Phylum Rotifera

PHYLUM ROTIFERAPHYLUM ROTIFERA

Philodina


Rotifera- Latin word meaning “wheel-Rotifera- Latin word meaning “wheel-bearer” (bearer” (rotarota=wheel + =wheel + ferofero=to bear).=to bear). composed of several composed of several ciliatedciliated tufts tufts

around the mouth that in motion resemble a around the mouth that in motion resemble a wheel wheel

Structure of Philodina; a live Philodina

2000 species throughout the world.2000 species throughout the world.- freshwater inhabitants- freshwater inhabitants- marine- marine- terrestrial- terrestrial- epizoic or parasitic- epizoic or parasitic- benthic – swim or creep on vegetation- benthic – swim or creep on vegetation

Range in size – 40Range in size – 40µµm- 3mm in length.m- 3mm in length. - most are between 100-500- most are between 100-500µm long.µm long.

Some have beautiful colors, most are Some have beautiful colors, most are transparent.transparent.


The morphology is very diverse, but their The morphology is very diverse, but their body is cylindrical or spherical.body is cylindrical or spherical.

Floaters - globular & saclikeFloaters - globular & saclikeCreepers & swimmers – elongated and Creepers & swimmers – elongated and

wormlikewormlikeSessile - vaselike Sessile - vaselike



Variety of form in rotifers

PHYLUM ROTIFERAPHYLUM ROTIFERA Morphology of rotifers:Morphology of rotifers:

HeadHead: bears a ciliated crown or corona: bears a ciliated crown or corona,, locomotion and feedinglocomotion and feeding.. The cilia create currents of water toward the mouth- draw in small planktonic food.The cilia create currents of water toward the mouth- draw in small planktonic food.

TrunkTrunk: contains visceral organs.: contains visceral organs.

FootFoot: segmented (when present).: segmented (when present). Ringed with joints that can telescope to shorten (in some sp.).Ringed with joints that can telescope to shorten (in some sp.). The 1-4 toes secrete a sticky substance from the The 1-4 toes secrete a sticky substance from the pedal glandspedal glands for for

attachment.attachment. Used by both sessile and creeping forms.Used by both sessile and creeping forms.

Digestive system- completeDigestive system- complete Omnivorous: feed by sweeping minute organic Omnivorous: feed by sweeping minute organic

particles / algae forward the mouth by the particles / algae forward the mouth by the beating of the coronal cilia.beating of the coronal cilia.

Carnivorous (some sp.)- feed on protozoa & Carnivorous (some sp.)- feed on protozoa & small metazoans- capture by trapping or small metazoans- capture by trapping or grasping.grasping. TrappersTrappers- funnel-shape area around the mouth to - funnel-shape area around the mouth to

capture prey.capture prey. HuntersHunters- trophi that can be projected & used like - trophi that can be projected & used like

forceps to seize prey.forceps to seize prey.


Pharynx (Pharynx (mastaxmastax) fitted with a muscular ) fitted with a muscular portion that is equipped with hard jaws portion that is equipped with hard jaws ((trophitrophi)- sucking & grinding up food )- sucking & grinding up food particles.particles.

Absorption occurs in the stomach.Absorption occurs in the stomach.


Reproduction:Reproduction:Female rotifers (have 1 or 2 syncytial Female rotifers (have 1 or 2 syncytial

ovaries ovaries (germovitellaria)(germovitellaria)..Produce yolk as well as oocytes.Produce yolk as well as oocytes.

Rotifers are dioecous, but males are Rotifers are dioecous, but males are unknown in many species.unknown in many species. (Dioecous- having male & female organs in separate (Dioecous- having male & female organs in separate

individuals).individuals).


Divided into 3 classes:Divided into 3 classes:


class

order

Class Seisonidea Class Seisonidea (most primitive)(most primitive)::MarineMarineElongate formElongate formCorona vestigialCorona vestigial♀♀ & ♂& ♂ similar in size and form similar in size and formSingle genus: Single genus: SeisonSeisonEpizoic on gills of a crustaceanEpizoic on gills of a crustaceanSeisonideaSeisonidea: females produce haploid eggs : females produce haploid eggs

that must be fertilized and develop into either that must be fertilized and develop into either males or females.males or females.


Crustacea: Nebalia

Seison annulatus

Class Bdelloidea:Class Bdelloidea:Swimming or creeping formsSwimming or creeping formsAnterior end rectractileAnterior end rectractileCorona usually with pair of trochal discsCorona usually with pair of trochal discsMales unknownMales unknown2 germovitellaria2 germovitellaria


BdelloideaBdelloidea: females are parthenogenetic : females are parthenogenetic (asexual)- produce diploid eggs that hatch (asexual)- produce diploid eggs that hatch into diploid females.into diploid females.

Examples: Examples: PhilodinaPhilodina & & RotariaRotaria


PhilodinaRotaria

Class Monogononta: Class Monogononta: Swimming or sessile formsSwimming or sessile formsSingle germovitellariumSingle germovitellariumMales reduced in sizeMales reduced in size

Examples: Examples: AsplanchnaAsplanchna & & EpiphanesEpiphanes


Asplanchna Epiphanes


MonogonontaMonogononta: females produce two kinds : females produce two kinds of eggs;of eggs;AmicticAmictic eggs- diploid eggs that have not eggs- diploid eggs that have not

undergone reduction division, cannot be undergone reduction division, cannot be fertilized & develop only into females. fertilized & develop only into females.

MicticMictic eggs- undergone meiosis and are eggs- undergone meiosis and are haploid- if:haploid- if:Unfertilized- develop quickly into males.Unfertilized- develop quickly into males.Fertilized- they secrete a thick shell and become Fertilized- they secrete a thick shell and become

dormant for several months before developing into dormant for several months before developing into females. females.

The importance of rotifers in the The importance of rotifers in the ecosystems???ecosystems???


Technology

Phylum Rotifera