This document provides an overview of rotifers including their: 1) Evolution, classification into three main classes, and general characteristics such as habitat and locomotion. 2) Internal anatomy including systems like nervous, excretory, and muscular. 3) Modes of nutrition, reproduction through sexual and asexual means, and life cycle. 4) Ecological roles in ecosystems and some economic importance as food for aquarium fish and as biological indicators of water quality.

1. Stella Maris Polytechnic University
Mother Pattern College of Health Sciences
UN Drive
Monrovia, Liberia
Topic: Lophophodata
Course: Invertebrate Zoology 201
Submitted to: Mr. Othello Zomonway
Submitted by: Group 1(0NE)
Date: March 31, 2022

2. LEARNING OBJECTIVES
 Evolution of Rotifera
 Overview of Phylum Rotifera
 General Characteristics
 Habitat and Habit
 Morphology
 Mode of nutrition and movement
 Reproduction
 Life cycle of Rotifers
 Ecological and economic importance

3. Objectives of this work
 By the end of this presentation, students will be able to:
 Define and discuss the term rotifera
 Discuss the types of reproduction in these organisms
 Classify rotifera
 Discuss the impacts of these organisms both
 Economically and ecologically

4. What is rotifera?
 The term rotifera derives from two Latin words: Rota, meaning
wheel and fera, meaning to bear.
 Rotifera are microscopic aquatic animals of the phylum rotifer.

5. Overview of Rotifers
 Rotifers are multicellular animals with body cavities lined by
mesoderm.
 These organisms have specialized organs systems and a
complete digestive tract that includes both mouth and anus.

6. Evolution of Rotifera
 Phylogenetic
 Natural Selection

7. General Characteristics
 Rotifers can also be known as Wheel Animalcules.
 Rotifer’s body can be divided into three: Head, Trunk and food
 The body has more than two cell layers, tissues and organs.
 All live in aquatic environments.
 Locomotion:
 Inch worming (some)
 Sessile

8. General Characteristics - Habitat
 Rotifers can be found in still water environments, such as rivers or
streams. Eg: Brachionus calyciflorus.
 They can also be found on mosses and lichens growing on tree
trunk and rocks.

9. General Morphology
 Rotifer’s body divided into three main regions.
 Head
• The head carries the corona.
 Trunk
• Digestive tract
• Excretory system
• Genital organs
 Foot
• Petal glands
• One to four toes

10. Nervous System
 Bilobed brain dorsal to mastax
 They have sensory structures
 0ne to five photosensitive eyespot maybe on
the head

11. Excretory system
 Flame cells perform excretion
 A short ciliated intestine extends posteriorly and becomes a
cloaca bladder, which receives water from the protonephridia
and eggs from the ovaries as well as digestive wastes.
 The cloaca bladder opens to the outside via an anus.

12. Muscular System
 Support and Protection
 The cuticle supports the Rotifera as do the muscles
 Pseudocoelom also offers support
 The muscles act as a hydrostatic skeleton
 The muscles also serve to retract the corona in some
species.

13. Systems cont’d

14. Mode of Nutrition
 Most rotifers are omnivores and some species are carnivorous.
 Their digestive tract : mouth pharynx, oesophagus , stomach
,intestine , cloaca bladder , and digestive gland.
 The whirling water movement produced by beating of the cilia
helps in feeding of rotifer.
 Digestion take place in the stomach and absorption in the
stomach and intestine.
 Rotifer diet includes the following :Bacteria ,Algae , protozoans
and particles eaten are 10 micrometers or less.

15. Mode of Nutrition cont’d

16. Locomotion
 Ciliary activity on the corona.
 Most are motile and quite swimmers and
crawlers.

17. Reproduction in Rotifers
 Rotifers are diocious
A female reproductive system includes:
 Germarium ( egg cells)
 Vitellarium (yolk cells)
 Oviduct
 Uterus
Germovitellarium

18. Reproduction cont’d
 Females reproduce
 Sexually ( Class Seisonidea)
 Parthenogenetically ( Class Bdelloidea)
 Alternation of Both reproductions ( Monogononta)
• environmental conditions trigger such the alternation
Two types of Eggs
• Amictic or Mictic egg

19. Reproduction cont’d
 A male reproductive organs include
 Single teste
 Ciliated sperms
 Genital pore
 Projected penis
Note: Offspring are born with adult features

20. Life cycle

21. Classification of Rotifera
 The phylum Rotifera has been divided into three
main classes:
 Seisonidae e.g. Paraseison annulatus
 Monogononta e.g. Lecane bulla, Keratella
serrulata
 Bdelloidea e.g. Ptygura pilula, Philodina roseola

22. Classification cont’d

23. Classification cont’d
 Class Seisonidae (most primitive):
 Marine
 Elongated form
 Corona vestigial
 Similar in size and form
eg: Seison nebaliae

24. Classification cont’d
 It has a single genus: Seison
 Epizoic on gills of the crustacean
 Seisonidae: females produce haploid eggs
that must be fertilized and develop into
either males or females.

25. Classification cont’d
 Class Monogononta:
 Swimming and sessile forms
 Males reduced in size
Eg: Polyarthra

26. Classification cont’d
 Monogononta: females produce two kinds of
eggs;
 Amictic eggs
 Mictic eggs

27. Classification cont’d
 Class Bdelloidea:
 Swimming or creeping forms
 Anterior end retractile
 Corona usually with pair of trochal discs
 Males unknown

28. Classification cont’d
 Bdelloidea: females are parthenogenetic (asexual)-
produce diploid eggs that hatch into diploid females.
 Eg: Rotaria
Rotaria

29. Rotifer’s Ecology
 Rotifers are cosmopolitan
 Most Rotifers can live on the bottom of
freshwater lakes or ponds, however a few are
marine and some are terrestrial.
 Most Rotifers eat plankton.
 Some Rotifers are parasitic.
 Some Rotifers are epizoic.

30. Economic Importance
 Rotifers in the wild have little significance to
humans.
 They may have some economic significance,
however, because many species are cultured
as a food source for aquariums and cultured
filter-feeding invertebrates and fish fry.

31. Economic Importance cont’d
 They also may be used as biological pollution indicators. Eg:
Filinia longiseta, heavy pollution

32. Ecological Importance
 There are three important roles of Rotifers in society:
 Feed on algae species
 Serve as important species
 Indicated water quantity. Eg: Synchaeta grandis, fresh and
clean water.