Accumulation and depuration of microcystin produced by the cyanobacterium Microcystis in a freshwater snail

Abstract

Seasonal changes in microcystin concentrations in a resident snail (Sinotaia histrica) and an edible clam (Corbicula sandai) in Lake Biwa were surveyed. To clarify both the accumulation and depuration of microcystins, experimental studies with microcystin were also carried out on the snail. In the field investigation, microcystin was detected from the hepatopancreas and intestine of S. histrica (up to 3.2 µg g Ϫ1 dry weight and 19.5 µgg Ϫ1 dry weight, respectively); however, no microcystin was detected in the hepatopancreas of C. sandai. In the laboratory experiment, the microcystin-LR concentration in the hepatopancreas of S. histrica reached a value of 436 µg g Ϫ1 dry weight on day 10 of 15 days of uptake, and a high value persisted despite a depuration period of 15 days. The depuration rate constant of microcystin and its biological half-life were 0.0828 day Ϫ1 and 8.4 days, respectively. These results indicate that S. histrica has a high ability to accumulate microcystin in its tissue. Because S. histrica is predated by fish and water fowl, it is likely to play an important role as a vector for microcystin in lakes with dense blooms of toxic cyanobacteria.

Bioaccumulation of microcystins in two freshwater gastropods from a cyanobacteria-bloom plateau lake, Lake Dianchi

“…Investigations on a resident snail [Sinotaia histrica (Gould, 1859)] for Lake Suwa (Japan) showed that the concentrations of MCs were significantly higher in digestive tracts than in the hepatopancreas (Ozawa et al, 2003;Xie et al, 2007), but was different from the pattern of another prosobranchia species [Bellamya aeruginosa (Reeve, 1863)] in two subtropical plain lakes (Lakes Caohu and Taihu). These studies of B. aeruginosa showed that concentrations of MCs in the hepatopancereas were not only significantly higher than those in digestive tracts, but also showed positive correlations with each other Zhang et al, 2007Zhang et al, , 2009.…”

“…Presumably, MCs not only promote the development of primary liver cancer (Sekijima et al, 1999), but also initiate liver tumors (Ito et al, 1997). Moreover, MCs can be transferred through food chains/webs by bioaccumulation in various organisms including zooplankton, mussels, snails, shrimp, fish and even turtles, ducks, and other waterfowl (Amorim and Vasconcelos, 1999;Ozawa et al, 2003;Lance et al, 2006;Xie et al, 2007;Chen et al, 2009;Martins and Vasconcelos, 2009).…”

“…They are also a major food resource for the higher consumers, playing an important role in transfer and concentration of MCs to the higher trophic levels through food chains/webs (Ozawa et al, 2003).…”

“…Moreover, accumulation of MCs was greater in juveniles than in adults for the pulmonate Lymnaea stagnalis (Lance et al, 2006). The various organs have different structures and functions, possibly resulting in their different abilities for bioaccumulation of MCs (Ozawa et al, 2003;Xie et al, 2007). However, up to now almost all the research about accumulation of MCs for pulmonates have been studied with regard to the whole body level (Kotak et al, 1996;Zurawell et al, 1999;Gérard et al, 2005Gérard et al, , 2009Lance et al, 2010a), and several at the digestive gland level (Lance et al, 2006;Zurawell et al, 2006Zurawell et al, , 2007, but fewer in other tissues.…”

“…In recent decades, regular massive cyanobacterial blooms have led to relatively high levels of MCs in the water (Pan et al, 2006). There are a few studies reporting the accumulation of MCs in some fish species in this lake (Peng et al, 2010).…”