Mass culture of Cladocerans as Livefeed in Finfish & Shellfish

Hatchery

Cladocerans are zooplanktons found in freshwater habitats.Most do not tolerate salinities >3ppt and not found in brackishwater.Exception is Diaphanosoma celebensis

Promising species are Evadne tergestina,Penilia avirostris,Podon polyphemoides

Advantages of CladoceransHigh reproduction rates,Wide temperature tolerance,Ability to thrive on phytoplankton and organic wastes.

INTRODUCTION

DAPHNIAare small crustaceans exclusively living in freshwater.At present 50 species of Daphnia are reported worldwide, of which 6 occur in tropical lowlands.The carapace encloses the whole trunk, except the head andthe apical spine. The head projects ventrally and somewhat posteriorly in abeak-like snout. The trunk appendages (5 or 6 pairs) are flattened, leaf-like structures that serve for suspension feeding (filter feeders) and for locomotion. Anterior part of the trunk, postabdomen is turned ventrally and forward and bears special claws and spines to clean the carapace.

The adult size is subjected to variations; when food is abundant, growth continues throughout life.Large adults may have a carapace length twice that of newly-mature individuals.

Daphnia magna

There are 4 to 6 Instar stages; Daphnia grows from nauplius to maturation through a series of 4-5 molts, with the period depending on temperature (11 days at 10°C to 2 days at 25°C) and the availability of food.

Daphnia species reproduce either by cyclical or obligate parthenogenesis.

Eggs are produced in clutches of two to several hundred and linked with the molting process. Parthenogenetic eggs are produced ameiotically and result infemales, but in some cases males can appear. The parthenogenetic eggs (number vary from 1-300 and depends upon the size of female and the food intake) are laid in the brood chamber shortly after ecdysis and hatch just before the next ecdysis.

Embryonic development occurs in the broodpouch and the larvae are miniature versions of the adults. Change in water temperature or food depreviation as a result of population increase, may induce the production of males. The males have 1 or 2 gonopores, open near the anus and are modified into a copulatory organ.The male clasps the female with the first antennae and inserts the copulatory processes into the single, median female gonopore. The fertilized eggs are large and two are produced in a single clutch(one from each ovary), and are thick-shelled: these resting or dormant eggs being enclosed by several protective membranes, the ephippium. They are resistant to dessication, freezing and digestive enzymes, and play an important role in colonizing new habitats or in the re-establishment of an extinguished population after unfavourable seasonal conditions.

NUTRITIONal value of daphnia

depends on chemical composition of food source.Daphnia is not a suitable food for marine organisms because of its low content of essential fatty acids & HUFA (n-3).

Daphnia contains digestive enzymes which serve as exoenzymes in the gut of fish larvae (proteinases, peptidases, amylases, lipases and cellulase)

The “stable tea” rearing system is a culture medium made up of a mixture of soil, manure and water.

The manure promote algal blooms on which the daphnids feed.

Fresh horse manure (200 g) mixed with sandy loam or garden soil (1 kg) in 10 l pond water to a stable stock solution; the solution diluted 2 to 4 times can be used as culture medium.

1. Detrital system

Two techniques to obtain the required algal densities

Cultured algae are used.Green water cultures (105 to 106 cells.ml-1) obtained from fish pond effluents are frequently used.Best control over the culture medium is obtained when using pure algal cultures.They are not able to sustain many Daphnia generations without the addition of extra vitamins to the Daphnia cultures.

2. Autotrophic system

Daphnia is very sensitive to contaminants.The optimal ionic composition of the culture medium is unknown.Hard water containing 250 mg/l of CO32- is used.Potassium and magnesium levels should be kept under 390 and 30-240 mg. l-1.pH - 7 to 8,Optimal culture temperature - 25°C. The tank are aerated to keep oxygen levels > 3.5 mg/l (Dissolved oxygen levels < 1.0 mg/l are lethal to Daphnia). Ammonia levels must be kept below 0.2 mg/l.Inoculation is carried out using adult Daphnia or resting eggs.The initial density is in the order of 20 to 100 animals per litre.

Procedure for tank culture

MASS CULTURE OF DAPHNIA

Procedure for pond culture

Daphnia can be produced in ponds of at least 60 cm in height. To produce 1 ton of Daphnia biomass per week, a 2500 m3 culture pond is required. The pond is filled with 5 cm of sun-dried (for 3 days) soil to which lime powder is added at a rate of 0.2 kg lime powder/ton soil. Then the pond is then filled with water up to 15 cm. Addition of poultry manure to the ponds on the 4th day at a rate of 0.4 kg.m-3 to promote phytoplankton blooms.Fertilization of the pond is done with organic manurebecause cladocerans utilizes the manure in the form of detritus.The inoculation of the ponds is carried out on the 15th day at a rate of 10 daphnids per litre.

On 12 th day,water level is raised to 50 cm and the pond is fertilized a second time with poultry manure (1 kg.m-3). Then weekly fertilization rates are maintained at 4 kg poultry manure per/m3. In addition, fresh cow dung may be used: in this instance asuspension is prepared containing 10 g.l-1, which is filtered through a 100 μm sieve.During the first week a 10 L extract is used per day per ton of water; the fertilization increasing during the subsequent weeks from 20 l.m-3.day-1 in the second week to 30 l.m-3.day-1 in the following weeks.One month after the inoculation, blooms of more than 100 g.m-3 can be expected. To maintain water quality in these ponds, fresh hard water is added at a maximum rate of 25% per day.

Harvesting carried out by concentrating the daphnids onto a 500 μm sieve.The harvested biomass is concentrated in an aerated container (< 200 daphnids.l-1).To separate the daphnids from unfed substrates and faecal material, the content of the container is brought onto a sieve and is provided with a continuous circular water flow.The unfed particles will collect in the centre on the bottom of the sieve,while the daphnids remain in the water column. The unwanted material are removed by using a pipette or sucking pump.

Harvesting can be complete or partial For partial harvesting a maximum of 30% of the standing crop may be harvested daily.

Production and use of resting eggsResting eggs are material for storage, shipment and starting of new Daphnia cultures.These eggs are produced due to stressful conditions(low food availability, crowding of the animals, lower temperatures and short photoperiods). Collection of the ephippia from the wild are carried out by taking sediment samples, rinsing them through a 200 μm sieve and isolating the ephippia under a binocular microscope. The embryos in dormancy require a diapause inhibition to terminate this status and hatch when conditions are optimal. Diapause termination techniques are exposing the ephippia to low temperatures, darkness, oxygen and high carbon dioxide concentrations for a minimal period of several weeks (Davison, 1969).

No standard hatching procedure for Daphnia. The hatching process is stimulated by exposing the ephippia to higher temperatures (17-24°C), bright white light (70 W.m-2), longer photoperiods and high levels of dissolved oxygen. These shocks are given while the resting eggs are still in the ephippium. After the shock the eggs may be removed from the ephippium. Then hatching takes place after 1-14 days.

Hatching procedure

Moina

thrives in ponds and reservoirsThey survive in oxygen poor environments. It reaches reproductive maturity within 4- 5days at 26°C. At maturity,sexual dimorphic characteristics are observed in the size of the animals and the antennule morphology. Males (0.6-0.9 mm) are smaller than females (1.0-1.5 mm). Long graspers are used for holding the female during copulation. Sexually mature females carry only two eggs enclosed in an ephippium (part of the dorsal exoskeleton).Moina is of a smaller size than Daphnia, with a higher protein content, and of comparable economic value.

Food RequirementsMoina feeds on bacteria,yeast,phytoplankton and detritus,BGA(Microcystis aeruginosa).

Both plants and animal detritus provides energy for growth and reproduction.

Nutritional value of MoinaNutritional content varies depending on the age and type of the food they are fed with.Protein content of Moina averages 50% of dry weight.Adults have higher fat content than juveniles.

Reproductive cycle has both sexual and asexual phases.Females reproduce asexually.

Under optimum conditions,Moina reproduces at 4-7 days of age with a brood size of 4-22/female.

Broods are produced every1.5-2 days with most females producing 2-6 broods during the lifetime.

Moina cultures reach densities of 19,000 individuals per gallon and better adapted for intensive culture.

Life Cycle

Procedure for Moina cultureBATCH CULTUREWhen fungal,bacterial and algal cells are consumed about 5-10 days after inoculation,Moina is completely harvested and culture is restarted.This culture maintains pure cultures & no chance of contamination with predators or competitors.

SEMICONTINUOUS CULTUREMaintains for 2 months by daily partial harvests of Moina,water changes and regular feeding.When Moina are not reproducing,then it is completely harvested and a new culture is started.Moina can be produced either in combination with their food or as separate cultures.Combined culture is simplest and production from separate culture is higher.

MASS CULTURE OF moina

Culture tanks are treated with groundnut oil cake(75ppm),single superphosphate(20ppm) and urea (8ppm).Then tank is inoculated with Chlorella or mixed phytoplankton.When algal blooms develop within 3-4days,Moina is inoculated @40-50 no:s/L depending on availability of stock culture.Moina multiplies rapidly,attains a peak density of 20,000-25,000no:s/L in 5-7days after inoculation.As a result of moina multiplication,chlorella concentration declines.To maintain optimum Chlorella concentration,partial water exchange from tank bottom and refertilization with GOC is done at interval of 4-5 daysafter commencement of 1st harvest of Moina

Cladocerans are zooplanktons found in freshwater habitats.do not tolerate salinities >3ppt and not found in brackishwater.

2 cladocerans namely Daphnia and Moina are important livefood in fin fish and shellfish hatcheries.

Cladocerans are selected as food sources in larviculture based on qualities Purity, availability, acceptance, nutritional indicators, easy obtainability, economically viability.

CONCLUSION