Pinguiococcus pyrenoidosus gen. et sp. nov. (Pinguiophyceae), a new marine coccoid alga

Abstract

SUMMARY A coccoid marine alga, collected from an aquaculture tank and maintained in culture as CCMP1144, was examined using light and electron microscopy. Young, rapidly growing cells were mostly spherical in shape, approximately 4–6 μm in diameter. Older cells often produced protrusions and pseudopodia-like extensions, giving cells an amoeboid-like appearance, but no amoeboid movement was observed and the pseudopodia-like extensions exhibited no active movement. The single chloroplast had a typical photosynthetic stramenopile ultrastructure. A large stalked pyrenoid was easily observed by light microscopy. Ultrastructurally, the granular portion of the pyrenoid was divided into sections by a penetrating chloroplast envelope. A mitochondrion was often, but not always, adjacent to the pyrenoid, and in some cases the mitochondrion formed a ‘cap’ over the protruding pyrenoid. The Golgi cisternae were (when viewed in cross-section) curved toward the nucleus. A peripheral network of anastomosing tube-like membranes was located immediately beneath the plasmalemma. Two centrioles were located adjacent to the nuclear envelope. Lipid-like and electron transparent vacuoles were present. Based on this investigation and data published elsewhere (large percentage of eicosapentaenoic acid, 18S rRNA and rbcL genes), this alga was described as Pinguiococcus pyrenoidosus gen. et sp. nov.