Gnorimosphaeroma oregonensis
Encyclopedia
Gnorimosphaeroma oregonensis, the Oregon pill bug, is a small intertidal macroinvertebrate isopod crustacean
.
, which is roughly uniform in colour except for a thin band that extends from the head
to the end of the organism, and progresses from dark grey to light grey respectively. At the head, G. oregonensis possesses antennae
, a mouth (for feeding), and eyes, and its body is lined with seven pairs of small legs
, used for crawling when the organism is young, and for swimming
later in life. Gill
s are located on the animal's belly, and are the mechanism by which the animal breathes.
of G. oregonensis is the mid-California
n to Alaska
n coast, where it inhabits tidal pools and the intertidal region up to depths of 24 metres (78.7 ft). They live in very large and frequent families, with dozens or even hundreds being found per tenth of a metre in places where they are most abundant, such as the San Francisco Bay
, where they are the most common isopod found. Their substrates
of choice are gravel
, sand
, and loose rocks on rocky beaches in the aforementioned areas, although they can also be found living amongst algae
.
that G. oregonensis is commonly found in ranges from 9 to 31‰, which is a relatively wide range, although they prefer areas of lower salinity. Osmoregulation
in G. oregonensis is primarily dependent on where the population
originated, and the organism is very proficient in adapting to changes in salinity, temperature
, and humidity
, meaning in can withstand fairly large ranges of all three of these factors. G. oregonensis also has the ability to tolerate relatively low levels of oxygen
, which is common to polluted
water. Competition with other marine isopods and crustacean
s, as well as mussel
s and barnacle
s, is a biotic
factor that limits the range of G. oregonensis, but its aforementioned abilities to withstand many changes in its environment
as well as to survive in polluted water make it a fairly successful competitor.
of pond
s and stream
s. G. oregonensis is therefore a primarily a detrivore, although it also feeds on diatom
s and the eggs
of other organisms. It generally prefers a herbivorous
diet. G. oregonensis is preyed on by a wide variety of consumer species, including other isopods and invertebrate
s, as well as many species of fish
.
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
.
Description
It is an oval-shaped organism roughly 6 mm in length, and about twice as long as it is wide. G. oregonensis is covered in a grey-coloured rigid shellExoskeleton
An exoskeleton is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. In popular usage, some of the larger kinds of exoskeletons are known as "shells". Examples of exoskeleton animals include insects such as grasshoppers...
, which is roughly uniform in colour except for a thin band that extends from the head
Head
In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....
to the end of the organism, and progresses from dark grey to light grey respectively. At the head, G. oregonensis possesses antennae
Antenna (biology)
Antennae in biology have historically been paired appendages used for sensing in arthropods. More recently, the term has also been applied to cilium structures present in most cell types of eukaryotes....
, a mouth (for feeding), and eyes, and its body is lined with seven pairs of small legs
Arthropod leg
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa , trochanter , femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus ,...
, used for crawling when the organism is young, and for swimming
Aquatic locomotion
Swimming is biologically propelled motion through a liquid medium. Swimming has evolved a number of times in a range of organisms ranging from arthropods to fish to molluscs.-Evolution of swimming:...
later in life. 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 are located on the animal's belly, and are the mechanism by which the animal breathes.
Habitat
The primary habitatHabitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
of G. oregonensis is the mid-California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
n to Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
n coast, where it inhabits tidal pools and the intertidal region up to depths of 24 metres (78.7 ft). They live in very large and frequent families, with dozens or even hundreds being found per tenth of a metre in places where they are most abundant, such as the San Francisco Bay
San Francisco Bay
San Francisco Bay is a shallow, productive estuary through which water draining from approximately forty percent of California, flowing in the Sacramento and San Joaquin rivers from the Sierra Nevada mountains, enters the Pacific Ocean...
, where they are the most common isopod found. Their substrates
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...
of choice are gravel
Gravel
Gravel is composed of unconsolidated rock fragments that have a general particle size range and include size classes from granule- to boulder-sized fragments. Gravel can be sub-categorized into granule and cobble...
, sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
, and loose rocks on rocky beaches in the aforementioned areas, although they can also be found living amongst algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
.
Tolerance of abiotic factors
The salinitySalinity
Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...
that G. oregonensis is commonly found in ranges from 9 to 31‰, which is a relatively wide range, although they prefer areas of lower salinity. Osmoregulation
Osmoregulation
Osmoregulation is the active regulation of the osmotic pressure of an organism's fluids to maintain the homeostasis of the organism's water content; that is it keeps the organism's fluids from becoming too diluted or too concentrated. Osmotic pressure is a measure of the tendency of water to move...
in G. oregonensis is primarily dependent on where the population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
originated, and the organism is very proficient in adapting to changes in salinity, temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
, and humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
, meaning in can withstand fairly large ranges of all three of these factors. G. oregonensis also has the ability to tolerate relatively low levels of oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, which is common to polluted
Pollution
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms. Pollution can take the form of chemical substances or energy, such as noise, heat or light...
water. Competition with other marine isopods and crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s, as well as 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 and barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s, is a biotic
Biotic component
Biotic components are the living things that shape an ecosystem. A biotic factor is any living component that affects another organism, including animals that consume the organism in question, and the living food that the organism consumes. Each biotic factor needs energy to do work and food for...
factor that limits the range of G. oregonensis, but its aforementioned abilities to withstand many changes in its environment
Natural environment
The natural environment encompasses all living and non-living things occurring naturally on Earth or some region thereof. It is an environment that encompasses the interaction of all living species....
as well as to survive in polluted water make it a fairly successful competitor.
Feeding
Other than for transport, G. oregonensis uses its legs for scavenging dead organic material from the substratesSubstrate (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...
of pond
Pond
A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake. A wide variety of man-made bodies of water are classified as ponds, including water gardens, water features and koi ponds; all designed for aesthetic ornamentation as landscape or architectural...
s and stream
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
s. G. oregonensis is therefore a primarily a detrivore, although it also feeds on diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s and the eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
of other organisms. It generally prefers a herbivorous
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
diet. G. oregonensis is preyed on by a wide variety of consumer species, including other isopods and invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s, as well as many species of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
.