142
ic development of Streptocephalus mackini Moore,
Herrera-Colmenero (1986) used Ankistrodesmus convolutus. For the laboratory culture of S. mackini, Roddguez-Garcia (1990) compared monodiets of
A. convolutus, Chlorella sp, Scenedesmus sp, and
dry baker's yeast. Roddguez-Garcia (1990) reported
Chlorella sp as the best food for growth, biomass and
maturation, and A. convolutus for survival.
De Walsche, Mertens & Dumont (1991) stressed
the importance of economic factors in the aquacultural
applications of S. proboscideus, and tested a series of
low-cost diets using bacteria, cyanobacteria, and baker's yeast as basic food components in static cultures.
They found that the best diet for cyst production was
composed of active silt of bacteria, Spirulina platensis, and baker's yeast, while the best diet in survival
tests consisted of Corynebacterium lilum, S. platensis, baker's yeast and a suspension of clay particles.
Mitchell (1991) studied the efficiency of S. macrourus to convert algal biomass into anostracan biomass
in semicontinuously and continuously fed cultures. He
reports S. macrourus to be tolerant of crowding, and to
yield higher productions than rotifers and cladocerans
(Mitchell, 1991). Maeda-MartInez (1991) described
an argillotrophic method, which is in principle Banta's
classical soil-manure medium (Banta, 1921).
For culturing Streptocephalus proboscideus, Brendonck et al. (1990) described a semiautomatic flowthrough system, with a capacity of ca 336 animals per
unit (a cage of ca 61), using Selenastrum capricornutum as food. Finally, using the system of Brendonck
etal. (1990), Ali & Brendonck(199; this volume) tested micronized agro-industrial waste by-products as a
diet for S. proboscideus. They report that in terms of
survival, growth and fecundity, the wastes of pea and
corn (YM20) gave the best results (Ali & Brendonck,
1995).
Material
Cysts of Thamnocephalus platyurus were produced in
a mass culture (Dr D. Weaver, California, USA) and
supplied to our laboratory by Dr D. Belk. Dr Weaver's
mass culture was a flow- through system, with water
quality and automatic feeders computer controlIed,
and a commercial artificial plankton supplied as food
(Dr Belk, pers. comm.). Cysts of Branchinecta lindahli
were obtained from Morrill, Nebraska, USA, collected
by Dr M. Fugate.
Incubation method and use of larvae
All culture tests were carried out using larvae hatched
under standard conditions. We considered the following factors (reviewed by Lavens & Sorgeloos, 1987):
(1) salinity (Horne, 1967; Brown, 1969; Belk, 1972;
Sam & Krishnaswamy, 1979; Scott & Grigarick,
1979), (2) pH (Scott & Grigarick, 1979), (3) temperature (Prophet, 1963b; Horne, 1967; Belk, 1977;
Scott & Grigarick, 1979), (4) oxygen (Brown, 1969),
and (5) light (Belk, 1972; Sorgeloos, 1973; Van der
Linden et al., 1985). Our method consisted of:
1. Incubator. A screw-capped transparent polystyrol
flask (67 mm height x 34 mm diameter) of 60 ml
capacity. Cap and bottom of the flask consisting of
a 100 JLm gauze, glued with cyanoacrylate. Scott &
Grigarick (1979) used glass vials (17.5 ml) covered
by nylon to prevent cysts of Triops longicaudatus
(LeConte) from floating and adhering to the walls
of the incubation jar. They demonstrated that only
2.7% hatched if floating, while 82% hatched in the
cyst containers (Scott & Grigarick, 1979).
2. Container for the incubator of 600 ml capacity.
3. Thermal bath. An aquarium of 74 x 36 x 34 em,
controlled by a heater and a cooler (MGW Lauda
Mn·
4. Light. Constant light was provided by two fluorescent lamps of 30 Watt, installed 30 cm above the
thermal bath.
5. Hatching medium. Distilled water, aerated for at
least 2 hours before use.
6. Aeration. Constant aeration was supplied to the
container of the incubator through Pasteur pipettes.
Cysts were placed in the incubator, which was submerged in the hatching medium. Air bubbles were
removed with a pipette, such that all cysts were permanently immersed in water. The aeration was strong
enough to provoke a constant rotation of the incubator
into the container. Belk (1977) reported that the optimal
hatching temperatures for Thamnocephalus platyurus
and Branchinecta lindahli from Arizona were 20 to
25 DC and 5 to 20 DC, respectively. On that basis, we
adjusted the incubation temperatures to 25± 1 DC for
T. platyurus and to 12± 1 DC for B. lindahli.
The hatching percentages reached a maximum after
the 72 and 120 h of incubation for both species. Murugan & Dumont (199 ; this volume) report the same
timing of hatching in T. platyurus. The larvae used in
the test cultures were those which hatched during the
maximum eclosion period, and differed in age by no
ic development of Streptocephalus mackini Moore,
Herrera-Colmenero (1986) used Ankistrodesmus convolutus. For the laboratory culture of S. mackini, Roddguez-Garcia (1990) compared monodiets of
A. convolutus, Chlorella sp, Scenedesmus sp, and
dry baker's yeast. Roddguez-Garcia (1990) reported
Chlorella sp as the best food for growth, biomass and
maturation, and A. convolutus for survival.
De Walsche, Mertens & Dumont (1991) stressed
the importance of economic factors in the aquacultural
applications of S. proboscideus, and tested a series of
low-cost diets using bacteria, cyanobacteria, and baker's yeast as basic food components in static cultures.
They found that the best diet for cyst production was
composed of active silt of bacteria, Spirulina platensis, and baker's yeast, while the best diet in survival
tests consisted of Corynebacterium lilum, S. platensis, baker's yeast and a suspension of clay particles.
Mitchell (1991) studied the efficiency of S. macrourus to convert algal biomass into anostracan biomass
in semicontinuously and continuously fed cultures. He
reports S. macrourus to be tolerant of crowding, and to
yield higher productions than rotifers and cladocerans
(Mitchell, 1991). Maeda-MartInez (1991) described
an argillotrophic method, which is in principle Banta's
classical soil-manure medium (Banta, 1921).
For culturing Streptocephalus proboscideus, Brendonck et al. (1990) described a semiautomatic flowthrough system, with a capacity of ca 336 animals per
unit (a cage of ca 61), using Selenastrum capricornutum as food. Finally, using the system of Brendonck
etal. (1990), Ali & Brendonck(199; this volume) tested micronized agro-industrial waste by-products as a
diet for S. proboscideus. They report that in terms of
survival, growth and fecundity, the wastes of pea and
corn (YM20) gave the best results (Ali & Brendonck,
1995).
Material
Cysts of Thamnocephalus platyurus were produced in
a mass culture (Dr D. Weaver, California, USA) and
supplied to our laboratory by Dr D. Belk. Dr Weaver's
mass culture was a flow- through system, with water
quality and automatic feeders computer controlIed,
and a commercial artificial plankton supplied as food
(Dr Belk, pers. comm.). Cysts of Branchinecta lindahli
were obtained from Morrill, Nebraska, USA, collected
by Dr M. Fugate.
Incubation method and use of larvae
All culture tests were carried out using larvae hatched
under standard conditions. We considered the following factors (reviewed by Lavens & Sorgeloos, 1987):
(1) salinity (Horne, 1967; Brown, 1969; Belk, 1972;
Sam & Krishnaswamy, 1979; Scott & Grigarick,
1979), (2) pH (Scott & Grigarick, 1979), (3) temperature (Prophet, 1963b; Horne, 1967; Belk, 1977;
Scott & Grigarick, 1979), (4) oxygen (Brown, 1969),
and (5) light (Belk, 1972; Sorgeloos, 1973; Van der
Linden et al., 1985). Our method consisted of:
1. Incubator. A screw-capped transparent polystyrol
flask (67 mm height x 34 mm diameter) of 60 ml
capacity. Cap and bottom of the flask consisting of
a 100 JLm gauze, glued with cyanoacrylate. Scott &
Grigarick (1979) used glass vials (17.5 ml) covered
by nylon to prevent cysts of Triops longicaudatus
(LeConte) from floating and adhering to the walls
of the incubation jar. They demonstrated that only
2.7% hatched if floating, while 82% hatched in the
cyst containers (Scott & Grigarick, 1979).
2. Container for the incubator of 600 ml capacity.
3. Thermal bath. An aquarium of 74 x 36 x 34 em,
controlled by a heater and a cooler (MGW Lauda
Mn·
4. Light. Constant light was provided by two fluorescent lamps of 30 Watt, installed 30 cm above the
thermal bath.
5. Hatching medium. Distilled water, aerated for at
least 2 hours before use.
6. Aeration. Constant aeration was supplied to the
container of the incubator through Pasteur pipettes.
Cysts were placed in the incubator, which was submerged in the hatching medium. Air bubbles were
removed with a pipette, such that all cysts were permanently immersed in water. The aeration was strong
enough to provoke a constant rotation of the incubator
into the container. Belk (1977) reported that the optimal
hatching temperatures for Thamnocephalus platyurus
and Branchinecta lindahli from Arizona were 20 to
25 DC and 5 to 20 DC, respectively. On that basis, we
adjusted the incubation temperatures to 25± 1 DC for
T. platyurus and to 12± 1 DC for B. lindahli.
The hatching percentages reached a maximum after
the 72 and 120 h of incubation for both species. Murugan & Dumont (199 ; this volume) report the same
timing of hatching in T. platyurus. The larvae used in
the test cultures were those which hatched during the
maximum eclosion period, and differed in age by no