''Strongylocentrotus purpuratus'' is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

of sea urchin in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Strongylocentrotidae commonly known as the purple sea urchin. It lives along the eastern edge of the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

extending from Ensenada,

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

, to

British Columbia British Columbia is the westernmost Provinces and territories of Canada, province of Canada. Situated in the Pacific Northwest between the Pacific Ocean and the Rocky Mountains, the province has a diverse geography, with rugged landscapes that ...

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

. This

sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

species is deep purple in color, and lives in lower inter-tidal and nearshore sub-tidal communities. Its eggs are orange when secreted in water. January, February, and March function as the typical active reproductive months for the species. Sexual maturity is reached around two years. It normally grows to a diameter of about 10 cm (4 inches), consisting of an exoskeleton called a test. They may live as long as 70 years. ''Strongylocentrotus purpuratus'' is used as a

model organism A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workings of other organisms. Mo ...

and its

genome A genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding genes, other functional regions of the genome such as ...

was the first echinoderm genome to be sequenced.

Role in biomedical research

The initial discovery of three distinct eukaryotic DNA-dependent RNA polymerases was made using ''S. purpuratus'' as a model organism. While

embryonic development In developmental biology, animal embryonic development, also known as animal embryogenesis, is the developmental stage of an animal embryo. Embryonic development starts with the fertilization of an egg cell (ovum) by a sperm, sperm cell (spermat ...

is still a major part of the utilization of the sea urchin, studies on urchin's position as an evolutionary marvel have become increasingly frequent. Orthologs to human diseases have led scientists to investigate potential therapeutic uses for the sequences found in ''Strongylocentrotus purpuratus''. For instance, in 2012, scientists at the

University of St Andrews The University of St Andrews (, ; abbreviated as St And in post-nominals) is a public university in St Andrews, Scotland. It is the List of oldest universities in continuous operation, oldest of the four ancient universities of Scotland and, f ...

began investigating the "2A" viral region in the ''S. purpuratus'' genome which may be useful for

Alzheimer's disease Alzheimer's disease (AD) is a neurodegenerative disease and the cause of 60–70% of cases of dementia. The most common early symptom is difficulty in remembering recent events. As the disease advances, symptoms can include problems wit ...

and cancer research. The study identified a sequence that can return cells to a 'stem-cell' like state, allowing for better treatment options. The species has also been a candidate in longevity studies, particularly because of its ability to regenerate damaged or aging tissue. Another study comparing 'young' vs. 'old' suggested that even in species with varying lifespans, the 'regenerative potential' was upheld in older specimens as they suffered no significant disadvantages compared to younger ones.

Online model organism database

Echinobase is the model organism database for the purple sea urchin and a number of other echinoderms.

Genome

The genome of the purple sea urchin was completely sequenced and annotated in 2006 by teams of scientists from over 70 institutions including the Kerckhoff Marine Laboratory at the California Institute of Technology as well as the Human Genome Sequencing Center at the Baylor College of Medicine. A new improved version of the purple sea urchin genome, ''Strongylocentrotus purpuratus'' v5.0, is now available on Echinobase. ''S. purpuratus'' is one of several biomedical research model organisms in cell and developmental biology. The sea urchin is the first animal with a sequenced genome that (1) is a free-living, motile marine

invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...

; (2) has a bilaterally organized embryo but a radial adult body plan; (3) has the endoskeleton and water vascular system found only in

echinoderms An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as larv ...

; and (4) has a nonadaptive

immune system The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...

that is unique in the enormous complexity of its receptor repertoire. The sea urchin genome is estimated to encode about 23,500 genes. The ''S. purpuratus'' has 353 protein kinases, containing members of 97% of human kinase subfamilies. Many of these genes were previously thought to be vertebrate innovations or were only known from groups outside the deuterostomes. The team sequencing the species concluded that some genes are not

vertebrate Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

specific as thought previously, while other genes still were found in the urchin but not the chordate. The genome is largely non-redundant, making it very comparable to vertebrates, but without the complexity. For example, 200 to 700 chemosensory genes were found that lacked

intron An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word ''intron'' is derived from the term ''intragenic region'', i.e., a region inside a gene."The notion of the cistron .e., gen ...

s, a feature typical of vertebrates. Thus the sea urchin genome provides a comparison to our own and those of other deuterostomes, the larger group to which both

echinoderm An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as ...

s and humans belong. Sea urchins are also the closest living relative to chordates. Using the strictest measure, the purple sea urchin and humans share 7,700 genes. Many of these genes are involved in sensing the environment, a fact surprising for an animal lacking a head structure. The sea urchin also has a chemica
'defensome'
that reacts when stress is sensed to eliminate potentially toxic chemicals. ''S. purpuratus'''s immune systems contains innate pathogen receptors like

Toll-like receptor Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate immune system. They are single-pass membrane protein, single-spanning receptor (biochemistry), receptors usually expressed on sentinel cells such as macrophages ...

s and genes that encode for LRR . There were genes identified for Biomineralization that were not counterparts of the typical human vertebrate variet
SCCPs
and encode for

transmembrane A transmembrane protein is a type of integral membrane protein that spans the entirety of the cell membrane. Many transmembrane proteins function as gateways to permit the transport of specific substances across the membrane. They frequently u ...

proteins like P16. Many orthologs exist for genes associated with human diseases, such as Reelin (from Norman-Roberts lissencephaly syndrome) and many cytoskeletal proteins of the Usher syndrome network like usherin and VLGR1. Increasing carbon dioxide concentrations affect the epigenome,

gene expression Gene expression is the process (including its Regulation of gene expression, regulation) by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, proteins or non-coding RNA, ...

, and

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

of the purple sea urchin. Carbon dioxide concentration also reduces the size of its larvae, which indicates that fitness of the larvae could be negatively impacted.

Ecology

The purple sea urchin, along with sea otters and abalones, is a prominent member of the

kelp forest Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on E ...

community. The purple sea urchin also plays a key role in the disappearance of kelp forests that is currently occurring due to climate change; when urchins completely eliminate kelp from an area, an urchin barren results.

Use as food

Sea urchins like the purple sea urchin have been used for food by the

indigenous peoples of California Indigenous peoples of California, commonly known as Indigenous Californians or Native Californians, are a diverse group of nations and peoples that are indigenous to the geographic area within the current boundaries of California before and afte ...

, who ate the yellow egg mass raw. In California, the peak gonad growth season (and therefore peak of edibility) is September–October. Early in the season, the gonads are still growing and the yield will be smaller. From November onwards the gonads are developed, however harvesting stress can induce spawning, decreasing quality.

References

External links

''Strongylocentrotus purpuratus'' information

Echinoderm Genome Information Web System

The ''Strongylocentrotus purpuratus'' genome at the UCSC Genome Browser
* {{Authority control purpuratus Echinoderms described in 1857 Seafood in Native American cuisine Sea urchins as food