Abstract
The burrowing and semiterrestrial crab Neohelice granulata actively and constantly builds its burrows in the intertidal zone of the Bahía Blanca Estuary during low tide. Differences in structural morphology of N. granulata burrows and burrowing activities in contrasting microhabitats (saltmarsh and mudflat) were analyzed and related to several conditions, such as tide level, substrate type, sediment properties, and population density. In the mudflat the higher density of total burrows in autumn (172 burrows·m–2) was associated with molt timing, and the higher density of active burrows in summer (144 burrows·m–2) was associated with reproductive migration. Sediments from biogenic mounds (removed by crabs) showed higher water content and penetrability than surface sediments (control), suggesting that bioturbation increases the values of these parameters. Grain size distribution profiles and mineralogical composition did not vary between microhabitats or between seasons. Burrows were all tunnel-shaped and only those from the saltmarsh had chambers inside the tunnels, possibly used for reproductive purposes. Burrows from the saltmarsh had narrow entrances and deep tunnels, and burrows from the mudflat presented very narrow entrances and surface tunnels. Differences in burrow features and burrow activity of N. granulata between microhabitats were confirmed and associated with biotic and abiotic factors, indicating that this species has an adaptive burrowing behavior.
Highlights
Sediments from biogenic mounds showed higher water content and penetrability than surface sediments, suggesting that bioturbation increases the values of these parameters
Neohelice granulata is a crab with a characteristic burrowing behavior
The Bahía Blanca Estuary, in the southwest region of the Buenos Aires Province, covers an area of approximately 3,000 km[2]. It is a mesotidal coastal plain estuary with a semidiurnal tidal regime, and it is characterized by the especie usa las cuevas para protegerse de la acción de las olas, las temperaturas extremas y la desecación
Summary
Ciencias Marinas, Vol 44, No 3, 2018 from wave action, extreme temperatures, and desiccation. Variations in the architecture of N. granulata burrows have been observed in studies conducted at other locations in Argentina, such as Mar Chiquita Lagoon, Buenos Aires Province (36o09 26′′S, 60o34′11′′W; Iribarne et al 1997, Botto et al 2006), and San Antonio Bay, Río Negro Province (40o44′51.43′′S, 64o52′5.10′′W; Sal-Moyano et al 2012, Luppi et al 2013, Bas et al 2014). These studies revealed differences in terms of size and shape of burrows (diameter, depth, volume, and angle) when different intertidal sites, relative to the tide line, were compared. We hypothesized that burrowing activity and burrow morphology would vary between contrasting habitats, which were selected on the basis of their differences in tide level, sediment characteristics, and substrate type
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