Zoology

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.