Rotifera rota ferre wheel-bearers

1. Rotifera (rota ferre = wheel-bearers) Very small- 0.1-0.5 mm (protist-size) eutelic- ~1000 cells Syncitial tissues wheel organ, mastax, adhesive glandssensory antenna Parthenogenesis Resting stages Pseudocoelom

10. Rotifer body wall includes a protein sheath that is sometimes called a cuticle, but is better called a lamina. The lamina is inside the epidermal syncitium. Rotifers do not molt

12. Rotifera diversity & ecology ~2,000 species, mainly in freshwater habitats Important ecological role as suspension feeders on phytoplankton and bacteria Trophic link- food source for larval fishes Sewage treatment Ephemeral waters- ability to survive dessication(cryptobiosis, anhydrobiosis)

13. Rotifer Reproduction No fission, fragmentation or regeneration Asexual reproduction by parthenogenesis production of amicitic diploid eggs(amictic=no meiosis) Many rotifer species consist only of parthenogenic females. "The study of rotifers is a study of ladies, sometimes beautiful, often capricious, always fascinating.� (Meglitsch)

15. Two major Clades of Rotifera 1. Bdelloidea ~30% of rotifer species, wide distribution and large numbers of individuals (most numerous metazoans in freshwater?) All parthenogenic- significant in research on evolution of sexual reproduction (they lack transposons- the mobile genetic elements that contribute to mutation rates)

16. 2. Monogononta ~70% of rotifer species Single ovary lobe (monogonont) males present in some species- alternation of sexual(mictic) and asexual (amictic) reproduction Variety of habits- pelagic, mobile benthic, sessile, tubicolous

25. Cyclomorphosis: Developmental plasticity distinct morphologies develop in response to different environments Temperature, food availability, predation pressure, etc Rotifers and several other phyla have members that do this. (e.g. Daphnia and Scaphiopus) Presence of predators induces spine development in prey rotifers in some species, e.g. Kellicottia

27. Phylum Acanthocephala(spiny-head worms) Parasitic clade near/in clade Rotifera ~850 species Heteroxenous- larval stages in arthropods, adults in vertebrate gut eutelic (presumably had tiny ancestor) lack mouth and digestive tract, have a tegument (analogous to cestodes). Feed by saproby. possess armed introvert (proboscis) used for attachment dioecious

33. Phylum Gnathostomulida (jaw-mouths) discovered in 1956 flatworm-like body plan: ciliated epidermis, protonephridia, acoelomate, incomplete digestive tract, hermaphroditic, internal fertilization

40. Higher-level classifications are changing Formerly were based on comparative anatomy and comparative embryology Hypotheses about phylogeny are now usually based on molecular comparisons Presumed homologies of anatomy sometimes don�t agree with the molecular data.

41. Anatomical and developmental features traditionally used to classify phyla Patterns of embryonic cell cleavage(spiral vs radial cleavage) Formation of mouth and anus (protostome vs deuterostome) Body cavitiesAcoel, pseudocoel, coelom (schizocoel and enterocoel)

42. Cleavage

43. Body cavities Internal fluid can be used for convective transport of gases, nutrients, wastes, endocrines Frees gut from body wall, allowing independent movements (peristalsis) Allows elaboration of hydrostatic system � �hydraulic fluid� compartment(s)

44. Body cavity types Acoelomate � no body cavity present Pseudocoelomate (=Blastocoelomate)body cavity present, derived from blastocoel, not within the mesoderm Eucoelomate (=Coelomate) � body cavity arises within the mesoderm Schizocoelous Enterocoelous