Phylum Porifera: Sponges

Polifera: Phylum of Sponges

• Polifera is a phylum of primitive invertebrate animals, commonly known as sponges.
• Sponges are multicellular organisms with a cellular grade of construction, lacking true tissues and organs.
• Their bodies are permeated by canals and chambers through which water flows.

Characteristics of Sponges

• Sponges are filter feeders, obtaining nutrients from the water that passes through their bodies.
• Sponges have four main classes, classified based on the presence or composition of their spicules and spongin, a fibrous protein.

Classes of Sponges

Calcarea (Calcareous Sponges)

• Have spicules made of calcium carbonate, the main component of seashells.
• Typically small and delicate, found in shallow marine waters.

Hexactinellida (Glass Sponges)

• Have a skeletal network of six-pointed spicules made of silica, the main component of glass.
• Found in deep, cold marine waters and can grow to be quite large.

Demospongiae (Demosponges)

• The largest and most diverse class of sponges, containing about 90% of all known sponge species.
• Can have spicules made of silica or spongin, or a combination of both.
• Found in a wide range of habitats, from freshwater to deep sea.

Homoscleromorpha (Encrusting Sponges)

• The rarest and most recently recognized class of sponges, with only about 117 known species.
• Have a simple body structure and lack spicules altogether.
• Found in marine waters, where they encrust on rocks and other hard surfaces.

Mollusca Phylum

• Mollusca is the second-largest phylum of invertebrate animals, after Arthropoda.
• Mollusks have a soft body, typically with a muscular foot for locomotion, a mantle that secretes a calcareous shell, and a visceral mass that contains internal organs.

Habitat and Diversity

• Mollusks can be found in various habitats, from the deepest ocean trenches to the tops of mountains.
• They play a crucial role in the marine ecosystem, including cleaning up the ocean floor and providing food for other animals.

Classes of Mollusks

• There are eight classes of mollusks, with one (Hyolitha) being extinct.

Aplacophora

• Worm-like, shell-less mollusks with a radula (a rasping tongue-like organ for feeding) but no tentacles.
• They live in deep ocean sediments and feed on microscopic organisms.

Monoplacophora

• Mollusks with a single, cap-like shell, thought to be related to an ancient group that gave rise to other mollusks.
• They live in deep ocean hydrothermal vents and cold seeps.

Polyplacophora (Chitons)

• Mollusks with a series of eight overlapping shell plates on their dorsal (back) side.
• They live in shallow marine waters and graze on algae.

Bivalvia (Bivalves)

• Mollusks with two hinged shells, including clams, oysters, mussels, scallops, and other shellfish.
• They live in marine, freshwater, and terrestrial habitats and feed on plankton or by filtering detritus from the water.

Gastropoda (Snails and Slugs)

• Largest and most diverse class of mollusks, including snails, slugs, limpets, sea slugs, and sea butterflies.
• They have a single, coiled shell that they can withdraw into for protection.
• They live in a wide variety of habitats, including marine, freshwater, and terrestrial environments.

Cephalopoda (Intelligent Invertebrates)

• Most intelligent and active invertebrates, including octopuses, squids, cuttlefish, and nautiluses.
• They have a well-developed nervous system and complex sense organs.
• They have no shell or a reduced internal shell and live in marine habitats as predators.

Scaphopoda (Tusk Shells)

• Foot-first burrowers with a long, pointed shell that is open at both ends.
• They live in marine sediments and feed on plankton and other small organisms that drift by.