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Phylum Pogonophora. Picture from http://www.cyhaus.com/marine/Worms.htm. Pogonophora. Also, known as “Beard Worms” Completely unknown until the twentieth century Tube-dwelling worms found throughout world’s oceans All 120 described species are marine. Attributes.
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Phylum Pogonophora Picture from http://www.cyhaus.com/marine/Worms.htm
Pogonophora • Also, known as “Beard Worms” • Completely unknown until the twentieth century • Tube-dwelling worms found throughout world’s oceans • All 120 described species are marine
Attributes • Size- 5cm-1.5m long and 1mm –4cm in diameter • Gonochoristic (having 2 distinct sexes) • Closed circulatory system with heart • Small brain with ventral nerve cord • Protostomic development • Picture taken from http://pubs.usgs.gov/publications//text/tube_worms.html
Defining Characteristics • No mouth or digestive tract • Organ known as Trophosome filled with chemoautotrophic mutualistic bacteria • Unsegmented except for rear portion of animal, (or opisthosoma). • Conspicuous red color at ends of plume due to hemoglobin
Life Style • Sessile, living in long chitinous tubes • Extends plume (anterior end) outward to obtain some nutrition and function in gas exchange • Most found at depths of 200 meters and up • Most often found by deep-sea hydrothermal vents, rifts and cold-water seeps
Body Structure • Divided into four sections: • The cephalic lobe • The glandular region • The trunk • And the opisthosoma • Picture from http://clouseart.com/Ron/weeklyinvert/archive/20010305.html
The Cephalic Lobe • Consists of a “plume” of one to many thousands of ciliated tentacles • Used for gas exchange, and some nutrient uptake • Also thought to be used to obtain Hydrogen Sulfide • Picture taken from http://www.cyhaus.com/marine/worms/worm2.jpg
The Glandular Region • Contains cells that secrete chitinous tube • Some species contain “girdle”, (or vestimentum) in this region, which aids in keeping the worm steady in its tube • Picture taken from http://www-biol.paisley.ac.uk/courses/Tatner/biomedia/pictures/pogon102.htm
The Trunk • The longest part of the pogonophoran body • Contains a pair of uninterrupted coelomic cavities • Bears a number of papillae, 2 regions of ciliation, and 2 girdles of setae • Contains organs and gonads • Picture taken from http://www-biol.paisley.ac.uk/courses/Tatner/biomedia/pictures/pogon.htm
The Opisthoma • Displays conspicuous segmentation • Contains 5-30 segments isolated by septa • Used to anchor worm in tube • Not discovered as part of body until 1965, since it is generally buried in sediment
Modes of Nutrition • Since pogonophora lack a digestive tract many speculations have been made as to how they obtain nutrients: • Via tentacles- many believe that some of the smaller species can obtain dissolved organic matter through their tentacles • Via chemoautotrophic bacteria-The tentacles absorb hydrogen sulfide and transport it using hemoglobin to the trophosome where it is converted to carbohydrates by the many bacteria that live there
Interesting Facts • Recent research shows that pogonophora contain three types of hemoglobin • This hemoglobin can simultaneously and reversibly bind to oxygen and sulfide at two different sites • Thus the hemoglobin protects the animal tissues from sulfide toxicity by binding to sulfide with a higher affinity than cytochrome c oxidase, which is responsible for the toxic effects
Pogonophora: Phylum or Not? • With recent discoveries in DNA sequencing, the classification of Pogonophora as its own phylum has come into question. • According to many recent studies involving the sequencing of the elongation factor-1 alpha and developmental studies comparing larvae and basic body plans has grouped the Phylum Pogonophora within the Phylum Annelida.
