Behaviour of albino and melanic variants of Biomphalaria glabrata Say, 1818 (Mollusca: Planorbidae) following infection by Schistosoma mansoni Sambon, 1907

Abstract

The behaviour of the albino and melanic variants of Biomphalaria glabrata of Belo Horizonte (MG. Brazil) was studied comparatively, in terms of their respective susceptibilities to infection by Schistosoma mansoni of the same origin, through observation of the elimination of cercariae for a three-month period and the calculation of mortality and infection rates, in control and in infected snails. The number of amoebocytes, granulocytes and hyalinocytes in the circulating hemolymph during different periods of infection was analyzed. The evolution of the infection in the tissues was observed by means of histological cross-sections. The melanic variant showed greater susceptibility to infection and a higher mortality rate. The albino variant showed a higher number of circulating amoebocytes, both granulocytes and hyalinocytes. A higher number of degenerated sporocysts were seen in the histological cross-sections of the albino variant. The results suggest that the melanic variant of B. glabrata was more susceptible to infection by S. mansoni than was the albino variant.Keywords: Biomphalaria glabrata, amoebocytes, Schistosoma mansoni, sporocysts. Comportamento de Biomphalaria glabrata variantes albina e melânica frente à infecção pelo Schistosoma mansoni ResumoFoi estudado comparativamente o comportamento das variantes albina e melânica de Biomphalaria glabrata de Belo Horizonte (MG. Brasil), em relação à susceptibilidade à infecção pelo Schistosoma mansoni de mesma origem, através da observação da eliminação de cercárias por um período de três meses e a verificação das taxas de mortalidade e infecção nos moluscos controles e infectados. Analisou-se também, o número de amebócitos granulócitos e hialinócitos na hemolinfa circulante em diferentes períodos de infecção. A evolução da infecção nos tecidos foi observada através de cortes histológicos. A variante melânica apresentou maior susceptibilidade à infecção e maior taxa de mortalidade. A variante albina apresentou maior número de amebócitos circulantes, tanto granulócitos quanto hialinócitos. Nos cortes histológicos foi verificado maior número de esporocistos degenerados na variedade albina. Por estes resultados sugere-se que nas populações estudadas a variante melânica de B. glabrata, foi mais susceptível à infecção pelo S. mansoni.

Morphology and kinetics of susceptible and resistant Biomphalaria alexandrina hemocytes during the first week of exposure to Schistosoma mansoni miracidia

“…This explains our results which showed that granulocytes were significantly higher in the control resistant snails than the corresponding susceptible snails, while hyalinocytes displayed a reverse profile. Allegretti et al [46] attributed the higher resistance of albino B. glabrata snails to S. mansoni infection to their increased granulocytes count. In the same context, Pila et al [47] suggested that high granulocytes' count is related to resistance.…”

Assessment of the impact of changes in temperature in Biomphalaria glabrata (Say, 1818) melanic and albino variants infected with Schistosoma mansoni (Sambon, 1907)

“…Variations on the pattern of pigmentation on the molluscs' mantles are genetic and can influence the susceptibility of molluscs (Chquiloff et al, 1978;Allegretti et al, 2009).…”

“…Previous studies suggest that the biochemistry of the melanin can interfere in the defense mechanisms of molluscs, so that melanic specimens show higher susceptibility to being infected by the Schistosoma mansoni when compared to albino specimens (Allegretti et al, 2009).…”

Comparative Analysis of the Growth Performance and Haemolymph Biochemical Properties of Normal and Albino Giant Land Snail- <i>Archachatina marginata</i>

“…It is believed to be caused by an enzyme deficiency involving the metabolism of melanin during prenatal development (Allegretti et al, 2009). There are two main types of albinism in snails: albino shelled and albino-bodied but the genes responsible for them had not been known.…”