Reproductive Ecology of the Giant African Snail in South Florida: Implications for Eradication Programs

Abstract

Giant African snail (Achatina fulica (Bowdich, 1822)), an important invasive snail, was recently found in South Florida, USA. An extensive eradication effort was initiated consisting of pesticide applications, debris removal and hand collections. We studied the reproduction capacity and population dynamics of snails collected from 22 populations for two years to help evaluate the likely success of the eradication program. A total of 23,890 snails, ranging from 25–131 mm, were measured, dissected and the number of eggs in each snail counted. Gravid snails ranged from 48–128 mm. Only 5% of snails had eggs, which were found year round. As the snails increased in size, they were more likely to include reproducing individuals. However, the percentage of gravid snails peaked when snails were approximately 90 mm. Although more prevalent, small (<65 mm) adults contributed fewer eggs to the population than the larger snails. We evaluated the effect of control measures on six populations having >1000 adult snails and used data from the two largest populations to investigate how environmental factors (temperature, humidity, and rainfall) interacted with population dynamics and control measures. More snails were collected in weeks with high humidity and more gravid snails were collected when the temperature was higher. The addition of metaldehyde pesticides had the greatest impact on population dynamics by reducing snail numbers. In populations with fewer snails, their numbers were already declining before the use of metaldehyde, although the new treatment accelerated the process. As a consequence of the eradication program, egg-producing snails were no longer collected from most populations by the end of the study. The aggressive and persistent control efforts apparently lead to reduced populations of egg producing snails, eventually resulting in local extinctions of this important pest.

Designing a trapping strategy to aid Giant African Snail (Lissachatina fulica) eradication programs

“…Field studies were conducted on residential properties located in Miami-Dade County, Florida from October 2011–December 2012. The properties were located in the most heavily infested quarantine zones [ 8 ]. These were established by the United States Department of Agriculture (USDA) and Florida Department of Agriculture and Consumer Services (FDACS) GAS joint eradication program [ 23 ].…”

“…No endangered or protected gastropod species were present on the quarantine properties. The properties were all subject to an eradication protocol, which entailed visual surveys, hand collection, debris removal, and pesticide treatments at least once every two weeks [ 8 , 9 ]. From October 2011 through October 2012 pesticide applications were limited to 1% iron phosphate granular bait (Sluggo ™ Loveland Products, Inc. Greeley, CO).…”

Effects of Physicochemical Factors and the Local Ecological Knowledge on the Population of Helicostyla Daphnis (Broderip, 1841) in Borbon and Sogod, Cebu, Philippines

“…However, he pointed out that moisture could be a limiting factor for abundance because high moisture is also associated with high abundance of predator and parasites (Moreno-Rueda, 2014). In a more recent study on the Giant African snail (Achatina fulica (Bowdich, 1822)) in South Florida USA, more land snails were found in time with high humidity (Roda et al, 2016).…”

Angistrongylus Cantonensis and Ancylostoma Caninum Detection in Snails of São Paulo City (2016-2017), Brazil.

“…Originated from east Africa, these molluscs were driven to the worldwide distribution since the 1800, reaching Asia in the middle of 1920s, the USA in the 60s and Guadeloupe in 1988 (Thiengo et al, 2007;Roda et al, 2016). They were illegally introduced in Brazil between 1988 and 1989, as a commercial alternative to the Helix aspersa (Müller) snail to be consumed as escargot (Thiengo et al, 2007;Pavanelli et al, 2017).…”

“…Besides causing environmental problems, this snail represents a public health hazard (Roda et al, 2016) as the intermediate host in the life cycles of various parasites, among them, Angiostrongylus cantonensis (Oliveira et al, 2015). First described in Canton, China, these nematodes are found in lung arteries of rodents (Rattus norvegicus and Rattus rattus) (Moreira et al, 2013), definitive hosts of this parasite.…”