Short description of Schizoporella japonica, Orange ripple bryozoan

Bright orange-red, calcified, encrusting bryozoan; forming extensive sheets that grow into foliose lobes. Zooids rectangular or polygonal, separated by a deep groove. Frontal wall covered with pores. Orifice semi-circular with a broad sinus, sloping at sides and flattened at the bottom.  Avicularia often occur, one or two per zooid to the side of orifice, there may also be larger frontal avicularia which point laterally. This species is difficult to distinguish from other species of Schizoporella (Dick, Grischenko, & Mawatari, 2005; Porter, 2012)

Impact summary: Schizoporella japonica, Orange ripple bryozoan

Can form encrustations on ships, piers, buoys and other man-made structures in harbours and marinas. May compete for space with natives and S. japonica is known to inhibit the growth of adjacent species.  Introductions in some areas could potentially contribute to community productivity by providing substratum.

Habitat summary: Schizoporella japonica, Orange ripple bryozoan

Worldwide it is usually found in harbours and marinas, on hard substrates such as pilings and hulls; or intertidally on rocks, boulders and on shellfish such as oysters and mussels. It is tolerant of salinities 18-34 and temperatures 7-19^oC.

Overview table

Environment	Marine
Species status	Non-Native
Native range	Northwestern Pacific
Functional type	Filter-feeder
Status in England	Non-Native
Status in Scotland	Non-Native
Status in Wales	Non-Native
Location of first record	Plymouth
Date of first record	5

Origin

Originally described from Japan as S. unicornis var. japonica, its native distribution is ascribed to the north-west Pacific from China to Japan (Dick et al., 2005).

First Record

Discovered in Holyhead in 2010; Stromness marina, Orkney in June 2011; then subsequently in Kirkwall marina, Orkney; various locations around the Scottish coast (2013); Millbay marina in Plymouth (2012) and King Point marina (2013) and Blyth (2016).

Pathway and Method

Worldwide introductions have been reported in association with aquaculture such as oyster transport (Powell, 1970); and ship and boat hull fouling (Ashton, Zabin, Davidson, & Ruiz, 2012; Davidson, Ashton, & Ruiz, 2010).

Species Status

S. japonica (described as S. unicornis) (Dick et al., 2005) was introduced to the north-eastern Pacific on oysters from Japan (Powell, 1970). It has been reported along the Pacific coast of North America from Alaska to California. It may also be present in Australia where S. unicornis  (possibly  S. japonica) was reported in 1975 following imports of Pacific oysters.

Dispersal Mechanisms

There is limited dispersal by non-feeding swimming larvae which attach and metamorphose within hours following release. Adults are sessile but may be dispersed by natural rafting on weed.

Reproduction

Each colony begins from a single, sexually produced, primary zooid which then buds asexually to form unilaminar, or sometimes bilaminar, sheets.  This species is hermaphroditic. Bright orange embryos are brooded in external ovicells which are prominent, globular with small pores (Dick et al., 2005). The larvae are ciliated and non-feeding, they attach and metamorphose within hours following release. Larval settlement has been observed year-round in Charleston, Oregon where water temperatures are between 10 -13oC (Treibergs, 2012).

Known Predators/Herbivores

New recruits of S. japonica may be vulnerable to predation immediately after metamorphosis and attachment to the substrate. Predation by flatworms of embryos and larvae still in ovicells has been observed (Gordon, 1972; Treibergs, 2012).

Resistant Stages

Zooidal regression and regeneration in bryozoan colonies may be a potentially important life history response to seasonal changes in temperature and food availability (Cummings, 1975).

Habitat Occupied in GB

Marinas and harbours e.g. sides and undersides of pontoon floats.  Along the Pacific coast of North America it also occurs intertidally on natural shores, on rocks and boulders, sometimes abundantly (Dick et al., 2005; Powell, 1970); but occurrence in natural habitats has not yet been documented in GB.

The north-west Pacific from China to Japan. The north-east Pacific from Alaska down to California. It may also be present in Australia where S. unicornis  (possibly  S. japonica) was reported in 1975 following imports of Pacific oysters. The exact introduced range is currently unknown, as it is commonly misidentified as S. unicornis or S. errata (Dick et al., 2005; Treibergs, 2012).

Environmental Impact

This species is a competitor for space and is known to inhibit the growth of adjacent species.  However it is a poor invader of previously occupied space (Sutherland, 1978)

Health and Social Impact

None known

Economic Impact

It could become a significant fouler of mussel and oyster culture gear, potentially competing for food with target species or smothering them, and rendering underwater gear and lines cumbersome. Growth on the mussels or oysters reduces their commercial value.

Identification

Dick, M. H., Grischenko, A. V., & Mawatari, S. F. (2005). Intertidal Bryozoa (Cheilostomata) of Ketchikan, Alaska. [Review]. Journal of Natural History, 39(43), 3687-3784. doi: 10.108000222930500415195

Porter, J. S. (2012). Seasearch Guide to Bryozoans and Hydroids of Britain and Ireland. Ross on Wye: Marine Conservation Society.

Ryland, J.S., Holt, R., Loxton, J., Spencer Jones, M.E. & Porter, J.S. (2014). First occurrence of the non-native bryozoan Schizoporella japonica Ortmann (1890) in Western Europe. Zootaxa,  3780(3), 481-502

Biology, ecology, spread, vectors

Ashton, G. V., Zabin, C. J., Davidson, I., & Ruiz, G. M. (2012). Aquatic Invasive Species Vector Risk Assessments: Recreational vessels as a vector for non-native marine species in California. The California State Lands Commission.

Cummings, S. G. (1975). Zoid regression in Schizoporella unicornis floridana (Bryozoa, Cheilostomata). Chesapeake Sci. 16(2): 93-103

Davidson, I., Ashton, G. V., & Ruiz, G. M. (2010). Biofouling as a vector of marine organisms on the US West Coast: a preliminary evaluation of barges and cruise ships. The California State Lands Commission.

Gordon, D. P. (1972). Biological relationships of an intertidal bryozoan population. Journal of Natural History, 6(5), 503.

Powell, N. A. (1970). Schizoporella unicornis — An Alien Bryozoan Introduced into the Strait of Georgia. Journal of the Fisheries Research Board of Canada, 27(10), 1847-1853. doi: 10.1139f70-201

Treibergs, K. A. (2012). Settlement and growth of the marine bryozoan Schizoporella japonica, and epifaunal development in the South Slough estuary. M.S. thesis, University of Oregon, United States. 

Management and impact

Sutherland, J. P. (1978). Functional Roles of Schizoporella and Styela in the Fouling Community at Beaufort, North Carolina. Ecology, 59(2), 257-264. doi: 10.23071936371

General

Dick, M. H., Grischenko, A. V., & Mawatari, S. F. (2005). Intertidal Bryozoa (Cheilostomata) of Ketchikan, Alaska. [Review]. Journal of Natural History, 39(43), 3687-3784. doi: 10.108000222930500415195

Ross, J.R.P and McCain, K.W., 1976. Schizoporella unicornis (Ectoprocta) in coastal waters of northwestern United States and Canada. Northwest Sci., 50(3), 160-171.