Lithophyllum insipidum Adey, Townsend et Boykins and L. flavescens sp. nov.: two flat lithophylloid coralline algae (Corallinales, Rhodophyta) abundant in shallow reef environments in Fiji

Abstract

Two unbranched species of Lithophyllum are characterized from Fiji, South Pacific, where both are common in the shallow reef environment. Lithophyllum insipidum Adey, Townsend et Boykins is characterized by a mainly lavender-colored thallus that is tessellate, with chalky white to brownish patches. Basal filaments are composed of nonpalisade cells that are rectangular prisms shaped like a book. The thallus surface, viewed by scanning electron microscopy, is of the Leptophytum type. Tetrasporangial pores are not blocked by occluding cells, and the tetrasporangial pore canal is lined by papillae that project into the pore canal. The floor of the tetrasporangial conceptacle chamber is six to nine cells deep, and the tetrasporangial conceptacle roof is formed from filaments that originate both peripheral to and central to a ring-shaped fertile area. A columella is present, and tetrasporangia are located at the conceptacle periphery. Tetrasporangial conceptacles are buried in the thallus after their senescence. Lithophyllum flavescens sp. nov. is characterized by a thallus that is mainly brilliant yellow, almost glossy, with a marble-like appearance under low magnification owing to the presence of small areas of low pigment concentration. The basal filaments are composed of mainly book-shaped, nonpalisade cells. The cell surface viewed by scanning electron microscopy is of the Phymatolithon type. Tetrasporangial pores are blocked by enlarged occluding cells that project above the surrounding roof surface in younger conceptacles and degenerate in mature conceptacles. The tetrasporangial conceptacle chamber floor is mainly five or six cells deep. The tetrasporangial conceptacle roof is formed from filaments that originate both peripheral to and central to a ring-shaped fertile area, and a columella is present. Tetrasporangia are located at the conceptacle periphery, and tetrasporangial conceptacles are buried in the thallus following their senescence.