Características físicas e químicas do habitat da Biomphalaria tenagophila (Mollusca, Planorbidae)

Abstract

Samples of water and snails collected through aleatory scoops in a small dam were done to obtain data concerning the physical and chemical characteristics of the water and their possible influence on biological aspects of the life cycle of snails. Among the 17 analysed parameters, Alkalinity and Conductivity showed a positive correlation with the density of B. tenagophila (r = +0.224 and r = +0.290), while CO2 and Acidity were negatively correlated with this populacional parameter (r = -0.592 and 0.601). Alkalinity and Total Hardness values were slightly higher than 100 mg/l CaCO3. Chlorides and Conductivity showed means of 94.9 +/- 38.7 and 680.1 +/- 643 microS/cm; these values are very high for that region. Other factors like pH and OD are according to the pattern for provision untreated waters. The density of B. tenagophila declined in the 6th month after a long period of torrential rains and in the rainy summers. In the colder months of the following year the density was higher (until 124 individuals/months/90 scoops). The monthly mean of the diameters of the snails was always larger than 13 mm, reaching 21.4 +/- 4.1 mm, but the mode was about 17 mm. There was no correlation between diameter/density (r = 0.037) and density/temperature (r = 0.065).

Modelling of the distribution of Biomphalaria glabrata and Biomphalaria straminea in the metropolitan region of Recife, Pernambuco, Brazil

“…In the rainy season (May to August), Biomphalaria spp. populations decrease due to flooding, but there is accelerated snail growth and production of new individuals leading to repopulation of breeding sites, which mainly occurs at the end of the rainy season (September to December), when increasing the number of stagnant water (Paraense, 1972;Grisolia and Freitas, 1985;Juberg et al, 1987). Despite being basically harmful, established snail populations may flush out snails leading to the formation of new habitats (WHO, 1957).…”

Malacological survey of Biomphalaria snails in municipalities along the Estrada Real in the southeast of the State of Minas Gerais, Brazil

“…However, it is important to highlight that the present study was conducted over four years, which means that seasonal cycles, such as temperature and rainfall, for example, may have affected the abundance of mollusk populations 28,29 . This study revealed several water collections colonized by mollusks of the Biomphalaria genus, including streams, dams and waterfalls, which could serve for sporting practices or for the construction of pools, providing further sources of infection by schistosomiasis among tourists 4,30 .…”

A Study of Schistosomiasis Prevalence and Risk of Snail Presence Spatial Distributions Using Geo-Statistical Tools

“…Another adaptation of molluscs is the acceleration of development during the rainy season to ensure the production of new individuals and thus the colony can withstand the next dry season. (Paraense, 1955(Paraense, , 1972Grisolia & Freitas, 1985;Juberg et al, 1987). The mollusc's reproductive mechanism has a fundamental role in the species' perpetuation.…”