Obelia longissima
| Obelia longissima | |
|---|---|
 |
|
| Obelia longissima | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Hydrozoa |
| Order: | Leptomedusae |
| Family: | Campanulariidae |
| Genus: | Obelia |
| Species: | O. longissima |
| Binomial name | |
|
Obelia longissima (Pallas, 1766) |
|
| Synonyms | |
|
|
Obelia longissima is a colonial species of hydrozoan in the order Leptomedusae. Its hydroid form grows as feathery stems resembling seaweed from a basal stolon. It is found in many temperate and cold seas world-wide but is absent from the tropics.
The sessile colonial stage of Obelia longissima is the most long-lived and the most easily observed of its life stages. The hydroid looks superficially like fronds of seaweed. It has a basal stolon growing in close proximity with the substrate. Out of this grow fragile, flexible stems up to 35 centimetres (14 in) high each with short side branches. As the stolon grows, new branches develop and the older ones are reabsorbed so the colony moves across the substrate. When the availability of food is high, further upright branches develop but when it is low, most growth takes place by way of stolon elongation and branching. The stems have dark-coloured, usually straight internodes between chitinous chambers called hydrothecae which are shaped like small wine-glasses. These protect the polyps.
Obelia longissima has a wide distribution. It occurs in the Atlantic Ocean as far north as the New Siberian Islands to the north of Siberia and as far south as the South Orkney Islands but is largely absent from the tropics. It is also found in the Mediterranean Sea, the Black Sea and the Baltic Sea. It is also present in the Indo-Pacific Ocean and is considered native from Alaska to southern California. It is one of the first species to colonise newly submerged surfaces and it can disperse widely because of the long-lasting larval stages and its ability to raft, attached to floating objects. It has wide tolerances of salinity and temperature but growth may not occur at above 27 °C (81 °F). It can sometimes be found in rock pools but mostly occurs in the shallow sublittoral zone and has been reported at depths as great as 500 metres (1,600 ft) off Patagonia. It grows on hard surfaces such as rocks, boulders, stones, shells, the stipes of kelp, floating objects and man-made structures and is part of the fouling community.
...
Wikipedia