The following points highlight the eleven representative types of Sponges. The types are: 1. Euplectella 2. Hyalonema 3. Pheronema 4. Oscarella 5. Cliona 6. Tethya 7. Halichondria 8. Spongilla 9. Chalina 10. Euspongia 11. Hippospongia.
Type # 1. Euplectella:
Euplectella aspergillum (Fig. 27.1) is commonly known as Venus’ flower basket. It is a glass sponge. The body is cylindrical and curved with thin walls, the upper end is closed by an oscular sieve formed of fused spicules, and the lower end has anchoring siliceous root spicules, inside is a spongocoel.
There is no epidermis of pinacocytes. Encircling the cylinder are projecting ledges of spicules, with many openings or parietal gaps in the meshwork of spicules, they connect with the spongocoel but are not a part of the canal system. Flagellated chambers lie radially in the sponge wall.
Skeleton is made of four and six- rayed siliceous spicules bound together by siliceous cement so that they form a network of great complexity, but the canal system is of the simple sycon type.
In the spongocoel very often a pair of Crustacea called Spongicola venusta live in commensal relationship feeding on plankton brought in with the water current. Euplectella is found attached by its siliceous roots to the bottom of deep sea near the Philippine Is., its curved structure is an adaptation to the slow, constant water current at great depth of the sea.
Type # 2. Hyalonema:
Hyalonema (Fig. 27.2) is commonly known as glass-rope sponge, is marine and is about 38 cm long. The body is rounded or oval, below which a bundle of long spicules projects as a root tuft which is often spirally twisted, the root tuft looks like a stalk.
The bundle of spicules also forms an axis as columella which passes through the body, the spicules are bound together by siliceous cement. Regularly growing in symbiotic relationship with Hyalonema are several polyps of a Zoanthid Palythoa or of Epizoanthus, an anemone.
Type # 3. Pheronema:
Pheronema (Fig. 27.3) has a cup or bowl- shaped thick-walled body with lateral pleural prostals and long twisted root tufts.
The spongocoel opens to the exterior at the summit by an osculum which is surrounded by spicules known as marginal prostals. Skeleton consists of siliceous glassy spicules and amphidiscs. They are attached to the muddy bottom of the sea by spirally twisted long root tufts of spicules. Pheronema is found in deep sea in the muddy bottom.
Type # 4. Oscarella:
Oscarella (Fig. 27.4) is a brightly coloured,small low encrusting sponge with the lobulated upper surface.
The basal part of the sponge is filled with eggs and embryos and the peripheral part encloses the canal system. Each lobe or fold encloses an ex-current canal surrounded by flagellated chambers. The incurrent canals are situated in depressions between the lobes of the body. Canal system leuconoid type. Skeleton entirely absent.
Type # 5. Cliona:
Cliona (Fig. 27.5), the boring sponge is found inhabiting the interior of coral skeletons, mollusc shells and other calcareous objects. It is a sulphur-yellow or green coloured sponge with small elevations on the surface, the skeleton is made of spongin fibres and siliceous spicules; it has the leucon type of canal system.
It secretes droplets of an acid which dissolves and bores channels into rocks or shells of living or dead molluscs, honeycombing and destroying them, then it grows into the channels and also over them forming a mass 15 to 20 cm in diameter. Boring is begun by the larva. It is cosmopolitan in all seas especially along the Atlantic coast.
Type # 6. Tethya:
Tethya (Fig. 27.6) is somewhat spherical in shape having a characteristic tuberculate surface. Skeleton consists of radiating bundles of monaxon spicules and asters. Spongin fibres are entirely absent.
Type # 7. Halichondria:
Halichondria (Fig. 27.7) has flattened elongated tubular growths opening by high delicate oscula. The sponge is soft and brownish yellow in colour. Skeleton consists of oxeas of various sizes. Halichondria is popularly known as Crumb of bread sponge. It occurs in shallow and deep waters of sea and worldwide in distribution.
Type # 8. Spongilla:
Spongilla (Fig. 27.8) is probably the best known of freshwater sponges. It is found in ponds, lakes and slow streams growing on submerged sticks and plants.
The colony of Spongilla is profusely branched exhibiting various shades of green colour due to the presence of Zoochlorellae, a green alga in the tissues. The body wall consists of very thin dermal membrane provided with dermal pores and several oscula. The canal system is rhagon type.
Skeleton consists of siliceous spicules in the form of network of smooth or spiny large and small oxeas embedded in the spongin. Reproduction both asexual and sexual. Asexual reproduction by gemmules. Sexual reproduction by way of unusual free swimming larva which is characteristic of Spongilla.
Type # 9. Chalina:
Chalina (Fig. 27.9) is popularly known as “dead man’s finger”, because it is shaped like a hand with many fingers. Each branch or finger-like structure is perforated by numerous oscula.
Skeleton comprises spongin fibres in which siliceous spicules are embedded. Reproduction both asexual and sexual. Asexual by regeneration and budding. Sexual by producing free swimming larva. The sponge is orange or red, yellowish brown in colour, is found in deep waters from Rhode Island to Labrador. It is not found in shallow waters except when it is broken from its stalk and washed ashore.
Type # 10. Euspongia:
Euspongia (Fig. 27.10) is the common bath sponge. Body is rounded and large, it is of light brown colour. There are many large and small oscula.
The body has a large number of small projections called conuli, which are due to strands of spongin fibres.
Inside the sponge are numerous inhalant canals, flagellated chambers and exhalant canals and spaces. The skeleton is made of spongin fibres only which form a network, the thickest fibres run radially and each ends in a conulus. Euspongia is regarded as a colony, but the individuals of the colony are unrecognisable. Sexes are separate but male colonies are rare.
The cleaned spongin skeleton of Euspongia is used as commercial bath sponge. E. officinalis is found in the Mediterranean, West Indies and Australia up to a depth of 180 metres. E. mollisima is the most valuable bath sponge, it is cup-shaped, light yellow, and found near Asia Minor.
Type # 11. Hippospongia:
Hippospongia (Fig. 27.11), the commercial horse sponge is a typical horny sponge, occurs in Florida on rocky bottoms at depths up to 10-15 metres. A single sponge is made up of few to many individuals provided with few to large number of oscula. The body of the sponge is covered by a dark thin membrane provided with numerous flagellated chambers internally.
Skeleton consists of spongin fibres without spicules forming an irregular network. Canal system is leuconoid type with aphodal chambers. Hippospongia carries small crustaceans and worms in its large cavities. The sponge may live up to 50 years and grows extremely large and massive.