Prime waterfront real estate: Apple snails choose wild taro for oviposition sites

Abstract

While difficult to prevent introductions, scientific research can help guide control efforts of exotic, invasive species. South American island apple snails Pomacea insularum have quickly spread across the United States Gulf Coast and few control measures exist to delay their spread. Usually occupying cryptic benthic habitats, female apple snails crawl out of the water to deposit large, bright pink egg clutches on emergent objects. To help identify the most likely place to find and remove clutches, we conducted four lab experiments to investigate what specific object qualities (i.e. material; shape and height; plant species; natural and artificial) attracted P. insularum females to lay clutches. In our fourth experiment, we specifically examined the relationship between female size and reproductive output. To further understand reproductive output, we quantified experimental clutch characteristics (height above water, dimensions, mass, approximate volume, number of eggs, hatching efficiency). Pomacea insu-larum females laid more clutches on plant material, chose round over flat surfaces and failed to differentiate between tall and short structures. In comparison to a common native plant in the eastern US, Pontederia cordata, snails clearly preferred to lay clutches on a widely distributed exotic, invasive plant (wild taro, Colocasia esculenta). Unexpectedly, smaller snails showed higher overall total fecundity as well as more eggs per clutch than larger snails. Therefore, hand removal efforts of large females may not be enough to slow down clutch production. Collectively, our results indicate that conservationists and managers should search emergent plants for P. insularum clutches carefully to guard against established populations.

Count Your Eggs Before They Invade: Identifying and Quantifying Egg Clutches of Two Invasive Apple Snail Species (Pomacea)

“…However, fortunate for managers, apple snails also possess highly visible egg masses. To reproduce, adult females of the two most common invasive species ( P. canaliculata and P. maculata ) climb up stems of riparian vegetation, or other emergent structures such as concrete walls, wooden docks or cisterns, to deposit vibrant pink egg clutches (Figure 1a-h) above the water line [16,20]. The conspicuousness and general accessibility of these egg clutches gives us an opportunity to develop tools that will help managers and researchers find and effectively respond to apple snail invasions as early and efficiently as possible [2].…”

Insights from an Integrated View of the Biology of Apple Snails (Caenogastropoda: Ampullariidae)

“…They require emergent surfaces including plants for laying eggs above the waterline and, in some cases, for climbing to the water's surface for respiration (Turner, 1996), and prefer marshes with low to moderate density of emergent plant stems over lily-pad dominated habitats (Karunaratne et al, 2006). In some cases, species of Pomacea exhibit preferences for specific vegetation types (Bryan, 1990;Kyle et al, 2011). For example, in the Everglades of Florida, the greatest concentrations of egg clutches occur along the ecotone created by sawgrass and wet prairie or slough habitat (Darby et al, 1999).…”

Tolerance of embryos and hatchlings of the invasive apple snail Pomacea maculata to estuarine conditions

“…Because estuaries of the region are productive and diverse ecosystems (Lydeard and Mayden 1995), the threat of P. maculata invasion is of concern given the high aquatic macrophyte diversity and nekton assemblages that these estuaries support Valentine 2011, 2012;Rozas et al 2013). P. maculata deposit masses of eggs above the water surface on emergent vegetation or structures, and as eggs hatch, juvenile snails fall into underlying waters (Horn et al 2008;Burks et al 2010;Kyle et al 2011).…”