A short synthesis of the present state of the ctenophore, Mnemiopsis leidyi, invasion in the Black Sea is given, together with a brief review of its status in other areas of the Mediterranean basin. The impact of M. leidyi on the main components of the pelagic community, mesozooplankton, ichthyoplankton and ®sh resources, based on published data and new ®eld studies (1992±1997) are analysed. Th...

The ctenophore Mnemiopsis leidyi A. Agassiz, 1865 is known to be eaten by the scyphomedusan Chrysaora quinquecirrha (Desor, 1948), which can control populations of ctenophores in the tributaries of Chesapeake Bay. In the summer of 1995, we videotaped interactions in large aquaria in order to determine whether M. leidyi was always captured after contact with medusae. Surprisingly, M. leidyi esca...

Two scenarios of neuronal evolution (monophyly and polyphyly) are discussed in the historical timeline starting from the 19th century. The recent genomic studies on Ctenophores re-initiated a broad interest in the hypotheses of independent origins of neurons. However, even earlier work on ctenophores suggested that their nervous systems are unique in many aspects of their organization and a pos...

High-speed cinematography of feeding Pleurobrachia revealed a stereo-typed sequence of ciliary motor responses underlying the feeding behaviour of this ctenophore. Prey capture by a tentacle first elicited high frequency beating in all comb rows, propelling the animal forward at a rapid speed for several seconds. This was followed by a brief period of inactivity on some or all comb rows. Then c...

The scyphomedusa Chrysaora quinquecirrha and lobate ctenophore Mnemiopsis leidyi are dominant consumers in the planktivorous food web in Chesapeake Bay, USA, and are important predators throughout much of their ranges. Our studies in the Patuxent River (a subestuary of Chesapeake Bay) and its tributary creeks suggest successive waves of population spread and trophic influence of these 2 gelatin...

We experimentally quantified predation rates between the native North Sea ctenophore Beroe gracilis and the introduced Mnemiopsis leidyi. A series of incubation experiments with varying M. leidyi prey concentrations (0.15 to 2.37 ind. l–1) and sizes (mean oral-aboral length: 5.9 to 20.6 mm) was conducted, and digestion rates were measured. B. gracilis fed readily on M. leidyi and reproduced on ...

Forty-five years ago a symposium on the ‘‘Lower Metazoa’’ was held in Pacific Grove, California. The resulting volume (Dougherty et al., 1963) sampled much of the then current study and thought about simple animals—sponges, cnidarians, ctenophores, flatworms, pseudocoelomates, and more. Extensive discussions of homology and phylogeny formed the basis for testing a variety of hypotheses concerni...