Ululania stellata gen. et sp. nov. (Rhodomelaceae), a new genus and species of parasitic red algae from Hawaii

Ululania stellata Apt et Schlech gen. et sp. nov. infects two species of Acanthophora (Rhodomelaceae, Ceramiales) in Hawaii. Thalli are minute (to 3 mm in diameter), colorless pustules consisting of a central, relatively undifferentiated mass of radially elongated cells that bears numerous short (to 1 mm in length), radiating, unbranched fertile axes. Trichoblasts occur on dioecious male and female gametophytes, but not on tetrasporophytes. Procarps develop on the suprabasal cells of trichoblasts and consist of a four-celled carpogonial branch and a single-celled sterile lateral borne on the supporting cell. Trichoblasts on male gametophytes form shallowly lobed to obcordate leaflets on which the surface and most marginal cells bear spermatangia, a consolidated margin of sterile cells being absent. Tetrahedrally divided tetrasporangia occur in whorls of up to seven per tier of pericentral cells within stichidioid branchlets. Features of the vegetative axes, procarp, spermatangial trichoblasts, and tetrasporangial stichidia show the new genus to be an adelphoparasite belonging to the Chondrieae.