Ultrastructural variations in Lethocerus niloticum (Insecta: Hemiptera) caused by pollution in Lake Mariut, Alexandria, Egypt.

Water bugs, Lethocerus niloticum (Hemiptera: Belostomatidae), were collected from polluted and unpolluted areas of Lake Mariut to study ultrastructural alterations of different organs as a response to mainly heavy metal water pollution in the lake. Malpighian tubules are described by light, scanning, and transmission electron microscopy. L. niloticum has four Malpighian tubules floating in the hemolymph. Each tubule opens separately into the hindgut, consisting of one type of epithelium cells, and is divided into four regions. Structural changes in cells of the third distinctive region are examined. The most prominent pathological changes are the occurrence of pleomorphic mitochondria, the presence of enlarged irregular laminated concretions, an increase in lysosomes, and lysis of cytoplasm. Indentations of the nucleus and chromatin clumping are observed. These results allowed determination of the impact of pollutants in Malpighian tubule cells of L. niloticum, and thus this insect can be used as a biomonitor. Copyright 2001 Academic Press.