Helena Matthews-Cascon

Thais (Stramonita) rustica (Lamarck, 1822) (Mollusca: Gastropoda: Thaididae), a potential bioindicator of contamination by organotin northeast Brazil

The use of antifouling paints containing the biocide compound tributyltin (TBT) has been shown as an inductor of imposex in neogastropods mollusks. Imposex is characterized by the development of male features in females, mainly the appearance of a no functional vas deferens and penis. Samples of Thais rustica were collected in eight sites in the metropolitan area of Natal city, Rio Grande do Norte state, northeast Brazil, and examined for occurrence of imposex, which was found in many females. The higher imposex levels were presented by samples from sites near city harbor.

Imposex in endemic volutid from Northeast Brazil (Mollusca: Gastropoda)

Imposex is characterized by the development of masc uline sexual organs in neogastropod females. Almost 120 mollusk species are known to present imposex when eto organic tin compounds as tributyltin (TBT ) and triphenyltin (TPT). These compounds are used as bio cide agents in antifouling paints to prevent the in crustations on boats. Five gastropod species are known to present imposex in Brazil: Stramonita haemastoma, Stramonit a rustica, Leucozonia nassa, Cymathium parthenopeum and Olivan cillaria vesica. This paper reports the first recor d of imposex observed in the endemic gastropod Voluta eb raea from Pacheco Beach, Northeast Brazil. Animals presenting imposex had regular female reproductive organs (capsule gland, oviduct and sperm-ingesting gland) and an abnormal penis. As imposex occurs in mollusks ex posed to organotin compounds typically found at har bors, marinas, shipyards and areas with high shipping act ivities, probably contamination of Pacheco Beach is a consequence of a shipyard activity located in the n earest areas.

Distribution pattern of zoanthids (Cnidaria: Zoantharia) on a tropical reef

Abstract Coastal reef environments support a great diversity of benthic species, which are physically arrayed according to their adaptations to biotic factors such as competition and to abiotic factors such as salinity and desiccation. Few studies have described adaptive strategies on rocky shores in tropical regions. This contribution deals with the spatial distribution of three species of zoanthids (Palythoa caribaeorum, Protopalythoa variabilis and Zoanthus sociatus) on flat sandstone reefs in north-eastern Brazil. Zoanthid distribution and abundances were determined as the percentage of cover along six transects, where 50 × 50 cm quadrats were sampled. Biotic data (influence of macroalgal cover) and abiotic data (relief, substrate type, temperature and salinity) were also taken along the transects to attempt to explain the zoanthid distribution. These species tended to colonize the middle and low intertidal zones, which are least exposed to air. Zoanthus sociatus apparently resists desiccation better than P. caribaeorum. Protopalythoa variabilis showed the highest abundance and frequency, occurring in the entire middle intertidal zone and colonized areas with high proportions of unconsolidated sediment. Desiccation was the main factor limiting the spatial distributions of the three species, although substrate composition and probably interspecific competition with macroalgae were also important. The results suggest that the zoanthids use a variety of these adaptive strategies, which account for their success on consolidated substrates. Continuous monitoring of changes in distribution patterns can be useful for indicating human impacts on marine biodiversity, providing insights for monitoring and conservation programmes.

Competitive interactions among zoanthids (cnidaria: zoanthidae) in an intertidal zone of northeastern Brazil

Sessile organisms that live in consolidated substrates frequently compete for space. Coral species have many strategies to face this competition, including harming their opponents or hindering their growth. In the present study, the competitive interactions between three species of zoanthids were investigated in the intertidal zone of a sandstone reef environment in northeastern Brazil. The competitive abilities of the three species were evaluated by periodic observation of the natural fringes of contact and experimental evaluation of their growth rate through removal of 100 cm2 of colonies of each species. Palythoa caribaeorum and Zoanthus sociatus had similar growth rates, and both species grew faster than Protopalythoa variabilis. The recolonization strategy seems to differ among species. The contact fringes between P. caribaeorum and Z. sociatus remained unchanged over time, without any type of aggressive interaction between them, suggesting that stand-off was the strategy used by these organisms. Palythoa caribaeorum and Z. sociatus grew among the polyps of P. variabilis, often killing its colonies. The coexistence of zoanthids reveals a capacity for survival in the face of competition for limited resources such as free substrate, which led to the colonization and establishment of zoanthids in intertidal environments.

Symbiodinium diversity associated with zoanthids (Cnidaria: Hexacorallia) in Northeastern Brazil

Some marine animals have a dynamic mutualistic association involving heterotrophic coral animals (hosts) and autotrophic dinoflagellate endosymbionts in the genus Symbiodinium, known as zooxanthellae, which are directly involved in their physiology. Currently, there is limited knowledge of the Symbiodinium diversity associated with zoanthids from the Brazilian coast. Hence, this study assessed the diversity of zooxanthellae associated with Palythoa caribaeorum, Zoanthus sociatus and Protopalythoa variabilis commonly found on the northeast coast. Zoanthids samples were collected from sandstone reefs, and the total DNA from the samples was extracted. Diversity was assessed by denaturing gradient gel electrophoresis (DGGE) and ITS region cloning library. Data from ITS region sequences showed that zoanthids hosted two phylogenetic subclades or subgenus (C1 and A3) closely related to Symbiodinium from previous studies. Subclade C1 was found in Pa. caribaeorum, Pr. variabilis and Z. sociatus, while subclade A3 was found exclusively in Z. sociatus. This suggests that Pa. caribaeorum and Pr. variabilis are extremely selective, whereas Z. sociatus shows greater flexibility in the selection of its symbionts, and these differences may be involved with living in different reef environments. Knowledge of zooxanthellae diversity associated with zoanthids can explain their large distribution in Brazilian coast and contribute to a better understanding of zoanthid’s sensitivity to thermal stress.

A survey of the Scyphozoa and Cubozoa (Cnidaria, Medusozoa) from the Ceará coast (NE Brazil)

Most of the scyphozoans and cubozoans recorded for the Brazilian coast are presumed to be distributed over the entire coastline, but little information on precise records is available. This paper presents the first published records for the Ceara state (northeastern region) of the cubozoan Chiropsalmus quadrumanus, and the scyphozoans Chrysaora lactea, Linuche unguiculata (polyp), Lychnorhiza lucerna, Nausithoe sp. (polyp), Phyllorhiza punctata, and Stomolophus meleagris. The medusoid species have been known by local fishermen and non-specialists for a long time in the area.

Mollusks: how are they arranged in the rocky intertidal zone?

Mollusks occupy different kinds of environments, including the intertidal zone. The present study investigated the spatial distribution of mollusks on beach rocks of the intertidal zone of Pacheco Beach in the state of Ceara, Brazil. Sampling occurred from August 2006 to September 2007. Across two transects, six samples of 0.25 m2 were collected monthly in gaps of 30 m (0 m, 30 m, 60 m, 90 m, 120 m and 150 m). The mollusks were counted in field, and samples of sediment and algae were taken for further analysis. A total of 74,515 individuals were found and classified into 67 species, 52 genera and 39 families. Gastropods were predominant, corresponding to 73.1% of the species, followed by bivalves (22.4%) and chitons (4.5%). Caecum ryssotitum de Folin, 1867 was the most abundant taxon, representing 68.8% of total specimen findings. In general, species were mostly found in Middle Littoral zone (samples 60 m and 90 m), suggesting that the greater number of microenvironments available in this area may contribute to establishment and survival.

Neritic jellyfishes (Cnidaria: Cubozoa and Scyphozoa) from the coast of Rio Grande do Norte state, northeast of Brazil

For the entire Brazilian coast, there are 22 published records of scyphozoans. On the other hand, only 35 species of cubozoans were described worldwide, four of them reported for the Brazilian coast. However, little is known about the species of cubozoans and scyphozoans in the Northeastern states of Brazil. The aim of this study was to perform a survey of the jellyfish (Cnidaria: Cubozoa and Scyphozoa) on the coast of Rio Grande do Norte state, Northeast of Brazil. Specimens were collected using trawl net on beaches in the counties of Natal (in 2003) and Tibau (in 2004). For the Rio Grande do Norte coast there were few records of large jellyfish, and new records of the following cubozoan and scyphozoan species were verified: Chiropsalmus quadrumanus; Chrysaora lactea; Lychnorhiza lucerna and Stomolophus meleagris. The studied species had their distributions expanded in the coast to the State of Rio Grande do Norte.

Ecological relations between mangrove leaf litter and the spatial distribution of the gastropod Melampus coffeus in a fringe mangrove forest

Leaf litter represents a food source to many organisms that may directly contribute to organic matter decomposition. In addition, the physical presence of these vegetal detritus contributes for the modification of some environmental areas and produce microhabitats that may act as a refuge against predators and desiccation for many animals. The pulmonate gastropod Melampus coffeus (Linnaeus, 1758) (Ellobiidae) is a very common specie in Atlantic Coast mangrove forests and feeds on fallen mangrove leaves. It was hypothesized that the spatial distribution of Melampus coffeus is directly affected by mangrove leaf litter biomass deposition. Thus, this research aimed at evaluating the spatial distribution of these gastropods in relation to the biomass of mangrove leaf litter through a twelve-month period. The study area was established in the middle estuary of Pacoti River, state of Ceara, Brazil where two adjacent zones with different topographic profiles were determined. Samples of Melampus coffeus and leaf litter were collected monthly, throughout a year, from the mangrove ground surface. The results indicated that the presence of twigs in mangrove litter favor the occupation by smaller individuals of M. coffeus, probably because smaller individuals are more susceptible to predator attacks and desiccation than larger ones, and twigs and branches may provide a safe microhabitat.

Mollusks from two estuarine areas in Ceará state, northeastern Brazil, with new state records for four species

We analyzed qualitatively the malacofauna found in the tidal zones of Banco dos Cajuais and Ilha Grande estuarine complex, both in Ceara State, northeastern Brazil. Qualitative data on the malacofauna from Banco dos Cajuais and the Ilha Grande estuarine complex were obtained by systematic sampling in 2008 and 2009 during field activities for the “Migratory Shorebirds Conservation and Shrimp Farming in Northeast Brazil” project. Twenty-two species of mollusks (13 bivalves and 9 gastropods) were found in Banco dos Cajuais, and 25 species (18 bivalves and 7 gastropods) were found in the Ilha Grande estuarine complex. Four species, Lucina muricata (Spengler, 1798), Tagelus divisus (Lightfoot, 1786), Crassinella martinicensis (d’Orbigny, 1853), and Periploma ovata Kuroda and Horikoshi, 1958 were recorded from Ceara for the first time.