The present study investigated the distribution and abundance of epibenthic molluscs and their feeding habits associated to substrate features (coverage and rugosity) in a sandstone reef system in the Northeast of Brazil. Rugosity, low coral cover and high coverage of zoanthids and fleshy alga were the variables that influenced a low richness and high abundance of a few molluscan species in the reef habitat. The most abundant species were generalist carnivores, probably associated to a lesser offer and variability of resources in this type of reef system, when compared to the coral reefs. The results found in this study could reflect a normal characteristic of the molluscan community distribution in sandstone reefs, with low coral cover, or could indicate a degradation state of this habitat if it is compared to coral reefs, once that the significantly high coverage of fleshy alga has been recognized as a negative indicator of reef ecosystems health.

No abstract

The invasion of marine species is a threat to local and global biodiversity and can have many ecological, economic and social impacts. The bivalve Isognomon bicolor has invaded the rocky shores of Brazil and spread along the coast, occurring from Rio Grande do Norte to the Santa Catarina State. The present study evaluated the distribution of I. bicolor on different rocky shores of Arvoredo Island (Santa Catarina State) and its relationship with other taxa. A high density of I. bicolor was found on the exposed shore, which was associated with the occurrence of articulated calcareous macroalgae. In addition, I. bicolor was also found in empty shells of the barnacles Tetraclita stalactifera and Megabalanus spp. The physical structure of these habitats probably plays an important role in the success of I. bicolor invasion. For these reasons, I. bicolor evidences an alteration on the benthic community of the rocky shores and its potential consequences become a threat to local species.

Summary1. Tagging animals is essential to evaluate animal population dynamics and behaviour. Using unique marks requires that tags must last for the duration of the study and not affect animal behaviour and health. Echinoderms, especially smaller species, are usually considered intractable for tagging because they readily discard both internal and external tags. 2. We compared the utility of two tagging techniques for marking the small starfish Parvulastra exigua: (i) branding with a soldering iron, and (ii) injection of visible implant elastomer (VIE) of different colours. The efficiency of these techniques was evaluated by assessing (i) the effects of the tag on the mortality, growth and mobility of P. exigua; and (ii) the persistence of the tags over 30 days. 3. VIE had no detectable effect on any variable tested, whereas brand marks caused a decrease in mobility. In addition, 95% of the starfish tagged with VIE were still tagged after 1 month. 4. This technique will facilitate research on the ecology of this and other small asteroid species, and is also relevant for ecological studies of other small soft-bodied invertebrates. The combination of VIE colours plus the viability to track individuals offers a wide range of opportunities to investigate the ecology and behaviour of small invertebrates in the field.

No abstract