Search results
Results From The WOW.Com Content Network
Hydra are diploblastic organisms, the body is composed of two embryonic cell layers; the ectoderm and the endoderm. The endoderm lines the gastrovascular cavity, which is a water-filled sac, this acts as a hydroskeleton and site for food digestion. They also have a simple nervous system that consist of a nerve net that covers the entire body. [5]
Hydramacin [5] is a bactericide recently discovered in Hydra; it protects the outer layer against infection. A single Hydra is composed of 50,000 to 100,000 cells which consist of three specific stem cell populations that create many different cell types.
Cnidarians range in size from a mere handful of cells for the parasitic myxozoans [31] through Hydra's length of 5–20 mm (1 ⁄ 4 – 3 ⁄ 4 in), [40] to the lion's mane jellyfish, which may exceed 2 m (6 ft 7 in) in diameter and 75 m (246 ft) in length. [41] Prey of cnidarians ranges from plankton to animals several times larger than ...
When the siphonophore encounters potential prey, their tentillum react to where the 30–50 cm (12–20 in) tentacles create a net by transforming their shape around the prey. [5] [20] [21] The nematocysts then shoot millions [19] of paralyzing, and sometimes fatal, toxin molecules at the trapped prey which is then transferred to the proper ...
Hydra and Craspedacusta sowerbii are distantly related and are not closely related to Polypodium. Also, the obligate parasite Myxobolus cerebralis lives in freshwater. Thus, it appears that in the evolution of cnidarians, invasion of freshwater habitats has happened at least three separate times.
Apart from Dickinsonia, the earliest widely accepted animal fossils are the rather modern-looking cnidarians (the group that includes jellyfish, sea anemones and Hydra), possibly from around 7] The Ediacara biota, which flourished for the last 40 million years before the start of the Cambrian, [8] were the first animals more than a very few ...
A polyp in zoology is one of two forms found in the phylum Cnidaria, the other being the medusa. Polyps are roughly cylindrical in shape and elongated at the axis of the vase -shaped body. In solitary polyps, the aboral (opposite to oral) end is attached to the substrate by means of a disc-like holdfast called a pedal disc , while in colonies ...
A few genera within this class live in freshwater habitats. Hydrozoans are related to jellyfish and corals , which also belong to the phylum Cnidaria . Some examples of hydrozoans are the freshwater jelly ( Craspedacusta sowerbyi ), freshwater polyps ( Hydra ), Obelia , Portuguese man o' war ( Physalia physalis ), chondrophores (Porpitidae ...