Molgula ficus

Invasion History

First Non-native North American Tidal Record: 1994
First Non-native West Coast Tidal Record: 1994
First Non-native East/Gulf Coast Tidal Record:

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General Invasion History:

Molgula ficus is native to the Indo-West Pacific region. It was described from Shark Bay, Western Australia in 1859 and has been collected from sites around the continent. It has also been collected in Thailand, Singapore, and Hong Kong (Kott 1985; Kott 2005). It was discovered in Southern California in 1994 and in Chile in 1997, having been introduced through ship fouling.

North American Invasion History:

Invasion History on the West Coast:

Molgula ficus was discovered in Southern California in 1994, but was originally confused with the native species Molgula verrucifera. Molgula ficus was originally misidentified by P. Kott as the native California species M. verrucifera, but is much larger, and is not a brooder (see Lambert 2007).  When Gretchen Lambert compared large numbers of M. verrucifera collected from sites along the coast and in harbors between 1994 and 1997, she realized that the larger harbor form was a distinct species and identified it as M. ficus. Since then it has been found from San Diego Bay north to Channel Islands Harbor, adjacent to Port Hueneme (Lambert 2007). One collection of M. ficus was made in San Francisco Bay in Ballena Bay, Alameda in 2005. In 2015-2016, two additional specimens were collected at Oyster Point and Coyote Point marinas, in San Francisco Bay (Tracy et al. 2017) - and we now consider this an established population. Ship fouling is a likely vector for the transport of M. ficus to California and Chile.

Invasion History Elsewhere in the World:

Molgula ficus was collected in Antofagasta Bay, Chile in 1997 (Clarke and Castilla 2000). It is now common on ropes used for scallop culture and in the intertidal beds of Pyura praeputialis, another Australian tunicate (Clarke and Castilla 2000; Lambert 2007).

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Description

Molgula ficus is a round solitary tunicate with both siphons on the upper surface directed away from one another. The oral siphon has six wedge-shaped lobes, while the atrial siphon has four. The siphons are usually separated by a thickened median ridge of tunic. In larger specimens, the ridge between siphons is often lost and the siphons are larger and more divergent with external longitudinal furrows between the lobes around the apertures. The siphons are fringed with two rows of small pointed papillae. In smaller specimens, the tunic is white, thin, and papery with some external irregular processes and usually with sand and mud adhering to it. In larger specimens the tunic is firmer, almost leathery and often clean of debris. This species often occurs in aggregations (Kott 1985). The size ranges from 20-40 mm in California and occasionally up to 89 mm in Australia (Kott 1985; Lambert 2007).

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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 is 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 the 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	Marinas & Docks	None
General Habitat	Vessel Hull	None
General Habitat	Rocky	None
Salinity Range	Polyhaline	18-30 PSU
Salinity Range	Euhaline	30-40 PSU
Tidal Range	Subtidal	None
Vertical Habitat	Epibenthic	None

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Tolerances and Life History Parameters

Minimum Length (mm)	20	California, Lambert 2007
Maximum Length (mm)	40	California, Lambert 2007, occasionally up to 80 mm in Australia (Kott 1985)
Broad Temperature Range	None	Warm temperate-Tropical
Broad Salinity Range	None	Polyhaline-Euhaline

General Impacts

Economic Impacts

Fisheries: In Antofagasta Bay, Chile, Molgula ficus is common on ropes used for scallop culture (Clarke and Castilla 2000), however, the impact on culture operations is unclear.

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References

Ali, H. Abdul Jaffar; Sivakumar, V.; Tamilselvi, M. (2009) Distribution of alien and cryptogenic ascidians along the southern coasts of Indian peninsula, World Journal of Fish and Marine Sciences 1(4): 305-312

Barnes, Robert D. (1983) Invertebrate Zoology, Saunders, Philadelphia. Pp. 883

California Department of Fish and Wildlife (2014) Introduced Aquatic Species in California Bays and Harbors, 2011 Survey, California Department of Fish and Wildlife, Sacramento CA. Pp. 1-36

Clarke, Marcela; Castilla, Carlos (2000) Two new records of ascidians (Tunicata: Ascidiacea) for the continental coast of Chile., Revista Chilena de Historia Natural 3(3): 1-11

de Rivera, Catherine, and 27 authors (2005) Broad-scale non-indigenous species monitoring along the West Coast in National Marine Sanctuaries and National Estuarine Research Reserves report to National Fish and Wildlife Foundation, National Fish and Wildlife Foundation, Washington, D.C.. Pp. <missing location>

Del Pasqua, Michela; Schulze, Anja; Tovar-Hernandez, Maria Ana; Keppel, Erica; Marco Lezzi;, Maria; Gambi, Maria Cristina ; Giangrande, Adriana (2018) Clarifying the taxonomic status of the alien species Branchiomma bairdi and (Annelida: Sabellidae) using molecular and morphological evidence, PLOS ONE 13(5): Published online

Kott, P. (2005) Catalogue of Tunicata in Australian waters, Queensland Museum, Brisbane. Pp. 1-301

Kott, Patricia (1985) The Australian Ascidiacea Part 1, Phlebobranchia and Stolidobranchia., Memoirs of the Queensland Museum 23: 1-440

Lambert, Gretchen (2007) The nonindigenous ascidian Molgula ficus in California, Cahiers de Biologie Marine 48: 95-102

Ruiz, Gregory M.; Geller, Jonathan (2018) Spatial and temporal analysis of marine invasions in California, Part II: Humboldt Bay, Marina del Re, Port Hueneme, and San Francisco Bay, Smithsonian Environmental Research Center & Moss Landing Laboratories, Edgewater MD, Moss Landing CA. Pp. <missing location>

Ruiz, Gregory; Geller, Jonathan (2021) Spatial and temporal analysis of marine invasions: supplemental studies to evaluate detection through quantitative and molecular methodologies, Marine Invasive Species Program, California Department of Fish and Wildlife, Sacramento CA. Pp. 153 ppl.

Simkanin, Christina; Fofonoff, Paul W.; Larson, Kriste; Lambert, Gretchen; Dijkstra, Jennifer A.; Ruiz, Gregory M. (2016) Spatial and temporal dynamics of ascidian invasions in the continental United States and Alaska, Marine Biology 163: Published online

Tracy, Brianna M.; Reyns, Nathalie B. (2014) Spatial and temporal patterns of native and invasive ascidian assemblages in a Southern California embayment, Aquatic Invasions 9: In press

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