Data/hora: 23/09/2024 20:29:30

Biblioteca(s): 	Embrapa Florestas.	
Data corrente: 	25/09/2008	
Data da última atualização: 	25/09/2008	
Autoria: 	LÓPEZ, M. G.; SALMON, S.; COSÍN, D. D.; FERNANDEZ, R.	
Título: 	The impact of the earthworm Aporrectodea giardi on the behavior of the collembola Heteromurus nitidus: discrimination between living space and nutrient resource supply.	
Ano de publicação: 	2008	
Fonte/Imprenta: 	In: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.	
Idioma: 	Inglês	
Conteúdo: 	The effect of earthworms on microarthropod abundance and distribution has been studied by
several authors (Marinissen and Bok, 1988; Loranger et al., 1998; Salmon and Ponge 1999,
2001; Maraun et al., 1999; Migge, 2001; Gutiérrez et al., 2003), but the results obtained were
variable. Salmon et al. (2005) demonstrated that the presence of some earthworm species
increased the population densities of Heteromurus nitidus when submitted to a predation
pressure. It is hypothesised that H. nitidus benefited from earthworm burrows to escape predators
and from their excreta, which are attractant for this collembolan species (Salmon and Ponge,
2001).
The objective of this study was to discriminate between (1) the impact of burrows at the mechanical
level, in terms of increasing of the living space for Collembola (habitat structure), and (2) their
role as nutrient resource supply (habitat quality), by comparing the effect of artificial galleries
and true earthworm burrows created by Aporrectodea giardi on the behaviour of H. nitidus.
Three series (with six replicates each) of experiment were done in plastic boxes (18x12x6.5
cm) divided in two compartments with a 2mm pore-size mesh in the middle. In Treatment 1,
compacted soil without galleries was compared with compacted soil with artificial galleries of 7
mm (the diameter of the earthworm). Treatment 2 allowed to compare compacted soil with
artificial galleries of 7 mm and soil inhabited by A. giardi. In Treatment 3, compacted soil with
artificial galleries of 7 mm was compared with soil previously worked by A. giardi, from which
the earthworm was removed.
The soil used was a calcic mull sieved (4 mm) and defaunated (frozen and thawed three times
for five days). The experiment was done with a controlled number of predators and with
compacted soil at a constant density. The artificial galleries were made introducing a cable (7
mm diameter) into the compacted soil. Natural galleries from A. giardi without A. giardi were
created introducing one individual in each microcosm for 15 days and extracting the earthworms
with a moisture gradient before the beginning of the experiment.
28 H. nitidus (14 in each compartment) and 12 predators Chilopods (six in each compartment)
were introduced in each microcosm. The experiment was maintained for 15 days at 15ºC. Then,
the fauna from each type of soil was extracted with the Berlese-Tullgren method and counted
under a stereomicroscope. The mean number H. nitidus in the two compartments was compared
by a paired t-test.
A greater number of adult H. nitidus were collected in compartments with artificial galleries of 7
mm than in compacted soil. The Collembola could use these galleries to escape from predators.
No significant differences were found in the abundance of adult H. nitidus between artificial
galleries of 7 mm and natural galleries with or without A. giardi. Those results mean that, over a
short period (15d), A. giardi could influence favourably the populations of H. nitidus increasing
their living space independently of its impact through resource supply (cast and mucus spread on the burrow wall). A contrasted result was observed for juveniles, which were significantly
more abundant in the artificial galleries of 7 mm than in soil with the earthworm; it could show
that adult H. nitidus prevent their eggs and juveniles from the physical disturbance resulting from
the activity of A. giardi, by selecting a large living space without disturbance (artificial galleries)
for their reproduction.
Therefore, earthworms would have a positive effect on the habitat structure for Collembola,
allowing them to escape predators but may also negatively affect the reproduction of Collembola
by physical disturbance and destabilization of habitat.	
Categoria do assunto: 	--	
Registro original: 	Embrapa Florestas (CNPF)	
Exemplares: 	CNPF - (43720-1) - UPE - PL - -- - CD0305 -  -  - DIS