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  Research study 1

photograph of sea pen Ptilosarcus gurneyi showing makeup of cology
Members of the Order Pennatulacea are colonies of polyps. The primary polyp of the sea pen after metamorphosis asexually buds off feeding (autozooid) and respiratory (siphonozooid) polyps that ultimately make up the colony.  The feeding polyps, located on the distal portions of the leaves, have tentacles for catching food, and the digestive cavities of all polyps are interconnected. The respiratory polyps are located on the rachis and these lack tentacles.  The seawater pumped into the colony by the respiratory polyps is probably less for gas exchange than for inflating and deflating the entire colony, a process that can happen quite quickly.

NOTE  lit. “tube or pipe animal” G., referring to its function of moving water into and out of the colony


Two individual colonies of Ptilosarcus gurneyi, one
expanded and the other pulled down into the soil 0.33X

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Research study 2

Colonies of sea pansies Renilla amethystina (koellikeri)are similar to sea pens in that they are made up of siphonozooids for water flow and autozooids for catching and ingesting food, but in this case the 2 types of polyps are scattered over the surface of the rachis.  There are many hundreds of inhalent siphonozooids, but only a single large exhalent one located on the midline of the rachis. A peduncle or holdfast support extends down into the sand from the under-surface of the rachis. The colonly undergoes periodic deflations and expansions. photograph of feeding polyps of a sea pansy Renilla amethystina courtesy Anderson & Case 1975 Biol Bull 149: 80Anderson & Case 1975 Biol Bull 149: 80.

Close view of autozooids (feeding polyps) of R. amethystina 5X



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