Gymnangium montagui is a hydroid that develops in erect feather-like
colonies from 8 to 10 cm high and covering areas of about 10 cm2. Colonies bud from a basal stolon and grow
in the same direction, parallel to each other. The outline of each plume is regular up to the 4/5th of
their height, then it ends in an angular way. The main stem, called hydrocaulus, has from 100 to 300
in two rows which are parallel and slightly curved. The tiny polyps, invisible to the eyes, are aligned
on the curved side of the branches. Their tentacles open out on both sides of the inter-branches.
The golden sea fern lives in moderatly current-swept areas between 10 and 40 meters deep, generally
attached to the horizontal side of rocks, and protected by overhangs in shallow waters.
It is reported in the North-West Atlantic Ocean and is rare in the English Channel.
(source : European Register of Marine Species)
Budding : Asexual reproduction forming a new individual.
Basal stolon : Linear base linking colonies together and from where the colonies bud and grow.
Hydrocaulus : Main stem of a hydroid colony.
Polyp : Individual of a colony.
Top photograph :
© Wilfried Bay-Nouailhat. Published with author's kind permission :
Gymnangium montagui, Anse de Camaret, West-Brittany, west of France. Depth 27 meters.
Bottom photograph : © Wilfried Bay-Nouailhat. Published with author's kind permission :
Gymnangium montagui, Golden sea fern.. Iles Glénan, South-Brittany, West of France. Depth 14 meters.
Text : Wilfried Bay-Nouailhat © 2007-2017.
Translation : Anne Bay-Nouailhat © 2007-2017.