Rotifers are a phylum of microscopic and small aquatic animals found in both marine and freshwater environments. They possess a rotating crown of cilia used for locomotion, feeding, and gathering food particles. Rotifers exhibit diverse morphologies including globular, elongated, and sac-like shapes. They are primarily omnivorous, filtering small particles from water, but some species are carnivorous, capturing prey using specialized jaws and trapping mechanisms. Rotifers reproduce asexually through parthenogenesis or sexually, producing haploid or diploid eggs depending on the class. There are three main classes that differ in their reproductive strategies and morphology.

1. PHYLUM ROTIFERA Philodina

2. PHYLUM ROTIFERA Rotifera- Latin word meaning “wheel-bearer” ( rota =wheel + fero =to bear). composed of several ciliated tufts around the mouth that in motion resemble a wheel Structure of Philodina ; a live Philodina

3. 2000 species throughout the world. - freshwater inhabitants - marine - terrestrial - epizoic or parasitic - benthic – swim or creep on vegetation Range in size – 40 µ m- 3mm in length. - most are between 100-500 µm long. Some have beautiful colors, most are transparent. PHYLUM ROTIFERA

4. The morphology is very diverse, but their body is cylindrical or spherical. Floaters - globular & saclike Creepers & swimmers – elongated and wormlike Sessile - vaselike PHYLUM ROTIFERA

5. PHYLUM ROTIFERA Variety of form in rotifers

6. PHYLUM ROTIFERA Morphology of rotifers: Head : bears a ciliated crown or corona , locomotion and feeding . The cilia create currents of water toward the mouth- draw in small planktonic food. Trunk : contains visceral organs. Foot : segmented (when present). Ringed with joints that can telescope to shorten (in some sp.). The 1-4 toes secrete a sticky substance from the pedal glands for attachment. Used by both sessile and creeping forms.

8. Digestive system- complete Omnivorous: feed by sweeping minute organic particles / algae forward the mouth by the beating of the coronal cilia. Carnivorous (some sp.)- feed on protozoa & small metazoans- capture by trapping or grasping. Trappers - funnel-shape area around the mouth to capture prey. Hunters - trophi that can be projected & used like forceps to seize prey. PHYLUM ROTIFERA

9. Pharynx ( mastax ) fitted with a muscular portion that is equipped with hard jaws ( trophi )- sucking & grinding up food particles. Absorption occurs in the stomach. PHYLUM ROTIFERA

12. Reproduction: Female rotifers (have 1 or 2 syncytial ovaries (germovitellaria) . Produce yolk as well as oocytes. Rotifers are dioecous, but males are unknown in many species. (Dioecous- having male & female organs in separate individuals). PHYLUM ROTIFERA

13. Divided into 3 classes: PHYLUM ROTIFERA class order

14. Class Seisonidea (most primitive) : Marine Elongate form Corona vestigial ♀ & ♂ similar in size and form Single genus: Seison Epizoic on gills of a crustacean Seisonidea : females produce haploid eggs that must be fertilized and develop into either males or females. PHYLUM ROTIFERA Crustacea: Nebalia Seison annulatus

15. Class Bdelloidea: Swimming or creeping forms Anterior end rectractile Corona usually with pair of trochal discs Males unknown 2 germovitellaria PHYLUM ROTIFERA

16. Bdelloidea : females are parthenogenetic (asexual)- produce diploid eggs that hatch into diploid females. Examples: Philodina & Rotaria PHYLUM ROTIFERA Philodina Rotaria

17. Class Monogononta: Swimming or sessile forms Single germovitellarium Males reduced in size Examples: Asplanchna & Epiphanes PHYLUM ROTIFERA Asplanchna Epiphanes

18. PHYLUM ROTIFERA Monogononta : females produce two kinds of eggs; Amictic eggs- diploid eggs that have not undergone reduction division, cannot be fertilized & develop only into females. Mictic eggs- undergone meiosis and are haploid- if: Unfertilized- develop quickly into males. Fertilized- they secrete a thick shell and become dormant for several months before developing into females.

19. The importance of rotifers in the ecosystems??? PHYLUM ROTIFERA