Dispersion in Populations of Tropiometra carinata (Crinoidea : Comatulida) in the Sao Sebastiao Channel, Sao Paulo State, Brazil

To understand the patterns of spatial distribution in populations of Tropimetra carinata (Lamarck), bi-monthly samples were collected in two areas of shallow water (Ponta do Baleeiro; PB, and Cabelo Gordo Beach; CG), in the Sao Sebastiao Channel, using a grid superimposed on the habitat. A pattern of clumped dispersion was observed, with values for Morisita's Index significantly different from those of a random pattern. The mean densities at PB and CG, from December 1997 to October 1998, were respectively 2.20 +/- 0.21 (SD) and 2.32 +/- 0.28 (SD) individuals m(-2). The length of the longest arm was used as an indicator of specimen size. The mean size at PB was 11.76 +/- 0.53 cm and at CG, 9.65 +/- 0.18 cm. The mean size of solitary individuals was greater than for clumped individuals in both areas. Small individuals tended to attach near clumps of greater individuals. The five principal microhabitats selected by these crinoids were lateral, upper and lower rock surfaces and lateral and upper rock crevices, with preferential attachment to lateral rock surfaces. The extent of substratum coverage by the zoanthid Palythoa caribaeorum varied between areas (74.1% at PB and 38.1% at CG), as did the association Tropimetra-Palythoa (81.4% at PB and 44.5% at CG). The clumped dispersion seen here optimizes filtration by enhancing the baffle effect. (C) 2002 Elsevier Science Ltd.54221922

Low genetic differentiation between isolated populations of the colonial ascidian Symplegma rubra Monniot, C. 1972

Pelagic larvae are highly important for maintaining the gene flow among populations of sessile marine invertebrates. Colonial ascidians consist, exclusively, of brooding species, with lecithotrophic larvae that have a limited dispersal. As a result, there is a marked differentiation among populations. In this work, we used allozyme electrophoresis to access the genetic variation in four populations of Symplegma rubra, a colonial ascidian frequently found in the intertidal zone of Southeastern Brazilian coast. High variability was found at three of the four sites sampled, the exception being Praia Grande in the State of Rio de Janeiro. At this site, there was a great preponderance of clones, which possibly reflected the enclosed nature of the location and its low water circulation that reduce the dispersal capabilities of these animals. S. rubra did not conform to expectations for random mating (Hardy-Weinberg equilibrium): there was a deficit of heterozygotes that was more related to the small population size than to inbreeding processes, since F (is) analysis per locus revealed a deficiency of heterozygotes at only one locus-MDH*. The greatest variation in allele frequency was found for GPI-2*. Analyses of genetic variability revealed moderate differentiation among the populations (F (ST)=0.051), which was unexpected for a species with a low dispersal capability. Rafting, a frequently underestimated means of dispersal, may be the main mode of gene flow in this species over large areas, since colonies of S. rubra are frequently seen growing on drift material and there is no evidence that the larva survive for a long time in the plankton.148480781

Consumption of bromeliad flowers by the crab Metasesarma rubripes in a Brazilian coastal forest

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How the timing of predation affects composition and diversity of species in a marine sessile community?

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Predation during the early life history stages, when organisms are susceptible to both biotic and abiotic factors, is likely to have pervasive effects on community development. However, few studies have examined the relative importance of predation during early life-history stages on long-term community composition. Using a sessile marine community, we conducted a manipulative experiment to measure the effect of timing and extent of predator exposure. Every month over a 5 month period we assessed taxa composition, dominance and taxa richness in each of the following five treatments: 1) never predated, 2) always predated, 3) early predated (during the first month of community development), 4) late predated and 5) uncaged panels. Predation was very important in determining taxa identity and dominance, reducing spatial monopolization by ascidians and increasing the area occupied by bryozoans, but overall predation did not result in a more diverse community. The localized extinction of ascidians in predation treatments was compensated by an increase in the diversity of bryozoans and barnacles. Interestingly, predation during the early stages of community development had only short-term effects on the taxa richness and composition. After 5 months, predator exclusion during the early life-history stages had no effect on community composition and only current levels of predation determined differences in composition. Our results show that predation can cause changes in community composition, directly and indirectly, without necessary changing the total number of co-occurring taxa. More important, we demonstrate to our study system that although predation during the early life-history stages can be strong and have important short-term effects, predation during the adult stages determines long-term community composition. (c) 2011 Elsevier B.V. All rights reserved.412126133Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)PIBIC-UNICAMPCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

TUBE EPIFAUNA OF THE POLYCHAETE PHYLLOCHAETOPTERUS-SOCIALIS CLAPAREDE

Animals greater than I mm, found among tangled tubes of Phyllochaetopterus socialis (Chaetopteridae) from Araca Beach, Sao Sebastiao district, Brazil, were studied for 1 year, with four samples in each of four seasons. They comprised 10 338 individuals in 17227 g dry weight of polychaete tubes, with Echinodermata, Polychaeta (not identified to species) and Crustacea as the dominant taxa. The Shannon-Wiener diversity index did not vary seasonally, only two species (a holothurian and a pycnogonid) showing seasonal variation. Ophiactis savignyi was the dominant species, providing 45.5% of individuals. Three other ophiuroids, the holothurian Synaptula hidriformis, the crustaceans Leprochelia savignyi, Megalobrachium soriatum and Synalpheus fritzmuelleri, the sipunculan Themiste alutacea and the bivalve Hiatella arctica were all abundant, but most of the 68 species recorded occurred sparsely. The assemblage associated with P. socialis was similar to the endofauna of the sponge Zygomycale parishii and the bryozoan Schizoporella unicornis, and to the epifauna of seaweed Sargassum cymosum, all of which occurred nearby. (C) 1995 Academic Press Limited4119110

Spatial-temporal distribution and recruitment of Stramonita haemastoma (Linnaeus, 1758) (Mollusca) on a sandstone bank in Ilhéus, Bahia, Brazil

We examined aspects of the population ecology of the gastropod Stramonita haemastoma at Ilhéus, Bahia, Brazil. We collected monthly from October 2007 through September 2008 on a sandstone bank 1.5 km long, on which two points and two sampling levels were defined. We took five previously randomised replicates at each level, using a square enclosing an area of 0.0625 m². The snails were photographed, counted, and measured at the site. Both recruits and other individuals in the population preferentially inhabit the regions closer to the lower shore, where they are submerged for longer periods and are less subject to physiological stresses caused by temperature variation and desiccation. The cracks and holes in the bank serve as refuges and places for S. haemastoma to lay their egg capsules. Recruits were observed throughout the study period, and the population showed continuous reproduction