1. The Lophotrochozoa 1

3. Protostomes Characteristics
Protostome groups consisting of two large clades the Lophotrochozoans and the Ecdysozoans.
Lophotrochozoans include 10 smaller protostome phyla.
Acoelomate, Pseudocoelomate or Eucoelomate bodies.

4. Protostome Characteristics
Development is characterized by:
blastopore becomes the mouth
Spiral / determinate cleavage
Schizocoely

5. Mouth Formation
Blastopore becomes the mouth and the anus forms secondarily
Future anus
blastopore
archenteron
(primitive gut)
mouth

6. Cleavage
Cleavage is the initial process of development after fertilization of the egg.

7. Radial Cleavage planes are symmetrical to the polar axis Produces regulative development

8. Spiral Cleavage: cleavage planes are oblique to the polar axis Produces mosaic development

9. Schizocoely blastocoel Mesodermal cells Split in mesoderm
Developing coelom
ectoderm
endoderm
mesoderm

10. Lophotrochozoans Characteristics
The name Lophotorochozoa comes from the names of the larval type of the two major animal groups including the Lophophorata and the Torchozoa.
Trochophore Larva

11. Lophotrochozoans Characteristics
Organ level of organization
Tissues are organized to form organs which are used to accomplish physiological functions.
Triploblastic
3 Germ Layers
endoderm
mesoderm
ectoderm
3 Tissue Layers
gastrodermis
mesoderm
epidermis

12. Lophotrochozoans Characteristics
Bilateral Symmetry
with anterior and posterior ends
Cephalization
concentration of sensory organs in the head of the animal

13. Lophotrochozoans Characteristics
Digestive System
complete (they have an anus!)
some regional specialization
Circulation System
no system (or organs)
performed by the pseudocoelom fluid

14. Gnathiferans and Smaller Lophotrochozoans

15. The Lophotrochozoa

16. There are 4 different phyla that are classified as Gnathifera.
Rotifera
Acanthocephala
Gnathostomulid
Micrognathozoa

17. Gnathifera Characteristics
Other than the Acanthocephalans all phyla posses small, cuticular jaws with a homologous microstructure.

18. Gnathifera Characteristics
Eutely
each individual of a species has the same number of cells
growth occurs by cells getting bigger rather than dividing

19. P: Gnathostomulida : gnatho, “jaw”; stoma, “mouth”
Benthic, interstitial
Monociliated epidermal cells
Jaws and muscular pharynx
Often vermiform
Hermaphroditic
About 80 species have been described
jaws and
basal plate
Gnathostomulid 19

20. 20

21. P: Micrognathozoa Limnognathia maerski
Three sets of paired jaws, interstitial, cellular epidermis. 21

22. Phylum Rotifera the rotifers
1st phyla we will talk about and what we will cover in the lab today is…
the rotifers

24. Phylum Rotifera: rota, “wheel”; fera, “to bear”
Includes about 1,800 described species.
Tiny metazoans (up to 3 mm), that are predominantly freshwater although some are marine and terrestrial (live in mosses).

25. The “wheel” animals {
Head {
Trunk {
Foot

26. Corona have a “crown” of cilia called a corona the corona creates a
current to bring food into
the mouth

27. Corona of Foscularia species

28. Body Wall and Support
Most rotifers possess a gelatinous cuticle outside the syncytial epidermis.
They possess a skeletal lamina which produces the lorica and other surface structures.

29. Rotifers of the genus Keratella donot possess a foot
Rotifers of the genus Keratella donot possess a foot. They are fast swimmers. Their lorica (shell) looks like a jigsaw puzzle and is covered with small spikes. There are long spines on each corner. The photograph shows how the cilia are grouped in tufts.

30. Kellicottia is a rotifer that lives in open waters of lakes
Kellicottia is a rotifer that lives in open waters of lakes. The long spines might prevent them from being eaten by predators.

31. Well developed and complex muscle bands

32. Body appears to be composed of segments, they are superficial segments.

33. Feeding have a specialized feeding structure called the:
mastax-trophi complex
modified jaws
within the mastax
a modified
muscular pharynx

34. Looking down into the corona….

35. Mastax-trophi complex

36. Some of the trophi (jaws):
Malleate mastax
Ramate mastax
These are crushing/grinding forms.

37. Some of the trophi (jaws):
Forcipate mastax
Incudate mastax
These are grasping, predatory forms.

38. Nervous and sensory system
cephalization, cerebral ganglia
dorsal and ventral nerve cords
eyes
Circulatory system
no system (no organs)
performed by fluid in pseudocoelom
Excretion
protonephridia and flame cells
cloacal bladder (collects wastes)

39. Reproduction Sexual complex life cycle with different types of eggs
usually dioecious but in some groups, males are absent (parthenogenesis)
Parthenogenesis:
unisexual reproduction where females produce offspring from unfertilized eggs (virgin birth)

40. Reproduction Amictic eggs – Asexual Reproduction
2 types of eggs: amictic & mictic
Amictic eggs – Asexual Reproduction
diploid (mitotically produced)
can’t be fertilized
develop into diploid, amictic females

41. Reproduction Mictic eggs- Sexual and Asexual Reproduction
haploid (meiotically produced)
produced after some sort of environmental stimulus (eg. high density, change in temperature)
if unfertilized, develop into haploid males
if fertilized, secrete a thick, protective shell until the environment is favorable again, after which they develop into diploid, amictic females

43. Brachionus is a very common genus. They carry their eggs on their foot
Brachionus is a very common genus. They carry their eggs on their foot. The various species can be identified by the spines on their lorica (shell).

44. Asplanchna is a large bag-shaped rotifer
Asplanchna is a large bag-shaped rotifer. This individual carries an almost fully developed embryo inside.

45. Eggs maintained in maternal tube

48. Resting eggs of monogonont rotifers

49. Reproduction
Because of the reduced role of males in reproduction, most males are incapable of feeding and do not even have a digestive tract (they are just there for sperm delivery!).
Males have never been recorded in Bdelloid rotifers. This means they haven’t had sex in millions of years!