Egg Clutch Collection

Author:  F. Lewis, PhD
Updated 2020: R. Herrera, MS, S. Li and T. Ogunbayo

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Introduction
The egg clutches (masses) of Biomphalaria glabrata and Bulinus truncatus typically contain a variable number of embryos. From the time the egg clutches are deposited by the adult snails, embryos begin to emerge in 1-2 weeks. Hatching time depends on a variety of factors such as the quality and temperature of the artificial pond water.

Snails prefer to deposit egg clutches on any solid surface, including the shells of other snails. Plastic strips, or pieces of Styrofoam (“floats”), placed in an aquarium or shallow pan containing adult snails serve as convenient materials on which to collect and manipulate the egg clutches (pictured).

Materials and reagents
Small pieces of Styrofoam (~10 cm x 4 cm)
Artificial pond H2O (“water”)
Pulverized limestone (0.5 g lime/1.5 L water)

Equipment
Shallow pan or aquarium (~1.5 L)
Featherweight forceps
Deck sprayer

Procedure

  1. Breeder: Place the floats on the surface of the pond water holding 20-25 truncatus and 17-20 B. glabrata adultsnails.
  2. FOOD: ¼ algae plate plus leaves of romaine lettuce. Avoid adding lettuce ribs- the snails cannot consume, and the uneaten food will breakdown and foul the water. Feed as needed. (e.g. Fridays)
  3. Change the water once per week: gently remove the snails and spray down with deck sprayer capturing the snails in a sieve; place the snails in a new pan of fresh water. Add limestone, ¼ algae plate and a leaf of romaine.
  4. Change the pan on ~day 7; remove the floats and place them in a clean tub with water and lime to allow hatching in the absence of adults (adult breeders will eat the clutches thereby reducing the number of snail offspring).
  5. Put the tub holding multiple floats into warm room 233.
  6. Once a majority of the eggs have hatched you may gently wash the remaining egg clutches off the float with a deck sprayer and rinse them into the water.
  7. Allow the hatchlings to emerge over 7-14 days. Minimize manipulation during this time.
  8. FOOD: Add multiple small pieces of algae to the tub holding the hatchlings 1-2 wk after egg collection. You may also add very small pieces of clean romaine (later , once they are >14d) as needed.

Comments
Periodically check the pans for stagnant water which can cause bacterial or another contaminant overgrowth. If this problem occurs, change out the stagnant water with fresh water. To avoid frequent changing consider aerating the pans with air stones and an aquarium pump. Refer to the SRC SOPs “Artificial Pond Water” and “Changing Containers of Snails” for more information.

  • Breeder status: the age of the breeders in a single pan should be similar. Treat each breeder pan as a single community and monitor the clutch production over-time.
  • Young breeders will yield few and small clutches. A pan of 20-25 optimal breeders will yield >50 clutches per week.
  • The aging process will result in fewer clutches overtime (8-10 months) If you observe fewer than ~20 clutches 3 weeks in a row, mark the pan and group low yield breeders into a single pan.
  • Do not add young snails to a pan of older breeders to try and boost clutch production.

References

  1. Chernin, E. 1957. A method of securing bacteriologically sterile snails (Australorbis glabratus).Proceedings of the Society for Experimental Biology and Medicine 96: 204-210.
  2. Olivier, L. and W.T. Haskins. 1960. The effects of low concentrations of sodium pentachlorophenate on the fecundity and egg viability ofAustralorbis glabratusAmerican Journal of Tropical Medicine and Hygiene 9: 199-205.
  3. Pimental, D. 1957. Life history ofAustralorbis glabratus, the intermediate snail host ofSchistosoma mansoni in Puerto Rico. Ecology 38: 576-580.
  4. Standen, O.D. 1951. Some observations upon the maintenance ofAustralorbis glabratusin the laboratory. Annals of Tropical Medicine and Parasitology 45: 80-83.

For further technical information, contact Sarah Li at sli@afbr-bri.org

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Biomedical Research Institute