R. cerebellata are diminutive sponges displaying an uneven body surface, ranging in structure from shallow cushions to bulbous forms. Prominent oscula and a well-developed dermal membrane are characteristic features. The presence of spongin is consistently minimal in quantity. The live sponge has a soft and loosely textured consistency. The coloration spans from yellowish-grey to dark green, attributed to the presence of unicellular algae, Chlorellae, residing in their tissues. The megascleres are fusiform, weakly curved to straight, featuring smooth amphioxea. Their dimensions range from 0.25-0.30 mm in length and 0.01 mm in width. True microscleres are notably absent. Gemmoscleres are curved, occasionally straight, and possess spined amphistrongyla. The spines are erect and less numerous on the central portion of the shaft, gradually becoming more recurved and increasing in number towards the terminus. The length and width of gemmoscleres range from 0.06-0.08 mm and 2-3 µm, respectively. Gemmules are spherical, numerous in mature sponges, and scattered throughout the body. The pneumatic coat is thick, consisting of small spherical air spaces in which gemmoscleres are embedded in two distinct layers. The foramen is characterized by a slender and straight porous tube. Gemmules have a diameter ranging from 0.45-0.50 mm.