Ciliophora and Cnidaria

Ciliophora

The ciliates, some 8,000 described species, comprise the phylum Ciliophora, of the Kingdom Protista and are cosmopolitan in distribution. These heterotrophic protests are characterized by two very distinctive features, nuclear dualism – diplod micronuclei and polyploidy macronuclei – and a unique infraciliature or kinetidal system, consisting of single or paired kinetosomones with closely associated microtubules, microfibrils, are various specialized organelles. Most individuals are ciliated over at least a portion of the body during some stage in the life cycle. Possession of pellicular alveoli is another feature characteristic of most ciliates. Feeding structures in these protests vary considerably between groups, with some forms lacking any while others possess very elaborate oral apparatuses. Replication is usually via binary fission of a homothetogenic nature, essentially transverse or perkinetal (across the kineties or rows of cilia). Ciliates have been described from a wide range of habitats, both marine and freshwater as well as terrestrial: and they may occur as free-swimming or sessile or sedentary forms, while still others are ecto- or endosymbionts of a diversity of hosts.
Ciliates play an important role in the food web, serving as prey for many metazoa and as predators (grazers) of/on bacteria. Ciliates act as nutrient recyclers for their bacterial prey.

Cnidaria

The phylum Cnidária is characterized by only two layers of their body wall, the ectoderm and the endoderm, separetd by a generally thin acellular jelly layer, the mesogloea. This layer become extensive in the mecusae. All cnidarians are equipped with cnidocists (nematocysts) of different types, which mainly have the function to catch prey but may be used for defense and in in fixing vagile specimens to substrates. The species may be solitary or colonial. Many of them secrete an outer skeleton, which may be the chitinous periderm in Scyphozoa, Cubozoa and hydrozoa or the calcareous exoskeleton in Anthozoa and some hydrozoa.
All four classes of the Cnidaria are represented in the meiofauna: two species in the Scyphozoan, four in the Cubozoa, one in the Anthozoa, and possibly 28 species in the 15 genera in the Hydrozoa. Actually, most cnidarians live in coarse sand and shell gravel, more or less vigorously moving around in the interstitial space. However, some species occur in muddy sediments or in detritus rich surface layers.