The Hydromedusae collected in six years (1961-1966) of macroplankton research at the Texel lightship, are discussed, with seasonal occurrence and dates of peaks, if possible, given. Of the Anthomedusae the following species were of regular occurrence: Sarsia tubulosa, Steenstrupia nutans, Turritopsis nutricola, Bougainvillia britannica and Leuckartiara octona; further species comprise: Sarsia gemmifera, Hybocodon prolifer, Podocoryne borealis, Rathkea octopunctata and Bougainvillia principes. In the Leptomedusae the extreme abundance of Phialidium hemisphaericum except for a short period in spring, proved a great handicap, since it was impossible to sort out and identify every single one of the thousands of Medusae. Therefore quite a number of specimens of other species may have gone undetected in the routine research. The following species were found. Laodicea undulata, Melicertum octocostatum, Mitrocomella brownei, Cosmetira pilosella, Phialidium hemisphaericum, Obelia spp, Lovenella clausa, Eucheilota maculata, Phialella quadrata, Eirene viridula, Helgicirrha schulzei, Aequorea vitrina (discussed in some detail with sizes etc. given), Eutima gracilis and E. gegenbauri, Tima bairdi (also with sizes given). Various hydroids of the Obelia Laomedea group were also collected. Of the Limnomedusae only Gossea corynetes was found. Of the Trachymedusae a remarkable influx of Aglantha digitale in 1962 is discussed. |
