Pseudofeces
Encyclopedia
Pseudofeces or pseudofaeces are a way that filter-feeding bivalve mollusks (and filter-feeding gastropod mollusks) get rid of suspended particles which have been rejected as unsuitable for food. The rejected particles are wrapped in mucus
, and are expelled without having passed through the digestive tract
. Thus although they may closely resemble the mollusk's real feces they are not actually feces, hence the name pseudofeces, meaning false feces.
Bivalves which exhibit this behavior are numerous and include Ostreidae
oyster
s (such as Crassostrea
) and Dreissenidae
false mussel
s (such as Dreissena
). Gastropods which filter feed are in a minority, but include the mudsnail genus Batillaria
http://www.springerlink.com/content/dj5t0t09hwy3ww4w/ and deep sea vent
limpets in the family Lepetodrilidae
http://www.biolbull.org/cgi/content/full/210/2/140.
Bivalves have two siphons or apertures at the posterior edge of their mantle cavity: an inhalant or incurrent siphon, and an exhalant or excurrent siphon or aperture. The water is circulated by the action of the gill
s. Usually water enters the mantle cavity through the inhalent siphon, moves over the gills, and leaves through the exhalent siphon. The water current is utilized for respiration, but also for feeding, and for reproduction. The mouth of the bivalve is situated anterior to the gills. The bivalve needs phytoplankton
as its food source, but the water circulating through the bivalve also usually contains other particles such as small grains of sand, detritus
, etc.
After moving over the gill margins, particles reach the mouth of the bivalve. Each side of the mouth of the bivalve has an inner and an outer appendage called a palp
. The outer palp has a long extensible proboscis
, which collects incoming particulate matter
. The particles are then sorted by both the inner and outer palps, which have ciliate
d grooves for collecting organic material. These food grooves sort the particles by both density and size. The inner pair of palps transfers smaller and lighter particles, such as phytoplankton
, to the mouth, using ciliary currents. Some material is rejected because it is too large or too dense: this is often pieces of sediment or detritus, but also includes some overly large edible particles. The outer palps send this rejected material into the mantle cavity as a mucus-bound mass. These mucus-bound masses are the pseudofeces.
Pseudofeces accumulate with, and look much like, the actual feces in the bottom of the mantle cavity. The unwanted material is periodically ejected (usually through the inhalant siphon or aperture) by contractions of the adductor muscles, which "clap" the shells together, pushing most of the water out of the mantle cavity and forcibly ejecting both the feces and the pseudofeces.
Plankton
ic food is not usually in short supply, and therefore accidentally rejecting a few larger edible particles along with the larger or denser inedible ones is a small price to pay in order to optimize the processing of the rest of the food.
Land runoff containing particulate
pollutants and excess nutrients can cause problems in estuaries
and coastal waters. Bivalves can filter the particulate pollutants, and either eat them or discharge them as pseudofeces deposits onto the substrate
, where they are relatively harmless. Chesapeake Bay's
once-flourishing oyster populations historically filtered the estuary's entire water volume of excess nutrients every three or four days.
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
, and are expelled without having passed through the digestive tract
Digestive system of gastropods
The digestive system of gastropods has evolved to suit almost every kind of diet and feeding behavior. Gastropods as the largest taxonomic class of the mollusca are very diverse indeed: the group includes carnivores, herbivores, scavengers, filter feeders, and even parasites.In particular, the...
. Thus although they may closely resemble the mollusk's real feces they are not actually feces, hence the name pseudofeces, meaning false feces.
Bivalves which exhibit this behavior are numerous and include Ostreidae
Ostreidae
Ostreidae are the true oysters, and include most species that are commonly eaten under the name oyster. Pearl oysters are not true oysters and belong to the distinct order Pterioida....
oyster
Oyster
The word oyster is used as a common name for a number of distinct groups of bivalve molluscs which live in marine or brackish habitats. The valves are highly calcified....
s (such as Crassostrea
Crassostrea
Crassostrea is a genus of true oysters containing the most important oysters used for food.- Species :* Crassostrea ** †Crassostrea alabamiensis...
) and Dreissenidae
Dreissenidae
The Dreissenidae are a family of small freshwater mussels, aquatic bivalve mollusks. They attach themselves to stones or to any other hard surface using a byssus.-Genera:Genera within the family Dreissenidae include:* Congeria...
false mussel
Mussel
The common name mussel is used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.The...
s (such as Dreissena
Dreissena
Dreissena is a genus of small freshwater mussels in the family Dreissenidae.-Species:* Dreissena polymorpha, the zebra mussel** Dreissena polymorpha polymorpha** Dreissena polymorpha andrusovi* Dreissena bugensis, the quagga mussel...
). Gastropods which filter feed are in a minority, but include the mudsnail genus Batillaria
Batillaria
Batillaria is a genus of small salt marsh or mudflat snails, marine gastropod mollusks in the family Batillariidae, the horn snails.-Species:Species within the genus Batillaria include:* Batillaria attramentaria Batillaria is a genus of small salt marsh or mudflat snails, marine gastropod mollusks...
http://www.springerlink.com/content/dj5t0t09hwy3ww4w/ and deep sea vent
Hydrothermal vent
A hydrothermal vent is a fissure in a planet's surface from which geothermally heated water issues. Hydrothermal vents are commonly found near volcanically active places, areas where tectonic plates are moving apart, ocean basins, and hotspots. Hydrothermal vents exist because the earth is both...
limpets in the family Lepetodrilidae
Lepetodrilidae
Lepetodrilidae is a family of gastropods in the clade Vetigastropoda .This family has no subfamilies.- Genera :Genera within the family Lepetodrilidae include:* Lepetodrilus...
http://www.biolbull.org/cgi/content/full/210/2/140.
Bivalves have two siphons or apertures at the posterior edge of their mantle cavity: an inhalant or incurrent siphon, and an exhalant or excurrent siphon or aperture. The water is circulated by the action of the gill
Gill
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water, afterward excreting carbon dioxide. The gills of some species such as hermit crabs have adapted to allow respiration on land provided they are kept moist...
s. Usually water enters the mantle cavity through the inhalent siphon, moves over the gills, and leaves through the exhalent siphon. The water current is utilized for respiration, but also for feeding, and for reproduction. The mouth of the bivalve is situated anterior to the gills. The bivalve needs phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
as its food source, but the water circulating through the bivalve also usually contains other particles such as small grains of sand, detritus
Detritus
Detritus is a biological term used to describe dead or waste organic material.Detritus may also refer to:* Detritus , a geological term used to describe the particles of rock produced by weathering...
, etc.
After moving over the gill margins, particles reach the mouth of the bivalve. Each side of the mouth of the bivalve has an inner and an outer appendage called a palp
Pedipalp
Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...
. The outer palp has a long extensible proboscis
Proboscis
A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...
, which collects incoming particulate matter
Particle (ecology)
In marine and freshwater ecology, a particle is a small object. Particles can remain in suspension in the ocean or freshwater, however they eventually settle and accumulate as sediment. Some can enter the atmosphere through wave action where they can act as cloud condensation nuclei...
. The particles are then sorted by both the inner and outer palps, which have ciliate
Ciliate
The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagella but typically shorter and present in much larger numbers with a different undulating pattern than flagella...
d grooves for collecting organic material. These food grooves sort the particles by both density and size. The inner pair of palps transfers smaller and lighter particles, such as phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
, to the mouth, using ciliary currents. Some material is rejected because it is too large or too dense: this is often pieces of sediment or detritus, but also includes some overly large edible particles. The outer palps send this rejected material into the mantle cavity as a mucus-bound mass. These mucus-bound masses are the pseudofeces.
Pseudofeces accumulate with, and look much like, the actual feces in the bottom of the mantle cavity. The unwanted material is periodically ejected (usually through the inhalant siphon or aperture) by contractions of the adductor muscles, which "clap" the shells together, pushing most of the water out of the mantle cavity and forcibly ejecting both the feces and the pseudofeces.
Plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
ic food is not usually in short supply, and therefore accidentally rejecting a few larger edible particles along with the larger or denser inedible ones is a small price to pay in order to optimize the processing of the rest of the food.
Land runoff containing particulate
Particle (ecology)
In marine and freshwater ecology, a particle is a small object. Particles can remain in suspension in the ocean or freshwater, however they eventually settle and accumulate as sediment. Some can enter the atmosphere through wave action where they can act as cloud condensation nuclei...
pollutants and excess nutrients can cause problems in estuaries
Estuary
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....
and coastal waters. Bivalves can filter the particulate pollutants, and either eat them or discharge them as pseudofeces deposits onto the substrate
Substrate (biology)
In biology a substrate is the surface a plant or animal lives upon and grows on. A substrate can include biotic or abiotic materials and animals. For example, encrusting algae that lives on a rock can be substrate for another animal that lives on top of the algae. See also substrate .-External...
, where they are relatively harmless. Chesapeake Bay's
Chesapeake Bay
The Chesapeake Bay is the largest estuary in the United States. It lies off the Atlantic Ocean, surrounded by Maryland and Virginia. The Chesapeake Bay's drainage basin covers in the District of Columbia and parts of six states: New York, Pennsylvania, Delaware, Maryland, Virginia, and West...
once-flourishing oyster populations historically filtered the estuary's entire water volume of excess nutrients every three or four days.
