Re: Caulerpa prolifera

March 14, 2003
From: Cynthia Trowbridge

Dear Bill and Rob,
Concerning Rob's message:
There are at least 3 invasive species of Caulerpa: C. taxifolia (aquarium strain), C. prolifera, and C. brachypus. For those of you unfamiliar with the last species, it is a NW Pacific species that recently appeared on Florida shores; it is overgrowing and killing the coral reefs.

All 3 species of Caulerpa are eaten by sacoglossan slugs and possibility of marine biological control keeps being suggested. I find it particularly disturbing that the suggestions for biological control are made extensively in the popular media (internet, newspapers, conference proceedings, books) but rarely in the scientific venue where peer review can put the issue in a more balanced light.

There are 2 major issues about biological control:
(1) does the potential consumer reduce the abundance or survival of the intended pest species?
(2) is the potential consumer highly specific?

Bill, you are entirely correct about the issue that sacoglossans rarely cause damage of host plants. I can think of only a few cases and they are primarily SPECIAL cases:
Placida dendritica controlling the distribution of the encrusting Codium setchellii on Oregon shores (Trowbridge 1992).
Placida dendritica causing extensive branch loss of the native Codium fragile on Oregon shores (Trowbridge 1993)
Placida cf. dendritica on New Zealand shores destroying the introduced C. fragile ssp. tomentosoides in high intertidal rockpools (Trowbridge 1996).
Placida cf. dendritica on Australian shores causing serious damage to the introduced C. fragile ssp. tomentosoides at Sisters in Port Phillip Bay, VIC (Trowbridge 1999, 2003/4).
Placida dendritica on Scottish shores causing serious damage to the introduced C. fragile ssp. tomentosoides at Oban, Argyll (Trowbridge 2002).

All of these studies demonstrate the potential role of sacoglossan herbivory. But in all of these cases, the slugs, at best, eliminate their host from a specific microhabitat (e.g., high pools or wave-protected shores). My recent JMBA note (2002) is the strongest case of herbivore control BUT I would emphasize that all of these cases are due to unusual circumstances. For example, Oregon shores have unusually high larval recruitment of invertebrates (due to oceanographic conditions) so large populations of sacoglossans develop. At Oban in Scotland, the currents between islands result in unusual hydrodynamic and larval settlement patterns. Thus, to extrapolate from these special cases to a general statement that sacoglossan herbivory will be important is presumptuous.

Now to the second point about the host-specificity paradigm (HSP). I would refer people to a recent invited review by Secord (2002). At the Marine Bioinvasions conference a few years ago, the proponents of marine biological control met and discussed the issues in a public forum. Secord was invited to review the issue. One of the 4 or so cases was the sacoglossan sea slug - Caulerpa proposal. Scientific consensus is that the proposal has too many unexplored risks.

A final brief word about risks, I have a paper accepted (pending minor revisions) about specialized sacoglossans that change their diets on ecological time-scales in Europe and Australia. Sacoglossans are specialized but their associations are dynamic. The view of static associations is not supported by field-based experimental data.

References:
• Secord, D. (2002) Biological control of marine invasive species: cautionary tales and land-based lessons. Biological Invasions (in press).
• Secord, D. & Kareiva, P. (1996) Perils and pitfalls in the host specificity paradigm. BioScience, 46: 448-453.
• Trowbridge, C.D. 1992. Mesoherbivory: the ascoglossan sea slug Placida dendritica may contribute to the restricted distribution of its algal host. Mar. Ecol. Prog. Ser., 83: 207-220.
• Trowbridge, C.D. 1993. Interactions between an ascoglossan sea slug and its green algal host: branch loss and role of epiphytes. Mar. Ecol. Prog. Ser., 101: 263-272.
• Trowbridge, C.D. 1996. Introduced versus native subspecies of Codium fragile: How distinctive is the invasive ssp. tomentosoides? Mar. Biol., 126: 193-204.
• Trowbridge, C.D. 1999. An assessment of the potential spread and options for control of the introduced green macroalga Codium fragile ssp. tomentosoides on Australian shores. Consultancy report, CSIRO/Centre for Research on Introduced Marine Pests: Hobart. 43 pp.
• Trowbridge, C.D. 2002. Local elimination of Codium fragile ssp tomentosoides: indirect
evidence of sacoglossan herbivory? J. Mar. Biol. Assoc., U.K., 82(6): 1029-1030 .
• Trowbridge, C.D. in press. Emerging associations on marine rocky shores: specialist herbivores on introduced macroalgae. J. Anim. Ecol. (accepted pending minor revisions).

Thank you for considering my comments.
Cordially,
Cynthia

trowbric@onid.orst.edu

Trowbridge, C., 2003 (Mar 14) Re: Caulerpa prolifera. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/9394

Thanks Cynthia,
Bill Rudman

Related messages

  1. Re: Eggs on Caulerpa taxifolia
    From: Kathe R. Jensen, December 20, 2003
  2. Eggs on Caulerpa taxifolia
    From: Jeannine Dietz, December 19, 2003
  3. Sea Slugs eating 'Killer Algae'
    From: Emily, October 23, 2003
  4. Do slugs eat Caulerpa taxifolia?
    From: Ronnie, October 6, 2003
  5. Re: Caulerpa prolifera & biological control
    From: Thierry Thibaut, March 28, 2003
  6. Re: Caulerpa prolifera & biological control
    From: Cynthia Trowbridge, March 21, 2003
  7. Re: Caulerpa prolifera & biological control
    From: Thierry Thibaut, March 20, 2003
  8. Caulerpa prolifera
    From: Rob Brown, March 13, 2003
  9. References for some sacoglossans
    From: Thierry Thibaut, February 25, 2003
  10. Re: Caulerpa toxins
    From: Kathe R. Jensen, October 3, 2002
  11. Caulerpa toxins
    From: Madhavi Agrawal, September 30, 2002
  12. Caulerpa taxifolia in Japan
    From: Nishina Masayoshi, March 28, 2002
  13. Caulerpa taxifolia in Japan... slug food?
    From: Cynthia Trowbridge, March 27, 2002
  14. Caulerpa taxifolia - economical consequences
    From: Hennes Zitzen, September 16, 2001
  15. Re: Oxynoe and Caulerpa taxifolia
    From: Cynthia Trowbridge, March 20, 2001
  16. Oxynoe and Caulerpa taxifolia
    From: French students, March 16, 2001
  17. Re: Sacoglossans vs Caulerpa taxifolia
    From: Kathe R. Jensen, July 23, 2000
  18. Thanks
    From: James Cobb, July 23, 2000
  19. Re: Sacoglossans vs Caulerpa taxifolia
    From: Cynthia Trowbridge, July 22, 2000
  20. Re: Sacoglossans vs Caulerpa taxifolia
    From: Kathe R. Jensen, July 21, 2000
  21. Re: Sacoglossans vs Caulerpa taxifolia
    From: Dr. Cynthia Trowbridge, July 18, 2000
  22. Sacoglossans vs Caulerpa taxifolia
    From: James Cobb, July 17, 2000

Show factsheet and all related messages