| Title | Obelia (Cnidaria, Hydrozoa, Campanulariidae): a microphagous filter-feeding medusa |
| Abstract | Obelia is used in many zoology textbooks to exemplify the Hydrozoa life cycle. The body plan of Obelia medusae, however, is unique among the Hydrozoa.
Contrary to all other hydromedusae, Obelia medusae do not derive from a
medusary nodule, have neither a velum nor a subumbrellar cavity, the umbrella
is flat, and swimming is achieved by umbrellar flapping and does not involve
jet propulsion. The medusae of most Obelia species do not grow well on a diet
of Artemia salina nauplii, the usual food for laboratory-reared hydrozoans, and
their rearing is often difficult. Previous observations reported that Obelia
medusae might eat phytoplankton, driven to the mouth by movements of both
the bell and the tentacles. To evaluate the efficiency of this feeding mechanism,
we gave a suspension of genetically modified Escherichia coli expressing GFP to
starved, newly released medusae of both O. dichotoma and Clytia hemisphaerica
(the other campanulariid genus with medusae). Obelia medusae are able to
concentrate bacteria in their gastric cavity, whereas Clytia medusae are not.
Contrary to other Hydromedusae that are macrophagous, Obelia is a microphagous
and filter-feeding medusa, at least at the onset of its medusan life. As
Cnidaria evolved before their current metazoan prey, their ancestral diet was
probably microphagous. Obelias microphagous feeding habits could thus represent
an example of the ancestral feeding condition in Cnidaria, but the apomorphic
characters of its medusa suggest that its body architecture is not
ancestral, and that its microphagy evolved relatively recently.
|
| Keywords | feeding strategyHydrozoaIonian SeamicrophagyObelia |
| Year | 2007 |
| Type | Articolo in rivista |
| Authors | Boero F., Bucci C., Colucci M.R., Gravilli C., Stabili L. |
| Text | 6442 2007 feeding strategy Hydrozoa Ionian Sea microphagy Obelia Obelia Cnidaria, Hydrozoa, Campanulariidae a microphagous filter feeding medusa Boero F., Bucci C., Colucci M.R., Gravilli C., Stabili L. Obelia is used in many zoology textbooks to exemplify the Hydrozoa life cycle. The body plan of Obelia medusae, however, is unique among the Hydrozoa. Contrary to all other hydromedusae, Obelia medusae do not derive from a medusary nodule, have neither a velum nor a subumbrellar cavity, the umbrella is flat, and swimming is achieved by umbrellar flapping and does not involve jet propulsion. The medusae of most Obelia species do not grow well on a diet of Artemia salina nauplii, the usual food for laboratory reared hydrozoans, and their rearing is often difficult. Previous observations reported that Obelia medusae might eat phytoplankton, driven to the mouth by movements of both the bell and the tentacles. To evaluate the efficiency of this feeding mechanism, we gave a suspension of genetically modified Escherichia coli expressing GFP to starved, newly released medusae of both O. dichotoma and Clytia hemisphaerica the other campanulariid genus with medusae . Obelia medusae are able to concentrate bacteria in their gastric cavity, whereas Clytia medusae are not. Contrary to other Hydromedusae that are macrophagous, Obelia is a microphagous and filter feeding medusa, at least at the onset of its medusan life. As Cnidaria evolved before their current metazoan prey, their ancestral diet was probably microphagous. Obelias microphagous feeding habits could thus represent an example of the ancestral feeding condition in Cnidaria, but the apomorphic characters of its medusa suggest that its body architecture is not ancestral, and that its microphagy evolved relatively recently. 28 S Obelia Cnidaria, Hydrozoa, Campanulariidae a microphagous filter feeding medusa Articolo in rivista loredana.stabili STABILI LOREDANA TA.P04.002.001 Fascia Costiera e Ambienti di Transizione analisi strutturale e funzionale delle componenti biotiche ed abiotiche degli ecosistemi per lo sviluppo sostenibile delle attivita |
