Molgula citrina

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Molgula citrina
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Subphylum: Tunicata
Class: Ascidiacea
Order: Stolidobranchia
Family: Molgulidae
Genus: Molgula
Species:
M. citrina
Binomial name
Molgula citrina
Alder & Hancock, 1848 [1]
Synonyms [1]
  • Caesira arctica (Kiaer, 1896)
  • Caesira birulai (Redikorzev, 1907)
  • Caesira citrina (Alder & Hancock, 1848)
  • Caesira littoralis (Verrill, 1871)
  • Caesira nana (Kupffer, 1873)
  • Gymnocystis comosa Giard, 1872
  • Molgula arctica Kiaer, 1896
  • Molgula birulai Redikorzev, 1907
  • Molgula echinosiphonica Lacaze-Duthiers, 1877
  • Molgula litoralis Verrill, 1871
  • Molgula littoralis Verrill, 1871
  • Molgula nana Kupffer, 1873
  • Molgula nuda Wagner, 1885

Molgula citrina is a species of solitary tunicate in the family Molgulidae. It is found on both sides of the northern Atlantic Ocean and in the Arctic Ocean. In 2008 it was found in Kachemak Bay in Alaska, the first time it had been detected in the Pacific Ocean.

Contents

Description

Molgula citrina takes the form of a globular or ovoid sac and can grow to a diameter of 18 mm (0.7 in). The tunic (outer surface of the sac) is greyish-green and firm, with few particles of sediment adhering to it, and this distinguishes it from many species in this genus. The siphons are widely separated. The buccal siphon, through which water is drawn into the body cavity, has six lobes while the atrial siphon, through which water leaves, is short and has four lobes. About fourteen branched tentacles surround the base of the buccal siphon, and prevent particles that are too large from entering the body cavity. [2]

Distribution

Molgula citrina is found in the Arctic Ocean and the northeastern Atlantic Ocean as far south as the British Isles and the northern coast of France. In the northwestern Atlantic it occurs as far south as the Gulf of Saint Lawrence and the Bay of Fundy. [1] It is usually found in shallow water but its maximum depth range is about 200 m (656 ft). [2] It is also a fouling organism, adhering to floating docks and associated structures. [3]

The appearance of M. citrina in Alaska in 2008 raised the question of whether this species is a naturally occurring, circumpolar species previously undetected in the northern Pacific Ocean, or whether it had arrived anthropogenically. The former is possible because the Pacific Northwest and Alaskan waters are not well surveyed. Alternatively, it could have colonised the Pacific naturally via the Northwest Passage which is becoming more accessible because of the decrease in sea ice caused by global warming. However this would be against the trend, as some species have spread from the Pacific to the Atlantic by this route but seldom vice versa. [3]

If M. citrina arrived in the Pacific with the help of man there are several possibilities. It is unlikely to survive in ballast water but may have been transported in the sea chest of a vessel, a recess on the hull covered with a grill and used for the intake of sea water for ballast, firefighting, engine cooling and other purposes. Sea chests house a community of organisms that would be unlikely to survive as fouling animals on the vessel's hull. M. citrina may have arrived in the Pacific in one of these, perhaps via the Northwest Passage. [3] Being a cold water species, it is unlikely this species would have arrived via the Caribbean Sea and Panama Canal where the water temperature would be outside the tunicate's survival range. [3]

Biology

As with other ascidians, Molgula citrina is a suspension feeder, capturing planktonic particles by filtering sea water through its body. Water is drawn in through the buccal siphon, the food particles are extracted, and the water and waste material exits via the atrial siphon. [4]

M. citrina is a hermaphrodite and is viviparous. Sperm is shed into the water column and enters another individual through its buccal siphon. A batch of eggs is liberated from the oviduct and these are fertilised within the body cavity. The eggs are opaque and have red or yellow yolks. They are about 0.20 mm (0.008 in) in diameter. The developing embryos are brooded in the body cavity. [5] Hatching is initiated by the release of enzymes which cause the egg membranes to rupture. The larvae have notochords (stiffening rods) and resemble salamander tadpoles. They have fluid-filled sensory organs known as otocysts. The larvae continue to be brooded for a while but are later liberated into the sea. In European waters about 80% undergo metamorphosis while still in the body cavity but in North America only about 2% are retained internally to metamorphosis. [5] When released, the larvae have a very short free-swimming period, ranging from a few minutes to an hour or two, before undergoing metamorphosis. The juveniles soon become sticky and attach to any hard surfaces with which they come in contact. [5] This often includes the tunic of the parent individual and this may form a small cluster of individuals. [3]

Related Research Articles

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A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata. It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords. The subphylum was at one time called Urochordata, and the term urochordates is still sometimes used for these animals. They are the only chordates that have lost their myomeric segmentation, with the possible exception of the 'seriation of the gill slits'.

Ascidiacea Group of non-vertebrate marine filter feeders comprising sea squirts

Ascidiacea, commonly known as the ascidians, tunicates, and sea squirts, is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" made of a polysaccharide.

<i>Corella willmeriana</i> Species of sea squirt

Corella willmeriana is a solitary tunicate in the family Corellidae. It is native to the eastern Pacific Ocean where it lives on the seabed at depths down to about 75 m (250 ft) between Alaska and California.

<i>Atriolum robustum</i> Species of sea squirt

Atriolum robustum is a colonial tunicate or sea squirt in the family Didemnidae. It is native to the western and central Indo-Pacific where it is usually found anchored to a hard surface in shallow water.

<i>Didemnum molle</i> Species of sea squirt

Didemnum molle is a species of colonial tunicate in the family Didemnidae. It is commonly known as the tall urn ascidian, the green barrel sea squirt or the green reef sea-squirt. It is native to the Red Sea and the tropical waters of the Indo-Pacific region.

<i>Didemnum vexillum</i> Species of sea squirt

Didemnum vexillum is a species of colonial tunicate in the family Didemnidae. It is commonly called sea vomit, marine vomit, pancake batter tunicate, or carpet sea squirt. It is thought to be native to Japan, but it has been reported as an invasive species in a number of places in Europe, North America and New Zealand. It is sometimes given the nickname "D. vex" because of the vexing way in which it dominates marine ecosystems when introduced into new locations, however the species epithet vexillum actually derives from the Latin word for flag, and the species was so named because of the way colonies' long tendrils appear to wave in the water like a flag.

<i>Ciona savignyi</i> Species of sea squirt

Ciona savignyi is a marine animal sometimes known as the Pacific transparent sea squirt or solitary sea squirt. It is a species of tunicates in the family Cionidae. It is found in shallow waters around Japan and has spread to the west coast of North America where it is regarded as an invasive species.

Perophora viridis, the honeysuckle tunicate, is a species of colonial sea squirt in the genus Perophora found in the tropical western Atlantic Ocean.

<i>Molgula oculata</i> Species of sea squirt

Molgula oculata, commonly known as the sea grape, is a species of solitary tunicate in the family Molgulidae. It is native to the north eastern Atlantic Ocean and the North Sea. The specific name oculata means "having eyes"; the species has orifices which "seem like dark eyes within a spectacle-formed frame".

Molgula occulta is a species of solitary tunicate in the family Molgulidae. It is native to the north eastern Atlantic Ocean, the North Sea and the Mediterranean Sea. The specific name occulta means "tailless" and refers to the tunicate's larva, which lacks the tail found in some other species in the genus Molgula.

Polycarpa fibrosa is a species of tunicate in the family Styelidae. It is brown and globular and its outer surface is covered with a mat of fibrils. It normally lies buried in soft sediment on the seabed with only its two siphons protruding. It occurs in the Arctic Ocean and northern Atlantic Ocean. P. fibrosa was first identified and described by the American malacologist William Stimpson in 1852.

<i>Morchellium argus</i> Species of sea squirt

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<i>Polycarpa pomaria</i> Species of sea squirt

Polycarpa pomaria is a species of tunicate or sea squirt in the family Styelidae. It is native to the northeastern Atlantic Ocean where it lives on the seabed at depths down to about 450 metres (1,500 ft).

<i>Phallusia mammillata</i> Species of sea squirt

Phallusia mammillata is a solitary marine tunicate of the ascidian class found in the eastern Atlantic Ocean and the Mediterranean Sea.

<i>Molgula manhattensis</i> Species of sea squirt

Molgula manhattensis, commonly known as "sea grapes", is a species of ascidian commonly found along the East Coast and Gulf Coast region of the United States. Although it is native to this region, it has been introduced to other areas of Europe, Australia, and the West Coast.

<i>Molgula occidentalis</i> Species of sea squirt

Molgula occidentalis is a species of marine invertebrate of the family Molgulidae. The scientific name of the species was validated and published for the first time in 1883 by Traustedt. It is a soft-bodied, intertidal ascidian, sac-like filter feeders in the subphylum tunicate characterized by a hard outer covering known as a “tunic,” abundant in the shallow subtidal and intertidal zones of the Northern Gulf of Mexico, where they establish pseudopopulations.

<i>Boltenia villosa</i> Species of sea squirt

Boltenia villosa is a species of tunicate, a marine invertebrate of the family Pyuridae. Common names include the spiny-headed tunicate, the hairy sea squirt, the stalked hairy sea squirt and the bristly tunicate. This species was first described in 1864 by the American marine biologist William Stimpson who gave it the name Cynthia villosa. It was later transferred to the genus Boltenia. The type locality is Puget Sound, Washington state, United States.

<i>Cnemidocarpa finmarkiensis</i> Species of sea squirt

Cnemidocarpa finmarkiensis is a species of solitary ascidian tunicate in the family Styelidae. Common names include broad base sea squirt, orange sea squirt, red sea squirt, shiny orange sea squirt, shiny red tunicate and Finmark's tunicate. It is native to shallow waters in the northern and northeastern Pacific Ocean.

<i>Pyura haustor</i> Species of chordates

Pyura haustor is a species of sessile ascidian, or sea squirt, that lives in coastal waters in the north-eastern Pacific Ocean, attached to rocks or artificial structures. Common names for this species include the wrinkled seapump, the wrinkled sea squirt and the warty tunicate.

Halocynthia igaboja, commonly known as the sea hedgehog, the bristly tunicate or spiny sea squirt, is a species of tunicate in the family Pyuridae. It is native to the northeastern Pacific Ocean. This species was first described in 1906 by the Japanese marine biologist Asajiro Oka, who gave it the name Cynthia ritteri. It was later transferred to the genus Halocynthia.

References

  1. 1 2 3 Sanamyan, Karen (2014). "Molgula citrina Alder & Hancock, 1848". WoRMS. World Register of Marine Species . Retrieved 2015-01-20.
  2. 1 2 de Kluijver, M.J.; Ingalsuo, S.S. "Molgula citrina". Macrobenthos of the North Sea: Tunicata. Marine Species Information Portal. Retrieved 2015-01-20.
  3. 1 2 3 4 5 Lambert, Gretchen; Shenkar, Noa; Swalla, Billie J. (2010). "First Pacific record of the north Atlantic ascidian Molgula citrina – bioinvasion or circumpolar distribution?". Aquatic Invasions. 5 (4): 360–378. doi: 10.3391/ai.2010.5.4.06 .
  4. ↑ Ruppert, Edward E.; Fox, Richard, S.; Barnes, Robert D. (2004). Invertebrate Zoology, 7th edition. Cengage Learning. p. 945. ISBN   81-315-0104-3.
  5. 1 2 3 Berrill, N. J. (1930). "Studies in Tunicate Development. Part I. General Physiology of Development of Simple Ascidians". Philosophical Transactions of the Royal Society of London B. 218: 37–78. doi: 10.1098/rstb.1930.0002 . JSTOR   92217.
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