L-Type – Brachionus plicatilis
Brachionus plicatilis is most easily distinguished by the blunt tips of the anterior spines of the lorica, easily seen when the corona is retracted. The most important attributes of L-Type rotifers for aquaculture are that they:
- Culture best at moderate temperatures (20-25 ºC).
- Easily tolerate cold storage. Cold storage allows rotifer enrichment to be carried out once per day and a portion of the rotifers stored for feeding later in the day.
- Are active at the low temperatures used to cultivate cold-water fish (7-10 ºC).
Brachionus plicatilis grows best at a moderate salinity (15-20 ppt) but tolerates full seawater salinity and even slightly hyper-saline conditions. Brachionus plicatilis is a broad species complex with considerable size variation. Mean lorica length has been reported to range from 150 to 280+ µm. Corresponding dry weight rotifer biomass ranges from 160 ng to over 900 ng per individual
A very small L-Type Brachionus plicatilis, the RMI “Mini-L 160” is commercially available from Reed Mariculture. Other culture strains are exchanged among hatcheries and universities. Live cultures and cysts are available from some suppliers.
S-Type, SS-Type – Brachionus rotundiformis
Brachionus rotundiformis is most easily distinguished by the pointed tips of the anterior lorica spines. Its most important attributes for aquaculture are that it:
- Cultures best at higher temperatures (28-35ºC).
- Is smaller (some strains)
B. rotundiformis grows best at 15-20 ppt salinity but tolerates full seawater salinity.
B. rotundiformis also constitutes a broad species complex with considerable size variation. Mean lorica length has been reported to range from 120 to 180+ µm. Corresponding dry weight rotifer biomass ranges from 90 to over 200 ng per individual.
Culture strains are exchanged among hatcheries and universities. A very small S-Type B. rotundiformis is commercially available from Aquatic Eco-Systems Inc. (Apopka, Florida, USA).