A new spore-forming protist, Nephridiophaga blaberi sp nov., in the death's head cockroach Blaberus craniifer

A new spore-forming protist, Nephridiophaga blaberi sp. nov., was found in the Malpighian tubules of the death's head cockroach Blaberus craniifer and investigated by light and electron microscopy, Mature spores have a flatte ned, oval form and measure 6.5 x 3.2 mum. They possess a single nucleus, al though sporoblast stages with one or two occur. Several spores are endogeno usly formed within sporogenic plasmodia, Thus, a pansporoblast may contain 8 to 20 spores. During spore-formation, a double membranous wall encloses a generative nucleus plus a portion of cytoplasm, and residual plasmodial nu clei degenerate. Uni- and multinucleate vegetative stages are further stage s of the life cycle. Both vegetative and sporogenic plasmodia grow within e pithelial cells of the Malpighian tubules or in the tubule lumen. However, sporogony is mainly intracellular, Mature spores are released and excreted via the faeces. All stages possess mitochondria, endoplasmic reticulum, and ribosomes. A typical Golgi apparatus is missing. The ultrastructure of the spore reveals a spore wall that is thickest at the borders, and a central bulb- or cap-like structure where an infectious sporoplasm may emerge. The spore wall is composed of several electron-light and electron-dense layers. Morphology, life cycle stages, host, and infection site specifity conform with the features of the family Nephridiophagidae (protists incertae sedis) . The main reasons for the creation of a new species name are the intracell ular location of sporogony, spore size, and number of spores in a sporogeni c plasmodium.