Word Finder - pneumatophore

definition

A gas-filled sac or float of some colonial marine coelenterates, such as the Portuguese man-of-war.

definition

An aerial root, in mangroves etc., specialized for gaseous exchange.

definition

An apparatus consisting of a bag with a tube and mouthpiece, which may be attached to the body. The bag contains oxygen to be breathed by the wearer in rescue work in mines, etc.

In cases where the cormus has no pneumatophore the topmost swimming bell may contain an oil-reservoir or oleocyst.

Never more than one pneumatophore is found in a cormus, and when present it is always situated at the highest point above the swimming bells, if these are present also.

In Velella the pneumatophore becomes of complex structure and sends air-tubes, lined by a chitin and resembling tracheae, down into the compact coenosarc, thus evidently serving a respiratory as well as a hydrostatic function.

Divergent views have been held as to the morphological significance of the pneumatophore.

Next the pit closes up to form a vesicle with a pore, and so gives rise to the pneumatophore.

As in the analogous swim-bladder of fishes, the gas in the pneumatophore can be secreted or absorbed, whereby the specific gravity of the body can be diminished or increased, so as to cause it to float nearer the surface or at a deeper level.

Woltereck [59], on the other hand, have shown that the ectodermal pit which gives rise to the pneumatophore represents an entocodon.

Haeckel regards it as the equivalent of the manubrium, and as it is implanted on the blind end of the pneumatophore, such a view leads necessarily to the air-sack and gland being a development on the ex-umbral surface of the medusa-person.

The subsequent development is slightly different according as the future cormus is headed by a pneumatophore (Physophorida, Cystophorida) or by a nectocalyx (Calycophorida).

The planula develops, on the whole, in a similar manner, but the ectodermal invagination arises, not at the pole of the planula, but on the side of its broader portion, and gives rise, not to a pneumatophore, but to a nectocalyx, the primary swimming bell or protocodon (" Fallschirm ") which is later thrown off and replaced by secondary swimming bells, metacodons, budded from the coenosarc.

Woltereck considers the siphonophores most nearly allied to the Narcomedusae, producing like the buds from an aboral stolon, the first bud being represented by the pneumatophore or protocodon, in different cases.

If sterile they remain attached and locomotor in function, forming the nectosome, the pneumatophore and swimming-bells.

With an apical pneumatophore, not divided into chambers, followed by a series of nectocalyces or bracts.

The Auronectae are peculiar deep-sea forms, little known except from Haeckel's descriptions, in which the large pneumatophore has a peculiar duct, termed the aurophore, placed on its lower side in the midst of a circle of swimming-bells.

With a very large pneumatophore not divided into chambers, but without nectocalyces or bracts.

The more complex umbrellashaped colonies of colonies (synrhabdosomes) described as provided with a common swimming bladder (pneumatophore?) may have attained a holo-planktonic or free-swimming mode of existence.