Project Work by
St. Paul's Co-educational College
Class:
F.2E
Group Leader:
Josh Wong (15)
Group Members:
Matthew Cheung (3)
Candy Kang (25)
Sylvia Tsang (31)
Phoebe Yeung (33)
Introduction
We are very interested in exploring the adaptation of apple snails. As apple snails are easily adapted, so we choose this species of animal as our target in our experiments. We also know that we will not harm the natural environment even if we get some of them for our experiments.
With the aid of Miss Lee and Mrs Lam, our project supervisors, we have got a permit to go to the non-entry area in the Hong Kong Wetland Park. We caught over two hundred apple snails for this experiment. That is really amazing. Through group activities and observation, we’ve learnt more about adaptation of apple snails.
In this study, we investigated about the environmental conditions that apple snails prefer. We also compared our results with those from other countries, which the apple snails may or may not be the same species (but the same genus) as what we have in Hong Kong.
Objective
1. To investigate the environmental conditions that apple snails like to live in.
2. To compare the Hong Kong apple snails with other species of apple snails in foreign countries.
About the apple snails
Appearance of apple snails in other countries:
Shell of wild-type colours snail
Shell of dark wild-form snail
The most special feature is the tube like organ (siphon) used to breathe while staying submerged.
The pale pink to reddish eggs are deposited above waterline and are closely attached to each other.
Appearance of apple snails in Hong Kong
Apple snails with dark brown shell.
The pink eggs deposited above water line.
Habitat of apple snails
The map below shows the worldwide distribution of apple snail (Pomacea canaliculata):
Characteristics of foreign apple snails (Pomacea)
They live in mainly quiet stretches of water, such as lagoons, ponds and swamps. However, field research suggests that the snail is frequently found in streams in its native area. In Japan, the snail is found in a wide variety of habitats, including rivers, ponds, swamps, drainage canals and paddy fields.
They can survive harsh environmental conditions such as pollutants in the water or low oxygen levels (reduced by organic materials like dead vegetation and high temperatures) as their lungs provide an adaptation to poor water conditions.
They bury themselves in moist soil during the dry season. They can aestivate for 6 months, and then become active again when the soil is flooded. They prefer living in lentic waters than turbulent water.
They need to live in tropical temperature, and no snail could survive in a temperature below 10ºC
Characteristics of Hong Kong apple snails (Pomacea)
Hong Kong apple snails belong to the type species of Pomacea lineata. They inhabit various ecosystems: ponds, swamps and rivers. Although they occasionally leave the water, they mainly spend time in the water.
Although they adapt to cold water, they are very resistant to the low temperature, arriving to even survive 5-8ºC during some hours. If they stay in hot water aquariums, over 25ºC, its metabolism and activity increases, but its service life is reduced.
Their behavior is just like the others’. Although they like living with the smaller snails, they will eliminate them. Also, the Hong Kong apple snails (Pomacea lineate) are more active than their cousins (Pomacea bridgesii) but similar to their brothers (Canaliculata Pomacea). It can remain in its shell 1 or 2 days until it feels necessary to feed itself again. The activity of the snail increases
with the ascent of temperature of the water (25ºC), and it is enough inactive below 18ºC.
They are considered as sexually mature when the diameter of their shells reach 2.5cm. They display themselves to the opposite sex, like the rest of Pomacea lineate when they are sexually mature. It’s because their reproduction count at least on a male and a female. Moreover, the reproduction is favored with an increase in temperature to 25ºC, because this temperature can help
simulate the spring.
The female, after a couple of days of the fertilization, it leaves the water by the night to deposit the eggs outside. The eggs are of intense pink color, and they form a cluster, which is less compact than those of Pomacea bridgesii. The cluster includes about 200 to 300 eggs and has about 3 mm in diameter. The egg must be kept in humid environment or near the water.
After 1-4 weeks, the egg needs to be given a sufficient amount of soft food so that they can chew it, for example pulverized seaweed, peas or food for fish. The females can keep the sperm for months.
The apple snail inhabits in slow current place:marshes, irrigation channels and pools.The apple snail has lungs and gills, which allow it to live in waters with insufficient amount of oxygen, and even to survive in a short period of drought in its own shell. It uses its special organ, the siphon to breathe in the remained air in the submerged.
Apple snails as pets
Apple snails are popular aquarium-pets because of their attractive appearance and size. The following are some popular types of apple snails treated as aquarium pets:
The snails will "play dead" on occasion, which may last for several days, especially when first introduced to a new tank, probably from the stress of moving from one habitat to another. But once the snail is acclimated it will become a surprisingly active participant in the community tank.
Wild coloured version pomacea canaliculata
Apple snails as food
In the 1980s, Pomacea canaliculata was introduced in Taiwan to start an escargot industry. It was thought that such food culture could provide valuable proteins for farmers, who primarily live on a rice diet. However, the snails did not become a culinary success.
Apple snails as pests
The imported Pomacea canaliculata snails and the native apple snail population, Pila in Taiwan were able to transfer a parasite called Angiostrongylus cantonensis. This parasite can infect humans if snails are eaten which have not been cooked thoroughly.
The introduced snails escaped and became a serious threat to rice production and the native ecosystems. During the 1980s the introduced snails rapidly spread to Indonesia, Thailand, Cambodia, Hong Kong, southern China, Japan and the Philippines, and there are indications that they are currently invading Australia.
Damages caused by HK apple snails
1. Loss of crops
Apple snails damage taro plants by chewing into the corm at the very top of the taro plant, which leaves a hole through which bacteria and other pathogens to enter. Damage either kills the plant or drastically reduces crop quality and yield. apple snails also eat the young shoots of taro. Damage to other water-based crops such as rice occurs in similar fashion and the other natural native plants.
2. Economic loss
According to the first point, the apple snails eat up a large amount of food and thus cause the loss of crops. This will lead to a great economic loss in the farming industry.
3. Disturbance of the ecosystems
Snails in natural systems eat plants that provide food or habitat for native fish and birds. Also, there will be food competition between the apple snails and the other sea animals such as shrimp. The Apple Snail is like a gigantic fortress and its size prevents access to the food. Therefore, these animals will die for they cannot adapt to their new living environment or because of the
insufficient amount of food. And this will break the food chain in the natural environment.
4. Blockage of drainage system
Apple snails have a fast rate of reproduction and they are also good survivors, they will not die easily. There fore, when they stay in the drainage, they may be the impediment for the water to flow through.
5. Spread of disease
Snails can carry and transmit rat lungworm (Angiostrongylus cantonensis), when improperly cooked and eaten, causing fever or death in extreme cases. Moreover, apple snails can hold very bad parasites that can also make people very sick or they may even die. In addition, a known vector for blood flukes (Schistosoma spp.) and an intestinal flukes (Echinostoma ilocanum) are
brought by them too.
Natural enemies of apple snails
As you know, apple snails can be found all over the world they have many different natural enemies, let me introduce some of them to you:
Raccoons:
They are originally found in N. America, but later brought to Europe. It lives mostly in wooded areas and usually feeds along lakes and streams. A good climber, it often nests in a hollow tree or climbs aloft for refuge. They are good destroyers to insects.
Paw of a raccoon
Black ants:
They are very active and appear at newly laid egg clusters, normally 1 –2 ants per egg cluster. One ant could attack many eggs with its sharp and powerful mandibles(jaws).
Fishes--Black carp, Catfish:
In South Viet Nam, catfish is more favorable. Testing in Can Tho showed that raising carp, black carp after 12 weeks showed that apple snails’ population decreases 80 – 96% compared to the first record. They mainly eat young apple snails (< 1cm) but catfish could eat both young and mature apple snails by eating flesh inside. Catfish is well suited to South Viet Nam condition while in North VietNam, carp and black carp are more important. They can eat 73-87% GAS
Catfish
Carp
People’s reaction on apple snails
Although there are some natural enemies that feed on them, places with apple snails introduced as foreign species has no natural enemy around. These invasive alien species adapt to the new environment easily thus reproduce rapidly and cause massive damage to that place (as mentioned in previous session). So people living in these “invaded” countries have developed different ways to combat with apple snails:
1. Handpicking. People usually handpick apple snails from rice paddies in the morning and afternoon as they are most active and
easy to find.
2. Use plants which contain toxic substances. For examples, gugo, makabuhay, sambong, tuba-tuba, asyang, tobacco and red
pepper
3. Use attractants .People place leaves of plants that attract snails to make their hand picking easier. For examples, Gabi leaves,
banana, trumpet flowers etc.
Gabi leaves banana trumpet flowers
4. Biological control. People also feed apple snails to ducks and pigs or eat them by themselves.
5. Setting a trap. During last harrowing, construct deep strips in the paddies by pulling a sack containing a heavy object. Provide 10-
15 m distance between strips. Likewise, construct small canals (25 cm wide and 5 cm deep) along the edges of rice paddies.
6. Preventing field entry. Place a wire or woven bamboo screen on the main irrigation water inlet and outlet. It is to prevent the entry
of hatchlings and adults. This also facilitates collection of trapped golden apple snails.
7. Growing fish in the rice fields. Successful field trials in the Philippines showed that growing fish in the rice fields could keep snail
populations down. It also supplemented the farmer's diet and generated extra income
8. Chemical control. Farmers use pesticides to control the snail. But many of them are now banned in Japan, Taiwan and the
Philippines.
9. Use of rotten jackfruit as bait. In Malaysia, farmers control snails simply by using rotten jackfruit as bait. It makes the collection
of apple snails becomes easier.
Methodology
On 10 November 2007 and 5 July 2008, we did the sampling for the experiments. Each time we collected about 200 apple snails and fifteen batches of eggs from the Hong Kong Wetland Park. They are then taken back to the laboratory and the following experiments were carried out.
We were washing the apple snails
They were so clean!
We kept them in tanks.
I. Hatching experiment
Materials:
3 x 50 eggs, Euglena culture
Apparatus:
3 x plastic boxes, refrigerator, incubator
Procedure:
First, pour equal numbers of apple snails into each box.
Next, place 50 eggs in each box.
Then, put the three boxes into three different places:
i. Refrigerator (4.)
ii. Incubator (37.)
iii. Long table next to the window in Biology Laboratory (room temperature, 25.)
We added in Euglena culture as food for baby apple snails (if any). Finally, some of our group
members observed the eggs and count those hatched eggs in three different boxes at different days.
II. “Light and dark” experiment
Materials:
Water, 70 snails, some vegetables
Apparatus:
Tank (15cm x 15cm x100cm), a black cloth, net, newspapers
Procedure:
First, pour some water into the box.
Next, place all the snails in the middle of the box and mark that area.
Then, put some vegetables in it.
After that, use the net to cover the whole box and we cover half of the box with the cloth.
Finally, put it under the light bulb and put newspapers under it to prevent leaking and observe the snails after one day.
Set-up of the “light and dark” experiment
III.“Water and Land” experiment
Materials:
Water, 70 snails, vegetables
Apparatus:
Tank (15cm x 20cm x 100cm), newspaper
Procedure:
First, put newspaper under it to make the box be a slanting position and prevent leaking.
Next, pour the water into the box.
Then, put the snails in the middle and mark the area.
After that, place the vegetables in the box.
Finally, observe the snails after one day.
Set-up of the “water and land” experiment
IV. Water and mud
Materials:
Water, mud, 50 snails, vegetables
Apparatus:
Tank (15cm x 15cm x 100cm), newspapers
Procedure:
First, pour the water into the box and put newspaper under the box to prevent leaking.
Next, place the mud on the left hand side of the box.
Then, place the snails in the middle and mark the area.
After that, place the vegetables in the box.
Finally, observe the snails after one day.
Results of experiments
I. Hatching experiment
Tables showing the cumulative number of eggs hatched at different temperatures.
Trial 1:
Trial 2:
II. “Light and Dark” experiment
Table showing the number of apple snails going to dark and light conditions after experiment.
Trial 1 2
Most snails moved to the “light” region
III.“Water and Land” experiment
Table showing the number of apple snails going into water and land after experiment.
Most snails moved into water
IV. “Water and Mud” experiment
Table showing the number of apple snails going into water and mud conditions after experiment.
Discussion
Analysis of results
I. Hatching experiment
The result shows that eggs of the apple snails hatch faster in 25ºC than 37ºC and 4ºC.This may be because the apple snails are used to live in ‘room’ temperature, and therefore their eggs hatched in the same range of temperature. Hence, the eggs cannot adapt to the temperature of 37ºC and 4ºC. 37ºC is too hot for the eggs to hatch whereas 4ºC is too cold for them to hatch.
As the eggs were closely stuck to each other so some eggs were broken when our group members tried to separate them.
II. “Light and Dark” experiment
The number of apple snails which move to light region is obviously larger than that which move to dark region. This result shows that apple snails prefer brighter environment than darker one.
III. “Water and Land” experiment
In all trials, there is obviously more apple snails move into water than staying in dry land. This result shows that apple snails prefer watery environment than dry land.
IV. “Water and Mud” experiment
More apple snails move into water rather than going to the mud region. This result shows that apple snails prefer watery environment than muddy environment. Probably the apple snails were not aware that there was mud adjacent to water. The mud for keeping the apple snails in the tank are taken from Hong Kong Wetland Park.
Sources of error and suggestions for improvement
The middle “starting” region where we put the apple snails at the beginning of the experiment is quite large as we didn’t want the apple snails to overlap each other in such a narrow tank. As a result, the apple snails which are at the edge of the starting region are closer to certain environmental condition than others. This may make our experiment less accurate as the starting position of all the snails differ quite a lot. To improve, we can use a wider tank with fewer snails so that they all start in more or less same position.
The tank leaked during the experiment. Although leakage is not serious, this may affect the water level inside the tank and affect our experimental results. To improve, we should check carefully whether the tanks leak or not before conducting the experiment. For instance, we should pour a large tank of water into a tank and let it stand for overnight (similar to the time we conduct our
experiment) to check for leakage instead of just observe over few hours.
When we set up the experiment, we have made sure that all apple snails used for experiment are living and active. However, some apple snails were found dead at the end of experiment. This will make our experiment results less accurate as only the living snails will show respond in choosing their desirable environment for living. The death of snails may due to the building up of waste in
such a small volume of water in tank, or may due to the lack of food (perhaps we didn’t put in enough vegetables for all snails), or may be due to the lack of ventilation in tank as we wrapped it up with black cloth, less oxygen can go into the tank and dissolve in water for respiration of snails. All these factors may cause death to our apple snails. To improve, we can shorten the time for
experiment and change water more often to prevent waste to accumulate. We can also provide more food (vegetables) to the snails. Instead of a large piece of black cloth, we can use wire gauze for covering the whole tank to prevent suffocation of snails but at the same time allow adequate ventilation.
Reflections
If we could spend more time on the experiments, we may find more life patterns about apple snails. After doing the project, we understand more about the characteristics of snails. When we were cleaning the snails and the plastic boxes, the smell was very bad and made us feel very uncomfortable. We wore plastic gloves for cleaning in the couple of weeks in sake of our hygiene and safety. We were afraid that we would get contagious disease if we did not wear plastic gloves.
However, we gained great satisfaction from this experience. We see the reproduction process – from eggs to little apple snails. We found that they ate quite a lot so we supplied them with more fresh leafy vegetables day by day,
During the project, we needed to distribute the work evenly and discussed the content together. We learnt to accept the others’ opinions and how to work with a group of team members. Also, it was very difficult for us to spare time and work on the project together. Although the process was very hard, we still had a good time and our friendship was enhanced.
References
The Apple Snail (Ampullariidae) Website. <http://www.applesnail.net/>
The Channeled Applesnail In Northeast Florida. <http://www.jaxshells.org/chan.htm>
Use of Rotten Jackfruit to Control Golden Apple Snails.
http://www.agnet.org/library/pt/2002041/#picf1
Golden Apple Snails. <
http://www.knowledgebank.irri.org/fa...AppleSnail.pdf>
The Golden Apple Snails.
http://www.kelabit.net/news/special_report_01.html
“Common aquarium pet” and “A pest”. Ampullariidae.
http://en.wikipedia.org/wiki/Apple_snail
Charlotte Observer.
http://www.charlotte.com/
Apple snail.
http://www.hawaiiinvasivespecies.org...pplesnail.html
Issg Database: Ecology of Pomacea canaliculata. <http://www.issg.org/database/species/ecology.asp?si=135&fr=1&sts=&lang=EN>
Acknowledgement
Thanks to the staff of HK Wetland Park for helping us to collect the apple snails for experiments:
Mr Lam
Miss Carrie Ma
李先生
李小姐
蘭姐
英姐
南哥
Thanks to teachers and staff of SPCC for helping us to conduct this study:
Miss Christina Lee
Mrs. Amy Lam
Mr. Lawrence Fung (Lab assistant of Biology Laboratory)
Mr. Raymond Koo (Lab assistant of Biology Laboratory)
Mr. Ng (D& T Teacher)
http://www.sbwr.org.sg/forum/upload/...%20college.pdf
The Adaption of Apple Snails
Reply for the questions
Linear Mode
