Rotifers are microscopic aquatic animals of the phylum Rotifera. Rotifers can be found in many freshwater environments and in moist soil, where they inhabit the. Phylum Rotifera. 1. PHYLUM ROTIFERA Philodina; 2. PHYLUM ROTIFERA Rotifera- Latin word meaning “wheel-bearer” (rota =wheel. Tujuan Instruksional Khusus: Menjelaskan morfologi, anatomi, reproduksi dan daur hidup dan klasifikasi serta arti ekonomis dari jenis Filum Rotifera. ROTIFERA.
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Phylum Rotifera is comprised of two classes, Eurotatoria which includes orders Monogononta and Bdelloidea and Seisonideawith over 2, currently known species. They are most commonly found in freshwater, although some species live in brackish or marine habitats, in soil, or on rootifera. Rotifers may be sessile or sedentary and some species are colonial. Their bodies can be clearly divided into three regions: Some species sexually reproduce, but parthenogenic reproduction is far more common, order Bdelloidea lacks males altogether.
Rotifers mainly feed on smaller animals, algae, and organic particulates, although some species are parasitic. Depending on the species, they filter feed or actively hunt and capture prey.
Brusca and Brusca, ; Ruppert, et al. Rotifers are considered broadly cosmopolitan, and are found in marine, brackish, and fresh waters throughout the world, excluding Antarctic. Several species are endemic to specific regions. Brusca and Brusca, ; Segers, The majority of rotifers are planktonic and are found in freshwater environments, though many are found in water films and droplets within soil, lichens and mosses.
Members of order Seisonidea are known only from marine environments and live on the bodies of leptostracan crustaceans. Other marine rotifers are mainly littoral, but have been found at depths of m and greater. All members of family Flosculariidae class Monogonontaabout rilum species, are colonial; colonies may be sessile or free-swimming, colony members do not appear to share resources. A few species are known endo- or ectoparasites.
Brusca and Brusca, ; Hyman, ; Segers, ; Wallace, These animals are small, most are less than 1 mm long, although a few species reach lengths up to 3 mm. They have many different body forms, ranging from sac-shaped to spherical or cylindrical, wide and flattened, or long and slender. They can be easily divided into three regions: Many rotifers also have a gelatinous layer outside the epidermis. Some have dorsal or lateral sensory antennae.
Many have bodies that are annulated to increase flexibility. In most species, males are extremely rare, and are completely absent in bdelloid species. When they are present, male rotifers tend to be much smaller, shorter lived, and filuj complex than females.
These animals are eutelic, with an average cell count of to 1, Rotifers are blastocoelomates, and body support and shape are maintained not by a muscular body wall but by the skeletal lamina and the fluid-filled body cavity itself. Organs are suspended within the blastocoel. Longitudinal muscle bands are present, which serve mainly to retract protruding body parts such as the foot. In sedentary species, pedal gland secretions cement the rotifer in place.
All rotifer species have a ciliary organ located rltifera the head, known as a corona, which is typically used for locomotion and feeding. It is from these cilia and their characteristic motion, resembling turning wheels, that this phylum derives its common name, ‘wheel animals’.
The appearance of the corona varies from species to species.
The area of the head anterior to this ring is known as the apical field. In many species, the corona is made up of two concentric rings, the trochus most anterior and rotitera, which may itself be made up of rings of cilia called trochal discs. The cilia of the trochus and cingulum move asynchronously.
Although fium mechanisms vary, general digestive structures are largely the same between species. The anterior portion of the digestive system consists of the corona, a muscular pharynx mastaxand trophi chitinous jaws.
Some may have a buccal tube leading from the mouth to the pharynx. These animals have two to seven salivary glands, which secrete digestive enzymes and lubricate food material. An esophagus connects the mastax to the stomach, where a pair of gastric glands secretes enzymes to further break down food matter, and absorption of nutrients rotifeera.
The short intestine is connected to the anus via a cloaca. A nephridioduct leads from a pair of flame bulb protonephridia located much farther forward in the body ; these empty into a collecting bladder, which also empties into the cloaca. This system controls osmoregulation and expels nitrogenous by-products of digestion. Waste, gases and nutrients are all diffused directly to the exterior environment through organ tissues and blastocoelomic fluid.
Brusca and Brusca, ; Hyman, ; Ruppert, et al. Once eggs are fertilized, they develop a multi-layered membranous shell and are either attached to substrate, or carried externally or internally by the female.
Some species alternate parthenogenic and sexual reproduction. In these cases, females produce diploid eggs amictic ova during favorable conditions, which develop without fertilization.
If conditions become less favorable, these eggs grow into mictic females who produce haploid mictic ova; these ova may develop, via parthenogenesis, into males. When they mate, these males produce hardy zygotes that hatch into amictic females. It is thought that embryos undergo modified spiral cleavage; unequal holoblastic early cleavage produces a sterobastula.
Development is direct, although some sessile species produce free-swimming “larvae” that settle quickly.
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There is no cell fulum following embryonic stages, as these species are eutelic. Each species may have alternative adult morphotypes due to differing ecological conditions, a phenomenon known as developmental polymorphism. Brusca and Brusca, ; Hyman, ; Wallace, Parthenogenesis is the most common method of reproduction in rotifers. When present, males are short-lived and have a greatly reduced gut. Brusca and Brusca, ; Wallace, Rotifers are dioecious, but in most species, males are extremely rare or even unknown.
Male rotifers, when present, most often have a single testis, which is connected to a sperm duct and a posterior gonopore, which is unconnected to the digestive system.
Most females have paired or single germovitellaria that provides eggs produced in ovaries with yolks. Yolked eggs pass through an oviduct to the cloaca. Depending on environmental conditions, eggs may be mictic or amictic.
No particular breeding season is associated with these animals. Females may parthenogenetically produce up to seven eggs at a time, eggs hatch within 12 hours. Sexual maturity is reached very quickly, within 18 hours of hatching. If conditions are unfavorable, mictic ova with thick shells are more likely to be produced. Mictic eggs are able to survive desiccation, low temperatures, and other unfavorable environmental conditions. These ova undergo a period of diapause and do not hatch until conditions are more favorable.
Brusca and Brusca, ; Hyman, ; Marini, Rotifers exhibit no parental investment beyond egg and gamete production.
Introduction to the Rotifera
Brusca and Brusca, Rotifers are short-lived; their total lifespan has been recorded at 6 to 45 days. Most rotifers are motile and planktonic; swimming is achieved by ciliary movement. Motile rotifers may also move by “creeping” along the bottom, attaching the foot with secretions from the pedal glands, extending the body, attaching the head to substrate, then releasing the foot and using muscle bands to move the body forward.
In sedentary species, pedal gland secretions cement the rotifer into place. Some rotifers also have moveable extremities bristles, setae, etc.
It is common for these animals to have at least one photosensitive pigment cup ocellus on the dorsal or ventral side of the cerebral ganglion and many species have one or two pairs of ocelli. Some may have lateral or apical ocelli that are also photosensitive.
Some rotifers have sensory hairs on their antennae, or the antennae themselves may be comprised of sensory hairs.
Filter feeding rotifers have well-developed coronal cilia and a mastax pharynx for grinding food. The cilia produce a feeding current, drawing particles into a ciliated feeding groove, which carries them to the buccal field.
Some rotifers feed by trapping prey; these have a funnel-shaped corona lined with long immotile bristles or spines rather than cilia. When a prey item enters the funnel, the bristles or spines keep it from escaping and it is drawn into the mouth, usually located in the center of the funnel.
Finally, some rotifers gather food using coronal tentacles and others are symbiotic, typically with crustaceans, or entoparasites of annelids and terrestrial slugs, snail egg cases, freshwater algae, and, in one species, a colonial protist Volvox.
Rotifers typically feed on protozoa, algae, bacteria, phytoplankton, nannoplankton, and detritus or other organic matter.
As planktonic animals, adult rotifers and their eggs serve as prey to many larger animals, including birds, insects and insect larvae, bugs, beetles, water fleas, copepods, nematodes, carnivorous plants, fungi, and other rotifers. As mainly planktonic organisms, rotifers provide food to many other animals. Adults and eggs may be parasitized by fungi. Some rotifers are symbiotic with, or parasitic on, other organisms. Members of the genera Seison and Paraseison live on the legs and gills of Nebaliaa genus of marine leptostracan crustaceans, feeding on their host’s eggs and detritus.
Members of genus Embata are known to live in the gills of amphipods and decapods. Some rotifra are endoparasitic sometimes epizoicmainly on invertebrates including crustaceans, brachiopods, algae, protists, bacteria, bryozoans, other rotifers, sponges, fungi, mosses, snail eggs, annelids, oligochaetes, and slugs.
As mainly planktonic animals, rotifers are an important food source for many animals, including some that are economically important to humans. They are also studied by scientists around the world. As a broadly cosmopolitan phylum, rotifers in general are not considered endangered or threatened in any way. It is the second largest ocean in the world after the Pacific Ocean. This includes Greenland, the Rotiferw Arctic islands, and all of the North American as far south as the highlands of central Mexico.