3. ROTIFERA
The rotifers make up a phylum of microscopic and near-
microscopic pseudocoelomate animals.
Rotifers can be found in many freshwater environments and in moist soil, where they
inhabit the thin films of water that are formed around soil particles. The habitat of rotifers
may include still water environments, such as lake bottoms, as well as flowing water
environments, such as rivers or streams. Rotifers are also commonly found on mosses
and lichens growing on tree trunks and rocks, in rain gutters and puddles, in soil or leaf
litter, on mushrooms growing near dead trees, in tanks of sewage treatment plants, and
even on freshwater crustaceans and aquatic insect larvae.
5. NERVOUS SYSTEM
Rotifers have a small brain, located just above the mastax, from which a number of nerves extend
throughout the body. The number of nerves varies among species, although the nervous system
usually has a simple layout. Close to the brain lies a retrocerebral organ, consisting of two glands
either side of a medial sac. The sac drains into a duct that divides into two before opening through
pores on the uppermost part of the head. The function of the retrocerebral organ is unclear.
The nervous system comprises about 25% of the roughly 1,000 cells in a rotifer.
Rotifers typically possess one or two pairs of short antennae and up to five eyes. The eyes are simple
in structure, sometimes with just a single photoreceptor cell. In addition, the bristles of the corona are
sensitive to touch, and there are also a pair of tiny sensory pits lined by cilia in the head region.
8. ACANTHOCEPHALA
Acanthocephala is a phylum of parasitic worms known as acanthocephalans, thorny-headed worms,
or spiny-headed worms, characterized by the presence of an eversible proboscis, armed with spines,
which it uses to pierce and hold the gut wall of its host. Acanthocephalans have complex life cycles,
involving at least two hosts, which may include invertebrates, fish, amphibians, birds,
and mammals. About 1420 species have been described.
13. REFERENCES
i. https://en.wikipedia.org/wiki/Rotifer
ii. https://courses.lumenlearning.com/wm-biology2/chapter/phylum-rotifera
iii. https://en.wikipedia.org/wiki/Acanthocephala
iv. https://www.slideshare.net/Arturo_Vega/phylum-acantocephala-caractersticas?qid=818ff60a-0541-
4c1a-839a-185ec5292b6d&v=&b=&from_search=11
v. https://keys.lucidcentral.org/keys/v3/TFI/start%20key/key/Starting%20key/Media/HTML/Acanthoce
phala.html
vi. https://www.researchgate.net/figure/Diagram-of-monogonont-rotifer-life-cycle-Asexual-females-
undergo-ameiotic-oogenesis-to_fig1_239941317
