Browsing by Author "Silva, Mariana Oliveira"
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- Diet and feeding activity of Olivella minuta (Link, 1807) (Mollusca, Gastropoda, Olividae) along the intertidal - subtidal zone of a dissipative sandy beach in the north coast of São Paulo - BrazilPublication . Silva, Mariana Oliveira; Chícharo, AlexandraThe present study aimed to investigate the diet and feeding activity of a sandy-mud snail, Olivella minuta along the gradient subtidal-intertidal of a dissipative morphodynamic beach: Barequeçaba (southeast coast of Brazil). Locomotor behavior of the species was also evaluated in laboratory conditions. The sampling was carried out in March, April and May, 2013 in the intertidal zone during low and high tide and in the subtidal zone during low tide, to further comparisons if these organisms change their diet according to the variation of the tide. Thirty specimens from 7 mm of length were caught in each situation and stomach contents were analyzed by means of qualitative (richness, diversity, evenness and Simpson) and quantitative indexes (numeric importance (NI) and frequency of occurrence (FO)). Also, the index of stomach repletion was calculated to complement the analysis of the feeding diet of this gastropod. A total of 49 items was registered in the digestive tracts of O. minuta being the most frequents: macroalgaes (48%), microalgaes (15%), artropodes (12%) and foraminiferans (12%). The remaining items had frequency of occurrence lower than 10%. The results of the diet composition of the individuals did not differ along the tidal range of the beach, suggesting that the species does not possess a preference for a single food resource, and the variation on NI e FO in all studied situations can be merely consequences of the dynamics of each food items during the tidal cycle. The results of the stomach repletion suggest that this snail feed in all studied situations, but with higher intensity when emerged during low tide and the results of locomotor behavior tested experimentally, reinforce this idea and still suggests that during the day this organisms have a higher feeding activity rather than at night, since a lesser movement was displayed in these conditions.
- Full stomachs at empty tides: tidal cycle affects feeding activity and diet of the sandy beach gastropod Olivella minutaPublication . Checon, Helio H.; Silva, Mariana Oliveira; Corte, Guilherme N.; Yokoyama, Leonardo Q.; Teodosio, Maria; Turra, AlexanderOlivella minuta is an abundant neogastropod on sandy beaches from Texas (USA) to southern Brazil. This study aimed to characterize and compare the feeding activity and diet of a Brazilian population of O. minuta in different tidal zones (intertidal and subtidall, and different tidal levels (high and low tides), with three combinations of tidal zone and level being studied (intertidal during low tide, intertidal during high tide and subtidal). The results showed that diet composition was generally similar among tidal conditions, with O. minuta being a generalist, feeding on 45 different food items. Feeding activity, however, was higher in the intertidal during low tide, whereas the richness and diversity of food items were higher in the intertidal during high tide. The higher feeding activity of O. minuta during low tide may be linked to a lower risk of predation; at low tide organisms may be able to feed for a longer time, arid this may be particularly true on beaches with fine sand, where water retention is higher than that on beaches with coarse sand. The higher diversity of food items consumed in the intertidal during high tide is likely related to the increased prevalence of planktonic food during high tide. Our results indicate that tidal zone and level may strongly influence the feeding activity of coastal soft-bottom species and that species may show higher feeding activity during low tide. Given the current loss of intertidal habitats due to anthropogenic activity and climate-change associated factors, our study has important implications, highlighting the importance of intertidal areas for the ecology and conservation of sandy beach species.