Spongites fruticulosus Kütz.

Scientific Description

Habit and structure. Thallus encrusting or warty, 0.3–30 mm thick, epilithic and affixed by cell adhesion or growing unattached as rhodoliths. Structure pseudoparenchymatous; organisation dorsiventral; construction monomerous, consisting of a single system of branched filaments that collectively contribute to a ventrally situated core, and a peripheral region where portions of core filaments or their derivatives curve outwards towards the thallus surface, each filament composed of cells 5–16 µm in diameter and 5–35 µm long; a single epithallial cell terminating filaments at the thallus surface, distal walls rounded or flattened but not flared; cells of adjacent filaments joined by cell-fusions, secondary pit-connections absent; trichocytes occurring present at thallus surface, arranged in horizontal fields or singly, not becoming buried within thallus.

Reproduction. Vegetative reproduction unknown. Gametangia, carposporangia and tetrasporangia produced in uniporate conceptacles; bisporangia unknown. Gametangial plants dioecious; carpogonia and spermatangia produced in separate conceptacles. Carpogonia terminating 3-celled filaments arising from the female conceptacle chamber floor. Mature female-carposporangial conceptacle roofs protruding above or flush with surrounding thallus surface, usually composed of 8–12 cells above the chamber, conceptacle chambers 575–595 µm in diameter and 295–320 µm high. Carposporophytes developing within older female conceptacles after karyogamy, when mature composed of a large central fusion cell and gonimoblast filaments bearing terminal carposporangia, pores not surrounded by coronas of filaments. Spermatangial filaments unbranched, arising from the floor of male conceptacle chambers, mature male conceptacle roofs flush with surrounding thallus surface, composed of 3 or 4 cells, conceptacle chambers 235–335 µm in diameter and 145–245 µm high. Tetrasporangial conceptacle roofs protruding above or flush with surrounding thallus surface, 8–12 cells thick above the chamber, pore canals lined with protruding cells, conceptacle chambers 350–595 µm in diameter and 275–410 µm high; tetrasporangia peripheral to a central columella, each mature sporangium 65–130 µm in diameter and 85–225 µm long, zonately divided.

Distribution. Mediterranean Sea; Red Sea. In southern Australia, Esperance, W. Aust., to Eagles Nest, Vic.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIB: 277–278 (1996)]