''Capitulum'' is a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

marine stalked barnacles. ''Capitulum mitella'' is the only

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

in the genus. It is commonly known as the Japanese goose barnacle or ''kamenote'' and is found on rocky shores in the

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

region.

Description

''Capitulum mitella'' has a short leathery stalk or

peduncle Peduncle may refer to: *Peduncle (botany), a stalk supporting an inflorescence, which is the part of the shoot of seed plants where flowers are formed *Peduncle (anatomy), a stem, through which a mass of tissue is attached to a body **Peduncle (art ...

supporting an upper region or capitulum, the whole being up to long. The peduncle is muscular and contractile and its surface is covered with fine scales. The capitulum is protected by eight large, sheathing scales and a ring of about twenty tiny scales surround the joint of capitulum and peduncle. Inside these scales is a cavity containing the head and thorax of the animal and its appendages.

Distribution and habitat

''Capitulum mitella'' occurs in the

South China Sea The South China Sea is a marginal sea of the Western Pacific Ocean. It is bounded in the north by the shores of South China (hence the name), in the west by the Indochinese Peninsula, in the east by the islands of Taiwan and northwestern Phil ...

and the

East China Sea The East China Sea is an arm of the Western Pacific Ocean, located directly offshore from East China. It covers an area of roughly . The sea’s northern extension between mainland China and the Korean Peninsula is the Yellow Sea, separated b ...

. It is found attached to rocks in the lower part of the

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...

in areas with strong currents. It typically occurs crowded with others in cracks and grooves on otherwise smooth rocky surfaces. The barnacle ''

Tetraclita squamosa ''Tetraclita squamosa'', the green volcano barnacle, is a species of symmetrical sessile barnacle in the family Tetraclitidae Tetraclitidae is a family of sessile barnacles in the order Balanomorpha The Balanomorpha are an order of barnacl ...

'' often occurs in the same locations and grows alongside it, and the primitive barnacle ''

Ibla cumingi Ragusa (; scn, Rausa ; la, Ragusia) is a city and ''comune'' in southern Italy. It is the capital of the province of Ragusa, on the island of Sicily, with 73,288 inhabitants in 2016. It is built on a wide limestone hill between two deep valley ...

'' may grow in between or on the larger capitulum plates.

Biology

When under water, ''Capitulum mitella'' extends its five hind pairs of thoracic legs and spreads them out in the current like a net. It uses the front pair of legs to manipulate the objects it catches and move them into its mouth. Its diet mainly consists of

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

. ''Capitulum mitella'' is a simultaneous

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...

. Each barnacle is capable of fertilising other nearby individuals by transmitting sperm through a long, fine tube and also of brooding its own eggs in its mantle cavity. When the eggs hatch, the larvae are released into the sea. They have six naupliar stages during which food reserves are built up and one non-feeding cyprid stage which seeks out a suitable hard surface on which to settle. It then fix itself in place, undergoes

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

and becomes a sessile juvenile. In

Hong Kong Hong Kong ( (US) or (UK); , ), officially the Hong Kong Special Administrative Region of the People's Republic of China ( abbr. Hong Kong SAR or HKSAR), is a city and special administrative region of China on the eastern Pearl River Delt ...

harbour, where this barnacle can be found growing on pilings, it often has a

nemertean worm Nemertea is a phylum of animals also known as ribbon worms or proboscis worms, consisting of 1300 known species. Most ribbon worms are very slim, usually only a few millimeters wide, although a few have relatively short but wide bodies. Many h ...

''(Nemertopsis quadripunctatus)'' living inside its mantle cavity and feeding on the eggs being brooded there. The worm can be long but only in diameter.

Uses

''Capitulum mitella'' is one of about a dozen species of goose barnacle that are gathered commercially and eaten by humans. These barnacles are a luxury food item in Japan, Taiwan, Korea and China.

References

{{Taxonbar, from1=Q5035994, from2=Q18607530 Barnacles Crustaceans described in 1758 Taxa named by Carl Linnaeus