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Cnidarians are also distinguished by the fact that they have only one opening in their body for ingestion and excretion i.e. they do not have a separate mouth and anus. Like sponges and ctenophores, cnidarians have two main layers of cells that sandwich a middle layer of jelly-like material, which is called the mesoglea in cnidarians; more ...
Siphonophorae (from Greek siphōn 'tube' + pherein 'to bear' [2]) is an order within Hydrozoa, which is a class of marine organisms within the phylum Cnidaria.According to the World Register of Marine Species, the order contains 175 species described thus far.
Conulariida are an extinct group of medusozoan cnidarians known from fossils spanning from the latest Ediacaran up until the Late Triassic. [1] [2] [3] They are almost exclusively known from their hard external structures (alternatively referred to as a theca, periderm or test), which were pyramidal in shape and made up of numerous lamellae.
Unlike other cnidarians however, the cavity is subdivided by a number of radiating partitions, thin sheets of living tissue, known as mesenteries. The gonads are also located within the cavity walls. The polyp is retractable into the corallite, the stony cup in which it sits, being pulled back by sheet-like retractor muscles. [5]
The comb jellies have more than 80 different cell types, exceeding the numbers from other groups like placozoans, sponges, cnidarians, and some deep-branching bilaterians. [ 23 ] Ranging from about 1 millimeter (0.04 in) to 1.5 meters (5 ft) in size, [ 22 ] [ 24 ] ctenophores are the largest non-colonial animals that use cilia as their main ...
Diurnality, plant or animal behavior characterized by activity during the day and sleeping at night. Cathemeral, a classification of organisms with sporadic and random intervals of activity during the day or night. Matutinal, a classification of organisms that are only or primarily active in the pre-dawn hours or early night.
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Just like all cnidaria, their tentacles are lined with cnidophores, that house harpoon-like stinging cells called nematocysts. These tentacles are used as a defense for both themselves and their host. [3] All of the species experience polyp and medusa stages, which vary in length depending on the species and other external factors. [3]