''Lytechinus pictus'', commonly known as the painted urchin, is a

sea urchin Sea urchins () are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin live on the seabed of every ocean and inhabit every depth zone from the intertidal seashore down to . The spherical, hard shells (tests) of ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Toxopneustidae Toxopneustidae is a family of globular sea urchins in the class Echinoidea. Characteristics All Camarodonts have imperforate tubercles and compound ambulacral plates. In addition, the Toxopneustids are characterised by the peristome, or opening ...

. It occurs on shallow reefs in the tropical and subtropical eastern Pacific Ocean, off the coasts of California, Central America and South America as far south as Ecuador.

Taxonomy

This sea urchin was first described in 1867 by the American zoologist

Addison Emery Verrill Addison Emery Verrill (February 9, 1839 – December 10, 1926) was an American invertebrate zoologist, museum curator and university professor. Life Verrill was born on February 9, 1839 in Greenwood, Maine, the son of George Washington Verrill a ...

who gave it the name ''Psammechinus pictus''. It was later transferred to the genus ''

Lytechinus ''Lytechinus'' is a genus of sea urchins. Species The following extant species are listed in this genus by the World Register of Marine Species:

'' and became ''Lytechinus pictus''. In 1912, another species ''Lytechinus anamesus'' was described by American zoologist

Hubert Lyman Clark Hubert Lyman Clark (January 9, 1870 – July 31, 1947) was an American zoologist. The son of Professor William Smith Clark, he was born at Amherst, Massachusetts, and educated at Amherst College and Johns Hopkins University. From 1899 to 1905 h ...

as ''Lytechinus anamesus''. He was the curator of echinoderms at the

Museum of Comparative Zoology A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make these ...

Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of higher le ...

at the time. It had long been suspected that ''L. pictus'' and ''L. anamesus'' were

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

ous, and this was confirmed by analysis of

mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

in 2004.

Description

The

test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film), ...

of this sea urchin is up to in diameter. The general colour is greyish or pale straw brown, sometimes with a pinkish flush. The spines are robust, short and blunt, the basal half of each spine usually being white while the rest of the spine varies in colour. Juvenile urchins sometimes have banded spines.

Distribution and habitat

''L. pictus'' is found in the tropical and subtropical eastern Pacific Ocean at depths down to about . Its range extends from central California southwards to Ecuador. In California it tends to inhabit the middle and lower intertidal zone but in the northern part of the

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja Ca ...

it mainly inhabits the

subtidal zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

. These sea urchins tend to form dense aggregations at the edge of, or inside, the

kelp bed 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 Ea ...

s that line this coast. At San Onofre, California in 1978–79, the density of individuals close to the kelp beds was recorded at 80 per square metre while inside the kelp bed it was 40. At Anacapa Island, California, the highest densities (36 per sq.m.) were found in barren areas with

coralline algae Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of re ...

near the kelp beds.

Ecology

This sea urchin tends to be more active at night. During the day it may semi-bury itself in sand, and it sometimes disguises itself with fragments of shell and gravel held in place by its

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on britt ...

. It feeds on kelp, particularly ''

Macrocystis ''Macrocystis'' is a monospecific genus of kelp (large brown algae). This genus contains the largest of all the phaeophyceae or brown algae. ''Macrocystis'' has pneumatocysts at the base of its blades. Sporophytes are perennial and the indiv ...

'', '' Gigartina'' and ''

Laminaria ''Laminaria'' is a genus of brown seaweed in the order Laminariales (kelp), comprising 31 species native to the north Atlantic and northern Pacific Oceans. This economically important genus is characterized by long, leathery laminae and relativ ...

'', but primarily grazes on young stages rather than fully-grown fronds. In the California

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 Ea ...

s, the painted urchin is preyed on by the

bat star ''Patiria miniata'', the bat star, sea bat, webbed star, or broad-disk star, is a species of sea star (also called a starfish) in the family Asterinidae. It typically has five arms, with the center disk of the animal being much wider than the stu ...

(''Patiria miniata'').

References

{{Taxonbar, from=Q2090126 Lytechinus Fauna of the Pacific Ocean Animals described in 1867 Taxa named by Addison Emery Verrill