Chesapeake Bay Introduced Species Database
Botryllus schlosseri |
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Common name(s): Golden Star Tunicate |
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| Have you ever seen a bright orange gelatinous mass growing on a rock at the seashore? Golden Star Tunicates are common in fouling communities in the lower Chesapeake Bay. They can grow on a variety of slow-moving submerged objects, even some plants and animals. Golden Star Tunicates are colonial meaning that they are made up of individual zooids sharing a single skin or tunic (nonliving cellulose layer) that are all connected by a network of blood vessels. The colony is organized into star-shaped grouping of zooids. Each zooid is small (2-4mm) but the colony is large (7-10cm, 3-4 inches). Like many tunicates, the Golden Star Tunicate?s distribution is widespread, so widespread that its native region is unknown, but some have suspected the Indo-Pacific and the Mediterranean as possible native regions. It was first seen in Chesapeake Bay in 1923 on a ship in Hampton Roads, VA and became abundant during the droughts of the mid-60s, covering bay grasses and oyster trays. However, during a normal year it?s rare and is nearly absent in wet years such as after Hurricane Agnes. | |||||||
| Image courtesy of Melissa Frey, Royal BC Museum. | |||||||
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Synonymy: |
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Alcyonium schlosseri; Botryllus gouldii; Botryllus namei; Botryllus polycyclus; Botryllus stellatus
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Potentially Misidentified As: |
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Botrylloides violaceus
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Common Names: |
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Golden Star Tunicate; Harbor Stars
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Comments: |
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Taxonomy- Tunicates of the genus Botryllus are colonial tunicates, in which groups of 5-20 zooids are organized around shared cloacal (excurrent) openings in a star-like pattern (Van Name 1945). Botryllus 'schlosseri' is a circumglobal form in the temperate zone, highly variable in colony shape and color (Van Name 1945), but whether it constitutes a single species is uncertain. Boyd et al. (1990) found that at Woods Hole MA and Monterey CA, Botryllus were morphologically similar and interfertile, but colonies from the two locations displayed 'allorejection' and did not fuse in the laboratory. They concluded that the Woods Hole and Monterey populations were the same species with slight genetic differences, but cited a number of morphological differences, and a difference in chromosome numbers, between these populations and those in Naples. Boyd et al. have suggested the need for worldwide studies of the species status of Botryllus populations because of their widespread use in embryological and immunological research. Rinkevich et al. (1992) found colony fusion in 4% of Israel vs. Monterey assays, and 12% of Monterey vs. Japan tests, suggesting a high degree of genetic similarity among populations. However, in a later study (Rinkevich et al. 1995), they found no fusion in either Israel vs. Japan assays or in comparisons between different populations along the Israel vs. Japan assays or in comparisons between different populations along the Israeli coast, suggesting a great local polymorphism of allorecognition alleles. The relation of immunological responses to differentiation of other genes and its relation to status of B. schlosseri as a single species (or a species complex) is unclear at this time (Boyd et al. 1990; Rinkevich et al. 1995).
A genetic comparison of East Coast (Maine and Woods Hole) vs. West Coast (Bodega Bay to Los Angeles) finds significant differences between populations, suggesting a possible difference in origin for East and West Coast populations (Europe vs. Asia) (Stoner et al. 2002). In another analysis, genotypes of B. schlosseri from Woods Hole and Maine grouped with those from European harbors (Lopez-Legentil 2006). (See comments under 'Taxonomy').
Potentially Misidentified Species - Botrylloides violaceus is a Pacific species, introduced to New England waters in the 1970s (Whitlach et al. 1995), and collected in Chesapeake Bay since 2000 (Ruiz et al. unpublished data).
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This data was last modified on Tuesday, January 14th, 2014.