Porifera

Outlines

SPONGES (PORIFERA)

Phylum Porifera

Class Calcarea
- Subclass Calcinia
- Subclass Calcaronia
- Subclass Pharetronidia
- Subclass Sphinctozoa
Class Hexactinellida [some have argued that this should be a separate phylum, "Symplasma"]
- Subclass Amphidiscophora
- Subclass Hexasterophora
Class Demospongiae
- Subclass Homoscleromorpha
- Subclass Tetractinomorpha
- Subclass Ceractinomorpha
Class Sclerospongiae [recently abandoned. Members to Calcarea and Demospongiae]

PHYLUM PORIFERA

Body Plan

Amorphous or radially symmetrical. Cellular level (parazoan). Basically two cellular layers: pinacoderm and choanoderm, with gelatinous fill (mesohyl) having a variety of cells in it: spicule-secreting (collenocytes, lophocytes, spongocytes, and sclerocytes), contractile (myocytes), and motile stem cells (archeocytes [also involved in food transport]; cellular totipotency, especially in archeocytes, is unique to poriferans).

Locomotion

None, except in larval forms. Some contractile properties of myocytes on ostia and osculum

Feeding and Digestion

Filter feeding by choanocytes using aquiferous system (channels and choanocytes; unique to poriferans). Digestion is intracellular (protozoan origin?). Archeocytes are involved in transport.

Sense Organs

None known, but sponges do respond to chemical and physical stimuli by altering water flow rate and direction, secreting chemicals, altering sex and reproductive condition, etc.

Nervous System

None known, but stimuli are propagated, though slowly (about 0.17 to 0.3cm/sec)

Respiration and gas exchange

Cellular. Uses simple diffusion. Aqueferous system ensures that no cell need be more than 1 mm fro the water surface.

Circulation

No organized system, though archeocytes act as food transport

Osmoregulation

No organized system. Marine sponges are osmoconformers; freshwater sponges use contractile-vacuole-like system (protozoan origin?)

Reproduction

Quite variable among species. Asexual (budding, gemmules) and sexual (most hermaphroditic sponges show protandry or protogyny, but some are permanently hermaphroditic. Some species are monoecious. All seem to use cross-fertilization, though some self-fertilization may be use.

Body Plan	Amorphous or radially symmetrical. Cellular level (parazoan). Basically two cellular layers: pinacoderm and choanoderm, with gelatinous fill (mesohyl) having a variety of cells in it: spicule-secreting (collenocytes, lophocytes, spongocytes, and sclerocytes), contractile (myocytes), and motile stem cells (archeocytes [also involved in food transport]; cellular totipotency, especially in archeocytes, is unique to poriferans).
Locomotion	None, except in larval forms. Some contractile properties of myocytes on ostia and osculum
Feeding and Digestion	Filter feeding by choanocytes using aquiferous system (channels and choanocytes; unique to poriferans). Digestion is intracellular (protozoan origin?). Archeocytes are involved in transport.
Sense Organs	None known, but sponges do respond to chemical and physical stimuli by altering water flow rate and direction, secreting chemicals, altering sex and reproductive condition, etc.
Nervous System	None known, but stimuli are propagated, though slowly (about 0.17 to 0.3cm/sec)
Respiration and gas exchange	Cellular. Uses simple diffusion. Aqueferous system ensures that no cell need be more than 1 mm fro the water surface.
Circulation	No organized system, though archeocytes act as food transport
Osmoregulation	No organized system. Marine sponges are osmoconformers; freshwater sponges use contractile-vacuole-like system (protozoan origin?)
Reproduction	Quite variable among species. Asexual (budding, gemmules) and sexual (most hermaphroditic sponges show protandry or protogyny, but some are permanently hermaphroditic. Some species are monoecious. All seem to use cross-fertilization, though some self-fertilization may be use.