Taxonomic name: Schizoporella unicornis (Johnston, 1874)
Synonyms: Lepralia unicornis (Johnston, 1874), Schizoporella unicornis (Lagaaiji, 1952)
Common names: single horn bryozoan (English)
Organism type: bryozoan
Schizoporella unicornis, or single horn bryozoan, is an encrusting bryozoan native to Japan. It has been unintentionally introduced along with the Pacific oyster (Crassostrea gigas), or by hull fouling, to several locations throughout the world. Schizoporella unicornis is an abundant fouling organism known to inhibit growth and settlement of native bryozoa.
Schizoporella unicornis is an encrusting, colonial bryozoan. Colonies are commonly orange in color however initial growth is white to yellowish brown, later becoming dark brownish, while growing edges are yellow to light brown. Mature colonies are typically 1-4cm in diameter and may form on a wide variety of substrata such as shells, stone, kelp, vessel hulls, piers, overhangs, and other bryozoans. Inner zooids are hexagonal and outer zooids are rectangular in shape with an inflated frontal wall and wide aperature. They are arranged in alternate rows radiated from the center (NIMPIS, 2008; Ross & McCain, 1976; Hayes et al., 2005).
estuarine habitats, marine habitats
Schizoporella unicornis occurs on hard substrates and is found in shallow waters of intertidal zones. It is tolerant of salinities 18-30% and temperatures 7-19°C. Preferred substrates are large flat shaded surfaces free from abrasion with adequate water flow. S. unicornis commonly occurs on shells, barnacles, algae, rocks, docks, hulls, pilings, and underwater debris (Ross & McCain, 1976; Prince William Sound Regional Citizens' Advisory Council. 2004)
Schizoporella unicornis is an abundant fouling organism capable of encrusting on a wide variety of substrata. This fouling can be a nuisance to shipping and ports, and has potenital to be a problem to industrial components, cooling vents, etc. as in the case with other bryozoans. Single horn bryozoans exclude or inhibit the settlement and growth of native species, thereby modifying natural communities. Their stolons are extensions that develop at colonial interfaces and have been demonstrated to redirect or reverse the growth of competitors (Prince William Sound Regional Citizens' Advisory Council. 2004; Ray, 2005).
Schizoporella unicornis is reported to have high mortality rates during "red tide" algal blooms (NIMPIS, 2004)
Native range: Japan.
Known introduced range: Australia, Belgium, Brazil, Canada, France, Galapagos Islands, Ireland, Mexico, United Kingdom, United States
Preventative measures: Prevention of introduction is the only effective means of combating Schizoporella unicornis, as there is no known, effective means of controlling it once it has established. Regulations concerning oyster trade and shipping targeting hull fouling, may prevent the introduction of S. unicornis to new locations as these are the two primary means of its dispersal (Prince William Sound Regional Citizens' Advisory Council. 2004; Ross & McCain, 1976).
Single horn bryozoans are suspension feeders which consume phytoplankton, algae, and bacteria. Zooids feed with ciliated lophophores (tentacle strauctures) that they extend from their orifice to sweep particles into its mouth (Prince William Sound Regional Citizens' Advisory Council, 2004).
Sexual. Schizoporella unicornis is a hermaphrodite. Reproduction may be seasonal or continuous depending on location. Its eggs are contained in their ovicells, or ooecium. Sperm is released into the water column where it is collected by other zooids. Eggs are fertilized and brooded in the ovicells where they mature to free swimming larvae. Parts of existing colonies may start a new colony if seperated (NIMPIS, 2004; Prince William Sound Regional Citizens' Advisory Council, 2004).
Coronate, free swimming larvae of Schizoporella unicornis settle to suitable substrata after 24-48 hours and metamorphose into a zooid which may settle to an existing colony or form a new colony. S. unicornis has high settlement and survival success rates. Settlement of larvae is positively correlated to exhisting colonies. Schizoporella unicornis is a long-lived perennial species (Prince William Sound Regional Citizens' Advisory Council, 2004; Hurlbut, 1991)
Principal sources: NIMPIS, 2002. Schizoporella unicornis species summary. National Introduced Marine Pest Information System (Eds: Hewitt C.L., Martin R.B., Sliwa C., McEnnulty, F.R., Murphy, N.E., Jones T. & Cooper, S.)
Ross, J.R.P and McCain, K.W., 1976. Schizoporella unicornis (Ectoprocta) in Coastal Waters of Northwestern United States and Canada.
Prince William Sound Regional Citizens' Advisory Council. 2004. Non-indigenous Aquatic Species of Concern for Alaska. Fact Sheet 9. Single Horn Bryozoan.
Fuller, Pam., 2008. Schizoporella unicornis. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
Compiled by: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Last Modified: Wednesday, 17 January 2007