Dr Hendrik SEGERS

Belgian Biodiversity Platform

Royal Belgian Institute of Natural Sciences Brussels, Belgium

The Rotifera

What are Rotifera? Eating… ….and not be eaten Survival through time and space:

Reproduction and dispersal

Problems and opportunities

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Phylum Rotifera

Ca. 2030 species: 3 Seisonida, 461 Bdelloidea,1566 Monogononta

Small (40-3500µm) worms

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Phylum Rotifera

Predominantly freshwater, some marine, brackish water;

Highly abundant: 103.L-1 to 105.L-1: soda waters;

One of the main zooplankton groups

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Phylum Rotifera

Uses: Aquaculture: Brachionis plicatilis group for fish

larvae;

Ecotoxicological assays (B. calyciflorus) Scientific test organisms (e.g., parthenogenetic

reproduction) Ecological and environmental studies (e.g.,

water quality assessment) …

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Phylum Rotifera

Pelagic, littoral, interstitial; Solitary or colonial

Free-living or sessileEpizoic, parasitic;

limnoterrestrial

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Phylum RotiferaMorphology: Body: head, trunk, foot Head: corona Body: lorica +

pseudocoelom, incl. digestive, excretory, reproductive system

Foot (no tail) with attachment glands

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Unique FeaturesMorphology: Corona ciliata; Mastax with trophi; Lorica; (Eutely, syncytia,

unique type of protonephridia)

ReproductionAnhydrobiosis

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Eating…Creation of water

current by corona ciliata:

Locomotion: swimming

Feeding: filtering

Food particle processing by mastax with trophi

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

CoronaHigly adaptible!

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Mastax with trophi

Differentiation of the pharynx Mastax = Muscular organ containing Hard elements = trophi

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Trophi Higly adaptible! Different “types”

GrindingFor GraspingAs « piston »

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Lorica: Intracytoplasmatic lamina

… and not being eaten

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

… and not being eaten

Protection by lorica

Function: Stiffness Buoyancy Protection:

passive Active

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Lorica

Phenotypic plasticity:morphological adaptation

to environment

• Simple: cyclomorphosis• Complex: predator-induced

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Cuticle

Gelatinous glycocalyx Secreted by tegumental glands (trunk, foot) Function:

Protection: Chemical (unpalatability) Mechanical

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Reproduction

Seisonida: bisexual, sexual repoduction

Bdelloidea: exclusive asexual parthenogenesis

Monogononta: heterogony

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Reproduction

Rapid population growth

Production of resting eggs

Heterogony

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Resting "eggs" Encapsulated embryos; Draught-resistent,

hatching at specific clues; Survival through time and

space; Highly effective dispersal

stages

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Bdelloids: anhydrobiosis

Survival through metabolic inactivity;

Draught-resistent, reversal at specific clue;

Survival through time and space; Highly effective dispersal stages

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Constraints for studying Rotifera…

Size… Taxonomic impedement Cryptic speciation

e.g., Brachionus plicatilis complex

Sampling and sample handling

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

… and opportunities:

The Bdelloidea of Thailand Ecology and diversity of sessile

rotifers

Molecular and morphological approach combined:

Cryptic diversity of Rotifera Phylogeny Genetics of bdelloids

•Hue University Rotifer Taxonomy workshop 6-12 March 2010

Thank you for your

attention

•Hue University Rotifer Taxonomy workshop 6-12 March 2010