How Does A Rotifer Travel Through Water

Learning Outcomes

Describe the unique anatomical and morphological features of rotifers

The rotifers are a microscopic (well-nigh 100 µm to xxx mm) group of mostly aquatic organisms that get their proper name from thecorona, a rotating, bicycle-like structure that is covered with cilia at their anterior end (Effigy 1). Although their taxonomy is currently in flux, ane handling places the rotifers in iii classes: Bdelloidea, Monogononta, and Seisonidea. The classification of the group is currently under revision, all the same, equally more phylogenetic evidence becomes available. It is possible that the "spiny headed worms" currently in phylum Acanthocephala will exist incorporated into this grouping in the future.

The torso grade of rotifers consists of a head (which contains the corona), a trunk (which contains the organs), and the human foot. Rotifers are typically free-swimming and truly planktonic organisms, but the toes or extensions of the foot can secrete a sticky material forming a holdfast to help them attach to surfaces. The head contains sensory organs in the form of a bi-lobed brain and pocket-size eyespots near the corona.

Scanning electron micrograph A shows rotifers from the class Bdelloidea, which have a long, tube-shaped body with a fringe surrounding the mouth. Light micrograph B shows that Polyarthra from the class Monogononta is shorter and wider than the bdelloid rotifers, with a smaller fringe.

Figure 1. Shown are examples from two of the three classes of rotifer. (a) Species from the class Bdelloidea are characterized by a big corona, shown separately from the whole animals in the center of this scanning electron micrograph. (b) Polyarthra, from the course Monogononta, has a smaller corona than Bdelloid rotifers, and a single gonad, which give the class its proper noun. (credit a: modification of work by Diego Fontaneto; credit b: modification of work by U.S. EPA; calibration-bar data from Cory Zanker)

The rotifers are filter feeders that will eat dead material, algae, and other microscopic living organisms, and are therefore very of import components of aquatic food webs. Rotifers obtain nutrient that is directed toward the mouth by the current created from the move of the corona. The food particles enter the oral cavity and travel to themastax (throat with jaw-like structures). Food then passes past digestive and salivary glands, and into the stomach, then onto the intestines. Digestive and excretory wastes are collected in a cloacal bladder before beingness released out the anus.

Watch the video below to encounter rotifers feeding. Note that this video has no audio.

You can view the descriptive transcript for "Rotifer Feeding II" here (opens in new window).

Rotifers are pseudocoelomates commonly found in fresh water and some common salt water environments throughout the world. Effigy 2 shows the beefcake of a rotifer belonging to course Bdelloidea. About 2,200 species of rotifers have been identified. Rotifers are dioecious organisms (having either male or female person genitalia) and exhibit sexual dimorphism (males and females have unlike forms). Many species are parthenogenic and exhibit haplodiploidy, a method of gender conclusion in which a fertilized egg develops into a female and an unfertilized egg develops into a male. In many dioecious species, males are short-lived and smaller with no digestive organization and a single testis. Females tin produce eggs that are capable of dormancy for protection during harsh environmental conditions.

The illustration shows long, tube-shaped animal with a crown-like corona on top. Cilia fringe the top of the corona. Between the two lobes of the corona is the mouth, which leads to the stomach, intestine, and anus. The mastax surround the mouth, and beneath the mastax is a digestive gland. The pseudocoel surrounds the stomach. At the bottom if the animal is a foot that stands on two toes.

Figure two. This illustration shows the beefcake of a bdelloid rotifer.

In Summary: Phylum Rotifera

The rotifers are microscopic, multicellular, generally aquatic organisms that are currently under taxonomic revision. The grouping is characterized by the rotating, ciliated, wheel-like structure, the corona, on their caput. The mastax or jawed pharynx is another structure unique to this group of organisms.