California sea slug - AbsoluteAstronomy.com

The California sea hare also known as the California sea slug, scientific name Aplysia californica, is a species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

of sea slug

Slug

Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...

, specifically a sea hare

Sea hare

The clade Aplysiomorpha, commonly known as Sea hares or Sea Bags , are medium-sized to very large Opisthobranchia with a soft internal shell made of protein...

, a marine

Marine (ocean)

Marine is an umbrella term. As an adjective it is usually applicable to things relating to the sea or ocean, such as marine biology, marine ecology and marine geology...

opisthobranch gastropod mollusk in the sea hare family, Aplysiidae

Aplysiidae

The superfamily Aplysioidea is a superfamily of mostly rather large sea slugs, marine gastropod mollusks in the clade Aplysiomorpha within the informal group Opisthobranchia.This superfamily contains only one family, the Aplysiidae; the sea hares...

Distribution

This species

Species

lives in the sea off 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...

and northern Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

but can be also found off the beaches of Florida

Florida

Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

Description

The California sea hare can be very large - the maximum recorded length is seventy-five cm (thirty inches) when crawling and thus fully extended, although most adult specimens are half this size or smaller.

A closely related species, Aplysia vaccaria
Aplysia vaccaria
Aplysia vaccaria, also known as the "black sea hare," and the "California black sea hare," is a species of extremely large sea slug, a marine, opisthobranch, gastropod mollusk in the family Aplysiidae. It is the largest known species of sea slug, and may be the world's largest living gastropod. -...

, the black sea hare, can grow to be larger still.

Genomics

Sequencing of the whole genome

Full genome sequencing

Full genome sequencing , also known as whole genome sequencing , complete genome sequencing, or entire genome sequencing, is a laboratory process that determines the complete DNA sequence of an organism's genome at a single time...

has been approved as a priority by National Human Genome Research Institute

National Human Genome Research Institute

The National Human Genome Research Institute is a division of the National Institutes of Health, located in Bethesda, Maryland.NHGRI began as the National Center for Human Genome Research , which was established in 1989 to carry out the role of the NIH in the International Human Genome Project...

on March 2005.
The draft genome is available on the UCSC Genome browser

UCSC Genome Browser

The University of California, Santa Cruz is an up-to-date source for genome sequence data from a variety of vertebrate and invertebrate species and major model organisms, integrated with a large collection of aligned annotations...

Life cycle

Like all sea hares, the California sea hare is hermaphroditic

Hermaphrodite

In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...

, acting as male and female simultaneously during mating

Mating

In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...

. The eggs are yellow, but after 8 to 9 days change into a brown color before hatching into larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e. When this annual animal is laying eggs, it has reached the end of its life. Its lifetime depends somewhat on the temperature of the water: 14-25 degrees Celsius is best, but a cooler temperature delays spawning and extends its life somewhat.

When it is considerably disturbed, as shown in the photograph at the top right, the sea hare is capable of releasing reddish-purple ink (much like an octopus

Octopus

The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms...

does) from a gland in its mantle cavity.

Feeding habits

Like all Aplysia species, the California sea hare is herbivorous. Its diet consists primarily of red algae

Red algae

The red algae are one of the oldest groups of eukaryotic algae, and also one of the largest, with about 5,000–6,000 species of mostly multicellular, marine algae, including many notable seaweeds...

, which gives the animal its typically reddish or pinkish coloration.

Laboratory use

Aplysia californica has become a valuable laboratory animal

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 organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...

, used in studies of the neurobiology of learning

Learning

Learning is acquiring new or modifying existing knowledge, behaviors, skills, values, or preferences and may involve synthesizing different types of information. The ability to learn is possessed by humans, animals and some machines. Progress over time tends to follow learning curves.Human learning...

and memory

Memory

In psychology, memory is an organism's ability to store, retain, and recall information and experiences. Traditional studies of memory began in the fields of philosophy, including techniques of artificially enhancing memory....

, and is especially associated with the work of Nobel Laureate Eric Kandel.

Its ubiquity in synaptic plasticity

Synaptic plasticity

In neuroscience, synaptic plasticity is the ability of the connection, or synapse, between two neurons to change in strength in response to either use or disuse of transmission over synaptic pathways. Plastic change also results from the alteration of the number of receptors located on a synapse...

studies can be attributed to its simple nervous system

Nervous system

The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...

, consisting of just a few thousand large, easily-identified neuron

Neuron

A neuron is an electrically excitable cell that processes and transmits information by electrical and chemical signaling. Chemical signaling occurs via synapses, specialized connections with other cells. Neurons connect to each other to form networks. Neurons are the core components of the nervous...

s. Despite its seemingly simple nervous system, however, Aplysia californica is capable of a variety of non-associative and associative learning tasks, including sensitization

Sensitization

Sensitization is an example of non-associative learning in which the progressive amplification of a response follows repeated administrations of a stimulus. An everyday example of this mechanism is the repeated tonic stimulation of peripheral nerves that will occur if a person rubs his arm...

, habituation

Habituation

Habituation can be defined as a process or as a procedure. As a process it is defined as a decrease in an elicited behavior resulting from the repeated presentation of an eliciting stimulus...

, and classical

Classical conditioning

Classical conditioning is a form of conditioning that was first demonstrated by Ivan Pavlov...

and operant conditioning

Operant conditioning

Operant conditioning is a form of psychological learning during which an individual modifies the occurrence and form of its own behavior due to the association of the behavior with a stimulus...

. Study typically involves a reduced preparation of the gill and siphon withdrawal reflex

Aplysia gill and siphon withdrawal reflex

The Aplysia gill and siphon withdrawal reflex is an involuntary, defensive reflex of the sea hare Aplysia californica, a large shell-less sea snail or sea slug...

External links

Aplysia californica photos, from the Sea Slug Forum
Learning in Aplysia californica, from brembs.net (photos)
Photos from MondoMarino.net

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.