Rhipilia nigrescens Coppejans & Prud'homme

Scientific Description

Habit and structure. Thallus spongy, green when living, with a short indistinct stipe c. 4 mm long, spreading gradually to a peltate or infunduliform blade to 10 mm tall and 20 mm wide, growing in clusters and often anastomosing marginally with adjacent thalli. Stipe polysiphonous, with numerous narrow rhizoidal siphons 10–25 µm diam., in addition to larger primary siphons typical of blades. Rhizoidal siphons also spreading laterally, possibly forming additional thalli. Blades thicker centrally (c. 2 mm) and becoming thinner marginally (c. 1 mm), composed of several layers of siphons, these dichotomously to laterally branched, often with constrictions above branching points. Short lateral siphons mostly without constrictions, straight or often curved, with 4–7-pronged terminal tenaculae; prongs occasionally further divided and forming attachments to adjacent siphons. Primary siphons 45–70 (–80) μm diam.

Distribution. Known from Indonesia, Papua New Guinea, and the Kimberley coast and Scott Reef in northern W.A.

Habitat. Epilithic in the subtidal.

[After Huisman & Verbruggen, Algae of Australia: Mar. Benthic Algae of North-western Australia, 1. Green and Brown Algae 141 (2015)]