Ascidia sydneiensis

Invasion History

First Galapagos Record: 2016

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General Invasion History:

Ascidia sydneiensis was first described from Port Jackson, near Sydney, Australia, in 1855. It is widely distributed in tropical waters around the world including the Indo-Pacific, where it is believed to be native, and the Caribbean Sea where it was first reported in the late 19th century (Traustedt 1882, cited by Kott 1985; Van Name 1945; Kott 1985; Nishikawa 1991; Lambert 2002; da Rocha and Kremer 2005; Carlton and Eldredge 2009). In the Indo-Pacific it occurs from southern Africa to Japan, Australia, and New Caledonia. However, its range within the Indo-Pacific, may have been expanded by shipping. In the US it occurs in Hawaii, Guam, the Virgin Islands, Biscayne Bay, and the southeastern tip of Florida. It has probably been introduced by shipping because in its introduced range it is most abundant on man-made structures in ports and marinas, including ships' hulls (Lambert 2002; Carlton and Eldredge 2009).

Invasion History in the Galapagos:

Ascidia sydneiensis was collected in 2015–2016 in Franklins Bay, Santa Cruz Island. Dense aggregations were photographed on a plate which had been caged to reduce predation (Lambert 2019). 

Invasion history elsewhere in the world:

Ascidia sydneiensis has a broad distribution in the Indo-Pacific leading some to consider it native here, but we consider it cryptogenic because of its great potential to be transported by shipping. It was collected at Port Jackson, Australia in 1855, and Japan in 1885 (Traustedt 1885, cited by Nisihkawa 1991). It can now be found on both coasts of India (Swami and Chhapgar 2002; Gaonkar et al. 2010; Ali et al. 2009), the Philippines (USNM 11744, US National Museum of Natural History 2009), all coasts of Australia and New Guinea (Kott 1985; Monniot and Monniot 2001), Palau, Polynesia (Tokioka 1950, cited by Kott 1985), Tonga (Monniot and Monniot 2001), and the port of Papeete in Tahiti (Monniot et al. 1985). Ascidia sydneiensis was collected in Guam in Apra Harbor in 1998 on artificial substrates in the harbor and was classified as introduced (Lambert 2002; Lambert 2003). 
 
In the East Pacific it was collected from the Gulf of California in 1889 (USNM 10636, US National Museum of Natural History 2009), and from near the Pacific entrance to the Panama Canal in 1972 (USNM 14614, US National Museum of Natural History 2009), where it was also collected more recently (2004, Ruiz et al. unpublished data; 2009, Carmen et al. 2010).  

In the Southwest Atlantic, Ascidia sydneiensis was first reported in 1956 from Sao Paulo/Brazil (Bjorberg 1956, cited by da Rocha and Kremer 2005). It occurs from the state of Santa Catarina north to Rio de Janeiro (da Rocha and Kremer 2005), with isolated occurrences near the equator in in Pecem and Mucuripe Harbors, Ceara State (Lotufo and Oliveira Filho 2010). 
 
This tunicate has been tentatively identified from the eastern Mediterranean Sea (Israel, as A. cf. sydneiensis, Izquierdo-Munoz et al. 2009; Shenkar and Loya 2009), but its establishment is uncertain. It has not been reported from the Red Sea. 

Description

Ascidia sydneiensis is a large solitary tunicate which can vary in color and may be white, cream, yellow, orange, red, or wine-colored. The tunic itself is translucent and the color is caused by pigmentation on the body wall. It has an elongate body shape that tapers into a long oral siphon with 35-200+ oral tentacles. A shorter atrial siphon projects off the left side of the body. The oral siphon typically has seven or eight lobes, and the atrial siphon has six. On both siphons, the lobes are separated by indented margins or long projections, and there is a dark spot (often red) between lobes (Bonnet and Rocha, 2011). The tunic is finely wrinkled with minute translucent hairs and can be encrusted with detritus, algae, and other invertebrates. When the tunic is removed the muscles on the oral and atrial siphons are conspicuous. The siphons have prominent circular muscle bands and some longitudinal bands. On the right side, 'there is a wide border of short, stout muscle bands extending inward from the margin for a varying distance. They lie for the most part parallel to each other and at right angles to the margin, but curve and cross each other irregularly to a slight extent.' (Van Name 1945). Muscle bands are largely absent from the left side of the body. The large S-shaped digestive tract covers the left side of the body. The largest Caribbean specimen examined by Van Name (1945) was 53 mm long and 27 mm wide, like that described by Nishikawa (1991), but Van Name noted that larger specimens had been reported from the Eastern Hemisphere.

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Taxonomy

Ecology

General:

Life History- A solitary tunicate is ovoid, elongate or vase-like in shape, with two openings or siphons. Most solitary tunicates attach to substrates by their side or base, but some attach with a conspicuous stalk. They are sessile filter feeders with two siphons, an oral and an atrial siphon. Water is pumped in through the oral siphon, where phytoplankton and detritus are filtered by the gills and passed on mucus strings to the stomach and intestines. Waste is then expelled in the outgoing atrial water.

Solitary ascidians are hermaphroditic, meaning that both eggs and sperm are released to the atrial chamber. Eggs may be self-fertilized or fertilized by sperm from nearby animals, but many species have a partial block to self-fertilization. Depending on species, eggs may be externally or internally fertilized. In external fertilizers, eggs and sperm are released through the atrial siphon into the surrounding water column were fertilization takes place. In internal fertilizers, eggs are brooded and fertilized within the atrial chamber and then released into the water column upon hatching. Fertilized eggs hatch into a tadpole larva with a muscular tail, notochord, eyespots, and a set of adhesive papillae. The lecithotrophic (non-feeding, yolk-dependent) larva swims briefly before settlement. Swimming periods are usually less than a day and some larvae settle immediately after release, but the larval period can be longer at lower temperatures. Once settled, the tail is absorbed, the gill basket expands, and the tunicate begins to feed by filtering (Barnes 1983).

Food:

Phytoplankton, detritus

Trophic Status:

Suspension Feeder

SusFed

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Habitats

General Habitat	Unstructured Bottom	None
General Habitat	Marinas & Docks	None
General Habitat	Rocky	None

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Life History

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Tolerances and Life History Parameters

Minimum Salinity (‰)	24	Field (Brazil, Marins et al. 2010)
Maximum Salinity (‰)	40	Approximate salinity for Mediterranean Sea, Israel (Shenkar and Loya 2009)
Maximum Length (mm)	53	Van Name 1945
Broad Temperature Range	None	Warm temperate-Tropical
Broad Salinity Range	None	Polyhaline-Euhaline

General Impacts

Economic Impacts- Ascidia sydneiensis is a common fouling organism on docks, ship hulls, and other man-made structures in tropical waters (Monniot and Monniot 1985; Carlton and Eldredge 2009).  Specific impacts are not known. In Brazil it was found on lantern nets used to culture oysters and scallops, especially in summer, but did not appear to cause serious problems (da Rocha et al. 2009).

Ecological Impacts- In Hawaii, Eldredge and Smith (2001) reported that Ascidia sydneiensis may compete with other shallow-water invertebrates for space, especially in the fouling community, but there are no studies confirming this.

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