Spongia (Spongia) obscura

Spongia (Spongia) obscura Hyatt, 1877
Dictyoceratida, Spongiidae

Common names:

Glove sponge.

Growth Form:

Massive, tending toward inverted conical, with steep furrowed sides; upper surface somewhat flattened with irregular depressions that tend to collect sediment; up to 30 cm across and tall.

Surface:

Generally rather irregular lumpy surface on sides and on top; sides furrowed; smaller specimens smoother.

Color:

Black outside, cream or light tan inside. Color becomes paler in alcohol.

Consistency:

Spongy, compressible.

Exudate:

None.

Oscules:

Round, in groups in apical depressions, with thin-walled collars the same color as the surrounding tissue, 0.5-1 cm across.

Skeletal components (Spicules, fibers):

Spongin fibers only, no proper spicules. Spongin orange, not laminated. Most fibers are simple, up to 25 μm across. Thicker fibers (50 μm) arise at intervals of up to 0.4-1.7 mm and may have a core of sand grains and broken spicules.

Skeletal Architecture:

Fibers make an irregular meshwork with meshes of variable size and shape, 50-380 μm across.

Ecology:

Common in mangrove lagoons and shallow bays; may occur on artificial substrates.

Distribution:

South Florida and throughout the Caribbean to at least 35 m.

Notes:

Difficult to distinguish from other local Spongia species. The flattened top and irregular surface are diagnostic. Two other species are also black: Spongia tubulifera has a similar habit but is more sprawling, with more separated oscules, and slightly coarser fibers and meshes. Spongia pertusa also tends to be more sprawling, with elevated, thick-walled oscules distributed among lobes and ridges. Three other species: cup-shaped S. tampa, globular S. barbara, and deeply grooved S. graminea, have not been verified in South Florida waters for decades. All Spongia species are much more compressible (“spongy”) than other local massive black or dark species, such as Spheciospongia vesparium, Ircinia strobilina, Aaptos pernucleata, Tectitethya keyensis and Geodia gibberosa.

Reference(s):

de Laubenfels & Storr (1958, as Spongia cheiris); Wiedenmayer (1977), van Soest (1984), Zea (1986).

Similar species:

Spheciospongia vesparium	Spongia pertusa	Spongia tubulifera	Geodia gibberosa
Aaptos pernucleata	Ircinia strobilina	Tectitethya keyensis