Carijoa riisei
System : Marine
Kingdom
Phylum
Class
Order
Family
Animalia
Cnidaria
Anthozoa
Alcyonacea
Clavulariidae
- General
- Distribution
- Impact
- Management
- Bibliography
- Contact
Common name
orange soft coral (English), snowflake coral (English), Branched pipe coral (English)
Synonym
Similar species
Summary
Carijoa riisei commonly known as \"snowflake coral\" or \"branched pipe coral\", is a soft coral species. Originally from the tropical Western Atlantic it was first reported in the Pacific Ocean around the Hawaiian Islands in the 1970's. Its introduction was thought to be benign until recent surveys began showing it proliferating at depths as far down as 120m off the island of Maui, where it is rapidly changing habitat and out-competing native black coral colonies.
Species Description
Carijoa riisei is an octocoral that forms erect, branching colonies with flexible stems. Each tall axial polyp has many short lateral polyps. Polyps, when extended, have eight white pinnate tentacles, like the rays of a snowflake, unlike stony corals which have six tentacles. The long stems or branches of the octocoral are a dirty white colour, but they are almost always covered with a very thinly encrusting orange-red sponge, which was identified as Desmapsamma anchorata on Carijoa identified as C. riisei from Indonesia (Cacinai et al. 2004). Two types of sclerites occur in the body wall (HBS, 2002). C. riisei colonies grow about 10-25cm high (Samuel Kahng., pers. comm., 2005).
Notes
While shallow-water octocorals (soft corals) are well described in the Caribbean, their taxonomy in the Indo-Pacific is less well defined. Many genera of soft corals in the Indo-Pacific are not defined to the species level.
In Hawai‘i, the Carijoa species was identified as C. riisei by a leading octocoral taxonomist. However, recent molecular sequencing work in progress is now casting doubt on the Caribbean/Atlantic origin for the Hawai‘ian population (Samuel Kahng., pers. comm., 2005).
Uses
Gasparini et al. (2004) reports that Carijoa riisei is used in the aquarium trade and can also be found in the souvenier trade.
Habitat Description
Carijoa riisei is reported to grow well in turbid waters rich in organic matter and zooplankton on which it feeds. It requires a firm surface on which it attaches using stolons (root-like structures). It also grows well on artificial hard surfaces such as metal, plastic, concrete, etc. It is commonly reported on artificial reefs visited by recreational scuba divers. It is a passive filter feeder and needs moderate amounts of water flow, which is provided by wave surges and tidal or long-shore currents. It does not proliferate in direct sunlight and is usually most abundant on rocky surfaces or other hard substrates at depths below significant light penetration (Kahng, Undated(b)). Grigg (2003) states that not only can this species be found on pier pilings in shallow water, but that it is also abundant in much deeper water (down to 120m), particularly in shaded environments.
Reproduction
Carijoa riisei is capable of single parent reproduction and has male, female and hermaphrodite colonies. It also spreads by vegetative growth through runners and stolons which spread and colonise adjacent areas in all directions. C. riisei also exhibits high fecundity, producing almost continously, and hundreds of eggs per axial polyp (Kahng, Undated(a)). HBS (2002) reports that, \"Polyps may reproduce asexually by simply splitting in two, or sexually by release and fertilisation of gametes (a cell connected with sexual reproduction, which is either a male sperm or a female egg) into the water column. The resulting planula larvae (flat ciliated free-swimming larva) settle to the bottom and develop directly into young polyps.\"
Nutrition
Carijoa riisei lacks symbiotic algae (unlike many stony corals), and is an obligate predator of zooplankton. Octocorals in general have weak nematocysts (stinging cells). From feeding trials in Hawai‘i, C. riisei does not appear to have effective nematocysts (Samuel Kahng., pers. comm.., 2005).
Pathway
Gasparini et al. (2004) reports that Carijoa riisei is used in the aquarium trade and can also be found in the souvenir trade.HBS (2002) reports that Carijoa riisei is most likely to be introduced as fouling on ships' hulls.
Principal source: Kahng, Undated(b) Carijoa riisei: Fact Sheet Department of Oceanography, University of Hawai‘i.
HBS, 2002 Carijoa riisei (Duchassaing & Michelotti, 1860).
Toonen, R. 2004. Reproduction and developmental characteristics of an alien soft coral (Carijoa riisei) in Hawai‘i (FY 2004-2005). Hawai’i Institute of Marine Biology.
Compiler: National Biological Information Infrastructure (NBII) & IUCN/SSC Invasive Species Specialist Group (ISSG)
Review: Steve. L. Coles, Ph. D. Research Zoologist. Bishop Museum, Department of Natural Science Honolulu, Hawaii USA
Sam Kahng
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Department of Oceanography
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University of Hawaii at Manoa Honolulu. Hawaii
Publication date: 2008-03-23
Recommended citation: Global Invasive Species Database (2024) Species profile: Carijoa riisei. Downloaded from http://iucngisd.org/gisd/species.php?sc=694 on 29-11-2024.
General Impacts
Carijoa riisei had been described as a shallow water species, but deep-water surveys conducted near Maui in Hawai‘i discovered C. riisei overgrowing >70% of the black coral colonies (Antipathes dichotoma and A. grandis) in certain areas at depths of 65-115m (Grigg 2003). C. riisei can settle and grow on other stationary organisms like shellfish and coral. When conditions are favourable it is capable of explosive growth, hence able to smother competitors and occupy any available space.
C. riisei is a voracious feeder and can consume large quantities of zooplankton (ecological impacts of this feeding habit are yet to be studied) (Kahng, Undated(b)). C. riisei exhibits high fecundity compared to other corals (clonal benthic marine invertebrates like corals in general exhibit much lower fecundity than aclonal benthic marine invertebrates like mussels). No significant predators have of C. riisei have been found in Hawai‘i with the possible exception of a recently discovered introduced nudibranch, Phyllodesmium poindimiei. Predators of Carijoa in other parts of the globe have been reported (Samuel Kahng., pers. comm., 2005).
Management Info
Preventative measures: Carijoa riisei has been described as the most invasive of the 287 non-indigenous marine invertebrates in Hawai’i (Toonen, 2004). Toonen (2004) points out that C. riisei has unique characteristics which aid its dispersal via maritime vectors. Research into its reproductive system and larval development are a primary requirement in the development of an effective management strategy aimed at preventing spread and containing existing populations.
\r\nA research programme supported by Sea Grant and the Hawai‘i Undersea Research laboratory (HURL) is underway to study the ecological impacts of C. riisei on Hawai‘i's deep water and shallow coral reef communities.
\r\nA research programme supported by Sea Grant and the Hawai‘i Undersea Research laboratory (HURL) is underway to study the ecological impacts of C. riisei on Hawai‘i's deep water and shallow coral reef communities.
\r\nBiological: Kahng (Undated(a)) has found that, \"A potential agent of C. riisei bio-control (introduced aeolid nudibranch soft coral predator) has recently been identified but must undergo further research before it can be considered as an actual management technique.\"
