golden apple snail
Do you know Gary? The fictional character in Spongebob who lives in a pineapple home and vocalizes like a cat? Of course, you do! In this blog, we will be learning more about its relative, the golden apple snail which sadly doesn’t produce meowing sounds like Gary. Do you see their similarities?
I. Classification
You probably have an idea or two about these infamous invasive species under Pomacea genus especially Pomacea canaliculata. After all, they are almost everywhere even in your backyard! That is if your backyard has a puddle of water.
Let’s dig deeper into these round, golden, and invasive snails. Let’s begin with their taxonomic classification:
Kingdom: Animalia
Subkingdom: Bilateria
Infrakingdom: Protostomia
Superphylum: Lophozoa
Phylum: Mollusca
Class: Gastropoda
Subclass: Prosobranchia
Order: Architaenioglossa
Family: Ampullariidae
Genus: Pomacea
Species: Pomacea canaliculata (Lamarck 1828) (ITIS 2020).
II. Biology
Unsurprisingly, they are under class Gastropoda. Why is that so, you may ask. Well, Mantle? Check! Radula? Check! Muscular ventral body acting as a foot? Check!
But wait, these are the characteristics of Mollusks! So how is the molluscan body plan modified in gastropods?
Does its head have well-developed eyes and sensory tentacles? Is there a foot and a visceral hump that includes the digestive gland and part of the gut? Is its visceral hump and mantle enclosed in a singular shell? If all your answers are yes, then it is a Gastropod. Well, actually, some may have no shell, but let’s focus on Golden Apple Snails in this blog, shall we?
A. Distribution
The species originated from Argentina going north to the Amazon basin and were then introduced to countries in the South, East, and Southeast of Asia such as the Philippines, Japan, Taiwan, Vietnam, Cambodia, Thailand, Laos, Korea, Sri Lanka, parts of Indonesia and Malaysia, southern China, Singapore; also Hawai‘i, Guam, and Papua New Guinea; the Dominican Republic; the USA (particularly in Florida, Texas, California) (ISSG 2005).
Do you know where this round, golden and invasive mollusk was first introduced in the Philippines?
Pomacea canaliculata was introduced in the Philippines, specifically in Batangas, from Taiwan 1983. In the same year, Pomacea vigas was introduced in Makati, Metro Manila from Florida. Another species was introduced in Cebu from Argentina in 1984 and at present, these species are almost present in all parts of the Philippines (Acosta and Pullin 1989).
B. Habitat
Most Pomacea snails inhabits the ponds, swamps, irrigated fields, and wetlands. During the dry season, the species bury themselves in the soil to keep them moist and this prolonged dormancy in the dry season can last for 6 months! They will return to being active when soil is flooded, a verification that they can withstand different conditions, even pollutants and low oxygen in the water (The Apple Snail Website 2020). Occasionally, some might appear on aquariums as mystery snails and some are actually treated as pets along with other fishes.
C. Anatomy
As mentioned earlier, they are gastropods, a prosobranch at that, under Phylum Mollusca so there is a presence of calcareous shell. Pomacea snails are overall globular in shape which can grow to a height of 40-60 mm, 40-75 mm wide, and 150 mm in length. Depending on species, apple snails can vary with their colors, some are yellow, brown, and green. Generally, it could have five to six whorls, with a deep intended suture to separate it. The same with other Prosobranchs, Pomacea has an operculum, a calcareous feature that is moderately thick, concentric, and has a light to dark brown color, that retracts at the shell opening as a protective response when threatened. Try knocking, maybe they’ll open up!
Although they are prosobranchs, a notable feature of apple snails under genus Pomacea is their possession of fully functional lungs used for breathing and floating in addition to their gills.
C.1 Male and Female Differences
Sexual dimorphism manifests in the Genus Pomacea. Just like how us humans differ in appearance and hormones based on sex, Pomacea snails also exhibit different appearances (but not that drastic though) based on their sex.
Males have larger, oval-shaped, and rounder apertures but they mostly smaller in size compared to females. The operculum of the female (a1) is concave while it is convex in male (a2). On the other hand, the female shell (b1) curves inward; the male shell (b2) curves outward. (Tripoli et. al. 2015; MS Dela Cruz et. al., cited by The Apple Snail Website 2020).
Have you noted their differences? The next time you get to see these snails, you’ll already have an idea of its sex based on looking its shell!
Try guessing the sex of these two! Which one is the male? Which one is the female? To check you answer: visit this link!
Did you guess it right?
C.2. Life Cycle
Briefly, the snail life cycle has the following steps:
1. Born and developed.
2. Reach sexual maturity.
3. Find a partner to mate.
4. Mating process.
5. Gestation period.
6. Egg dropping.
7. Egg hatching.
Let’s go on a journey and find more about the life cycle of Golden Apple Snails.
C.3. Mating and Beyond
When you see a snail that seemed to be like eating another snail, ask yourself: Do they not look the same? That’s probably predation. Do they look the same? They’re wrestling.. kidding! They’re mating!
Finding partners on GAS occurs by expelling some chemicals to attract others ready to mate and use touching as a way of courting. Snail sex can be quiet confusing and AMUSING. Yep, you read that right. We recommend watching this video:
We have to take note of one thing though, unlike most other snails, P. canaliculata is not hermaphroditic, and due to sexual dimorphism, they need to copulate in pairs. Once the mating is over, they go in separate directions. Pomacea snails are oviparous but the eggs are fertilized within the female’s body. When fertilization occurs, eggs develop and once the eggs are mature they are laid about 50cm above the water surface. And voila! The cute little pinkish red eggs are out in the open and they are of very little size.
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They are not really the best maternal figure as they are observed to have shown no parental care after adults have laid their eggs They, however, have at least the slightest conscience to lay their eggs out of the water to protect it against predation. They even go out their way to lay them in a thorny plant so the eggs won’t get easily eaten by predators. Somehow, these snails aren’t really the villain as we paint them out to be.
For a close up view on the golden apple snail laying eggs, check out this video.
Generally, after 10-20 days these eggs hatch. The newly hatched snails are about 2.5mm or 0.09inch in diameter. Just how cute they are! And they immediately feed to grow fast by being voracious feeders and become mature and be ready for mating and lay baby snails that become mature snails that lay baby snails and the cycle goes on! The Pomacea species or can reproduce rapidly and produce 1000-1200 eggs for a month (The Apple Snail Website 1998-2003).
You have ventured the life cycle of the golden apple snail! Wanna know more? Just keep scrolling down
III. Ecology
These snails are able to resist water velocities if exposed although they avoid fast-paced places due to the interferences in their activities and movements, thus, Pomacea dwells in the lentic area, and may also sometimes thrive in the lotic system. They are classified as scrapers, shredders, and collectors (Cummins and Klug 1979, cited by Martin et. al. 2017) and they mostly feed on a variety of plants to algae. It is a highly generalist and voracious macro phytophagous herbivore and would often eat any plant but it does show some preferences (Cowie, 2005). They would even eat detritus and dead insects sometimes! The reason for their extreme polyphagous habit is because as their food intake increases, the more they are reproductively active (Ghesquiere, 2005a; Tamburi and Martín, 2009, cited by Holswalde and Kondapalli 2013). See this video to see how a Pomacea snail scrapes off algae off the glass aquarium.
Local farmers from the Philippines claim that the edible native snail, Pila luzonica, has decreased drastically since golden snails were introduced (Halwart 2008). In fact, the species has since become extinct in the Cagayan Valley ever since the golden snail has been introduced and proliferated (Acosta and Pullin 1989). Not only were they destructive to the economy but they also present a problem by competing for resources against native species. They not only attacked rice species but other vegetations such as azolla, taro, and lotus (Halwart 2008).
E. Relationship with Humans
The golden snail is introduced in the Philippines by a private sector in the guise of offering a livelihood improvement countrywide, with the rationale that an existence of a huge market for ‘escargots’ can possibly be supplied by farming golden snails (Acosta and Pullin 1989). The private entrepreneurs, however, failed to mention its potential to become a pest, as was known from experience in South America and instead focused on promoting it as an export potential.
Damages and losses due to infestation of golden snail in rice farming has been detected and and was considered a pest in both irrigated and rainfed environments because of its resilience from harsh environments. In December 1988, 5 years after its introduction in the country, the total area infested with these invasive snails has accounted up to 426,000 ha and the most affected regions were region VI (Western Visayas), region XII (Central Mindanao), and Region II (Cagayan Valley) (Acosta and Pullin 1989).
The picture below shows missing plants in direct seeded rice in the Philippines (upper left), missing hills in transplanted rice in the Philippines (upper right), high density of golden apple snails feeding on rice seedlings in the Philippines (lower left) and distinctive egg masses of P. canaliculata laid on the stems of taro plants in Hawaii (lower right) (Cowie).
Efforts were made to put these snails into use and so small scale aquaculture of P. canaliculata provides fishmeal for fish, shrimp and prawn farming (Castillo and Casal, 2006) as they are a good protein source. In fact, golden snails are also eaten by poor people as a protein source (Acosta and Pullin 1989).
Because of the disastrous outcome in the rice industry brought upon by these snails, farmers have resorted to the use of chemical controls but this posed a threat in the human and environment (Halwart, 2008). Pesticides and molluscicides were utilized in attempts to get rid of them, however, water bodies served as a run-off for all the pchemicals causing the environment to be toxic and detrimental for non-targeted aquatic organisms. It also affected the workers as the pesticides have proven to be damaging to the skin, fingernails, and toenails.
Locally, ducks had also been employed to get rid of these pests. Apparently, not only have the ducks lessened their number, the ducks also laid higher quality eggs when fed with snails. The high protein content of snails also makes excellent food for broilers and snails (Catalma et al 1991).
IV. Fun Facts; Did you know?
P. canaliculata has been nominated as among 100 of the “World’s Worst” invaders (ISSG 2005).
Egg clutches of P. canaliculata are remarkable in three aspects:
they are cemented outside water
they are brightly colored
have virtually no predators
Each cluster of eggs is about as long as your little finger
P. canaliculata is more resistant to lower temperatures than most other snails from the genus Pomacea.
P. canaliculata eggs are considered to be toxic to most animals. Study shows that P. canaliculata eggs have unusual defenses of toxins that is manifested in its coloration that explains it having virtually no predators at all but fire ants.
Males must attain a minimum age, regardless of size, for the onset of reproductive maturity, whereas females must reach a minimum size regardless of age.
The average lifespan of these snails is up to 4 years
V. References
Acosta B.O., Pullin R.S., 1989. Environmental Impact of the Golden Snail (Pomacea sp.) on Rice Farming Systems in the Philippines. Nueva Ecija: Freshwater Aquaculture Center, Central Luzon State University
Castillo LV, Casal CMV, 2006. Golden apple snail utilization in small-scale aquaculture in the Philippines. In: Global advances in ecology and management of golden apple snails [ed. by Joshi, R. C.\Sebastian, L. S.]. Los Baños, Philippines: Philippine Rice Research Institute (PhilRice), 475-482.
CATALMA, M. T. E., CAPIL, D. T., ANTALAN, R. A., SERRA, A. B., BARROGA, A. J. and ORDEN, E. A., 1991. Golden snail (Pomacea sp.) use in animal feeds. International Rice Research Newsletter, 16, 26.
Cowie H.R., (n.d.) The Golden Apple Snail: Pomacea species including Pomacea canaliculata (Lamarck, 1822) (Gastropoda: Ampullariidae) DIAGNOSTIC STANDARD. Retrieved from: https://www.planthealthaustralia.com.au/wp-content/uploads/2013/03/Golden-apple-snail-DP-2005.pdf
Dreaon, M., Fernandez, P., Gimeno, E., and Heras, H. (2014) Insights into Embryo Defenses of the Invasive Apple Snail Pomacea canaliculata: Egg Mass Ingestion Affects Rat Intestine Morphology and Growth. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4063725/ Ghesquiere, S. 2005. “Apple Snails” (On-line). Accessed January 31, 2013 at www.applesnail.net.
GBIF (Global Biodiversity Information Facility. (2020). Pomacea canaliculata (Lamarck, 1822). Global Biodiversity Information Facility, Copenhagen. Retrieved 2020 September 28. Available from:https://www.gbif.org/species/2292582
Halwarte, M. 2008. The golden apple snail Pomacea canaliculata in Asian rice farming systems: Present impact and future threat. International Journal of Pest Management, 40:2, 199-296
Holswade, E. and A. Kondapalli 2013. “Pomacea canaliculata” (On-line), Animal Diversity Web. Accessed October 05, 2020 at https://animaldiversity.org/accounts/Pomacea_canaliculata/
ISSG (Invasive Species Specialist Group). (2005). Pomacea canaliculata (mollusc) Database. Retrieved 2020 September 26. Available from:http://issg.org/database/species/ecology.asp?si=135&fr=1&sts=sss
ITIS (Integrated Taxonomic Information System). (2020). Pomacea canaliculata. Retrieved 2020 September 26. Available from: https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=568121#null
Martin, P., Seuffert, M., Tamburi, N., Burela, S., Saveanu, L. (2017). Behavior and ecology of Pomacea canaliculata from Southern Pampas (Argentina). Retrieved 2020 September 28. Available from: https://www.cabi.org/ISC/FullTextPDF/2017/20173354472.pdf
The Apple Snail Website. (1998- 2003). Management options for the Golden Apple Snail. (. Retrieved 26 September 2020. Available from:https://www.applesnail.net/pestalert/management_guide/pest_management.php#foreword
Tripoli, F., Genecera, J., Matela, M.N., Fanuga, K., Velasco, D., Landero, R., Cataluña, R., Torres, M., Requieron, E., Bigsang, R. (2015). AACL BIOFLUX Aquaculture, Aquarium, Conservation & Legislation International Journal of the Bioflux Society Sexual dimorphism in the shell shape of the golden apple snail, Pomacea canaliculata. AACL Bioflux, 2015, Volume 8, Issue 6. Retrieved 2020 September 28. Available from: https://www.researchgate.net/publication/286455766_AACL_BIOFLUX_Aquaculture_Aquarium_Conservation_Legislation_International_Journal_of_the_Bioflux_Society_Sexual_dimorphism_in_the_shell_shape_of_the_golden_apple_snail_Pomacea_canaliculata
Rawlings, T.A., Hayes, K.A., Cowie, R.H., Collins, T.M. (2007). The identity, distribution, and impacts of non-native apple snails in the Continental United States. BMC Evolutionary Biology 7(1):97. Retrieved 2020 September 28. Available from DO:10.1186/1471-2148-7-97