Live food aquaculture training course

1
Rotifer Biology and Strains
2
Systematics

• Phylum Nemahelminthes eller Aschelminthes
• Class Rotifera (lat. Hjulbærer)
• Order Monogononta
• Familiy Branchionidae
• 90 are freshwater species

3
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

4
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
5
Temperature and reproduction
Effect of temperature on the reproduction
activity of Brachionus plicatilis. (After
Ruttner-Kolisko, 1972).
6
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)

7
Strain recognition

• SS-type
• S-type lorica shows pointed spines
• L-type lorica shows obtuse angled spines

SS
8
Rotifer strain information
Strain Lorica length (?m) Temperature range Fits for
L-type (Brachionus plicatilis) 130-340 18-25C Larvae until Artemia nauplii is small enough
S-type (Brachionus rotundiformis) 100-210 28-35C Initial feed for larvae with small gapes (sea brea)
SS-type (small strain of S-type) 28-35C Larvae with gapes lt 100 ?m