TWAInv3

Invertebrates, Algae and Vascular Plants of The Tropical West Atlantic: Bahamas to Brazil, Part 3

To: Part 1, Part 2, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9,

Bob Fenner

Hydrozoans...

Hydrozoans... Little Christmas Trees and More that Sting Like Bejeesus! Don't Touch!!!

Hydrozoans are the "other" Class of cnidarians (Anthozoans making up the mainly polypoid corals, anemones, sea fans... and Scyphozoans the "real" Jellyfishes that live most of their lives as medusas, inverted bell-shapes). Most of the Hydrozoans are small, obscure not-so funny to touch Christmas tree sort of affairs, but they include such notables as Portuguese Man of War, Fire Corals (Millepora), and the beautiful delicate Stylasterines (Lace Corals) amongst their ranks.

These are colonial animals, sometimes a branch per colony, other times a specialized part (like the "Sail" in the Man 'O War...).

Order Hydrocorallina: These are colonial polypoid hydrozoans that secrete calcium carbonate skeletons, though they are not true corals... The Order comprises two suborders, the Milleporina and Stylasterina

Fire Coral, Millepora: Most Common and (Ouch!) Most Commonly Encountered!


Millepora alcicornis Belize	Millepora complanata Tobago	Millepora sp. Cebu


Living on and being lived on by/with Seafans, molluscs, algae, fishes... it's the pest/wet-pet Millepora!

Suborder Stylasterina: Characterized by having a thick layer of tissue overlying their skeletons. Their specialized feeding and defensive polyps are imbedded within star-shaped openings in their calcareous skeletons.

Stylaster roseus

Here in the Bahamas and St. Lucia in the TWA.

Order Hydroida: Often small, cryptic to the point of being unseen... on rock, mooring lines...

Halocordyle disticha, the Christmas Tree Hydroid. Branches alternately arranged on single stalks in colonies. Bearing prominent white polyps at ends like Xmas ornaments. To three and a half inches in height. St. Lucia pix.

Rapharia gorgoniae, Solitary Gorgonian Hydroid. Size: 1/4-1 in. diameter. Singular polyps with thin, clearish tentacles. Usually found attached to sea fans, particularly Sea Plumes (Pseudopterogorgia). Cozumel pic by Di.

Thyroscyphus ramosus, the Algae Hydroid. Uneven alternately arrayed branches, often covered by algae. "Clean" in St. Lucia, and more typical appearance in Belize and a close-up in Cozumel.

To: Part 1, Part 2, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 12, Part 13, Part 14, Part 15,

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