Protostome Animals

1. Protostome Animals Overview of protostome evolution Themes in diversification Key lineages: lophotrochozoans Key lineages: Edcysozoans

2. Overview of Protostome Evolution Protostomes: Spiral cleavage in zygote formation First pore formed during gastrulation is mouth Protostomes are a monophyletic group Lophotrochozoa Ecdysozoa

3. Lophotrochozoans Molluscs, annelids, and flatworms Shared characters Growth by incremental additions to the body Feeding structure called lophophore Larve called trochophore

5. Ecdysozoan Includes nematodes and arthropods Shared characters Grow by molting- sheds exoskeleton Between shedding the old exoskeleton and the new one hardening, Ecdysozoans are very secretive No feeding, little movement Very vulnerable to predators

8. Diversification Themes- Body Plans All protostomes are triploblastic, bilateral; all have similar embryonic development Acoelomate- Platyhelminthes Pseudocoelomate- Nematoda Reduction in coelom Worm-like phyla: well-developed coelom Arthropoda and Mollusca: drastically reduced coelom

9. Body Plans- Arthropoda Segmented bodies: tagma Head, thorax, abdomen Exoskeleton of chitin Movement by muscles applying force to exoskeleton Hemocoel: body cavity that provides space for organs, etc.

10. Body Plan- Mollusca Muscular foot, visceral mass, and the mantle Functions of coelom replaced by visceral mass and muscular foot Visceral mass allows space for organs and circulation of fluids In some species, visceral mass serves as hydrostatic skeleton; in others the mantle

11. Water To Land Transition Transition occurred several times in protostome lineages Independent evolution in annelids, nematodes, molluscs, and arthropods (2+) Easier for protostomes than plants Some tissue support already existed in aquatic forms, adaptations for locomotion also worked well on land Needed gas exchange and dehydration adaptations to survive on land

12. Protostome Adaptations Feeding Suspension, deposit, liquid, and food-mass feeders From tubes to pincers as mouthparts Movement No limbs- movement run by hydrostatic skeleton Jointed limbs- flying, running, swimming

13. Protostome Adaptations Reproduction Asexual: many worm-like phyla Parthenogenesis: some crustaceans, arthropods Sexual: some use internal fertilization, some external Key adaptations Metamorphosis Eggs that do not dry out on land

14. Lophotrochozoa- Platyhelminthes 3 classes Turbellaria, Cestoda, and Trematoda Unsegmented; lack a coelom and structures for gas exchange No blood vessels or circulatory system 1 entrance to the gut Movement limited, some only during juvenile period

15. Lophotrochozoa- Platyhelminthes Reproduction Turbellarians: asexual by fragmentation; sexual, too Trematodes and Cestodes reproduce sexually (some cross, some self)

18. Lophotrochozoa- Annelida Segmented body, coelom that serves as hydrostatic skeleton Polychaeta: chaetae extend from parapodia Clitellata: Oligochaeta and Hirudinea Feeding: Deposit feeding, suspension feeding, hunting Leeches suck body fluids from hosts

19. Lophotrochozoa- Annelida Reproduction Asexual: fragmentation in oligochaetes, polychaetes Sexual: polychaetes have separate sexes, typically release gametes into water Sexual: oligochaetes and leeches exchange gametes in internal fertilization (cross)

21. Lophotrochozoa- Mollusca Four main lineages Bivalves: clams and mussels Gastropods: snails and slugs Chitons Cephalopods: squid and octopus

22. Class Bivalvia

23. Class Gastropoda

24. Class Cephalopoda

25. Ecdysozoa- Nematoda Roundworms: unsegmented, pseudocoleomate Plant or animal parasites, or free-living Major agricultural pests Live in soil or their host Sexual reproduction involving internal fertilization

27. Ecdysozoa- Arthropoda Segmented bodies with paired, jointed exoskeleton Highly reduced coelom, but extensive hemocoel (body cavity) Metamorphosis is common Most have compound eyes and antennae Most likely monophyletic

28. Class Chelicerata

30. Class Insecta

36. The Crustaceans