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Potentially Misidentified Species:
In the IRL, Styela plicata may be mistaken for the co-occurring solitary
tunicate Molgula occidentalis. This species is smaller and smoother
than S. plicata, and side-by-side comparisons should easily
differentiate these species. It is somewhat more difficult to distinguish
S. plicata from the co-occurring congener (and fellow nonindigenous
species) S. canopus (=S. parita). S. canopus is smaller,
approximately 20-40 mm, and typically has externally striped siphons.
II. HABITAT AND DISTRIBUTION
Regional Occurrence:
Various authors list Styela plicata native or cryptogenic on the U.S.
east coast (ISSG, NIMPIS 2002), but other authors consider the organism to be
non-native in the western Atlantic (Da Rocha and Kremer 2005). The putative
native range of the species is the the Indo-Pacific (Carlton and Ruckelshaus
1997, Lambert and Lambert 1998, Lambert 2001).
Bingham (1992) and Carlton and Ruckelshaus (1997) list S. plicata as an
introduced species in Florida.
IRL Distribution:
Styela plicata is a widespread and abundant component of the IRL
fouling community, commonly encountered near inlets and also well into the
interior of the lagoon (Mook 1983).
III. LIFE HISTORY AND POPULATION BIOLOGY
Age, Size, Lifespan:
NIMPIS (2002) reports Styela plicata individuals commonly range from
40-70 mm in size and that they may reach 90 mm.
Kott (1972) reports a life span of less than 1 year for S. plicata
populations examined from Moreton Bay, Australia.
Abundance:
In the IRL, Mook (1981, 1983) noted that Styela plicata was an abundant
organism that dominated the fouling community, often to the exclusion of
barnacles, in areas where large predatory fish were not present.
Reproduction:
Styela plicata is a protandric hermaphrodite, with individuals starting
out as functional males and then becoming functional females later in life.
Sequential hermaphroditism insures fertilization through outcrossing. Sperm
and eggs are shed to the water column via excurrent siphons and fertilization
is external (Yamaguchi 1975, NIMPIS 2002).
S. plicata have been reported to reach sexual maturity in 2 months
during the summer and 5 months in the winter (Yamaguchi 1975).
Embryology:
Gamete release and fertilization in Styela plicata reportedly occurs in
the late afternoon, with free-swimming, tadpole-like larval hatching out the
following morning and typically becoming capable of settling to the benthos the
same day (Yamaguchi 1975, NIMPIS 2002). Although larvae begin probing for
suitable settlement sites shortly after hatching, they can extend their time in
the water column for up to 2 days without negative consequence (Thiyagarajan
and Qian 2003).
Sciscioli et al. (1978) note the tendency for larvae to settle onto previously
colonized experimental settlement panels, suggesting environmental cues from
adult conspecifics may be important. Larval nutrition is in the form of
maternally supplied yolk contained in an envelope surrounding the eggs (Pisut
and Pawlik, 2002).
IV. PHYSICAL TOLERANCES
Temperature:
Temperatures in the range of 11-28°C permit spawning, and optimal spawning
temperature occurs around 28°C (West and Lambert 1975, Yamaguchi 1975).
Salinity:
Baker et al. (2004) report that Styela plicata in the greater Tampa Bay
ecosystem occur in salinities ranging from full seawater down to around 20 ppt.
V. COMMUNITY ECOLOGY
Trophic Mode:
Styela plicata 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 class before water is pumped from the animal via the
excurrent siphon.
Associated Species:
Styela plicata occurs alongside a number of different animal and algal
taxa that comprise hard fouling intertidal and subtidal communities, although
none of these associations are likely to be obligate.
Burrowing molluscs are found in the tests of some
solitary tunicates including Styela spp., and copepods, amphipods, shrimps, crabs, and other
small crustaceans often take up residence within Styela and other ascidians (Kott 1997, Pearse 1947).
VI. INVASION INFORMATION
Invasion History:
Styela plicata is among the most common introduced ascidian species
worldwide (Baker et al. 2004). It's present-day distribution is widespread but
disjunct (da Rocha and Kremer 2005). The true native range of S.
plicata is unknown but believed by several authors to be roughly the
Indo-Pacific (Carlton and Ruckelshaus, 1997, Lambert and Lambert 1998, Lambert
2001).
Although ballast water transport has been suggested as a potential invasion
pathway, it may be of only minor importance. The short larval duration
indicates that S. plicata is unlikely to have been transported across
great distances either as free-living water column inhabitants or as larvae in
ballast water. Long-distance transport as adult fouling inhabitants on ship hulls is
considerably more likely as a recurring means of introduction. S.
plicata is a common hull-fouling species in tropical and warm temperate
ports throughout much of the world. Accidental transport in shipments of live
bivalves is another probable introduction route (Carlton 1979, Lambert 2001).
Despite considerable evidence supporting the contention that the organism is
not native to U.S. waters, Styela plicata was originally described in
1823 from specimens collected from the hull-fouling community on a ship in
Philadelphia PA. The organism was reported from U.S. coastal waters ranging
from North Carolina to Texas in the 1880s, and had been reported from
California by 1915. S. plicata had also been reported from Australia by
the 1870s and from Brazil by 1883 (Fofonoff et al. 1999, Da Rocha and Kremer
2005). The presence of the organism in Chesapeake Bay was only conclusively
documented when it was recovered on experimental fouling plates in 2002
(Fofonoff and Ruiz unpublished data).
Potential to Compete With Natives:
Styela plicata appears capable of outcompeting native species. Lambert
and Lambert (1995) report that S. plicata appears to have replaced the
native solitary tunicates Pyura haustor and Ascidia ceratodes in
parts of their California range.
Possible Economic Consequences of Invasion:
Styela plicata is a widespread and common fouler buoys, pilings, nets
and other floating or submerged manmade structures. It is also a common fouler
of aquaculture cages, bags, and nets. If fouling is severe costly cleaning of
culture gear is required to avoid still costlier loss of stocks (Da Rocha and
Kremer 2005).
VII.
REFERENCES
Baker P., Baker S.M., and J. Fajans. 2004. Nonindigenous marine species in the
greater Tampa Bay ecosystem. Tampa Bay Estuary Program Technical Publication
#02-04. 131p.
Carlton J.T. 1979. History, biogeography, and ecology of the introduced
invertebrates of the Pacific Coast of North America. Ph.D. Thesis, University
of California, Davis, CA. 904 pp.
Carlton J.T., and M.H. Ruckelshaus. 1997. Nonindigenous marine invertebrates and
algae. Pp 187-201 in: Simberloff D., Schmitz D.C., and T.C. Brown (eds).
Strangers in Paradise. Island Press, Washington, D.C. 467 p.
Da Rocha R.M., and L.P. Kremer. 2005. Introduced Ascidians in Paranagua Bay,
Parana, southern Brazil. Revista Brasileira de Zoologia 22:1170-1184.
Fofonoff P.W., Ruiz G.M., Hines A.H., Steves B.P., and J.T. Carlton. 1999. Four
centuries of biological invasions in Chesapeake Bay. Presented paper. First
National Conference on Marine Bioinvasions, January 24 -27, 1999, Massachusetts
Institute of Technology, Cambridge, MA.
Kaplan E.H. 1999. A Field Guide to Southeastern and Caribbean Seashores: Cape
Hattaras to the Gulf Coast, Florida, and the Caribbean. Peterson Field Guide
Series. Houghton Mifflin Company, NY. 425 p.
Kott P. 1972. Some sublittoral ascidians in Moreton Bay, and their seasonal
occurrence. Memoirs of the Queensland Museum 16:233-260.
Kott P. 1997. Chapter 23. Tunicates (Sub-phylum Tunicata). In: Shepherd S.A.,
and M. Davies, M. (eds). Marine Invertebrates of Southern Australia - Part
III. South Australian Reseach and Development Institute South Australia. 489 p.
Lambert G., and C.C. Lambert. 1995. Nonindigenous sea squirts in California
Harbors. Aquatic Nuisance Species Digest 1:17-20.
Lambert C.C., and G. Lambert. 1998. Non-indigenous ascidians in southern
California harbors and marinas. Marine Biology 130:675-688.
Lambert G. 2001. A global overview of ascidian introductions and their possible
impact on the endemic fauna. Pp 249-257 In: Sawada, H., Tokosawa, H., and
C.D. Lambert (eds). The Biology of Ascidians. Springer-Verlag, Tokyo, Japan. 470 p.
Mook D. 1981. Effects of disturbance and initial settlement on fouling
community structure. Ecology 62:522-536.
Mook D. 1983. Responses of common fouling organisms in the Indian River,
Florida, to various predation and disturbance intensities. Estuaries 6:372-379.
NIMPIS. 2002. Styela plicata species summary. CSIRO National Introduced
Marine Pest Information System (Hewitt C.L., Martin R.B., Sliwa C., McEnnulty,
F.R., Murphy, N.E., Jones T. and S. Cooper, eds). Available online.
Pearse A.S. 1947. On the Occurrence of Ectoconsortes on Marine Animals at Beaufort, NC. The Journal of Parasitology 33:453-458.
Pisut P., and J. Pawlik. 2002. Anti-predatory chemical defenses of ascidians:
Secondary metabolites or inorganic acids? Journal of Experimental Marine
Biology and Ecology 270:203-214.
Sciscioli M., Lepaore E., and A. Tursi. 1978. Relationship between Styela
plicata (Les.) (Tunicata) settlement and spawning. Mem. Biol. Mar.
Oceanogr. 8:65-75.
Thiyagarajan V., and P. Qian. 2003. Effect of temperature, salinity and delayed
attachment on development of the solitary ascidian Styela plicata
(Lesueur). Journal of Experimental Marine Biology and Ecology 290:133-146.
West A., and C. Lambert. 1975. Control of spawning in the tunicate Styela
plicata by variations in a natural light regime. J. Exp. Zool., 195:
263-270.
Yamaguchi M. 1975. Growth and reproductive cycles of the marine fouling
ascidians Ciona intestinalis, Styela plicata, Botrylloides
violaceus, and Leptoclinum mitsukurii at Aburatsubo-Moroiso Inlet
(Central Japan). Ymrine Biology 29:253-259.
Report by:
J. Masterson, Smithsonian Marine Station
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