Euryrhynchidae Holthuis, 1950 (Crustacea: Decapoda: Cariddea)

“…Contudo, vale notar que há uma diferença de apenas dois anos entre a descrição original (em alemão) e o registro de Gomes , sendo possível que a autora não tenha tomado conhecimento da publicação de Tiefenbacher (1978). Uma série de trabalhos envolvendo E. amazoniensis utilizaram material da bacia do Rio Tarumã-Mirim (ou Tarumãzinho), a noroeste de Manaus Odinetz Collart & Magalhães, 1994;Walker, 1994Walker, , 2001). Todavia, a análise de material oriundo desta área frequentemente resultou na presença de ambas as espécies E. amazoniensis e E. n.sp.…”

“…Esses camarões estão atualmente distribuídos na América do Sul, exclusivamente na região amazônica, e na África Ocidental (Figura 2), sugerindo uma origem gondwânica . Os euryrhynchídeos vivem preferencialmente em ambientes lênticos ou de baixo hidrodinamismo, como lagos, poças e riachos, onde habitam troncos submersos, folhiço e vegetação aquática, podendo formar grandes populações Walker, 1994;2001). Estes camarões desempenham papel importante nas relações tróficas de ambientes de água doce, alimentando-se de larvas de insetos, oligoquetas, algas, esponjas, microcrustáceos e fungos, além de serem presa de vertebrados aquáticos, como peixes (raias) e répteis crocodilianos Magnusson et al, 1987;Shibuya et al, 2009;Catarino & Zuanon, 2010).…”