Johnny Braun, Luxemburg
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Olindias tenuis (Fewkes, 1882)
Olindiidae are relatively small hydrozoa with a polyp stage and usually a free-living medusa stage. The small polyps usually live solitary and only rarely form colonies. Members of the family are distributed worldwide in both warm and cold seas; some live in freshwater and brackish water. They are carnivorous.
Olindias tenuis is a shallow-water hydromedusa from the Caribbean, which is cryptically hidden between seagrass and algae during the day. Only after sunset does it swim into the water column. During the day, the medusae remain crumpled on the bottom with their bells folded in half. The medusae are then often attached to seagrass, with their tentacles fully contracted in spiral coils.
The medusae search for food at night by swimming to the surface and then slowly drifting downwards, with the bell pointing upwards and the long primary tentacles hanging downwards. The positive buoyancy of the umbrella reduces the sinking speed. Both the activity cycle and buoyancy appear to be regulated by light.
Feeding takes place as soon as the medusae have entered the water column. Olindias tenuis feed mainly on copepods (mostly Acartia spp.), arrowworms of the genus Sagitta sp.(Chaetognatha), bristle worms (polychaetes), fish larvae and amphipods.
The type locality for the description of Olindias tenuis is Key West, Florida, USA.
Synonymised names
Halicalyx tenuis Fewkes, 1882 · unaccepted (basionym)
Olindiidae are relatively small hydrozoa with a polyp stage and usually a free-living medusa stage. The small polyps usually live solitary and only rarely form colonies. Members of the family are distributed worldwide in both warm and cold seas; some live in freshwater and brackish water. They are carnivorous.
Olindias tenuis is a shallow-water hydromedusa from the Caribbean, which is cryptically hidden between seagrass and algae during the day. Only after sunset does it swim into the water column. During the day, the medusae remain crumpled on the bottom with their bells folded in half. The medusae are then often attached to seagrass, with their tentacles fully contracted in spiral coils.
The medusae search for food at night by swimming to the surface and then slowly drifting downwards, with the bell pointing upwards and the long primary tentacles hanging downwards. The positive buoyancy of the umbrella reduces the sinking speed. Both the activity cycle and buoyancy appear to be regulated by light.
Feeding takes place as soon as the medusae have entered the water column. Olindias tenuis feed mainly on copepods (mostly Acartia spp.), arrowworms of the genus Sagitta sp.(Chaetognatha), bristle worms (polychaetes), fish larvae and amphipods.
The type locality for the description of Olindias tenuis is Key West, Florida, USA.
Synonymised names
Halicalyx tenuis Fewkes, 1882 · unaccepted (basionym)
