Phylum Porifera Overview

Phylum Porifera

• Porifera is the phylum of sponges
• Sponges are multicellular animals
• They are asymmetrical mostly but some have a distinct apical-basal polarity
• Larvae are usually anterior-posterior
• Cells have adherens junctions, no gap junctions
• Suspension feeders
• Water is drawn through canals and chambers by choanocytes
• Adults are sessile (sedentary)
• Larval stages are usually motile and lecithotrophic
• The middle layer is variable, includes motile cells, and often skeletal material
• Skeletal elements can be calcium carbonate and/or silicon dioxide (spicules), or collagen fibers ("spongin")
• Neurons are absent
• Osculum is the only true sense organ, detects water flow rate
• Some larvae have biciliated cells (possible defective cell division product).

Sponge Structure

• Aquiferous system powered by choanocytes
• This system is for feeding, gas exchange, and waste expulsion
• Pinacoderm (outer surface of the sponge) is made of pinacocytes
• Mesohyl is between the dermal layers and may contain spicules, amebocytes, etc.
• Choanoderm is an inner layer of choanocytes creating water currents.
• Osculum - the opening

Sponge Body Forms

• Ascon, sycon, and leucon are differing body forms in sponges
• Ascon has simple/tubular body plan
• Sycon has a more complex body plan with multiple channels
• Leucon has the most complex structure with folded chambers.

Skeletal Support

• Sponges can be supported by spicules or collagen
• Spicules can be siliceous or calcium carbonate
• "Spongin" is a unique type of collagen
• Spicule composition and shape are crucial for classifying sponge species.

Spicule Diversity

• Spicules come in a variety of shapes and sizes
• They are made of silica (or glass) and/or calcium carbonate.

Cell Type Flexibility in Sponges

• Choanocytes, archaeocytes, and pinacocytes can transform into each other
• Flexibility allows for regeneration

Sponge Regeneration

• Sponges have a strong regenerative capacity

Sponge Feeding

• Most sponges are filter feeders

Sponge Predation

• Some sponges are predatory

Sponge Location

• Some sponges live in trees
• Many sponges are aquatic

Sponge Role in Trophic Levels

• Sponges play a role in cycling organic matter to higher trophic levels

Sponge Defenses

• Sponges have mechanical defenses (spicules) and chemical defenses.
• Some compounds in sponges have medicinal properties.

Sponge Reproduction

• Sponges can reproduce asexually (fragmentation)
• They can reproduce sexually via external fertilization (release of sperm and egg into the water) and oviparity (egg develops outside the sponge). Other sponges have internal fertilization and viviparity.

Diversity of Developmental and Larval Forms

• Sponge larval forms have different developmental patterns.
• These developmental patterns are not always homologous to other animal groups.
• Some developmental processes in sponges are controversial.

Phylogeny of Sponges

• The evolutionary relationships among sponge classes (Hexactinellida, Demospongiae, Homoscleromorpha, Calcarea) is shown via a branching diagram.
• There may be simplification in the phylogenetic relationships.

Class Hexactinellida

• Spicules are composed of silica (glass), six-rayed, and often fused into a lattice or cup shape.
• Found in deep water.

Class Demospongiae

• Over 80% of extant sponges.
• Usually vibrant colors (due to the presence of pigments)
• Skeletons include spicules, spongin, or both.
• May have a leucon body form.
• Can be up to 1m in height and diameter.

Class Homoscleromorpha

• Anatomically simple, often encrusting or forming leuconoid bodies.
• Spicules are small, simple, or absent.
• Found in shallow to deep waters.

Class Calcarea

• Spicules are composed of calcium carbonate.
• Spicules typically have three or four rays.
• Found in both leucon, sycon, and ascon body forms.
• All marine.

Glass Sponge - Shrimp Symbiosis

• Glass sponges harbor shrimp in symbiosis.
• Shrimp are too large to leave once the symbiosis has been established.

Explore the fascinating world of Phylum Porifera, the sponges known for their unique characteristics and structures. This quiz covers the anatomy, feeding mechanisms, and reproductive traits of sponges. Test your knowledge of these simple yet essential multicellular animals.