Glaucus atlanticus
Encyclopedia
Glaucus atlanticus is a species
of small-sized blue sea slug
, a pelagic aeolid nudibranch
, a marine
gastropod mollusk
in the family
Glaucidae
. This is the only species in the genus Glaucus, but is closely related to Glaucilla marginata
, another member of the family Glaucidae
.
.
Its radular teeth bear serrated teeth on their blades.
and tropical
waters. Regions where this slug is found include the East and South Coast of South Africa
, European waters, the east coast of Australia and Mozambique
. This species floats upside down on the surface tension of the ocean.
on other larger pelagic organisms: the dangerously venom
ous Portuguese Man o' War
Physalia physalis; the by-the-wind-sailor Velella velella
; the blue button Porpita porpita
; and the violet snail, Janthina janthina
. Occasionally, individual Glaucus become cannibals
given the opportunity.
G. atlanticus is able to feed on P. physalis due to its immunity to the venom
ous nematocysts. The slug consumes the entire organism and appears to select and store the most venomous nematocysts for its own use. The venom is collected in specialized sacs (cnidosacs), on the tip of their cerata
, the thin feather-like "fingers" on its body. Because Glaucus stores the venom, it can produce a more powerful and deadly sting than the Man o' War upon which it feeds.
With the aid of a gas-filled sac in its stomach, Glaucus atlanticus floats at the surface. Due to the location of the gas sac the sea swallow floats upside down. The dorsal
surface, actually the foot and underside, has either a blue or blue-white coloration. The true dorsal surface is completely silver-grey. This coloration is an example of counter shading, which helps protect it from predators from below, sides and above.
Scientists have often argued over whether Glaucus atlanticus moves on its own or depends on wind for locomotion.
Glaucus is, like most sea slug
s, a hermaphrodite
, containing both male and female reproductive organs. Unlike most nudibranch
s, which mate with their right sides facing, sea swallows mate with ventral sides facing. After mating, both animals produce egg strings.
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 small-sized blue 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...
, a pelagic aeolid 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...
, a marine
Marine biology
Marine biology is the scientific study of organisms in the ocean or other marine or brackish bodies of water. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather...
gastropod mollusk
Mollusca
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Glaucidae
Glaucidae
Glaucidae is a taxonomic family of colorful sea slugs. These are specifically aeolid nudibranchs. They are marine gastropod molluscs in the superfamily Aeolidioidea.-Genera and species:Genera and species within the family Glaucidae include:...
. This is the only species in the genus Glaucus, but is closely related to Glaucilla marginata
Glaucilla marginata
Glaucilla marginata is a species of small, floating, blue sea slug; a pelagic aolid nudibranch; a marine opisthobranch gastropod mollusk in the family Glaucidae.-Distribution:...
, another member of the family Glaucidae
Glaucidae
Glaucidae is a taxonomic family of colorful sea slugs. These are specifically aeolid nudibranchs. They are marine gastropod molluscs in the superfamily Aeolidioidea.-Genera and species:Genera and species within the family Glaucidae include:...
.
Description
The normal size of this species is up to 3 cm. It is silvery grey on its dorsal side and dark and pale blue ventrally. It has dark blue stripes along the edge of its foot. It has a tapering body which is flattened and has six appendages which branch out into rayed cerataCerata
Cerata are anatomical structures found in nudibranch sea slugs, marine opisthobranch gastropod mollusks.They are dorsal and lateral outgrowths on the upper surfaces of the body....
.
Its radular teeth bear serrated teeth on their blades.
Distribution and habitat
This nudibranch is pelagic, and is distributed throughout the world's oceans, in temperateTemperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
and tropical
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
waters. Regions where this slug is found include the East and South Coast of South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
, European waters, the east coast of Australia and Mozambique
Mozambique
Mozambique, officially the Republic of Mozambique , is a country in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west and Swaziland and South Africa to the southwest...
. This species floats upside down on the surface tension of the ocean.
Life history and behavior
G. atlanticus preysPredation
In ecology, predation describes a biological interaction where a predator feeds on its prey . Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of its prey and the eventual absorption of the prey's tissue through consumption...
on other larger pelagic organisms: the dangerously venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous Portuguese Man o' War
Portuguese Man o' War
The Portuguese Man o' War , also known as the Portuguese man-of-war, man-of-war, or bluebottle, is a jelly-like marine invertebrate of the family Physaliidae...
Physalia physalis; the by-the-wind-sailor Velella velella
Velella
Velella is a genus of free-floating hydrozoans that lives on the surface of the open ocean, worldwide, and is commonly known by the names by-the-wind sailor, purple sail, little sail, or simply Velella...
; the blue button Porpita porpita
Porpita porpita
Porpita porpita, commonly known as the blue button, is a marine organism consisting of a colony of hydroids found in tropical waters from California to the tropical Pacific, the Atlantic and Indian oceans It is often mistaken for a jellyfish, but although jellyfish and the blue buttons are part of...
; and the violet snail, Janthina janthina
Janthina janthina
Janthina janthina, common name the common purple snail, is a species of holoplanktonic sea snail, a marine gastropod mollusk in the family Janthinidae, the violet snails or purple storm snails.-Distribution:...
. Occasionally, individual Glaucus become cannibals
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...
given the opportunity.
G. atlanticus is able to feed on P. physalis due to its immunity to the venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
ous nematocysts. The slug consumes the entire organism and appears to select and store the most venomous nematocysts for its own use. The venom is collected in specialized sacs (cnidosacs), on the tip of their cerata
Cerata
Cerata are anatomical structures found in nudibranch sea slugs, marine opisthobranch gastropod mollusks.They are dorsal and lateral outgrowths on the upper surfaces of the body....
, the thin feather-like "fingers" on its body. Because Glaucus stores the venom, it can produce a more powerful and deadly sting than the Man o' War upon which it feeds.
With the aid of a gas-filled sac in its stomach, Glaucus atlanticus floats at the surface. Due to the location of the gas sac the sea swallow floats upside down. The dorsal
Dorsum (biology)
In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...
surface, actually the foot and underside, has either a blue or blue-white coloration. The true dorsal surface is completely silver-grey. This coloration is an example of counter shading, which helps protect it from predators from below, sides and above.
Scientists have often argued over whether Glaucus atlanticus moves on its own or depends on wind for locomotion.
Glaucus is, like most sea slug
Sea slug
Sea slug is a common name used for several different groups of saltwater snails that either lack a shell or have only an internal shell, in other words this name is used for various lineages of marine gastropod mollusks that are either not conchiferous or appear not to be.The phrase "sea slug" is...
s, a hermaphrodite
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...
, containing both male and female reproductive organs. Unlike most 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...
s, which mate with their right sides facing, sea swallows mate with ventral sides facing. After mating, both animals produce egg strings.
Further reading
- Valdés Á. (2008).