Demospongiae

(Demosponges)

Phylum Porifera

Class Demospongiae

Number of families 80

Thumbnail description
Soft, elastic, but also tough, friable, or hard, frequently brightly colored sponges; varying in shape from encrusting, massive, tubes, or branches to cups or vases; the body reinforced by spongin, siliceous (containing silica) spicules, or a combination of both

Evolution and systematics

The demosponges originated in the Cambrian period and form the largest class of the phylum Porifera, containing about 85% of all described Holocene species. The class Demospongiae is divided into three subclasses:

1. Subclass Homoscleromorpha, with one order, Homosclerophorida; one family; and about 60 species.
2. Subclass Tetractinomorpha, with four orders, Astrophorida (also known as Choristida), Chondrosida, Hadromerida, and Spirophorida; 22 families; and several hundred species.
3. Subclass Ceractinomorpha, with nine orders, Agelasida, Dendroceratida, Dictyoceratida, Halichondrida, Halisarcida, Haplosclerida, Poecilosclerida, Verongida, and Verticillitida; 57 families; and several thousand species.

The names of these subclasses have been in use for several decades. As of 2002, however, with the publication of Systema Porifera, several changes in classification have been made and definitions refined. These changes have made the subclasses more homogeneous, though still not completely so.

The subclass Homoscleromorpha is a small and well-defined group of sponges with or without a skeleton, characterized by viviparous reproduction and a unique incubated cinctoblastula type of larva. If skeletal elements are present, they are relatively small, consisting of tetraxonic (four-rayed) siliceous spicules without a clear distinction between megascleres (large spicules) and microscleres (small spicules). The Tetractinomorpha have monaxonic (single-rayed) spicules in addition to large tetraxonic spicules; asterose (star-shaped) microscleres; a skeleton that is usually radial or axially compressed; predominantly oviparous reproduction and parenchymellar (solid) or blastular (hollow) larvae. Ceractinomorpha is the largest and most diverse subclass, with a wide variety of monactine megascleres and various kinds of microscleres, with the exception of asterose forms. In general, sponges in this subclass have skeletons made of spongin and spicules in different proportions, with a variety of skeletal structures. Their reproduction is predominantly viviparous and their larvae are parenchymellar.

The former class of Sclerospongiae, which was proposed in 1970 ("sclerosponges"), together with the former order Ceratoporellida, formed a polyphyletic (descended from more than one line of ancestors) group of coralline sponges that included several Holocene species as well as fossil sponges. The Sclerospongiae are hard, stony sponges with a rigid calcareous basal skeleton in addition to an otherwise "normal" demosponge type of skeleton and spicule complement. Since 1985 the class name Sclerospongiae has been discarded and its families

reassigned to different orders on the basis of characteristics reflecting common ancestry.

Another polyphyletic group is the former order Lithistida, which included many fossil and several Holocene species characterized by a special type of spicules called desmas. Most species in this group were deep-water sponges. The evolutionary history of these sponges is still far from resolved; some appear to be related to the Astrophorida and others to the Hadromerida. Most taxa (categories) in this group, however, have been classified as an artificial fifth order (Lithistida) in the subclass Tetractinomorpha.

Axinellida, another polyphyletic group, is no longer defined as an order. Its families have been reassigned to various orders of Tetractinomorpha and Ceractinomorpha.

Verticillitida consists of the fossil family Verticillitidae. It belongs to an unrelated assemblage of mainly calcified fossil sponges with chambered structures known as Sphinctozoa. One Holocene genus, Vaceletia, which has one known polymorphic species and possibly other "living fossil" species, has been assigned to this order.

Physical characteristics

The demosponges as a group display a wide variety of shapes, colors, textures, skeletal architectures, and spicule morphology. There are species that are capable of hollowing out limestone, penetrating deep inside rocks, coral heads, and shells. Most demosponges have skeletons made of siliceous spicules, spongin fibers, or a combination of both; one group, however, has no skeleton at all. The architecture varies widely among the different groups; it may be reticulate (netlike), confused, radial (spreading outward from a common center), plumose (feathery) or axially compressed. The spicules are usually divided into two size categories (megascleres and microscleres) with a distinct morphology.

The order Poecilosclerida is the largest and most diverse order, with 25 families and several thousand species. Although this group displays a wide variety in form and skeletal architecture, it has a unique feature— chelae, which are meniscoid (crescent-shaped) microscleres with a curved shaft and recurved, winglike or broadly rounded structures at each end. These chelae are extremely diverse, and new ultrastructural characteristics are still being discovered.

The order Haplosclerida comprises 13 families and hundreds of species. All freshwater sponges belong to this order as the suborder Spongillina. They are frequently cushionshaped; however, encrusting, branching, tubular, vase-, and fan-shaped forms are also quite common. Their coloring is not very intense; most sponges in this order come in delicate shades of purple, lavender, light brown or blue. Most freshwater sponges are green. They are rather soft and easily squeezed except for species of the suborder Petrosina, which are firm and cannot be compressed. All haplosclerids have a netlike skeleton of smooth, single-rayed, one-pointed short megascleres bound together by different amounts of spongin. Most

marine haplosclerids have no microscleres. Where microscleres are present, they are very simple in structure and none are unique to the order. The spicules of the Spongillina are more elaborate, with smooth or variably ornamented megascleres and several kinds of microscleres. The simple structure of the spicules, combined with a very high degree of variability in skeletal architecture in some species, make the marine Haplosclerida among the most difficult sponges to identify.

The Dendroceratida, Dictyoceratida, and Verongida, also known as Keratosa, are sponges with a skeleton made up only of spongin without spicules. All commercial bath sponges belong to the Dictyoceratida. Taken together, these orders contain 10 families and about 450 species. The sponges are often rather tough and flexible; in one family, the Spongiidae, both the surface and the spongin fibers may be heavily coated with foreign spicules and detritus. Species of the order Verongida are easily noticed tube-, fan-, or vase-shaped sponges, frequently colored a deep sulphur yellow. When these sponges are damaged or exposed to air, their color changes rapidly to a deep purple or black.

Distribution

The Astrophorida, Chondrosida, Hadromerida, Halichondrida, both the marine and freshwater Haplosclerida, the Homoscleromorpha, Poecilosclerida and most Spirophorida have a worldwide distribution. The Agelasida, Dictyoceratida, and the sclerosponges, however, are found mostly in the tropics. The Verticillitida; the spirophorid family Spirasigmidae; and two families of the Verongida, the Pseudoceratinidae and the Aplysinellidae, are restricted to the Indian and Pacific Oceans; while the Halisarcida, the dendroceratid family Dictyodendrillidae, and the dictyoceratid family Thorectidae are not found in the polar regions.

Habitat

Most demosponges occur in all habitats at all depths. The Homoscleromorpha, Chondrosida, Agelasida, Dendroceratida, Halisarcida, and most Dictyoceratida occur mainly in the shallower parts of the oceans. The sclerosponges prefer cryptic (hidden) habitats.

Behavior

Most demosponges are immobile animals attached at the base to a substrate, or surface on which they live. Some species, however, successfully compete with corals and other sponges for space by releasing toxic chemicals.

Feeding ecology and diet

Like all other sponges, the Demospongiae are filter-feeders. One genus consists of carnivorous species that engulf and digest small crustaceans.

Reproductive biology

Some demosponges are hermaphroditic while others have distinct sexes. Their reproduction may be viviparous, oviparous, or asexual. Asexual reproduction occurs by means of budding, fragmentation, or the production of resistant globular bodies called gemmulae. Demosponge larvae are partly or completely ciliated, usually somewhat elongated blastulae (hollow larvae) or parenchymellae (solid larvae) about 300 µm long. The larvae swim or crawl around for a few hours or days at most, after which they settle on a substrate and metamorphose into an adult sponge.

Conservation status

In response to the overfishing of commercial sponges, patrimonial interest, and rare and remarkable characteristics of certain sponges, eight Mediterranean sponges are protected under the Bern Convention of 1998, and an additional seven species are protected in Italy.

Significance to humans

Several species are of pharmacological interest because of the production of bioactive compounds with antiviral (spongothymidine) and antibacterial (polybrominated diphenyl ethers) properties. Mediterranean and Caribbean horny sponges have commercial value as bath sponges.

Species accounts

List of Species

Eyed finger sponge

Haliclona oculata

order

Haplosclerida

family

Chalinidae

taxonomy

Haliclona oculata Pallas, 1766, British Isles.

other common names

Dutch: Geweispons.

physical characteristics

Clusters of thin, commonly somewhat flattened branches, up to 12 in (30 cm) high, arising from a common stalk and attached to the substrate with a small pedicel or foot. In places with strong water currents, branches may fuse to the point of becoming flabellate, or fan-shaped. Oscules (small mouthlike openings) are small and circular, regularly distributed along the narrower sides of the branches. Sponges have a soft, velvety consistency and are light-brown or pinkish-brown in color.

distribution

Arctic-boreal.

habitat

Infralittoral to about 328 ft (100 m), on shores with rocky or sandy bottoms.

behavior

Little is known besides feeding ecology and reproductive biology.

feeding ecology and diet

Filter-feeder, like all other sponges.

reproductive biology

Viviparous. White oval larvae are produced from July to November. Asexual reproduction occurs occasionally by means of gemmules attached to the base of the stalk.

conservation status

Not threatened.

significance to humans

An elegant, attractive sponge; as such, a pleasure for snorklers and divers to collect.

Barrel sponge

Xestospongia testudinaria

order

Haplusclenda

family

Petrosiidae

taxonomy

Xestospongia testudinaria Lamarck, 1815, Cape Denison, Queensland, Australia.

other common names

English: Great vase sponge, volcano sponge; German: Grosser Vasenschwamm.

physical characteristics

A large erect reddish brown, barrel- or cup-shaped, thick-walled sponge as much as 4.92 ft (1.5 m) high, with prominent ridges or knobs at the surface. The upper edge of the cup is irregularly indented; the cup itself forms a conspicuous central cavity occupying as much as a third of the total height of the sponge. The sponge is firm and slightly compressible in consistency.

distribution

Western and Central Indian Ocean, Indo-Malesia, northeastern Australia, New Caledonia.

habitat

Reefs and lagoons, on rock or dead coral substrates.

behavior

Little is known besides feeding ecology and reproductive biology.

feeding ecology and diet

Filter-feeder like all other sponges.

reproductive biology

Individual sponges are of separate sexes. Mass release of the gametes takes place in September ('smoking' sponges), after which fertilization occurs in the sea water.

conservation status

Not threatened.

significance to humans

A pleasure for snorklers and divers to find or collect.

Stove-pipe sponge

Aplysina archeri

order

Verongida

family

Aplysinidae

taxonomy

Aplysina archeri Higgin, 1875, Yucatán, Mexico.

other common names

Italian: Spugna a tuba di stufa.

physical characteristics

Large pink or purplish gray tubes, growing in groups of several isolated tubes arising from a common base, gradually tapering towards a terminal thick-walled vent. Individual tubes as large as 5 ft (1.5 m) high and 3 in (8 cm) thick. Surface finely conulose (cone-shaped), commonly with a pattern of rounded disc-shaped elevations.

distribution

Caribbean.

habitat

Grows in reef localities, 6.5-130 ft (2–40 m) in depth.

behavior

Little is known besides feeding ecology and reproductive biology.

feeding ecology and diet

Filter-feeder, like all other sponges.

reproductive biology

Oviparous, separate sexes, simultaneous spawning during a short period.

conservation status

Not threatened.

significance to humans

An attractive sponge to snorklers and divers.

Yellow boring sponge

Cliona celata

order

Hadromerida

family

Clionaidae

taxonomy

Cliona celata Grant, 1826, Firth of Forth, Scotland.

other common names

Spanish: Esponja perforadora

physical characteristics

An excavating, bright yellow sponge occurring in two different forms: a boring stage appearing as low, rounded papillae sticking out from such limestone substrates as calcareous rocks and shells; and a so-called gamma stage that consists of massive lobes as large as 3 ft (1 m) across and 20 in (50 cm) high. Lobes have raised rounded ridges and small round nodules spread over the surface.

distribution

Northeastern Atlantic from Norway south to the Gulf of Guinea; Mediterranean; eastern coast of North America from Newfoundland south to North Carolina.

habitat

Infralittoral zone, 0-650 ft (0–200 m).

behavior

Little is known besides feeding ecology and reproductive biology.

feeding ecology and diet

Filter feeder, like all other sponges.

reproductive biology

Hermaphroditic; oocytes and sperm develop between June and November. Occasionally reproduces by means of asexual buds.

conservation status

Not threatened.

significance to humans

A pest to oyster growers.

Bath sponge

Spongia officinalis

order

Dictyoceratida

family

Spongiidae

taxonomy

Spongia officinalis Linnaeus, 1759, Mediterranean.

other common names

German: Meerschwamm; Greek: Fino, Matapas; Italian: Spugna da bagno.

physical characteristics

Globular-massive sponges, usually over 4 in (10 cm) in diameter, varying in color from white to black depending on environmental circumstances, with a finely conulose (cone-shaped) surface and spongy-elastic consistency.

distribution

Atlantic coasts of Spain; Mediterranean.

habitat

On rocks and in caves from the shoreline to the edge of the continental shelf.

behavior

Little is known besides feeding ecology and reproductive biology.

feeding ecology and diet

Filter-feeder, like all other sponges.

reproductive biology

Viviparous; separate sexes. The parenchymellar larvae are large (to 500 µm) and elliptical in shape with short cilia over most of the body.

conservation status

As of 1986 populations declined as a result of an epidemic disease; protected under the Bern Convention 1998.

significance to humans

Regarded as the finest quality bath sponge in Europe.

No common name

Carteriospongia foliascens

order

Dictyoceratida

family

Thorectidae

taxonomy

Carteriospongia foliascens Pallas, 1766, India.

other common names

German: Blattschwamm.

physical characteristics

Lamellate (thinly layered) or foliose (leaflike) greyish-blue sponges, the surface heavily coated with foreign debris, with a characteristic pattern of mounds or ridges. Consistency coarse and flexible.

distribution

Indo-Pacific, Red Sea.

habitat

Shallow waters around reefs.

behavior

Little is known besides feeding ecology and reproductive biology.

feeding ecology and diet

Filter-feeder, like all other sponges.

reproductive biology

Viviparous.

conservation status

Not threatened.

significance to humans

Produces cytotoxic chemicals named sesterterpenoids with biomedical properties.

Carnivorous sponge

Asbestopluma hypogea

order

Poecilosclerida

family

Cladorhizidae

taxonomy

Asbestopluma hypogea Vacelet & Boury-Esnault, 1996, La Ciotat, Mediterranean.

other common names

French: Éponge carnivore.

physical characteristics

Small white sponge with an ovoid body as large as 0.25 in (6.5 mm) high and 0.04 in (1.2 mm) thick, attached to the substrate with a long, thin stalk up to 0.5 in (14 mm) long and .007 in (0.18 mm) in diameter. The body bears 30–60 filaments up to 2.3 in (60 mm) long and 50–80 µm in diameter. The filaments are sticky and shaggy because of their dense cover of tiny raised hook-shaped microscleres (anisochelae).

distribution

Known from two caves near Marseille, France, and one in La Croatia, (Mediterranean).

habitat

Rocky surfaces in caves where water is trapped all year long and thus has a constant low temperature of 55-58° F (13–14.7°C), 50-195 ft (15–60 m) away from the entrance, at a depth of 55-75 ft (17–23 m).

behavior

Their carnivorous feeding behavior makes these sponges unique.

feeding ecology and diet

These sponges have no aquiferous system or choanocyte chambers. Their diet consists of small crustaceans that they capture in their filaments. The prey is completely surrounded by new filaments and digested within a few days.

reproductive biology

Viviparous; however, little is known as of 2003 regarding the exact time of reproduction and structure of the embryos.

conservation status

Known only from La Ciotat; protected under the Bern Convention of 1998 due to its patrimonial interest.

significance to humans

None known.

Freshwater sponge

Spongilla lacustris

order

Haplusclenida

family

Spongillidae

taxonomy

Spongilla lacustris Linnaeus, 1759, Lake of Småland.

other common names

French: Éponge d'eau douce; German: Süsswasserschwamm.

physical characteristics

Encrusting, branched, arborescent or massive sponges with a fragile, soft consistency and whitish or green color, with irregularly scattered and inconspicuous oscula. Surface uneven and roughened by tiny spines. Gemmules subspherical to oval, occurring in dense clusters or irregularly scattered in the skeletal network.

distribution

Palaearctic.

habitat

In standing and running fresh water.

behavior

Little is known besides feeding ecology and reproductive biology.

feeding ecology and diet

Filter-feeder, like all other sponges.

reproductive biology

Overwinters as gemmules, the dormant stage. Viviparous, with sexual reproduction during the summer.

conservation status

Not threatened.

significance to humans

None known.

Resources

Books

Bergquist, Patricia R. Sponges. London: Hutchinson; Berkeley and Los Angeles: University of California Press, 1978.

Hooper, John N. A., and Rob W. M. van Soest, eds. Systema Porifera: A Guide to the Classification of Sponges. New York: Kluwer Academic/Plenum Publishers, 2002.

Hooper, John N. A., and Felix Wiedenmayer. "Porifera." In Zoological Catalogue of Australia. Vol. 12, edited by A. Wells. Melbourne, Australia: CSIRO, 1994.

Moss, David, and Graham Ackers, eds. The UCS Sponge Guide. Ross-on-Wye: The Underwater Conservation Society, 1982.

Other

van Soest, Rob W. M., Bernard Picton, and Christine Morrow. Sponges of the North East Atlantic. [CD-ROM] World Biodiversity Database CD-ROM Series. Windows version 1.0. Amsterdam: Biodiversity Center of ETI, Multimedia Interactive Software, 2000.

Wallie H. de Weerdt, PhD