•Represent the largest of the five kingdoms– More species than any other kingdom

Includes organisms which are…•Eukaryotic: have a true nucleus•Multicellular•Heterotrophic: do not make their own food

•Common in freshwater•Few saltwater series•Class: Bdelloidea

•Free swimming & truly planktonic•Move by inchworming along substrate•Sessile -- live inside tubes or gelatinous holdfasts

•Philodina vermiform body –Permit shortening & lengthening of body by telescoping

Philodina feeding

•About 25 species are colonial•May be found in waters with dense vegetation•Inhabit plant debris, surfaces of aquatic plants, capillary water films in soils or moss•Important to trophic dynamics of freshwater planktonic communities•Reproduce rapidly account for 50+% of zooplankton production

–Important food source for insects, fish, copepods, & rotifers

•Four main regions: head (with corona), neck, body, & foot

•Corona: composed of several ciliated tufts around mouth

– In motion, resemble a wheel– Creates current that sweeps food into mouth, where it is chewed by a mastax (characteristic pharynx) with tiny jaws– Pulls the animal through water

•Microscopic; have a fixed number of cells

•Foot usually has 2 toes– May vary from 0-4

•Foot may have pedal glands–Secrete sticky cement for temporarily attaching to substrates

•No respiratory/circulatory systems•Eutely: Consistent number of nuclei in each organ throughout life

•Uniform morphology•Exclusively females; dioecious; 2 ovaries•Asexual parthenogenesis

–Maternal individual produces diploid eggs via mitosis

•Eggs develop into new embryos without fertilziation

–Clonal offspring that are genetically identical to parent

•No meiosis or syngamy females produce other females via parthenogenesis

•Dominant form: most are 0.1-0.5mm long–All parts of reproductive cycle take place in dominant form–Majority of life cycle spent in dominant form

•Anhydrobionts: can survive prolonged periods of adverse conditions after desiccation

–Under drought conditions, contract into inert form & lose almost all body water–When rehydrated, resume activity within a few hours

•No metamorphosis before becoming adult•No alternation of generations

–Stress can cause females to produce eggs that hatch as males – no mouth/digestive tract – followed by sexual reproduction

•Can produce multiple times before death•Average lifespan: 1-3 weeks

•"BIOL 335: INVERTEBRATE ZOOLOGY." CBU. 15 Aug. 2002. Christian Brothers University. 6 Nov. 2006 <http://www.cbu.edu/~seisen/BIOL335.htm>.

•"Philodina Rotifer." Nikon MicroscopyU. 2006. Molecular Expressions. 6 Nov. 2006 <http://www.microscopyu.com/galleries/dxm1200/philodinarotifersmall.html>.

•"Rotifera (Rotifers)." Answers.Com. 2005. The Gale Group, Inc. 6 Nov. 2006 <http://www.answers.com/topic/rotifera-rotifers-biological-family>.

•"Rotifer." Wikipedia. 23 Oct. 2006. Wikimedia Foundation, Inc. 2 Nov. 2006 <http://en.wikipedia.org/wiki/Rotifer>.

•Wallace, Robert L., and Terry W. Snell. "Phylum Rotifera." Ecology and Classification of North American Freshwater Invertebrates. San Diego: Academic P, 2001. 195-228.