Re: Caulerpa taxifolia Moreton Bay, QLD

April 1, 2002
From: Cynthia Trowbridge

Dear Bill,
I was hoping that Alan Millar would answer this one since he is the person doing the work. But, since he has not yet responded, my answer is based on an abstract by Millar (Royal Botanic Gardens Sydney) & Talbot (NSW Fisheries) from the Caulerpa conference in San Diego. The full paper will be published in the Proceedings of Calif. Fish & Game probably later this year.

There have been seemingly 2 separate introductions of Caulerpa taxifolia into New South Wales (Millar & Talbot 2002) with a total of 6 populations now being known from Australia (Withgott 2002). Genetic information on the introductions was published by Jousson et al. (2000).

Native Caulerpa taxifolia occurs in Australia as far south as Southport, QLD and at Lord Howe Island (Millar & Talbot 2002). Thus, I think the Morton Bay population is thought to be native. To make it really complex, northern Australia is thought to be the probable original source of the algal material cultured in Europe; the modified cultured strain is now known as the "aquarium strain" of C. taxifolia.

As far as I can learn, no one in Australia or Calif. has really looked to see if there have been sacoglossan grazers associated with native vs. introduced Caulerpa taxifolia. In California, research scientists were not permitted access to the algal incursions for over a year (see Withgott 2002) despite the issues of sacoglossan herbivory that have clear bearing on the topic. Access was denied because the invasive alga unfortunately invaded a lagoon that was privately owned (in contrast to most other U.S. coastal regions). The folks involved in the eradication efforts are not trained scientists so there has been a large and serious communication gap (see Science paper).

In my talk at San Diego (Trowbridge 2002a), I discussed the implications of Placida spp. and Elysia spp. in switching diets from native hosts to the introduced Codium fragile ssp. tomentosoides on European and Australasian shores. I also discussed briefly the sacoglossan spp. that are possible candidates for feeding on Caulerpa taxifolia (aquarium strain) on NE Pacific shores. All that we know about these species is summarized in my recent review (Trowbridge 2002b); none of the sacoglossan species are yet known from California -- probably as there is no native Caulerpa so far north.

A major issue with studying pests is legal access for scientists. Most marine labs do not treat outflowing seawater so cannot ethically or legally hold pest species, even for scientific research. Thus, sacoglossan herbivory experiments in labs are often not permitted unless under a quarantine system with subsequent treatment of seawater, algae, and slugs.

With the Mediterranean species, sacoglossan herbivory experiments can be conducted with native Oxynoe or Lobiger spp. in the field or lab. Experiments with introduced, potential biological control sacoglossan species must be conducted according to internationally recognized guidelines in the lab. Field trials are only permitted if, and when, internationally recognized criteria have been met.

• Jousson, O. et al. (2000) Invasive alga reaches California. Nature 408:157.
• Millar, A. & Talbot, B. (2002) The introduction of Caulerpa taxifolia in New South Wales, Australia. Proc. International Caulerpa taxifolia Conference, San Diego, CA in Jan. 2002.
• Trowbridge, C.D. 2002a. Invasion ecology of Codium fragile ssp. tomentosoides: Implications for Caulerpa taxifolia incursions. Proc. International Caulerpa taxifolia Conference, San Diego, CA in Jan. 2002.
• Trowbridge, C.D. 2002b. Northeastern Pacific Sacoglossan Opisthobranchs: Natural history review, bibliography, and prospectus. The Veliger, 45:1-24.
• Withgott, J. (2002) California tries to rub out the monster of the lagoon. Science, 295: 2201-2202.

Hope this answer helps clarify a bit.
Cordially,
Cynthia

trowbric@onid.orst.edu

Trowbridge, C., 2002 (Apr 1) Re: Caulerpa taxifolia Moreton Bay, QLD. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/6650

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