Elysia chlorotica
Encyclopedia
Elysia chlorotica, common name
the eastern emerald elysia, is a small-to-medium-sized species
of green sea slug
, a marine
opisthobranch gastropod mollusc. This sea slug superficially resembles a nudibranch
, yet it does not belong to that suborder of gastropods. Instead it is a member of the closely related suborder Sacoglossa
. The suborder Sacoglossa
are known as the 'sap-sucking Opisthobranchia
s'. Many members of this group use chloroplast
s from the algae
they eat; a phenomenon known as kleptoplasty
. Elysia chlorotica is one of the "solar-powered sea slugs", utilizing solar energy via chloroplasts from its algal food. It lives in a subcellular endosymbiotic
relationship with chloroplasts of the marine heterokont
alga
Vaucheria litorea
.
, including the states of Massachusetts
, Connecticut
, New York
, New Jersey
, Maryland
, Florida
(east Florida and west Florida) and Texas
. They can also be found as far north as Nova Scotia
, Canada
.
chloroplast
s in the cells
of the slugs digestive diverticula. However, they can occasionally appear reddish or greyish in colour, thought to depend on the amount of chlorophyll
in the branches of the digestive gland which ramify throughout the body. This species can also have very small red or white spots scattered over the body. A juvenile
, prior to feeding, is brown with red pigment
spots due to the absence of chloroplasts. Elysia chlorotica have a typical elysiid shape with large lateral parapodia which can fold over to enclose the body. Elysia chlorotica can grow up to 60mm in length but are more commonly found between 20mm to 30mm in length.
Vaucheria litorea
by puncturing
the algal cell wall with its radula
. The slug then holds the algal strand firmly in its mouth and, as though it were a straw
, sucks out the contents. Instead of digesting the entire cell contents, or passing the contents through its gut unscathed, it retains only the algal chloroplast
s, by storing them within its own cells
throughout its extensive digestive system. The acquisition of chloroplasts begins immediately following metamorphosis
from the veliger stage when the juvenile
sea slugs begin to feed on the Vaucheria litorea
cells. Juvenile slugs are brown with red pigment spots until they feed upon the algae
, at which point they become green. This is caused by the distribution of the chloroplasts throughout the extensively branched gut. Initially, the slug needs to continually feed upon algae to retain the chloroplasts, but over time the chloroplasts become more stably incorporated into the cells of the gut enabling the slug to remain green without further feeding.
The incorporation of chloroplasts within the cells of Elysia chlorotica allow the slug to capture energy directly from light, as most plants do, through the process known as photosynthesis
. This is significantly beneficial for Elysia chlorotica because during time periods where algae is not readily available as a food
supply, the Elysia chlorotica can survive for months on the sugars produced through photosynthesis
performed by their own chloroplasts. Kept within the slug's own cells, it has been found that the chloroplasts can survive and function for up to nine or even 10 months. In one study Elysia chlorotica were deprived of alga ingestion for a period of eight months. After the eight month period, despite the fact that the Elysia chlorotica were less green and more yellowish in colour, the majority of the chloroplasts within the slugs appeared to have remained intact while also maintaining their fine structure. Although Elysia chlorotica are unable to synthesize their own chloroplasts, the ability to maintain the chloroplasts acquired from Vaucheria litorea
in a functional state indicates that Elysia chlorotica must possess photosynthesis-supporting genes within its own nuclear genome
; most likely acquired through horizontal gene transfer
. Since chloroplast DNA
alone encodes for just 10% of the protein
s required for proper photosynthesis, scientists investigated the Elysia chlorotica genome for potential genes that could support chloroplast survival and photosynthesis. The researchers found a vital algal gene, psbO (a nuclear gene
encoding for a manganese
-stabilizing protein within the photosystem II
complex) in the sea slug's DNA, identical to the algal version. They concluded that the gene was likely to have been acquired through horizontal gene transfer
, as it was already present in the eggs and sex cells of Elysia chlorotica.
s. When sexually mature, each animal produces both sperm
and eggs
at the same time. However, self-fertilization is not common within this species. Instead, Elysia chlorotica cross-copulate. After the eggs have been fertilized within the slug (fertilization is internal), Elysia chlorotica lay their fertilized eggs in long strings.
angle
to the animal-vegetal axis of the egg
. The result of this is that tiers of cells are produced, each tier lying in the furrows between cells of the tier below it.
At the end of cleavage, the embryo
forms a stereoblastula, meaning a blastula
without a clear central cavity
.
is by epiboly
: the ectoderm
spreads to envelope the mesoderm
and endoderm
.
passes through a trocophore like stage during development, it then hatches as a veliger larva. The veliger larva has a shell and ciliated velum. The larva uses the ciliated velum to swim as well as to bring food to its mouth. The veliger larva feed on phytoplankton
in the sea-water column. After the food is brought to the mouth by the ciliated velum, it is moved down the digestive tract to the stomach
. In the stomach, food is sorted and then moved on to the digestive gland where the food is digested and the nutrients are absorbed by the epithelial cells of the digestive gland.
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
the eastern emerald elysia, is a small-to-medium-sized 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 green sea slug
Opisthobranchia
Opisthobranchs are a large and diverse group of specialized complex marine gastropods previously united under Opisthobranchia within the Heterobranchia, but no longer considered to represent a monophyletic grouping...
, 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 mollusc. This sea slug superficially resembles a nudibranch
Nudibranch
A nudibranch is a member of what is now a taxonomic clade, and what was previously a suborder, of soft-bodied, marine gastropod mollusks which shed their shell after their larval stage. They are noted for their often extraordinary colors and striking forms...
, yet it does not belong to that suborder of gastropods. Instead it is a member of the closely related suborder Sacoglossa
Sacoglossa
Sacoglossa, commonly known as the sacoglossans or the "sap-sucking sea slugs", are a clade of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia...
. The suborder Sacoglossa
Sacoglossa
Sacoglossa, commonly known as the sacoglossans or the "sap-sucking sea slugs", are a clade of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia...
are known as the 'sap-sucking Opisthobranchia
Opisthobranchia
Opisthobranchs are a large and diverse group of specialized complex marine gastropods previously united under Opisthobranchia within the Heterobranchia, but no longer considered to represent a monophyletic grouping...
s'. Many members of this group use chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
s from the 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...
they eat; a phenomenon known as kleptoplasty
Kleptoplasty
Kleptoplasty or kleptoplastidy is a symbiotic phenomenon whereby plastids from algae are sequestered by host organisms. The alga is eaten normally and partially digested, leaving the plastid intact. The plastids are maintained within the host, temporarily retaining functional photosynthesis for use...
. Elysia chlorotica is one of the "solar-powered sea slugs", utilizing solar energy via chloroplasts from its algal food. It lives in a subcellular endosymbiotic
Endosymbiont
An endosymbiont is any organism that lives within the body or cells of another organism, i.e. forming an endosymbiosis...
relationship with chloroplasts of the marine heterokont
Heterokont
The heterokonts or stramenopiles are a major line of eukaryotes currently containing more than 100,000 known species. Most are algae, ranging from the giant multicellular kelp to the unicellular diatoms, which are a primary component of plankton...
alga
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...
Vaucheria litorea
Vaucheria litorea
Vaucheria litorea is a filamentous species of Xanthophyceae or yellow-green algae. V. litorea is a common intertidal species of coastal brackish waters and salt marshes of the Northern Atlantic, along the coasts of Europe and North America. It is also found in the Eastern Pacific coasts of...
.
Distribution
Elysia chlorotica can be found along the east coast of the United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, including the states of Massachusetts
Massachusetts
The Commonwealth of Massachusetts is a state in the New England region of the northeastern United States of America. It is bordered by Rhode Island and Connecticut to the south, New York to the west, and Vermont and New Hampshire to the north; at its east lies the Atlantic Ocean. As of the 2010...
, Connecticut
Connecticut
Connecticut is a state in the New England region of the northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, and the state of New York to the west and the south .Connecticut is named for the Connecticut River, the major U.S. river that approximately...
, New York
New York
New York is a state in the Northeastern region of the United States. It is the nation's third most populous state. New York is bordered by New Jersey and Pennsylvania to the south, and by Connecticut, Massachusetts and Vermont to the east...
, New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
, Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
, 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...
(east Florida and west Florida) and Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
. They can also be found as far north as Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
.
Ecology
Elysia chlorotica are most commonly found in salt marshes, tidal marshes, pools and shallow creeks, at depths of 0 m to 0.5 m.Description
Adult Elysia chlorotica are usually bright green in colour, due to the presence of Vaucheria litoreaVaucheria litorea
Vaucheria litorea is a filamentous species of Xanthophyceae or yellow-green algae. V. litorea is a common intertidal species of coastal brackish waters and salt marshes of the Northern Atlantic, along the coasts of Europe and North America. It is also found in the Eastern Pacific coasts of...
chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
s in the cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
of the slugs digestive diverticula. However, they can occasionally appear reddish or greyish in colour, thought to depend on the amount of chlorophyll
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
in the branches of the digestive gland which ramify throughout the body. This species can also have very small red or white spots scattered over the body. A juvenile
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
, prior to feeding, is brown with red pigment
Pigment
A pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
spots due to the absence of chloroplasts. Elysia chlorotica have a typical elysiid shape with large lateral parapodia which can fold over to enclose the body. Elysia chlorotica can grow up to 60mm in length but are more commonly found between 20mm to 30mm in length.
Feeding
Elysia chlorotica feeds on the intertidal algaeAlgae
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...
Vaucheria litorea
Vaucheria litorea
Vaucheria litorea is a filamentous species of Xanthophyceae or yellow-green algae. V. litorea is a common intertidal species of coastal brackish waters and salt marshes of the Northern Atlantic, along the coasts of Europe and North America. It is also found in the Eastern Pacific coasts of...
by puncturing
Puncturing
In coding theory, puncturing is the process of removing some of the parity bits after encoding with an error-correction code. This has the same effect as encoding with an error-correction code with a higher rate, or less redundancy...
the algal cell wall with its radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
. The slug then holds the algal strand firmly in its mouth and, as though it were a straw
Straw
Straw is an agricultural by-product, the dry stalks of cereal plants, after the grain and chaff have been removed. Straw makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has many uses, including fuel, livestock bedding and fodder, thatching and...
, sucks out the contents. Instead of digesting the entire cell contents, or passing the contents through its gut unscathed, it retains only the algal chloroplast
Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy to conserve free energy in the form of ATP and reduce NADP to NADPH through a complex set of processes called photosynthesis.Chloroplasts are green...
s, by storing them within its own cells
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....
throughout its extensive digestive system. The acquisition of chloroplasts begins immediately following metamorphosis
Metamorphosis
Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation...
from the veliger stage when the juvenile
Juvenile (organism)
A juvenile is an individual organism that has not yet reached its adult form, sexual maturity or size. Juveniles sometimes look very different from the adult form, particularly in terms of their colour...
sea slugs begin to feed on the Vaucheria litorea
Vaucheria litorea
Vaucheria litorea is a filamentous species of Xanthophyceae or yellow-green algae. V. litorea is a common intertidal species of coastal brackish waters and salt marshes of the Northern Atlantic, along the coasts of Europe and North America. It is also found in the Eastern Pacific coasts of...
cells. Juvenile slugs are brown with red pigment spots until they feed upon the 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...
, at which point they become green. This is caused by the distribution of the chloroplasts throughout the extensively branched gut. Initially, the slug needs to continually feed upon algae to retain the chloroplasts, but over time the chloroplasts become more stably incorporated into the cells of the gut enabling the slug to remain green without further feeding.
The incorporation of chloroplasts within the cells of Elysia chlorotica allow the slug to capture energy directly from light, as most plants do, through the process known as photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
. This is significantly beneficial for Elysia chlorotica because during time periods where algae is not readily available as a food
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...
supply, the Elysia chlorotica can survive for months on the sugars produced through photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
performed by their own chloroplasts. Kept within the slug's own cells, it has been found that the chloroplasts can survive and function for up to nine or even 10 months. In one study Elysia chlorotica were deprived of alga ingestion for a period of eight months. After the eight month period, despite the fact that the Elysia chlorotica were less green and more yellowish in colour, the majority of the chloroplasts within the slugs appeared to have remained intact while also maintaining their fine structure. Although Elysia chlorotica are unable to synthesize their own chloroplasts, the ability to maintain the chloroplasts acquired from Vaucheria litorea
Vaucheria litorea
Vaucheria litorea is a filamentous species of Xanthophyceae or yellow-green algae. V. litorea is a common intertidal species of coastal brackish waters and salt marshes of the Northern Atlantic, along the coasts of Europe and North America. It is also found in the Eastern Pacific coasts of...
in a functional state indicates that Elysia chlorotica must possess photosynthesis-supporting genes within its own nuclear genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
; most likely acquired through horizontal gene transfer
Horizontal gene transfer
Horizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...
. Since chloroplast DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
alone encodes for just 10% of the protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s required for proper photosynthesis, scientists investigated the Elysia chlorotica genome for potential genes that could support chloroplast survival and photosynthesis. The researchers found a vital algal gene, psbO (a nuclear gene
Nuclear gene
A Nuclear gene is a gene located in the cell nucleus of a eukaryote. The term is used to distinguish nuclear genes from the genes in the mitochondrion, and in case of plants, also the chloroplast, which host their own genetic system and can produce proteins from scratch...
encoding for a manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
-stabilizing protein within the photosystem II
Photosystem II
Photosystem II is the first protein complex in the Light-dependent reactions. It is located in the thylakoid membrane of plants, algae, and cyanobacteria. The enzyme uses photons of light to energize electrons that are then transferred through a variety of coenzymes and cofactors to reduce...
complex) in the sea slug's DNA, identical to the algal version. They concluded that the gene was likely to have been acquired through horizontal gene transfer
Horizontal gene transfer
Horizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...
, as it was already present in the eggs and sex cells of Elysia chlorotica.
Life cycle
Adult Elysia chlorotica are simultaneous hermaphroditeHermaphrodite
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...
s. When sexually mature, each animal produces both sperm
Sperm
The term sperm is derived from the Greek word sperma and refers to the male reproductive cells. In the types of sexual reproduction known as anisogamy and oogamy, there is a marked difference in the size of the gametes with the smaller one being termed the "male" or sperm cell...
and 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...
at the same time. However, self-fertilization is not common within this species. Instead, Elysia chlorotica cross-copulate. After the eggs have been fertilized within the slug (fertilization is internal), Elysia chlorotica lay their fertilized eggs in long strings.
Cleavage
In the life cycle of Elysia chlorotica, cleavage is holoblastic and spiral. This means that the eggs cleave completely (holoblastic); and each cleavage plane is at an obliqueOblique
Oblique may refer to:*Oblique angle, in geometry, an angle that is not a multiple of 90 degrees*Oblique angle, synonym for Dutch angle, a cinematographic technique*Oblique , by jazz vibraphonist Bobby Hutcherson...
angle
Angle
In geometry, an angle is the figure formed by two rays sharing a common endpoint, called the vertex of the angle.Angles are usually presumed to be in a Euclidean plane with the circle taken for standard with regard to direction. In fact, an angle is frequently viewed as a measure of an circular arc...
to the animal-vegetal axis of the egg
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...
. The result of this is that tiers of cells are produced, each tier lying in the furrows between cells of the tier below it.
At the end of cleavage, the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
forms a stereoblastula, meaning a blastula
Blastula
The blastula is a hollow sphere of cells formed during an early stage of embryonic development in animals . The blastula is created when the zygote undergoes the cell division process known as cleavage. The blastula is preceded by the morula and is followed by the gastrula in the developmental...
without a clear central cavity
Cavity
A cavity is a hole. It may refer to:*Dental cavity, damage to the structure of teeth*Body cavity, a fluid filled space in many animals where organs typically develop*Cavity wall, a wall consisting of two skins with a cavity....
.
Gastrulation
Elysia chlorotica gastrulationGastrulation
Gastrulation is a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a trilaminar structure known as the gastrula. These three germ layers are known as the ectoderm, mesoderm, and endoderm.Gastrulation takes place after cleavage...
is by epiboly
Epiboly
Epiboly is a cell movement that occurs in the early embryo, at the same time as gastrulation. It is one of many movements in the early embryo that allow for dramatic physical restructuring . The movement is generally characterized as being a thinning and spreading of cell layers...
: the ectoderm
Ectoderm
The "ectoderm" is one of the three primary germ cell layers in the very early embryo. The other two layers are the mesoderm and endoderm , with the ectoderm as the most exterior layer...
spreads to envelope the mesoderm
Mesoderm
In all bilaterian animals, the mesoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and endoderm , with the mesoderm as the middle layer between them.The mesoderm forms mesenchyme , mesothelium, non-epithelial blood corpuscles and...
and endoderm
Endoderm
Endoderm is one of the three primary germ cell layers in the very early embryo. The other two layers are the ectoderm and mesoderm , with the endoderm as the intermost layer...
.
Larval stage
After the embryoEmbryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
passes through a trocophore like stage during development, it then hatches as a veliger larva. The veliger larva has a shell and ciliated velum. The larva uses the ciliated velum to swim as well as to bring food to its mouth. The veliger larva feed on 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...
in the sea-water column. After the food is brought to the mouth by the ciliated velum, it is moved down the digestive tract to the stomach
Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
. In the stomach, food is sorted and then moved on to the digestive gland where the food is digested and the nutrients are absorbed by the epithelial cells of the digestive gland.
External links
- Solar-powered Sea Slug Harnesses Stolen Plant Genes, New Scientist, 2008-11-24
- Half Plant, Half Animal Videos w/additional info.
- Science News
- Live Science