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Ecteinascidia turbinata

Close-up image showing individual tunics of the mangrove tunicate, Ecteinascidia turbinata. Siphons of each transparent tunic are pigmented orange. Photo courtesy of Kevin B. Johnson, Florida Institute of Technology.

Individual tunic of E. turbinata, showing the mesh-like pharyngeal basket and anus leading to the excurrent siphon. Photo courtesy of Kathy Hill, Smithsonian Marine Station at Fort Pierce.

The tiger flatworm, Maritigrella crozieri, consuming zooids of E. turbinata. Photo courtesy of Kate Rawlinson, Smithsonian Marine Station at Fort Pierce.

Tadpole larva of E. turbinata. Notochord is visible through the tail, and white adhesive papillae are located at the anterior end of the yellow trunk (far left). Photo courtesy of Kevin B. Johnson, Florida Institute of Technology.

Species Name: 
Ecteinascidia turbinata Herdman 1880

Common Name:
Mangrove Tunicate

Species Description:
The mangrove tunicate, Ecteinascidia turbinata, is a colonial ascidian comprised of individual zooids connected through a series of root-like stolons at the base of the colony. These stolons provide blood to zooids, linking them to one another, and serve as attachment points between the colony and substratum. Each zooid is surrounded by a tunic opening to the water column via an orange siphon. Pigmentation of this area is achieved by carotenoids found in organelles accumulated at the anterior portion of the tunic (Lyerla et al. 1975). Sparse pigments in other portions of the tunic give colonies a transparent appearance. However, in some populations, the zooids within each tunic may have a yellow, orange or pink cast (Voss 1980).

Potentially Misidentified Species:
Several species of colonial ascidians are found throughout the Indian River Lagoon. However, coloration, size and habitat preferences of E. turbinata distinguish it readily from other species.

II.  HABITAT & DISTRIBUTION
 
Regional Occurrence:
The range of E. turbinata extends throughout the warm, shallow waters of the Gulf of Mexico, the east coast of Florida, Bermuda and the Caribbean (Van Name 1945). Seasonal populations are common in the Mediterranean (Carballo 2000), and colonies have been found in Chesapeake Bay (Calder et al. 1966) and on reefs off the Carolinas (Pearse & Williams 1951) in the spring and summer months.

IRL Distribution:
Colonies of the mangrove tunicate are found throughout the lagoon, growing on prop roots of the red mangrove, Rhizophora mangle (eg. Vázquez & Young 1996), hence the common name. However, E. turbinata can also be found attached to docks, floating debris, rocks and seagrass blades (eg. Ruppert & Fox 1988, Young & Bingham 1987).

III. LIFE HISTORY & POPULATION BIOLOGY

Age, Size, Lifespan:
Individual zooids are approximately 2.0 to 2.5 cm in height (Young & Bingham 1987, Ruppert & Fox 1988), and colonies may reach a diameter of 14 cm and weigh up to 350 g (Carballo et al. 1997). Although the maximum age of E. turbinata in the field is unknown, maturation from fertilized egg to adult can occur in a few months (Carballo 2000).

Abundance:
Distribution of E. turbinata can be patchy and abundance may vary with season. In the IRL, large clusters can carpet the undersides of floating docks, and the submerged lengths of red mangrove prop roots. In the Mediterranean, densities can reach 175 zooids per square meter (Carballo 2000).

Reproduction:
Adult E. turbinata are simultaneous hermaphrodites, but can reproduce sexually or asexually. Sexual reproduction occurs most frequently in the spring and summer when water temperatures are warm. The mangrove tunicate is ovoviviparous, and larvae are brooded in the peribranchial cavity for approximately 7 to 9 days after fertilization before being released into the water column (Carballo et al. 2000).

Embryology:
Ascidians produce tadpole larvae with a visible notochord. Hence, they are placed in the phylum Chordata, along with mammals, birds and fishes. Tadpole larvae of E. turbinata are conspicuous, bright orange to yellow and approximately 4.5 mm in length (Young & Bingham 1987). They are lecithitrophic (Carballo 2000), obtaining nutrients from yolk reserves instead of feeding on plankton (planktotrophic). Because of this life-history trait, the planktonic stage of E. turbinata is short, and larvae must find a suitable habitat to settle before food reserves are exhausted. Locomotion throughout the water column facilitates this search. Larvae swim in a similar fashion to fishes, bending at the junction between the trunk and the tail to undulate through the water (McHenry 2005). After finding a suitable habitat, larvae attach themselves to the substratum via a series of adhesive-producing structures at the front of the trunk called papillae. When attachment is complete, larvae metamorphose into juvenile tunicates.

IV.  PHYSICAL TOLERANCES

Temperature:
The mangrove tunicate is generally found in warm tropical and sub-tropical waters, where it commonly encounters average temperatures of 25 to 32 °C (Vázquez & Young 1996). It occurs in the Mediterranean in the summer months, but dies back at temperatures below 17 °C, when only the stolons remain. From these remnants, colonies usually recover when waters begin to warm (Carballo 2000).

Salinity:
As a common inhabitant of estuarine ecosystems, E. turbinata can withstand relatively large salinity fluctuations. However, the presence of haloclines causing stratification in the water column has been shown to reduce the ability of larvae to migrate vertically (Vázquez & Young 1996). Vertical migrations are a critical dispersal mechanism for many zooplankton. When prevented, genetic mixing between populations and/or expansion of newly recruited tunicates to other habitats may be inhibited.

V.  COMMUNITY ECOLOGY

Trophic Mode:
Ecteinascidia turbinata is a sessile, benthic filter-feeder. The incurrent siphon takes water into a sieve-like pharyngeal basket that filters out food of the appropriate size range before water is pumped from the animal via the excurrent siphon.

Predators:
Anti-predator compounds are present in both larval and adult mangrove tunicates. In the case of adults, high concentrations of vanadium are likely to reduce palatability of the tissues (Stoecker 1980). This defense, coupled with yellow or orange warning coloration at nearly all life stages, eases predatory pressure on the species (Young & Bingham 1987) with the exception of the tiger flatworm, Maritigrella crozieri. By extruding its pharynx into individual zooids, the flatworm feeds exclusively on E. turbinata (Ruppert & Barnes 1994), with one individual consuming an average of 19 zooids in 24 hours (Newman et al. 2000).

Associated Species:
As a component of coastal and estuarine fouling communities, E. turbinata is found alongside several species of invertebrates, namely sponges and other ascidians. In addition, at least three species of amphipods, dwelling inside the tunic, are found in association with E. turbinata. The amphipod, Anamixis hanseni appears to be host-specific, occurring only in this species (Theil 1999), and Leucothoides pottsi and Leucothoe spinicarpa have been found in individual tunics as well (Thomas 1979). Although details of such symbiotic relationships are unclear, it appears that the amphipods gain protection from predators and feed on particulates entering the tunic through the incurrent siphon (Thomas 1979).

VI. SPECIAL STATUS

Special Status:
Biomedical applications

Economic Importance:
The mangrove tunicate produces a compound called ecteinascidin-743 (ET-743, also known as trabectedin), which has gained attention for its anti-cancer properties (eg. Carballo et al. 2000). Although clinical trials support its effectiveness in reducing various solid-type tumors, the size and abundance of this ascidian make large-scale production of ET-743 difficult and costly. Approximately one metric ton of E. turbinata must be collected and extracted to produce one gram of the cancer-fighting agent (Proksch et al. 2003). In recent years, the medical industry has been producing trabectedin through semisynthesis (Cuevas & Francesch 2009), currently eliminating the need for the original natural product. Trabectedin, marketed under the brand name Yondelis, is the first marine anticancer agent approved in the European Union for use in patients with soft tissue sarcoma (STS) (Cuevas & Francesch 2009). In the United States, the drug is undergoing clinical trials where it has been shown to reduce or stabilize the growth of STSs, including leiomyosarcomas and liposarcomas (Amant et al. 2009, Schöffski et al. 2008).

VII. REFERENCES

Amant, F, Coosemans, A, Renard, V, Everaert, E & I Vergote. 2009. Clinical outcome of ET-743 (Trabectedin; Yondelis) in high-grade uterine sarcomas: report on five patients and a review of the literature. Int. J. Gynecol. Cancer. 19: 245-248.

Bingham, BL & CM Young. 1991. Larval behavior of the ascidian Ecteinascidia turbinata Herdman; an in situ experimental study of the effects of swiming on dispersal. J. Exp. Mar. Biol. Ecol. 145: 189-204.

Calder, DR, Thornborough, JR & JK Lowry. 1966. Record of Ecteinascidia turbinata (Ascidiacea, Perophoridae) in the York River, Virginia. Chesapeake Science. 7: 223-224.

Carballo, JL. 2000. Larval ecology of an ascidian tropical population in a Mediterranean enclosed system. Mar. Ecol. Prog. Ser. 195: 159-167.

Carballo, JL, Naranjo, S, Hernández-Zanuy A & B Kukurtzü. 1997. Estudio de la población de Ecteinascidia turbinata Herdman 1880 (Ascidacea) en la isla de Formentera (Mediterráneo, España): Distribución, densidad y crecimiento. Ciencias del Mar UAS 15: 7-15.

Carballo, JL, Naranjo, S, Kukurtzü, B, de La Calle, F & A Hernández-Zanuy. 2000. Production of Ecteinascidia turbinata (Ascidiacea: Perophoridae) for obtaining anticancer compounds. J. World Aquaculture Soc. 31: 481-490.

Cuevas, C & A Francesch. 2009. Development of Yondelis (trabectedin, ET-743). A semisynthetic process solves the supply problem. Nat. Prod. Rep. 26: 322-337.

Lyerla, TA, Lyerla, JH & M Fisher. 1975. Pigmentation in the orange tunicate, Ecteinascidia turbinata. Biol. Bull. 149: 178-185.

McHenry, MJ. 2005. The morphology, behavior, and biomechanics of swimming in ascidian larvae. Can. J. Zool. 83: 62-74.

Newman, LJ, Norenburg, JL & S Reed. 2000. Taxonomic and biological observations on the tiger flatworm, Maritigrella crozieri (Hyman, 1939), new combination (Platyhelminthes, Polycladida, Euryleptidae) from Florida waters. J. Nat. Hist. 34: 799-808.

Pearse, AS & LG Williams. 1951. The biota of the reefs off the Carolinas. J. Elisha Mitchell Sci. Soc. 67: 133-161.

Proksch, P, Edrada-Ebel, R & R Ebel. 2003. Drugs from the sea - opportunities and obstacles. Mar. Drugs. 1: 5-17.

Ruppert, EE & RD Barnes. 1994. Chapter 6: Platyhelminthes, Gnathostomulids and Mesozoans. In: Invertebrate Zoology, 6th edn. Saunders College Publishing. Fort Worth, Texas, USA. 1056 pp.

Ruppert, EE & RS Fox. Seashore animals of the Southeast: A guide to common shallow-water invertebrates of the southeastern Atlantic coast. Univ. South Carolina Press. Columbia, SC, USA. 429 pp.

Schöffski, P, Dumez, H, Wolter, P, Stefan, C, Wozniak, A, Jimeno, J & AT Van Oosterom. 2008. Clinical impact of trabectedin (ecteinascidin-743) in advanced/metastatic soft tissue sarcoma. Expert Opin. Pharmacother. 9: 1609-1618.

Stoecker, D. 1980. Relationships between chemical defense and ecology in benthic ascidians. Mar. Ecol. Prog. Ser. 3: 257-265.

Theil, M. 1999. Host-use and population demographics of the ascidian-dwelling amphipod Leucothoe spinicarpa: indication for extended parental care and advanced social behavior. J. Nat. Hist. 33: 193-206.

Thomas, JD. 1979. Occurrence of the amphipod Leucothoides pottsi Shoemaker in the tunicate Ecteinascidia turbinata Herdman from Big Pine Key, Florida, USA. Crustaceana 37: 107-109.

Van Name, WG. 1945. The North and South American ascidians. Bull. Amer. Mus. Natur. Hist. 84: 1-476.

Vázquez, E & CM Young. 1996. Responses of compound ascidian larvae to haloclines. Mar Ecol. Prog. Ser. 133: 179-190.

Voss, GL. 1980. Seashore life of Florida and the Caribbean. Dover Publications. Mineola, New York, USA. 199 pp.

Young, CM. 1986. Direct observations of field swimming behavior in larvae of the colonial ascidian Ecteinascidia turbinata. Bull. Mar. Sci. 39: 279-289.

Young, CM & BL Bingham. 1987. Chemical defense and aposematic coloration in larvae of the ascidian Ecteinascidia turbinata. Mar. Biol. 96: 539-544.

Report by: LH Sweat, Smithsonian Marine Station at Fort Pierce
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Page last updated: 7 May 2009

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