Marine Invertebrates of Bermuda Porous Sea Rod (Pseudoplexaura porosa) By Melissa Parr Dr. James B. Wood and Kim Zeeh - Editors Abstract  Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

This is a Bermudian Sea Rod, but not Pseudoplexaura porosa

Abstract


Pseudoplexaura porosa is a soft coral commonly found off the shores of Bermuda. It is better known as the Porous Sea Rod and even more generally referred to as a Sea Rod or simply a gorgonian. It thrives in coral reef environments with shallow waters and high light levels (Sterrer 1986). P. porosa reproduces like many other coral species with mass spawning events governed by the lunar cycle (Kapela and Lasker 1999). It is abundant off Bermuda in both Marine-Protected areas and non-protected areas and contributes to increasing ecological diversity and Bermuda’s unique underwater environment (Jordan-Dahlgren 2002). P. porosa has an interesting symbiotic relationship with algae known as zooxanthellae. This symbiotic algae provides P. porosa with nutrients and carbon. Pseudoplexaura porosa is currently being used in cancer research to develop antitumor drugs.


Taxonomy


Phylum: Cnidaria
  Class: Anthozoa
    Subclass: Octocorallia or Alcyonaria
      Order: Gorgonacea
        Suborder: Holaxonia
          Family: Plexauridae



Habitat


The gorgonian Pseudoplexaura porosa is easily spotted off Bermuda, and is part of one of the most typical groups found in a coral reef community (Coma et al. 1998). P. porosa prefers shallow waters with high light levels. It is commonly found near shore and in patch reef, back reef, and outer reef environments in anywhere from 1-15 meters of water (Lasker 1981, Coffroth 1984, Sterrer 1986). The primary factor which determines the original settlement and successful growth of gorgoneans is the availability of hard substrata (Kinzie 1973, Diaz et al. 1997). In addition to this, P. porosa also thrives in areas with good water flow and continual currents. It flourishes in high wave energy areas where there is an abundance of suspended organic material (Diaz et al. 1997, Sprung 2004).



Ecology


The common name of Pseudoplexaura porosa, the Porous Sea Rod, is rooted in the gorgonian’s appearance when its polyps eight pinnate tentacles are fully retracted. The polyps have no sclerites and can completely draw themselves into the coral skeleton, when they do this, they leave the surface of the branch covered in large gaping elliptical shaped pores (Sterrer 1986). This withdrawing reaction is primarily a defense mechanism, and in general the large polyps (approximately 5 mm.) are expanded both day and night (Lasker 1981). P. porosa is identifiable by it’s large arborescent colonies stretching to 225 cm. tall (Lasker 1981, Sterrer 1986). Some colonies have even been reported as large as 3 meters in height (Kapela and Lasker 1999). The colonies range in color from reddish purple to yellow or brownish (Sterrer 1986).


Pseudoplexaura porosa is a sedentary benthic animal. It is rooted to its supporting substrate by a single holdfast (Jordan-Dahlgren 2002). Because of this, the animal needs to find a suitable environment to settle in as a larvae since once settled, it is there for the remainder of its life span of a few decades.


In regards to defense, P. porosa has very little. This is in part because it is a simple animal, and also in part because it has so few predators. Cnidarians in general have specialized defense mechanisms know as nematocysts. These nematocysts are stinging cells used in prey capture and defense. While all anthozoans do have these nematocysts, P. porosa happens to have an extremely reduced nematocyst density (Lasker 1981). The few predators P. porosa has are the common flamingo tongue snails (Cyphoma spp.), seaslugs like Tritonia spp. and Tritoniopsis spp., butterfly fish, and some angelfish (Sprung 2004).


Like most corals, the tissues of Pseudoplexaura porosa are inhabited by a symbiotic algae known as zooxanthellae. These zooxanthellae provide food for the coral animal in the form of dissolved organic material containing glucose and various vitamins and amino acids (Sterrer 1986). Unfortunately P. porosa colonies don’t get a completely free meal, as they have to feed to get the remainder of the nutrients they need. While the natural diet of P. porosa is still inadequately studied, it does filter plankton and other suspended particulates from the surrounding water (Lasker 1981, Coffroth 1984, Coma et al. 1998, Sprung 2004). In a 1998 study where the gut contents of a P. porosa colony were analyzed it was determined that in the particular colony investigated the gut contents were dominated by zooplankton remnants such as gastropod larvae. There were also a few protozoans and diatoms found (Coma et al. 1998). In addition to a diet of microzooplankton and zooxanthellae products it is also suspected that suspended bacteria and coral mucus aggregates may play an important role in soft corals supplemental diets (Lasker 1981, Coffroth 1984).


In addition to the natural life process of feeding, Pseudoplexaura porosa must also reproduce. P. porosa is a gonochoric, broadcast spawner (Coffroth et al. 2001). It has been suggested that there is an important relationship between size and gamete production in gorgonians. In a 1999 study it was determined that only colonies over 50cm. were reproductive (Kapela and Lasker 1999). Colonies that are reproductive spawn in synchrony on a lunar cycle. Spawning usually lasts for a period of approximately 30 minutes and takes place 5-6 days after the summer full moons. The spawning lasts for several days with a night of heavy spawning flanked by nights of lighter spawning (Kapela and Lasker 1999). The new larvae typically settle out after around 5 days. They rapidly acquire zooxanthellae of multiple clades which is interesting because adult Pseudoplexaura porosa harbors only clade B zooxanthellae (Coffroth et al. 2001). The life span of a colony of P. porosa is only a few dacades compared to the milenia of a hard coral. The primary cause of mortality in gorgonians is detachment from the substrate to which they are attached. This is often caused by heavy storms (Jordan-Dehlgren 2002).


Recent Research


The research recently done on Pseudoplexaura porosa is primarily on “cytotoxic anti-tumor diterpenoids of the cembrane class”. These antitumor extractions are called 14-deoxycrassin and pseudoplexaurol. Both of these were isolated specifically from P. porosa by scientists working in the Department of Chemistry at the University of Puerto Rico (Martinez and Rodriguez 1993).


In addition to medical studies, there was also some recent research to discover if newly settled P. porosa larvae had a preference for a specific clade of zooxanthellae and if so did they maintain the same clade throughout life. It was determined that newly settled larvae do in fact harbor different clades of zooxanthellae than adult colonies. Juveniles contain multiple clades including A, B, and C, while adults contain only clade B. It was also determined that newly settled juveniles acquired zooxanthellae rapidly after settlement both in the field and also in laboratory settings. (Coffroth et al. 2001).


In addition to this, a study done in 1999 by Kapela and Lasker suggests that sexual reproduction for Pseudoplexaura porosa is size dependant. Their study showed that only colonies taller than 50 cm were reproductive. Their study also showed that polyp fecundity increased with height up to 200 cm (Kapela and Lasker 1999).



Commercial Importance


The primary importance of Pseudoplexaura porosa in a commercial sense it that it is being studied by the pharmacological industry and hopefully will someday help yield new anti-tumor drugs to help cancer patients. It is also an integral part of the Bermuda coral reef ecosystem and of course in that sense is beneficial to tourism and tourist recreation (Sterrer 1986). In addition to these factors, P. porosa is also a popular purchase for aquarists as it makes a great addition to the salt water tropical tank since it is a hearty yet aesthetically appealing warm water native.



Bermuda Laws


Pseudoplexaura porosa is protected by the Coral Reef Preserve Act.  It is illegal to remove or damage marine life from that is attached to the reef, such as corals from the South Shore and North Shore preserves.  These preserves cover the Bermuda Platform.  In addition, all marine life is protected from collection in Bermudas 29 marine-protected areas (Wood and Jackson 2005).


Personal Interest


My personal interest in corals began as an infatuation solely with their beauty and mesmerizing dance under the waves. It progressed from there onto a more scientific track when I began to wonder what else made them so special. It was then that I discovered how interesting corals, and most specifically soft corals really were. Not only are they beautiful, but they are also complex and interesting creatures. They are so outwardly simply looking, like some plant or swaying tree that grows under the waves. But in fact they are animals, not just any animal, but an animal that holds promising secrets which may eventually help to cure cancer. That fact is probably what endears them most to me, as I have lost more than my share of loved ones to that wretched sickness. My hope is that someday these intriguing anthozoans will help save lives.



References

Coffroth, MA. 1984. Ingestion and incorporation of coral mucus aggregates by a gorgonian soft coral. Marine Ecology Progress Series. Vol. 17:193-199.

Coffroth, MA., Santos, SR., Goulet, TL. 2001. Early ontogenic expression of specificity in a cnidarian-algal sybiosis. Marine Ecology Progress Series. Vol. 222:85-96.

Coma, R, Gili, J-M, Ribes, M. 1998. Heterotrophic feeding by gorgonian corals with symbiotic zooxanthellae. Limonology and Oceanography. Vol. 43 Iss. 6:1170-1179.

Diaz, JM, Sanchez, JA, Zea, S. 1997. Gorgonian communities in two contrasting environments on oceanic atolls of the southwestern Caribbean. Bulletin of Marine Science. Vol. 61 Iss. 2:453-465.

Jordan-Dahlgren, E. 2002.Gorgonian distribution patterns in coral reef environments of the Gulf of Mexico: evidence of sporadic ecological connectivity? Coral Reefs. Vol. 21, Iss. 2:205-215.

Kapela, W, Lasker, HR. 1999. Size-dependant reproduction in the Caribbean gorgonian Pseudoplexaura porosa. Marine Biology. Vol. 135:107-114.

Kinzie, RA. 1973. The zonation of West Indian gorgonians. Bulletin of Marine Science. Vol. 23:93-155.

Lasker, HR. 1981. A Comparison of the Particulate Feeding Abilities of Three Species of Gorgonian Soft Coral. Marine Ecology Progress Series. Vol. 5:61-67.

Martinez, N, Rodriguez, AD. 1993. Marine antitumor agents: 14-deoxycrassin and pseudoplexaurol, new cembranoid diterpenes from the Caribbean gorgonian Pseudoplexaura porosa. Experientia. Vol. 49 Iss. 2:179-181.

Sprung, J. “Caribbean Gorgonians: Beauty in Motion” Advanced Aquarist’s Online Magazine. March 2004. www.advancedaquarist.com

Sterrer, Wolfgang. ed. Marine Fauna and Flora of Bermuda: A Systematic Guide to the Identification of Marine Organisms. New York: John Wiley and Sons, 1986.

Wood, J, Jackson. 2005. "Bermuda" in (Caribbean Marine Biodiversity; the Known and the Unknown.) Pennsylvania. DEStech Publications, Inc.


Links

The Coral Reef Alliance

Coral Reef Conservation

Reef Base

Coral Reefs for Kids

Coral Reefs

BBSR