Методики выращивания древесников в неволе

REARING TROPICAL ARBOREAL SNAILS IN THE LABORATORY
By Pete Krull

More articles may have been written about tree snails in the genus Liguus than any other group of snails. We know much about their life history (e.g., Close, 2000). However, we do not know for sure if they came to Florida from Cuba or vice versa. We also know almost nothing about how they inherit all those wonderful color patterns. And the biggest thing we have not known until recently is how to maintain and propagate them in captivity. This article outlines a method for doing that.
Pilsbry (1912) stated that “there remain many points which can be elucidated only by breeding the snails”. Later authors also indicated the need for captive breeding studies especially to determine the genetics of color inheritance (Roth & Bogan, 1984; Emmel & Cotter, 1995). At least a couple of attempts were made to perform these experiments but none has been successful.
During the 1960s and 1970s I became obsessed with the idea of raising Liguus tree snails in captivity. I had read several articles by people who had collected a couple, taken them home and put them in a ‘terrarium’ to keep as pets. I did the same. However, much to my dismay, the snails always died. I persevered, yet time after time the snails perished.
Collecting Liguus was legal in Florida until some time in the 1980s when they were listed as ‘Species of Concern’. Prior to this, collectors would wait until the growing season was over, around mid August, and collect until October when the snails would begin aestivation and become more difficult to find. Mating season is between July and August and eggs are laid in mid September.
If you collected snails in August or early September they would often readily lay eggs in captivity. They would then proceed to aestivate, as in the wild, and would emerge from aestivation in the spring, ready to begin growing. That is when they would die. Young hatched in captivity would also begin growing and then they too would die.
Liguus in the wild are often seen on tree trunks in the middle of a hot July day, resting in full sunlight. However, upon closer study it turns out that they spend much of their daylight hours on the underside of a leaf, perhaps hiding from predators, yet still exposing part of their shell and soft body to the rays of the sun.
It finally occurred to me that perhaps Liguus actually required sunlight to survive and produce new shell growth. When I realized this, I had three snails that had recently come out of aestivation. One died and another was showing signs that it would not live long. It could no longer hold on to a branch, did not eat and was clearly just days from dying, as all the previous snails had done. I took it outside and set it in direct sunlight, sure that it would quickly cook. But it did not cook, so the next day I did the same thing and left it out even longer. After just a few days the snail climbed onto a branch and began to eat. I put the other surviving snail through the same process then put both on a tree in my yard. Both snails lived two more years in captivity, grew new shell both years, mated, laid eggs, and were then returned to the wild.
I continued my study of Liguus off and on until collecting them became illegal. I discovered that artificial ultraviolet light worked as well as sunlight in maintaining Liguus, so the captive snails were able to complete their entire life cycle in a laboratory setting. I kept the snails in 10 gallon [~ 38 liter] aquariums and tried as many different ultra-violet bulbs (sold in pet stores for lizards) as were on the market. All seemed to work equally well. The small size of the tank kept the snails close to the light source. I stood the tanks up with the top facing out, covered the opening with mesh screen and attached the light to the outside of the screen. Except during egg-laying season I used one inch [2.54 cm] thick foam on the bottom of the tank to cushion the snails if they fell. For egg laying this was replaced by sterilized peat moss about 2 inches [5.08 cm] deep.
I developed an artificial food that was blended to the consistency of a thick milk shake. This was painted onto the sides of the tank and left to dry. The tanks were misted two to four times a day with water and food was added every couple of days as it was eaten.
The basic ingredients of the food included broccoli (high in calcium), beer (because snails like it), buttermilk, a chewable multi-vitamin and calcium carbonate, with oat flour used to thicken the mixture to a paintable consistency. Other ingredients often added were baby food vegetables, honey, bananas, carrots, tropical fish food (especially algae-derived formulas), papaya, yogurt, dry non-fat milk. Almost any nutritious food that was not too acid was used. The fresh vegetables were boiled in beer and all ingredients blended until smooth.
The final ingredient used when setting up a new tank was black sooty mold spores from a citrus or gardenia bush. This mold is often seen on tree branches in the hardwood hammocks where Liguus is found in the wild. It is also eaten off citrus plants by species of Drymaeus and off coffee plants by species of Polymita in Cuba (Fernandez Milera, 1999). A similar mold is eaten by achatinelline tree snails in Hawaii (Kobayashi & Hadfield, 1996). Blended into the food the mold quickly grew and consumed the rest of the food. Mold made it unnecessary to clean the inside glass as it did not go sour like the food itself might. Whenever new food was added the mold would spread. If the tank was used for several months algae would often grow as well. By having a screen cover on the tank, the inside would dry out completely between mistings. This created an almost perfect environment for the Liguus.
Do other arboreal snails require sunlight? I don’t know. I would guess that species of Orthalicus do, and maybe species of Drymaeus, Polymita, Achatinella and Amphidromus. Indonesian Asperitas species do not, nor do tropical American species of Pleurodonte, which can both be successfully raised in the same tank without the UV light.
I hope that this article will spark the interest of researchers by providing information about the special requirements of Liguus and possibly other tropical arboreal snails.
Close, H.T. 2000. The Liguus Tree Snails of South Florida. University Press of Florida, Gainesville.
Emmel, T.C. & Cotter, A.J. 1995. A Summary of the historical distribution and current status of the Florida tree snail, Liguus fasciatus. Florida Game and Fresh Water Fish Commission, Nongame Wildlife Project Report GFC-86-034, Tallahassee.
Fernandez Milera, J.M. 1999. Polymita forma y color integrados a la naturaleza. Instituto Cubano del Libro, Habana.
Kobayashi, S.R. & Hadfield, M.G. 1996. An experimental study of growth and reproduction in the Hawaiian tree snails Achatinella mustelina and Partulina redfieldii. Pacific Science 50: 339-354.
Pilsbry, H.A. 1912. A study of the variation and zoogeography of Liguus in Florida. Journal of the Academy of Natural Sciences of Philadelphia 15: 429-470.
Roth, B. & Bogan, A.E. 1984. Shell color and banding parameters of the Liguus fasciatus phenotype (Mollusca: Pulmonata). American Malacological Bulletin 3:1-10.
Pete Krull, 5304 Pagnotta Place, Lutz, Florida 33558, USA. Tel +1 813 731 4562, pete@netmarkinc.com
Опубликовано в Tentacle No. 14—January 2006
http://www.hawaii.edu/cowielab/tentacle/tentacle_14.pdf