Böttger's Argonaut
Encyclopedia
Argonauta bottgeri, also known as Böttger's argonaut, is a species
of pelagic octopus
belonging to the genus
Argonauta. The female of the species, like all argonaut
s, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell (hence the name paper nautilus).
A. bottgeri is the smallest argonaut species. The eggcase rarely exceeds 50 mm in diameter, although exceptional specimens have been known to grow up to 67.0 mm. A. bottgeri is similar to Argonauta hians, but differs in having more pronounced ribs and prominent tubercle
s on the keel. The eggcase does not have winged protrusions as is sometimes the case with A. hians. It is generally darker than that of any other species, ranging in colour from ochre-yellow to almost black, although completely white specimens have been reported from South Africa
n waters. The eggcase is finely granulated and normally lacks the porcelain-like shine of other species.
A. bottgeri is best known from the waters off southern and eastern Africa
, although it has also been reported from other parts of the Indian Ocean
and from the western Pacific Ocean
. The locus classicus of A. bottgeri is Mozambique
.
A. bottgeri feeds primarily on pelagic molluscs, especially heteropods and pteropods, with other octopods constituting a smaller portion of the animal's diet. Females from Japan
ese waters have been reported to prey on the pteropod Carolina tridentata. The species is preyed on by numerous predators. A. bottgeri has been reported in the stomach contents of yellowfin tuna
from the Indian Ocean.
Males of this species reach sexual maturity at a mantle
length (ML) of about 7 mm, presumably the maximum size attained. Females begin to secrete an eggcase at 6.5 to 7 mm ML. Female A. bottgeri as small as 11 to 13 mm ML have been reported with hectocotyli
in the mantle cavity. They mature at about half the size of Argonauta argo. Eggs are usually laid when females reach 14 or 15 mm ML, although the size at which this takes place differs across the animal's range.
It has been reported that the egg clusters of A. bottgeri can be clearly divided into three portions, each with eggs at a similar developmental stage. The first lies closest to the aperture of the eggcase and contains eggs
at an early stage of development. The second is located in the middle of the mass and contains eggs at a later stage of development, ranging from the appearance of red eye pigmentation to the beginning of chromatophore
formation. The third portion lies furthest from the aperture of the eggcase and consists of eggs with embryo
s that are ready to hatch, having a fully formed ink sac, chromatophores, and dark coloured eyes. Similar development has been observed in the egg masses of Argonauta nodosa from southern Australia
. Egg laying is thought to occur at night and it has been suggested that the three stages of development may represent the products of three successive nights.
A. bottgeri is known to cling to objects floating on the surface of the sea, including other argonauts. Chains of up to 30 argonauts of similar size have been reported. The first female in such chains usually clings to some inanimate object, while the other females hold onto the ventral part of the shell of the preceding animal.
A. bottgeri is named after Oskar Boettger
. The orthographic variant "Argonauta boettgeri" is sometimes encountered. A. bottgeri does not appear to have any nomenclatural synonyms. The type locality and type repository of A. bottgeri are unknown.
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 pelagic 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...
belonging to the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Argonauta. The female of the species, like all argonaut
Argonaut (animal)
The argonauts are a group of pelagic octopuses. They are also called paper nautiluses, referring to the paper-thin eggcase that females secrete...
s, creates a paper-thin eggcase that coils around the octopus much like the way a nautilus lives in its shell (hence the name paper nautilus).
A. bottgeri is the smallest argonaut species. The eggcase rarely exceeds 50 mm in diameter, although exceptional specimens have been known to grow up to 67.0 mm. A. bottgeri is similar to Argonauta hians, but differs in having more pronounced ribs and prominent tubercle
Tubercle
A tubercle is generally a wart-like projection, but it has slightly different meaning depending on which family of plants or animals it is used to refer to....
s on the keel. The eggcase does not have winged protrusions as is sometimes the case with A. hians. It is generally darker than that of any other species, ranging in colour from ochre-yellow to almost black, although completely white specimens have been reported from 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...
n waters. The eggcase is finely granulated and normally lacks the porcelain-like shine of other species.
A. bottgeri is best known from the waters off southern and eastern Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, although it has also been reported from other parts of the Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
and from the western Pacific Ocean
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
. The locus classicus of A. bottgeri is 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...
.
A. bottgeri feeds primarily on pelagic molluscs, especially heteropods and pteropods, with other octopods constituting a smaller portion of the animal's diet. Females from Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
ese waters have been reported to prey on the pteropod Carolina tridentata. The species is preyed on by numerous predators. A. bottgeri has been reported in the stomach contents of yellowfin tuna
Yellowfin tuna
The yellowfin tuna is a species of tuna found in pelagic waters of tropical and subtropical oceans worldwide.Yellowfin is often marketed as ahi, from its Hawaiian name ahi although the name ahi in Hawaiian also refers to the closely related bigeye tuna. The species name, albacares can lead to...
from the Indian Ocean.
Males of this species reach sexual maturity at a mantle
Mantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the visceral mass and usually protrudes in the form of flaps well beyond the visceral mass itself.In many, but by no means all, species of molluscs, the epidermis of the mantle secretes...
length (ML) of about 7 mm, presumably the maximum size attained. Females begin to secrete an eggcase at 6.5 to 7 mm ML. Female A. bottgeri as small as 11 to 13 mm ML have been reported with hectocotyli
Hectocotylus
A hectocotylus is one of the arms of the male of most kinds of cephalopods that is modified in various ways to effect the fertilization of the female's eggs. It is a specialized, extended muscular hydrostat used to store spermatophores, the male gametophore...
in the mantle cavity. They mature at about half the size of Argonauta argo. Eggs are usually laid when females reach 14 or 15 mm ML, although the size at which this takes place differs across the animal's range.
It has been reported that the egg clusters of A. bottgeri can be clearly divided into three portions, each with eggs at a similar developmental stage. The first lies closest to the aperture of the eggcase and contains 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 an early stage of development. The second is located in the middle of the mass and contains eggs at a later stage of development, ranging from the appearance of red eye pigmentation to the beginning of chromatophore
Chromatophore
Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans, and cephalopods. They are largely responsible for generating skin and eye colour in cold-blooded animals and are generated in the neural crest during embryonic development...
formation. The third portion lies furthest from the aperture of the eggcase and consists of eggs with 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...
s that are ready to hatch, having a fully formed ink sac, chromatophores, and dark coloured eyes. Similar development has been observed in the egg masses of Argonauta nodosa from southern Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. Egg laying is thought to occur at night and it has been suggested that the three stages of development may represent the products of three successive nights.
A. bottgeri is known to cling to objects floating on the surface of the sea, including other argonauts. Chains of up to 30 argonauts of similar size have been reported. The first female in such chains usually clings to some inanimate object, while the other females hold onto the ventral part of the shell of the preceding animal.
A. bottgeri is named after Oskar Boettger
Oskar Boettger
Oskar Boettger was a German zoologist who was a native of Frankfurt am Main. He was an uncle of the noted malacologist Caesar Rudolf Boettger ....
. The orthographic variant "Argonauta boettgeri" is sometimes encountered. A. bottgeri does not appear to have any nomenclatural synonyms. The type locality and type repository of A. bottgeri are unknown.