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| Author(s): |
Fernando Rafael De Grande
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Botucatu. 2016-05-24. |
| Institution: | Universidade Estadual Paulista (Unesp). Instituto de Biociências. Botucatu |
| Defense date: | 2016-04-29 |
| Advisor: | Tânia Marcia Costa |
| Abstract | |
Crabs of the genus Uca are important benthic macrofauna in estuarine environments. Several Uca species coexist on intertidal mud- and sand-flats where they feed on microorganisms or sediment debris. Species have relatively distinct zones, and zone establishment is based on biotic and abiotic factors. Sediment organic matter is thought to be one of the most important zoning factors. We tested the effects of organic matter content on intra-specific distribution of U. thayeri and U. uruguayensis in their habitats. Organic matter content, crab density, and size frequency were observed in quadrates at each meter along intertidal transects (length of transect). In laboratory microcosms with- and without-options were used to test any preference of crabs for high- or low-organic content sediment. We also assessed feeding (scoops into sediment) and the number of burrows dug into each sediment for two categories of U. uruguayensis (large and small individuals). Both species showed a negative relationship between crab size and organic content, and both showed higher densities in field sites with more organic matter. This pattern was not due to a preference behavior of crabs for sediments that vary only by organic matter. Both sizes of crabs fed less frequently in sediments with high organic content. Small crabs feed more than large crabs regardless of the sediment type. Our results indicate that food organic matter influences the amount of food available to fiddler crabs. Because of this, sites with high organic content support populations at higher densities. In a mono specific patch, small crabs occupy the lower level of the intertidal zone, which contains more organic matter. Large crabs are predominant in the intertidal zone high level. (AU) | |
| FAPESP's process: | 14/00456-7 - Intraspecific distribution of fiddler crabs depending on the organic matter content of the sediment: a question of preference? |
| Grantee: | Fernando Rafael de Grande |
| Support Opportunities: | Scholarships in Brazil - Master |