Descriptions of Acrasid Cellular Slime Molds: Pocheina Rosea and a New Species, Pocheina Flagellata

Abstract

Numerous collections of the orange-colored Pocheina have been obtained in North Carolina and other areas of the United States, and in Australia and England. All but one were found on bark of live gymnosperm and frondose trees. A single collection from a dead Juniperus virginiana tree most closely resembles the type collection of P. rosea. Further studies may reveal that the majority of our collections of P. rosea represent a new variety. The new species, P. flagellata, found on the bark of live gymnosperm trees in Wisconsin and North Carolina, has sorocarps that resemble those of our common P. rosea collections but differs in having flagellate cells, spores with more abundant punctations, and nuclei that, during mitosis, lack divided nucleolar parts at the polar areas, which are present in the mitotic nuclei of P. rosea. Pocheina and Acrasis are considered related genera that are unrelated to other acrasid cellular slime molds. As previously noted by Loeblich and Tappan (1961), Guttulina Cienkowsky (1873), a cellular slime mold genus, was antedated by Guttulina d'Orbigny, a foraminiferan genus. Since we have considered both groups of organisms as members of the Kingdom Protista, reclassification of the cellular slime mold genus as Pocheina Loeblich & Tappan and the single known species as P. rosea (Cienk.) Loeblich & Tappan was accepted but retained in the Class Acrasea, Subphylum Mycetozoa, and Phylum Gymnomyxa of the Kingdom Protista (Olive, 1975). At the same time, the acrasid and dictyostelid cellular slime molds were classified separately because of a number of major differences among them. Also, as will be indicated later, Pocheina appears to be related to the genus Acrasis but to no other genus of cellular slime molds presently known. Cienkowsky discovered his cellular slime mold on dead wood containing lichens in a part of Russia that is now Poland, and he described the rose-colored sorocarp as having a round mass of spores at the top of a stalk composed of rows of wedge-shaped cells. In the presence of water the sorocarp cells germinated, yielding amoebae with lobose pseudopodia. The organism was not discovered and described again until it was found on bark of a live cypress tree sent to K. B. Raper from the Netherlands by Nannenga-Bremekamp. Raper (1973) found it to be very similar to the one described by Cienkowsky, although the spores failed to germinate. Our numerous collections of Pocheina in the past several years have turned out to comprise more than a single species. In the following discussion, we will describe what may be two varieties of P. rosea and a new species of the genus. Both species have been grown in culture.