Daily Invader

Chesapeake Bay Hydroids

Hydrozoan Clytia kincaidi


Hydroid Clytia kincaidi is so small and hard to identify its status remains a mystery.



The hydrozoan Clytia kincaidi is tiny, predatory marine species whose origin and history remain a mystery. This hydroid has two stages, one stage, the hydra, attaches to seaweeds and wood and the other reproductive stage is the free-living medusa or jellyfish. The species was described in Puget Sound in 1899 and subsequently reported in Vancouver Island and the Caribbean in 1935. Clytia kincaidi was not reported from the Atlantic coast of North America by Fraser in 1944 but were seen in surveys from 1968-1969 in Chesapeake Bay and South Carolina in 1976. We now suspect that they occur from Chesapeake Bay to the Caribbean but we can’t say for sure how long they have been here or if they are native or introduced, so they remain cryptogenic in Chesapeake Bay and elsewhere on the North American Atlantic coast. Adding more to the mystery is the debate about whether the Atlantic and Pacific populations are the same species or two similar species that are difficult to identify. Complete Record 


Hydrozoan Moerisia lyonsi


The hydra stage of Moerisia lyonsi. This small hydrozoan is part of a group of hydroids from the Caspian Sea.



The hydrozoan Moerisia lyonsi has both a fixed hydroid and a swimming jellyfish (medusa) stage in its life cycle- both are tiny. The jellyfish are only 2 to 8 mm wide, and the hydroids only 1-2 mm tall. This hydrozoan is only known from Lake Quarun Egypt, a lagoon of the Nile Delta, where it was first discovered, and the East and Gulf coasts of North America. Other similar species in the genus Moerisia are known from the Caspian Sea, Japan, and the Mediterranean and due to similarities within this group of Moerisia species we believe that Moerisia lyonsi likely evolved in Caspian and Black Seas. The first record of this hydroid in Chesapeake Bay was in 1965 when one was collected in low salinity waters of the James and Pamunkey Rivers. There are few other reports of the species, but in 1992-93 they were found in an experimental tank at the University of Maryland Horn Point Laboratory and the adjacent Choptank River, and SERC’s Marine Invasions Research Laboratory found specimens on settling plates from Baltimore Harbor in 1995. Because this hydroid is so small and poorly understood, there is some doubt as to its origin. Complete Record


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