Species Description: The peacock’s tail, Padina pavonica, is a brown macroalga found throughout the Indian River Lagoon (see “IRL Distribution”).
The thallus, or body, of the alga is brown to tan, forming fan-shaped clusters. Each blade is calcified, more heavily above and lightly below, and curls inward near the edges. Both the upper and lower blade surfaces bear minute surface hairs arranged in a series of bands approximately 1.5 to 6 mm apart (Taylor 1979; Littler & Littler 2000; Littler et al. 2008). The blades attach to the substratum via a holdfast, which is often matted.
Potentially Misidentified Species: Several species within the genus Padina appear quite similar and may be misidentified. However, only one other species, P. gymnospora, is commonly recorded within the IRL (Littler et al. 2008). The thallus of P. gymnospora is similar in size and color to P. pavonica. However, the blades of P. gymnospora are more elongate and leaf-like, and clusters are more likely to be found attached to surfaces like jetties or seawalls that are exposed to moderate wave action (Littler et al. 2008).
Regional Occurrence: The range of P. pavonica extends throughout the world in warm temperate to tropical locales, including: North Carolina to Florida in the United States; the Gulf of Mexico; throughout the Caribbean and tropical Atlantic (Taylor 1979; Littler & Littler 2000; Littler et al. 2008); and the Eastern Atlantic, Mediterranean and Adriatic seas (Orlando-Bonaca et al. 2008). Clusters are commonly attached to shell fragments and rocks from the lower intertidal zone down to 20 m (Taylor 1979), in seagrass beds and coral reefs, on tidal flats, and attached to mangrove prop roots (Littler & Littler 2000).
Age, Size, Lifespan: P. pavonica can occur as small clusters or as mats covering several centimeters (e.g. Littler & Littler 2000). Individuals reach dimensions of 22 cm high x 37 cm wide, with each blade measuring up to 12 cm wide (Littler & Littler 2000; Littler et al. 2008).
Little information exists concerning factors that affect age and lifespan of P. pavonica. However, growth and mortality of populations is likely tied to nutrient levels, temperature, salinity and predator abundance.
Reproduction & Embryology: The peacock’s tail is known as haplodiplontic, reproducing alternately via haploid gametes or through diploid spores (e.g. Garreta et al. 2007). Spores can develop independently into new individuals, which appears to be quite common. In contrast, sexual reproduction via the release of male and female gametes does exist, but is considered rare.
Regardless of the method of propagation, reproductive organs, called sori, and their associated structures are responsible for the production of gametes or spores. In spore-producing individuals, the spherical sori are 90-140 um in diameter, and are found along one or both sides of the bands of hairs growing on the lower surface of the blades (Littler & Litter 2000; Littler et al. 2008). Male and female gamete-producing sori are also found on the lower surfaces of the blades in certain plants. The female, or oogonial, sori are spherical and 40-50 um in diameter (Littler & Litter 2000; Littler et al. 2008); whereas male sori, called antheridia, are ovoid or rectangular, measuring 39-122 x 28-72 μm (Garreta et al. 2007).
Once a plant has developed and attached to the substratum, growth of new blades originates at the holdfast (Littler et al. 2008). This process isolates individuals during growth, even though tightly-packed plants may appear as large, connected mats at a glance.
It has been suggested that water temperature is the predominant factor determining the process of reproduction among populations of P. pavonica (Garreta et al. 2007). Spore-producing individuals are common during different seasons, depending on location and climate (Garreta et al. 2007). In the IRL, plants are most abundant in the spring and summer, dying back in the winter months (Littler et al. 2008).
Temperature & Salinity: Little information is available concerning the temperature and salinity tolerances of P. pavonica. However, the natural range and habitats of the species suggests it prefers and/or requires warm temperate to tropical waters in brackish to marine salinity ranges. As mentioned above, populations in the IRL are more abundant in spring and summer, suggesting a preference or requirement for warmer waters, or possibly higher nutrient levels associated with the rainy season.
Trophic Mode: Like most other species of algae and vascular plants, P. pavonica is autotrophic, converting energy from the sun into usable food via photosynthesis.
Predators: Information regarding the common grazers of P. pavonica is scarce, but it is likely that the species is fed upon by a variety of organisms, including: urchins, hermit crabs, sea turtles, and herbivorous fishes. In particular, studies have documented algal grazing on this species by urchins of the genera Diadema and Echinothrix (Tuya et al. 2001; Coppard & Campbell 2007).
Economic Importance: Extracts isolated from P. pavonica have been added to homeopathic medicinal remedies and several cosmetic solutions, including shampoos, topical creams and lotions, and tablets or capsules taken orally. These extracts are reported to improve skin tone and texture, reduce wrinkles, and support bone and cartilage health. However, most or all of these claims have not been evaluated by the Food & Drug Administration.
In addition to the possible benefits to human health, P. pavonica may also have agricultural implications. Studies conducted by Omezzine and others in 2009 showed that various extracts from the brown alga acted as effective fertilizers, promoting crop growth and nutrient composition of the surrounding soil, while simultaneously retarding the growth of potentially harmful fungi.
Coppard, SE & AC Campbell. 2007. Grazing preferences of diadematid echinoids in Fiji. Aquat. Bot. 86: 204-212.
Garreta, AG, Lluch, JR, Martí, MCB & MAR Siguan. 2007. On the presence of fertile gametophytes of Padina pavonica (Dictyotales, Phaeophycea) from the Iberian coasts. Anales Jardín Bot. Madrid 64: 27-33.
Littler, DS & MM Littler. 2000. Caribbean Reef Plants. Offshore Graphics. Washington, DC. USA. 542 pp.
Littler, DS, Littler, MM & MD Hanisak. 2008. Submersed Plants of the Indian River Lagoon: A Floristic Inventory and Field Guide. Offshore Graphics. Washington, DC. USA. 286 pp.
Neto, AI. 2000. Observations on the biology and ecology of selected macroalgae from the littoral of São Miguel (Azores). Bot. Mar. 43: 483-498.
Omezzine, F, Haouala, R, Ayeb, AE & N Boughanmi. 2009. Allelopathic and antifungal potentialities of Padina pavonica (L.) extract. J. Plant Breed. Crop Sci. 1: 94-203.
Orlando-Bonaca, M, Lipej, L & S Orfanidis. 2008. Benthic macrophytes as a tool for delineating, monitoring and assessing ecological status: the case of Slovenian coastal waters. Mar. Poll. Bull. 56: 666-676.
Taylor, WR. 1979. Marine Algae of the Eastern Tropical and Subtropical Coasts of the Americas. University of Michigan Press. Ann Arbor, MI. USA. 870 pp.
Tuya, F, Martín, JA, Reuss, GM & A Luque. 2001. Food preferences of the sea urchin Diadema antillarum in Gran Canaria (Canary Islands, central-east Atlantic Ocean). J. Mar. Biol. Ass. U.K. 81: 845-849.