New observations and corrections concerning the trio of invasive hydromedusae <i>Maeotias marginata (=M. inexpectata), Blackfordia virginica</i>, and <i>Moreisia</i> sp. in the San Francisco Estuary

Abstract

SUMMARY: New observations of Maeotias, Blackfordia, and Moerisia in low salinity waters of the San Francisco Bay estuary allow better understanding of the life cycles and natural history of these three genera of invading hydrozoans. Maeotias inexpectata Ostroumoff, 1896 is found to be a junior synonym of Maeotias marginata (Modeer, 1791). Moreover, M. inexspectata Ostroumoff, 1896b is an incorrect subsequent spelling of M. inexpectata Ostroumoff, 1896a. The clear presence of marginal statocysts in the medusa of this species places it back in the family Olindiidae of the Limnomedusae. Polyps previously attributed to Maeotias in San Francisco Bay are now known to belong to a Moerisia sp., whose medusa has also recently been found in the estuary system. Solitary Moerisia polyps have been found in the field amongst the general fouling fauna on floating docks in the Napa River. Small simple primary polyps of M. marginata were obtained in the laboratory. Polyps of Blackfordia virginica have been found in abundance in the field covering the valves of nonindigenous barnacles in the Napa River and laboratory-cultured colonies are pictured here along with their newly-released and juvenile medusae.

Fauna of the Mediterranean Hydrozoa.

“…References : Mills and Sommer (1995);Mills (2000); Rees and Gershwin, (2000); Mills and Rees (2000). Ostroumoff, 1896 (Figs.…”

“…References : Valkanov (1935); Logvinenko (1959); Naumov (1960Naumov ( , 1969; Denayer (1973);Zhang Jinbiao (1977; Moore (1987); Bouillon et al (1988b);Mills and Somner (1995); ; ; Mills and Rees (2000).…”

“…References: Borcea (1929);Calder and Burrell (1969);Denayer (1973); Mills and Sommer (1995); Rees and Gershwin, (2000); Mills and Rees (2000) Genus Monobrachium Mereshkowsky, 1877…”

First record of two invasive hydromedusae <i>Maeotias marginata</i> (Modeer, 1791) (Hydrozoa: Limnomedusae) and <i>Blackfordia virginica</i> Mayer, 1910 (Hydrozoa: Leptomedusae) in Japan

“…Another invasive brackish-water hydromedusae, Moerisia sp., which has been recorded from North America along with the present two species (Calder & Burrell 1967, Mills & Rees 2000, Rees & Gershwin 2000, was not found during our survey. It is possible that the species will be found in future samplings.…”

Non-indigenous hydromedusae in California's upper San Francisco Esturary: life cycles, distribution, and potential environmental impacts

“…Agassiz, 1865 (Harbison andVolovik, 1994), could also result from hydrozoan introductions into estuarine habitats with depauperate faunas and vulnerable populations of native species. These nonindigenous hydrozoan species, including also Blackfordia virginica (see Mills and Rees, 2000), should be monitored as part of a Bay-wide effort to track both native and introduced coelenterate species. Monitoring results can be used to assess effects of introduced species on valuable fisheries resources, and to assess future efforts to limit further aquatic introductions.…”