(Schmidt, 1862)
Species Overview
Erylus discophorus (Schmidt, 1862) is a blackish or dark brown massive sponge with smooth surface and cheesy consistency. It is a southern species with its main occurrence in the Mediterranean.
Taxonomic Description
Colour: Black or dark brown (lighter inside).
Shape, size, surface and consistency: A very irregular, flattened, tuberose mass. Surface smooth. Small oscules. Consistency cheesy, incompressible, easily damaged.
Spicules: Megascleres : Oxeas, fusiform, sharply pointed, occasionally strongylote: 1060-1240 x 35 µm; dichotriaenes, rhabdome conical, sharply pointed: 556 x 52 µm, length protoclads 125-145 µm, length deuteroclads 175-370 µm.
Microscleres : Aspidasters, disciform, thin, circular or elliptical in outline: 105 x 75 µm, thickness 15 µm; oxyasters with 3-12 slender rays of 23 µm in length; microrhabds, microspined, fusiform or cylindrical, often centrotylote: 28 x 3.5 µm.
Skeleton: Ectosomal : Thin black cortex: 0.2-025 mm in thickness. Its skeleton consists chiefly of tangentially disposed oxeas and aspidasters covered extrenally by a feltwork of microrhabds, which also line the canals leading to the oscules. These canals are 80-240 µm in diameter and have a sphincter-type opening. Choanosomal : The cortex is carried by the cladomes of the dichotriaenes and by bundles of oxeas; dichotriaenes are also found scattered throughout the choanosome. Oxyaster are likewise scattered and lining the internal canals.
Ecology: On rocks at the low water mark and in shallow sublittoral.
Distribution: Mediterranean, Canary Islands, NW coast of Spain.
Etymology: The name refers to the aspidasters.
Type specimen information: The type specimens are in the Graz Museum, LMJG 15703 and 15273. Dry specimen (under Stelletta ) in London: BMNH 1877.5.21.337 (Bk.337) Bowerbank Coll. from O. Schmidt. Also 2 Schmidt slides BMNH 1867.3.11.33 and 1870.5.3.40.
Remarks
This is the only Erylus species of the area, so microscopic examination revealing the presence of aspidasters would make its identification certain. In habit it is rather similar to Plakortis simplex , but that is much lighter brown in colour.
Source: Sollas, 1888.