Population dynamics ofNarapa bonettoiRighi and Varela, 1983 (Oligochaeta: Narapidae) from the main channel of the Middle Paraná River, Argentina
✍ Scribed by M. Marchese
- Book ID
- 104639684
- Publisher
- Springer
- Year
- 1994
- Tongue
- English
- Weight
- 416 KB
- Volume
- 278
- Category
- Article
- ISSN
- 1573-5141
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✦ Synopsis
The aim of the present study was to determine the life-cycle of Narapa bonettoi in the main channel of the Middle Parana River. The average density varied between 17 and 624 ind. sample-'. The spatial distribution was contagious with a higher degree of aggregation during the first months of the observed cycle, than during the last months. Mature specimens were more abundant in September 1985-86, resulting in greater breeding activity in early summer, when there was a large population increase. Two reproductive strategies were observed: asexual and sexual. After breeding, worms undergo a resorption process of their reproductive organs, returning to a non-sexual condition. Narapa bonettoi probably uses asexual reproduction as an adaptative strategy, because cocoon development will be affected by environmental factors such as the drift in the Parana River which is highly erodable. Population growth was rapid during the first four months and then stabilized.