Didemnum psammatodes

Invasion History

First Non-native North American Tidal Record: 1988
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 1988

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General Invasion History:

Didemnum psammatodes was first described in Northern Australia. It is native to the tropical and subtropical regions of the Indo-West Pacific (Monniot and Monniot 1985; Monniot and Monniot 1994; Carlton and Eldredge 2009; Gretchen Lambert, personal communication 2005). The presumed native range extends from East Africa to China, Japan, Fiji, Tonga, and New Zealand. Lambert (2002) considers it cryptogenic in Guam and it is considered introduced to the Hawaiian Islands and the Pacific entrance of the Panama Canal (Calton and Eldredge 2009; Carman et al. 2010).

Didemnum psammatodes is introduced to the Atlantic and was probably overlooked for decades before being reported in Guadeloupe in 1980-1981 (Monniot and Monniot 1985). In the 1980s it was reported from the Indian River Lagoon, Florida and Sao Sebastiao, Brazil (Bingham 1992; da Rocha and Monniot 1995) and in 1990 it was collected from Sierra Leone, West Africa (Monniot and Monniot 1994). It was probably transported to the Atlantic through ship fouling (Farrapeira et al. 2007).

North American Invasion History:

Invasion History on the East Coast:

Didemnum psammatodes was reported from the Indian River Lagoon, Fort Pierce, Florida in 1988, where it is abundant on mangrove roots and in seagrass beds (Bingham 1992; Ruiz et al., unpublished data). It occurs in Biscayne Bay (reported in 2004, Ruiz et al., unpublished data) and north to St. Augustine in Florida (Smithsonian Marine Station at Fort Pierce 2011). 

Invasion History on the Gulf Coast:

On the Gulf Coast, Didemnum psammatodes was collected in a marina at Port Isabel, Texas in 2004 (Lambert et al. 2005), but was not identified on settling plates in other Gulf Coast ports in 2000-2003 (Ruiz et al., unpublished data).

Invasion History in Hawaii:

Didemnum psammatodes has been introduced to Hawaii, where it was first collected in Oahu in 1998. It has since been found in several harbors and marinas on the island (Carlton and Eldredge 2009).

Invasion History Elsewhere in the World:

Didemnum psammatodes has been collected in Panama Bay, near the entrance to the Pacific side of the Panama Canal (Carman et al. 2010).

In the Atlantic, it was first reported from Guadeloupe (in 1980-81, Monniot and Monniot 1983) and subsequently found in Sao Sebastio, Brazil (in 1985, da Rocha and Monniot 1995), northeastern Brazil (in 2001, Gama et al. 2006), French Guiana (Monniot and Monniot 1994), Bocas del Toro, Panama (da Rocha et al. 2005), Colon, Panama (in 2004, Ruiz et al., unpublished data), Belize (in 1985, Goodbody 2000), and Jamaica (Goodbody and Webber 2003). In the Eastern Atlantic it was collected in Freetown, Sierra Leone, West Africa (Monniot and Monniot 1994).

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Description

Didemnum psammatodes is a colonial tunicate. Colonies form thin encrusting sheets that sometimes produce fleshy lobes or irregular twig-like branches up to 8 cm long and 1 cm diameter. It is sometimes called the chocolate tunicate and appears smooth and glossy, but is gritty to the touch (Smithsonian Marine Station 2011). The color of colonies varies with the substrate, ranging from cream-colored in coral reef habitats to brown in muddy habitats (Kott 2001). The brown color of the colony derives from dense packing of fecal pellets throughout the tunic (Gretchen Lambert, personal communication 2012). Chlorophyte microalgae are often embedded in the colony surface and spicules (small crystalline structures embedded in the tunic) are scattered throughout. Some spicules have 11-13 relatively short conical pointed rays with bases separated on the central mass. Other spicules are burr-like with cylindrical or paddle-shaped rays. The spicules are very small, sparse and dissolve easily, making them difficult to find or absent in preserved specimens. Colonies have characteristically constricted common cloacal cavities that are shallow with brown fecal pellets embedded throughout (Kott 2001). Zooids are very small, being less than 1mm long, with a wide atrial aperture, which exposes much of the branchial sac to the cloacal cavity. The branchial sac has eight stigmata in the first row, but numbers of stigmata in other rows could not be determined accurately (Kott 2001). The gut loop is bent at right angles to the long axis of the thorax (Kott 2001). Larvae have three adhesive papillae and four pairs of ampullae (da Rocha and Monniot 1995).

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Taxonomy

Ecology

General:

Life History- A colonial tunicate consists of many zooids, bearing most or all of the organs of a solitary tunicate, but modified to varying degrees for colonial life. Colonial tunicates of the family Didemnidae have small zooids, completely embedded in an encrusting and thin tunic. Each zooid has an oral siphon and an atrial aperture which opens to a shared cloacal chamber. Water is pumped into the oral siphon, through finely meshed ciliated gills on the pharynx, where phytoplankton and detritus is filtered, and passed on mucus strings to the stomach and intestines. Excess waste is expelled in the outgoing atrial water (Van Name 1945; Barnes 1983).

Colonial tunicates reproduce both asexually by budding and sexually from fertilized eggs that develop into larvae. Buds can form from the body wall of the zooids. Colonies vary in size ranging from small clusters of zooids to huge spreading masses. The zooids are hermaphroditic, which means both eggs and sperm are released into the atrial chamber. Eggs may be self-fertilized or fertilized by sperm from nearby animals, but some species have a partial block to self-fertilization. Fertilized eggs are brooded within the tunic until they hatch into lecithotrophic (non-feeding, yolk-dependent) tadpole larvae. The larva has a muscular tail and a notochord, eyespots, and a set of adhesive papillae. The larvae are expelled upon hatching and swim briefly before settlement. Swimming periods are usually less than a day, but some larvae settle immediately after release or swim for longer periods if the water temperature is low. On settlement the tail is absorbed, the gill basket expands, and the tunicate begins to feed by filtering (Van Name 1945; Barnes 1983).

Ecology- Didemnum psammatodes s known from tropical and subtropical climates in marine waters on rocks, mab=ngroves, coral reefs, ship hulls, and marinas and docks ( da Rocha et al. 2009). Large biomasses of colonial tunicates can filter large volumes of water, removing phytoplankton and other particles.

Food:

Phytoplankton, detritus

Trophic Status:

Suspension Feeder

SusFed

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Habitats

General Habitat	Rocky	None
General Habitat	Marinas & Docks	None
General Habitat	Mangroves	None
General Habitat	Coral reef	None
General Habitat	Vessel Hull	None
General Habitat	Grass Bed	None
Salinity Range	Polyhaline	18-30 PSU
Salinity Range	Euhaline	30-40 PSU
Tidal Range	Subtidal	None
Tidal Range	Low Intertidal	None
Vertical Habitat	Epibenthic	None

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Tolerances and Life History Parameters

Broad Temperature Range	None	Warm temperate-Tropical
Broad Salinity Range	None	Polyhaline-Euhaline

General Impacts

Impacts of Didemnum psammatodes have not been reported.

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References

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