2. Live food aquaculture training course www.aquatrain.org Rotifer Biology and Strains

3. Live food aquaculture training course www.aquatrain.org Systematics Phylum: Nemahelminthes eller Aschelminthes Class: Rotifera (lat. Hjulbærer) Order: Monogononta Familiy: Branchionidae 90% are freshwater species

4. Live food aquaculture training course www.aquatrain.org Morphology Corona: movements and generation of water currencts for ingestion of feedparticles up to 30  m Mastax: crushes the ingested particles Stomach with glands Unpaired gonads Primitive excretion system and bladder Pseudocoelom: function as a hydrostatic skeleton and cardiovascular system Common opening for bladder and uterus; cloaca Foot: the pedal has glands tha secreets glue for fastening to the susbstrate

5. Live food aquaculture training course www.aquatrain.org Life cycle I Optimal environmental conditions Amictic females produce genetic idendical offspring from diploid eggs Usually one egg/female is observed Suboptimal environmental conditions (mixis stimulus) Mictoc female produce mictic (haploid eggs) from which males hatch Resting eggs are produced after fertilization of the mictic egg Hatching is initiated after stimulus (e.g temperature/salinity changes) Resting egg with amictic females Resting egg

6. Live food aquaculture training course www.aquatrain.org Temperature and reproduction Effect of temperature on the reproduction activity of Brachionus plicatilis. (After Ruttner-Kolisko, 1972).

7. Live food aquaculture training course www.aquatrain.org Population dynamics Specific growth rate: u = (lnN2 – lnN1)/t Instant production : P =  N Relation between growthrate (  ) and eggfrequency (ER):  = ER – 0,2 Expected production the next day: P = N(ER – 0,2)

8. Live food aquaculture training course www.aquatrain.org Strain recognition SS-type S-type: lorica shows pointed spines L-type lorica shows obtuse angled spines SS

9. Live food aquaculture training course www.aquatrain.org Rotifer strain information StrainLorica length (  m) Temperature range Fits for L-type (Brachionus plicatilis) 130-34018-25°CLarvae until Artemia nauplii is small enough S-type (Brachionus rotundiformis) 100-21028-35°CInitial feed for larvae with small gapes (sea brea) SS-type (small strain of S-type) 28-35°CLarvae with gapes < 100  m