Feeding and digestive system , other organ system; reproduction and development of Phylum Rotifera

1. PHYLUM ROTIFERA
(Feeding and digestive system , other organ
system; reproduction and development of
Phylum Rotifera)

2. OUTLINES
Feeding and digestive system of Phylum Rotifers
Other organ systems of Rotifera
Reproduction and development in Rotifers

3. FEEDING AND DIGESTIVE SYSTEM OF
PHYLUM ROTIFERA
Most rotifers feed on small microorganisms and
suspended organic material.
 The coronal cilia create a current of water that brings food
particles to the mouth.
The pharynx contains a unique structure called the mastax
(jaws).

4. CONT…
 The mastax is a muscular organ that grinds food.
The inner walls of the mastax contain several sets of
jaws called trophi.
 The trophi vary in morphological detail, and
taxonomists use them to distinguish species.

6. CONT…
From the mastax, food passes through a short,
ciliated esophagus to the ciliated stomach.
Salivary and digestive glands secrete digestive
enzymes into the pharynx and stomach.
Complete extracellular digestion and absorption of
food occur in the stomach.

7. CONT…
In some species, 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 waste.
The cloacal bladder opens to the outside via an
anus at the junction of the foot with the trunk.

8. OTHER ORGAN SYSTEMS OF ROTIFERS
All visceral organs lie in a pseudocoelom filled with
fluid and interconnecting amoeboid cells.
Protonephridia that empty into the cloacal bladder
function in osmoregulation.
 Rotifers, like other pseudocoelomates, exchange gases
and dispose of nitrogenous wastes across body surfaces.

9. CONT…
The nervous system is composed of two lateral nerves
and a bilobed, ganglionic brain on the dorsal surface of
the mastax.
Sensory structures include numerous ciliary clusters
and sensory bristles concentrated on either one or more
short antennae or the corona.
One to five photosensitive eyespots may be on the
head

10. REPRODUCTION AND DEVELOPMENT
IN ROTIFERS
Some rotifers reproduce sexually, although several types
of parthenogenesis occur in most species.
Smaller males appear only sporadically in one class
(Monogononta), and no males are known in another class
(Bdelloidea).

11. CONT…
In the class Seisonidea, fully developed males and
females are equally common in the population.
Most rotifers have a single ovary and an attached
syncytial vitellarium, which produces yolk that is
incorporated into the eggs.

12. CONT..
The ovary and vitellarium often fuse to form a single
germovitellarium.
After fertilization, each egg travels through a short
oviduct to the cloacal bladder and out its opening.
In males, the mouth, cloacal bladder, and other
digestive organs are either degenerate or absent.

13. CONT…
A single testis produces sperm that travel through a
ciliated vas deferens to the gonopore.
Male rotifers typically have an eversible penis that
injects sperm, like a hypodermic needle, into the
pseudocoelom of the female (hypodermic impregnation)

14. CONT..
In one class (Seisonidea), the females produce haploid eggs
that must be fertilized to develop into either males or
females.
In another class (Bdelloidea), all females are
parthenogenetic and produce diploid eggs that hatch into
diploid females.

15. CONT…
The third class (Monogononta) produces two different
types of eggs.
Amictic eggs are produced by mitosis, are diploid,
cannot be fertilized, and develop directly into amictic
females.
Thin-shelled, mictic eggs are haploid.

16. CONT…
If the mictic egg is not fertilized, it develops
parthenogenetically into a male; if fertilized, mictic eggs
secrete a thick, heavy shell and become dormant or
resting winter eggs.
Dormant eggs always hatch with melting snows and
spring rains into amictic females, which begin a first
amictic cycle, building up large populations quickly.

17. CONT…
 By early summer, some females have begun to produce
mictic eggs, males appear, and dormant eggs are
produced.
 Another amictic cycle, as well as the production of
more dormant eggs, occurs before the yearly cycle is
over. Winds or birds
often disperse dormant eggs, accounting for the unique
distribution patterns of many rotifers.

18. CONT…
Most females lay either amictic or mictic eggs, but not
both.
Apparently, during oocyte development, the
physiological condition of the female determines whether
her eggs will be amictic or mictic.

19. Life Cycle of Monogont Rotifers

20. REFERENCE
A text book of Zoology by Miller and Harley, 5th edition