Watersipora mawatarii


Scientific Name: Watersipora mawatarii

Phylum: Bryozoa

Class: Gymnolaemata

Order: Cheilostomatida

Family: Watersiporidae

Genus: Watersipora


mawatarii [Describe here as A. iricolor]

Native Distribution

Origin Realm:

Temperate Northern Pacific

Native Region:

Origin Location:

Temperate Northern Pacific [Japan] Hokkaido; Otaru (Vieira et al 2014) STATUS STATED [Japan] Oshoro Marine Station, near Otaru City and Chikko, Otaru City, Hokkaido and Amakusa Marine Biological Laboratory, Kyushu. (Vieira et al. 2014) Note: Chiko appeared in the paper may show an address in Otaru City and may be misspelling of Chikko. (opinion by Otani) (Described as new species) STATUS NOT STATED

Geographic Range:

[Western Pacific] Japan (Vieira et al 2014)

General Diversity:


Non-native Distribution

Invasion History:

No records of invasion (Global Invasive Species Database 2016)

Non-native Region:

Not applicable

Invasion Propens:

Not applicable

Status Date Non-native:

Not applicable

Vectors and Spread

Initial Vector:


Second Vector:


Vector Details:


Spread Rate:


Date First Observed in Japan:

First collected in April 1996 (Vieira et al 2014)

Date First Observed on West coast North America:



Impact in Japan:


Global Impact:



Native Temperature Regime:

Mild temperate, Warm temperate

Native Temperature Range:

Oahoro Bay: max 21.8ºC at surface and 21.4ºC at 5m deep both in August and min 4.9ºC at surface and 5.0ºC at 5m deep both in Feburuary during 1992 and 1999. (Nakata et al. 2001) Ariake Sea, near Amakusa Marine Biological Laboratory: max 28.4ºC and min 8.9ºC both at 5m deep during 1974 and 2006, months are unknown. (Yamagata et al. 2008) Mild temperate, Warm temperate (M. Otani, pers. comm.)

Non-native Temperature Regime:

Not applicable

Non-native Temperature Range:

Not applicable

Native Salinity Regime:

Polyhaline, Euhaline

Native Salinity Range:

Oahoro Bay: max 33.50psu at surface and 33.60psu at 5m deep both in February and min 26.72psu at surface in May and 32.06psu at 5m deep in April during 1992 and 1999. (Nakata et al. 2001) Ariake Sea, near Amakusa Marine Biological Laboratory: max 34.1psu and min 24.8psu both at 5m deep during 1974 and 2006, months are unknown. (Yamagata et al. 2008)

Non-native Salinity Regime:

Not applicable

Temperature Regime Survival:


Temperature Range Survival:


Temperature Regime Reproduction:


Temperature Range Reproduction:


Salinity Regime Survival:


Salinity Range Survival:


Salintiy Regime Reproduction:

Polyhaline, Euhaline

Salinity Range Reproduction:


Depth Regime:

Lower intertidal; Shallow subtidal; Deep subtidal

Depth Range:

[Japan] Collected at intertidal; near shore, as well as 40-50m dredging (Vieira et al 2014) [Japan] Oshoro Marine Biological Station, nera Otaru City, Hokkaido: intertidal. (Veira et al. 2014) [Japan] Chikko, Otaru City, Hokkaido: near shore. (Veira et al. 2014) [Japan] Amakusa Marine Biological Laboratory: 40-50m deep. (Veira et al. 2014)

Non-native Salinity Range:

Native Abundance:



Fertilization Mode:


Reproduction Mode:


Spawning Type:


Development Mode:

Lecithotrophic planktonic larva (non-feeding)

Asexual Reproduction:

Budding/fragmentation (Splitting into unequal parts. Buds may form on the body of the “parent”)

Reproduction Details:

RELATED: [Watersipora] Autozooids are hermaphroditic and brood embryos in embryo sacs (Mawatari 1952, cited in Temkin 1991; Ostrovsky 2013) [Gymnolaemates] Internal fertilization, whether intracoelomic or intraovarian, is obligatory (Temkin 1994 and 1996, cited in Ostrovsky 2013) [Gymnolaemates] Differ from most organisms in that sperm-egg fusion does not stimulate egg activation. Egg activation may not occur until "spawned" outside of maternal zooid (Temkin 1991) [Bryozoans] While sperm is spawned through pores in lophophore tentacles, eggs are usually harbored inside the body wall, and are internally fertilized by sperm, coming in on lophophore feeding currents (Brusca and Brusca 2003, cited in Rouse 2011; Kozloff 1990, cited in Rouse 2011) [Bryozoans] Colonial hermaphrodites, with testes (spermatogenic tissue) and ovaries developing either within the same zooid (zooidal hermaphroditism) or in different zooids within the same colony (zooidal gonochorism) (Ostrovsky 2013) [Bryozoa] Members of the phylum Bryozoa are hermaphroditic. Both fertilization and egg brooding may either be internal or external (Ruppert et al. 2004) [Bryozoa] All bryozoan colonies are hermaphroditic. Autozooids may be dioecious; or monoecious, and protandrous or protogynous. (Hayward & Ryland 1999) [Bryozoa] Reproduces asexually by budding. (Mawatari 1976)

Adult Mobility:


Adult Mobility Details:

Encrusting (Vieira et al 2014) RELATED: [Bryozoa] The abundance and taxonomic diversity of benthic bryozoan faunas are directly related to substratum. (Hayward & Ryland 1999) [Bryozoa] Bryozoan colonies are sessile (Hayami 1975) [Bryozoa] Bryozoans are a phylum of sessile, colonial suspension feeders found throughout the world in both marine and freshwater environments. (Tilbrook 2012)

Maturity Size:

Zooid: 818-999 x 395-510µm (Vieira et al 2014)

Maturity Age:


Reproduction Lifespan:




Broods per Year:


Reproduction Cues:

RELATED: [Bryozoans] Experiments often used light as a cue to collect embryos/larvae (Woollacott and Zimmer 1977) [Bryozoa] In coastal species light is an important stimulus to larval release, and many cheilostomates shed larvae during the first few hours of daylight. (Hayward & Ryland 1999) [Bryozoa] In various degrees of intensity according to the species temperature also stimulates sexual reproduction. (Winston 1977)

Reproduction Time:




Egg Size:

RELATED: [Gymnolaemata] About 200µm (Woollacott and Zimmer 1977)

Egg Duration:


Early Life Growth Rate:

RELATED: [Gymnolaemata] Two phases of larvae metamorphosis: first stage about 20mins; second stage 1-6 days (Woollacott and Zimmer 1977)

Adult Growth Rate:


Population Growth Rate:


Population Variablity:




Coastal shore, Sediment subtidal, Rocky subtidal, Fouling

Habitat Type:

Epibenthic, Epizoic


Gravel, Rock, Biogenic, Artificial substrata


Semi-exposed, Protected

Habitat Expansion:


Habitat Details:

[Japan] Chikko, Otaru City, Hokkaido: on dead barnacles near shore (Veira et al. 2014) [Japan] Amakura Marine Biological Laboratory: dredged. (Veira et al. 2014) Coastal shore, Sediment subtidal, Rocky subtidal, Fouling. Epibenthic, Epizoic. Gravel, Rock, Artificial substrata. Semi-exposed, Protected (M. Otani, pers. comm.)

Trophic Level:

Suspension feeder

Trophic Details:

RELATED: [Bryozoans] Suspension feeder...filter phytoplankton less than 0.045mm in size from the water column. (Hill 2001) [Bryozoa] Many phytoplankton species are cleary unsuitable as food for bryozoans. (Hayward & Ryland 1999) [Cheilostomata] Main food is diatom, protozoans and etc. and unappropriate sized particles are ejected (Mawatari 1976)

Forage Mode:


Forage Details:

RELATED: [Bryozoans] Suspension feeder...filter phytoplankton less than 0.045mm in size from the water column. (Hill 2001) [Bryozoa] Many phytoplankton species are cleary unsuitable as food for bryozoans. (Hayward & Ryland 1999) [Cheilostomata] Main food is diatom, protozoans and etc. and unappropriate sized particles are ejected (Mawatari 1976)

Natural Control:

RELATED: PREDATION [Predation] [Bryozoa] Browsers and grazers, including sea urchins, fish, crabs and some prosobranchs, are known to include bryozoans in their diet. (Hayward & Ryland 1998) [Predation] [Bryozoa] Bryozoans are also the prey of very many small, selective predators, some of which may be adapted to a very narrow spectrum of prey species. Among them opisthobranch predators of bryozoans are well known. (Hayward & Ryland 1999) [Predation] [Bryozoa] Other than opisthobranchs as a predator, amphipods, isopods, mites and pycnogonids have all been recorded preying on bryozoan colonies. (Hayward & Ryland 1998) EPIBIONTS [Epibionts] [Cheilostomata] It is frequently observed in Japan that several species of hydroids flourish on Cheilostomata cause damages to them. (Mawatari 1976)

Associated Species:


References and Notes


Global Invasive Species Database. http://www.iucngisd.org/gisd/ Access Date: 13-April-2016. Hayami T (1975) Neogene Bryozoa from northern Japan. Science Reports of the Tohoku University, Ser. 2 (Geology) 45: 83-126. http://ci.nii.ac.jp/els/110004646784.pdf?id=ART0007368357&type=pdf&lang=jp&host=cinii&order_no=&ppv_type=0&lang_sw=&no=1458033798&cp Hayward PF & Ryland JS (1999) Cheilostomatous Bryozoa part 2. Hippothooidea - Celleporoidea. Synopses of the British Fauna (New Series). Barnes RSK & Crothers JH (eds.) No. 14 (Second Edition). The Linnean Society of London and The Estuarine and Coastal Sciences Association by Field Studies Council: 416pp. Hill, K. (2001) Smithsonian Marine Station at Fort Pierce. Retrieved from http://www.sms.si.edu/irlspec/Electr_bellul.htm Mawatari S (1976) Bryozoa (Ectoprocta). In: Animal systematics. Uchida T (ed.) Nakayama-shoten Co. Ltd., Tokyo: 35-229. (in Japanese) Nakata A, Yagi H, Miyazono A, Yasunaga T, Kawai T, Iizumi H. (2001) Relationships between sea surface temperature and nutrient concentrations in Shoro Bay, Hokkaido, Japan. Scientific reports of Hokkaido Fisheries Experimental Station 59: 31-41. (in Japanese with English abstract) http://agriknowledge.affrc.go.jp/RN/2010630408.pdf Ostrovsky, A. N. (2013). Evolution of Sexual Reproduction in Marine Invertebrates – Example of gymnolaemate bryozoans. Dordrectht: Springer Netherlands. Doi: 10.1007/978-94-007-7146-8 Rouse, S. (2011). Aetea anguina. Bryozoa of the British Isles. Retrieved from http://britishbryozoans.myspecies.info/content/aetea-anguina-linnaeus-1758 Ruppert, E.E., Fox, R.S., and Barnes, R.D. (2004). Invertebrate Zoology: A functional evolutionary approach. Ann Arbor, MN: Thomson Brooks/Cole. Temkin, M. H. (1991). Fertilization in the Gymnolaemate Bryozoa (Doctoral dissertation). Retrieved from ProQuest Dissertations and Theses database. (DP23819). Tilbrook KJ (2012) Cheilostomata: first records of two invasive species in Australia and the northerly range extension for a third. Check List 8: 181-183. http://www.checklist.org.br/getpdf?NGD192-11 Vieira, L. M., Jones, M. S., & Taylor, P. D. (2014). The identity of the invasive fouling bryozoan Watersipora subtorquata (d’Orbigny) and some other congeneric species. Zootaxa, 3857(2), 151-182. Doi: 10.11646/zootaxa.3857.2.1 Winston JE (1977). Distribution and ecology of estuarine ectoprocts: A critical review. Chesapeake Science, 18: 34‐57. doi:10.2307/1350363. https://fau.digital.flvc.org/islandora/object/fau%3A6214/datastream/OBJ/view/Distribution_and_ecology_of_estuarine_ectoprocts__A_critical_review.pdf Woollacott, R. M., & Zimmer, R. L. (Eds.). (1977). Biology of Bryozoans. New York, NY: Academic Press Yamagata S, Sakurada K, Oyama N, Itoyama R (2008) Long-terrn transtition of water quality in Ariake Sea and Yatsushiro Sea. Report of Kumamato prifectural fisheries research center 8: 59-71. (in Japanese) http://agriknowledge.affrc.go.jp/RN/2010772140.pdf


Little or no information; expert opinion based on general knowledge