By-the-Wind Sailor, Velella velella
By-the-Wind Sailor, Velella velella. Hydrazoan collected off the ocean surface in coastal waters off Loreto, Baja California Sur, July 2016. Collection, photograph and identification courtesy of Chris Wheaton, Fullerton, California.
Phylogeny: The By-the-Wind Sailor, Velella velella (Linnaeus, 1758), is a member of the Porpitidae Family of Condronophores. The Porpitidae Family consists of two genera – Porpita and Velella. The Velella Genus is monospecific. While this species and the Portuguese Man-of-War look similar, and are both free floating hydrozoans, this species more closely related to the Blue Button, Porpita porpita. They are also known as Vellella, the Purple Sail, and the Little Sail and in Mexico as Veleta Azul. The name Velella comes from the Latin word meaning “little sail”.
Morphology: By-the-Wind Sailors have an oval disk with a sail that is set at an angle to the longitudinal axis. They are generally blue to bluish-purple in color, though some may appear brownish due to algae living within the organism. Each apparent organism is actually a hydroid colony, floating on the surface of the water with a triangular chitinous sail. Organisms that live at the surface of the ocean like this are known as neuston. The colonies are composed of different types of polyps. The ones associated with feeding and reproduction are called gonozooids, and the protective ones are called dactylozooids. The By-the-Wind Sailors can reach a maximum of 8.0 cm (3.1 inches) in length.
Habitat and Distribution: By-the-Wind Sailors are an open water species, generally found at the ocean surface. During the medusa phase they will sink into deeper water, reaching depths up to 1,000 m (3,280 feet). The By-the-Wind Sailor is found worldwide, in temperate to tropical seas and in all Mexican waters of the Atlantic and Pacific Oceans.
Diet: The By-the-Wind Sailor is carnivorous suspension feeder. They have tentacles that are 1.0 cm (0.4 inches) in length that are equipped with nematocysts (or cnidocysts) that delivers a toxic sting to capture prey or repel predators. They prey on fish eggs, euphausiid eggs, copepods, larvaceans and crustacean larvae. By-the-Wind Sailors are zooxanthellate. They have a symbiotic relationship with single-cell dinoflagellates, known as zooxanthellae. Zooxanthellae live within certain coral polys, jellyfish, nudibranchs and sea anemones. The zooxanthellae produce energy, during daylight, by means of photosynthesis. This energy is passed along to their hosts, sometimes providing up to 90% of the host’s total energy needs. In return, the host provides nutrients, carbon dioxide, and a secure, sunlit, platform for the zooxanthellae.
Predation: By-the-Wind Sailors are preyed upon by sea birds, fish, such as the Ocean Sunfish, Mola mola, Glaucus nudibranches, Janthina purple snails, and sea turtles.
Reproduction: By-the-Wind Sailors have a bipartite life cycle, with a polyp form and a medusa form. The photograph above exhibits the most commonly seen polyp form, but this polyp will release tiny medusae during asexual reproduction. These medusae mature and reproduce sexually when egg and sperm meet to form a new polyp.
Ecosystem Interactions: Beyond the symbiotic relationship that By-the-Wind Sailors have with zooxanthellae, their commensal and parasitic relationships have not been formally documented.
Human Interactions: By-the-Wind Sailors can sting and cause contact dermatitis in extremely sensitive individuals. Otherwise, they have a very limited impact on human activities. From a conservation perspective they have not been evaluated, but are common with a widespread distribution and should be considered to be of Least Concern.
Synonyms: Armenista sigmoides, Holothuria spirans, Medusa pocillum, Medusa velella, Rataria cordata, Rataria mitrata, Velella antarctica, Velella aurora, Velella australis, Velella caurina, Velella cyanea, Velella emarginata, Velella indica, Velella lata, Velella limbosa, Velella meridionalis, Velella mutica, Velella oblonga, Velella oxyothone, Velella oxyothone var. brachyothone, Velella oxyothone var. oxyothone, Velella pacifica, Velella patellaris, Velella pyramidalis, Velella radackiana, Velella sandwichiana, Velella scaphidia, Velella septentrionalis, Velella sinistra, Velella tentaculata, Velella tropica, and Velella vella.