First record of Chantransia macrospora Wood , 1887 ( Batrachospermales , Rhodophyta ) in semi-arid northeastern Brazil

This study presents the irst record of Chantransia macrospora in the state of Rio Grande do Norte, in the semi-arid region of northeastern Brazil. Analyses of periphytic algae revealed C. macrospora individuals associated in particular with shells of Melanoides tuberculatus, a non-native species, suggesting that C. macrospora have been introduced into systems associated with the gastropods. In this context, new records of C. macrospora are still expected for the Brazilian semi-arid region in the next years.

Chantransia macrospora usually grows in streams and rivers in North and South America (NECCHI et al., 1993;NECCHI;ZUCCHI, 1995;KUMANO, 2002), yet no records exist for this species in lentic systems in the Brazilian semiarid northeastern region.C. macrospora can grow in highly eutrophic systems, although other species of Chantransia and Batrachospermum are typically reported in less polluted streams (NECCHI et al., 1993;NECCHI;ZUCCHI, 1995).This may indicate that C. macrospora has a high tolerance for polluted conditions.The discovery of tiny, freshwater algae such as C. macrospora indicates that currently unknown introduced organisms on which C. macrospora grows may also be present.
In Brazil, C. macrospora has been recorded in the southwestern and southern states of São Paulo (NECCHI; ZUCCHI, 1995), Paraná (BRANCO et al., 2009) and Santa Catarina (BRANCO et al., 2011) (Figure 1).Here, we present the irst record of C. macrospora for the Brazilian semiarid region in Rio Grande do Norte First record of Chantransia macrospora in Brazilian semi-arid state (RN), thereby considerably extending the known geographical distribution of this species.
The observed organisms presented dense tufts and were 2.0-2.5 mm in height.The thallus was composed of uniseriate erect ilaments, branching with narrow angles (Figure 2B).These ilaments were cylindrical to tapered along their height.Axial cells of the erect ilaments were 14-22 µm in diameter and 41-72 µm in height.Chloroplasts were discoid to elongate, with three to ive pyrenoids (Figure 2B).
The highest organism densities were observed on macrophytes and on the shells of Melanoides tuberculatus.The sampled reservoirs have relatively low water transparency and high water temperatures (about 31°C), with neutral pH and eutrophic conditions.Interestingly, C. macrospora was found in reservoirs with lower Shannon-Weiner diversity indices, which suggests that this species could be competing with the other species of periphyton and consequently causing a decrease in local diversity.
Another aspect to considerer is that these organisms are perhaps introduced into systems associated with M. tuberculatus.The red-rimmed melania Melanoides tuberculatus is an Afro-Asian Thiaridae gastropod (PILSBRY; BEQUAERT, 1927), which was introduced into Latin America in the late 1960s and is now widespread in almost all regions (FERNANDEZ et al., 2003).The irst record of this species in Brazil was in 1967, in Santos, São Paulo state (VAZ et al., 1986), the same region where C. macrospora was recorded (NECCHI; ZUCCHI, 1995).Furthermore, M. tuberculatus is frequently found associated with bioilm (BEESTON; MORGAN, 1979) and has been recorded in reservoirs in the Brazilian semi-arid region (SANTOS; ESKINAZI-SANT'ANNA, 2010).
No records of deleterious effects of C. macrospora exist for these ecosystems, however, the presence of non-native species should be widely discussed due to the potential effects related to competition with and parasitism upon native species, and the potential for subsequent decrease in local biodiversity and transformation of habitats (FACON et al., 2007).New records of C. macrospora are expected for the Brazilian semi-arid region in the next years.

FIGURE 1 :
FIGURE 1: New records of Chantransia macrospora in Rio Grande do Norte state, and its recorded occurrence in southeastern and southern Brazil.