Distribution and Management of Pomacea Canaliculata in the Northern Region of Malaysia: Mini Review

Collecting differently sized particles on water surface by maneuvering pedal waves on the foot of the water snail Pomacea canaliculata

The water snail (Pomacea canaliculata) features both broad dietary scope and high feeding rate, possibly making it one of the most successful mollusc invaders globally. The water snail can collect differently sized food particles on the air-water interface by generating pedal waves on the foot surface, such as granular duckweed and animal carrion in wild aquatic environment. While foraging by pedal waves, the biomechanical challenges by manipulating the differently sized particles might be overcome by mediating the waveform for optimized energy costs, the physics and the function of which have not been uncovered yet. Herein, we study the two-dimensional topographic features of the snail foot in the pedal wave feeding pattern by a laser sensor. Feeding on differently sized particles, the average wavelength of the pedal waves remains nearly constant, whereas the amplitude increases while transporting larger particles. We develop a hydrodynamical model and discover that applying a larger amplitude to transport the particle can shorten the transport time, facilitating the food transport rate. However, to maintain a relatively constant mass uptake rate, the water snail exhibits a flexible strategy of collecting larger particles with increased amplitudes. This work demonstrates that the water snail implements a strategy by generating varying waveforms on the foot surface to take up the floating food at an optimized feeding rate. This feeding fashion may open up a new way for developing bio-inspired solid waste collectors at the gas-liquid interface.

Farming the Edible Aquatic Snail Pomacea canaliculata as a Mini-Livestock

In the present paper, we describe the farming system of Pomacea canaliculata, an edible freshwater snail, as it is practiced by a farmer as mini-livestock in the vicinity of Andong in Korea. We visited the snail farm several times in the summer and winter of the year and conducted interviews with the farm manager using a semi-structured questionnaire. The farm is housed in polythene tunnels and uses a tank pen of trench type made up of propylene and measuring 1 m × 2 m × 0.5 m (length × width × height) in size. A regulated inflow of fresh water and outflow of used water was installed, with water level not exceeding 5 to 7 cm. As feed of snails, commercial fish feed is generally provided. The life cycle of the P. canaliculata might differ in captivity under the controlled environmental conditions than that of an individual in the wild environment. The farming system of snails, particularly P. canaliculata, does not involve high labor-intensive, high capital investment and also does not require high through-put cutting edge technology. In addition to providing nutrient-dense snail meat, establishing a snailery could therefore augment the economic condition of farmers in the poorer regions of the world and encourage sustainability and biodiversity conservation.

The efficiency of universal mitochondrial DNA barcodes for species discrimination of Pomacea canaliculata and Pomacea maculata

Invasive apple snails, Pomacea canaliculata and P. maculata, have a widespread distribution globally and are regarded as devastating pests of agricultural wetlands. The two species are morphologically similar, which hinders species identification via morphological approaches and species-specific management efforts. Advances in molecular genetics may contribute effective diagnostic tools to potentially resolve morphological ambiguity. DNA barcoding has revolutionized the field of taxonomy by providing an alternative, simple approach for species discrimination, where short sections of DNA, the cytochrome c oxidase subunit I (COI) gene in particular, are used as ‘barcodes’ to delineate species boundaries. In our study, we aimed to assess the effectiveness of two mitochondrial markers, the COI and 16S ribosomal deoxyribonucleic acid (16S rDNA) markers for DNA barcoding of P. canaliculata and P. maculata. The COI and 16S rDNA sequences of 40 Pomacea specimens collected from six localities in Peninsular Malaysia were analyzed to assess their barcoding performance using phylogenetic methods and distance-based assessments. The results confirmed both markers were suitable for barcoding P. canaliculata and P. maculata. The phylogenies of the COI and 16S rDNA markers demonstrated species-specific monophyly and were largely congruent with the exception of one individual. The COI marker exhibited a larger barcoding gap (6.06–6.58%) than the 16S rDNA marker (1.54%); however, the magnitude of barcoding gap generated within the barcoding region of the 16S rDNA marker (12-fold) was bigger than the COI counterpart (approximately 9-fold). Both markers were generally successful in identifying P. canaliculata and P. maculata in the similarity-based DNA identifications. The COI + 16S rDNA concatenated dataset successfully recovered monophylies of P. canaliculata and P. maculata but concatenation did not improve individual datasets in distance-based analyses. Overall, although both markers were successful for the identification of apple snails, the COI molecular marker is a better barcoding marker and could be utilized in various population genetic studies of P. canaliculata and P. maculata.

Cryptic diversity: Two morphologically similar species of invasive apple snail in Peninsular Malaysia

Invasive snails in the genus Pomacea have spread across Southeast Asia including Peninsular Malaysia. Their effects on natural and agricultural wetlands are appreciable, but species-specific effects are less clear because of morphological similarity among the species. Our objective was to establish diagnostic characteristics of Pomacea species in Malaysia using genetic and morphological criteria. The mitochondrial COI gene of 52 adult snails from eight localities in Peninsular Malaysia was amplified, sequenced, and analysed to verify species and phylogenetic relationships. Shells were compared using geometric morphometric and covariance analyses. Two monophyletic taxa, P. canaliculata and P. maculata, occurred in our samples. The mean ratio of shell height: aperture height (P = 0.042) and shell height: shell width (P = 0.007) was smaller in P. maculata. P. maculata co-occurred with P. canaliculata in five localities, but samples from three localities contained only P. canaliculata. This study is the first to confirm the presence of two of the most invasive species of Pomacea in Peninsular Malaysia using a molecular technique. P. canaliculata appears to be the more widespread species. Despite statistical differences, both quantitative and qualitative morphological characteristics demonstrated much interspecific overlap and intraspecific variability; thus, shell morphology alone cannot reliably verify species identity. Molecular techniques for distinguishing between these two highly invasive Pomacea species are needed to understand their specific ecological niches and to develop effective protocols for their management.

Egg extract of apple snail for eco-friendly synthesis of silver nanoparticles and their antibacterial activity

Green synthesis of silver nanoparticles (AgNPs) provides the alternative method with cost effectiveness and the eco-friendly process by using natural biomolecules as reducing and stabilizing agents. Alternative to the most studies of plant extracts, this work demonstrated a use of egg extract of apple snail (Pomacea canaliculata) for an eco-friendly production of AgNPs. The extract contained at least six proteins with the molecular weight in a range of 24-65 kDa that exhibited the reducing activity. The dispersive AgNPs were produced in the reaction containing only the extract and silver nitrate, as determined by the characteristic surface plasmon resonance peak of silver at 412 nm. The synthesized AgNPs were spherical with the average diameter of 9.0 ± 5.9 nm. The X-ray diffraction pattern and selected area electron diffraction (SAED) analyses confirmed the face-cubic centre (fcc) unit cell structure of AgNPs. The synthesized AgNPs exhibited the antibacterial activity against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. Results of this work clearly showed the potential use of the egg extract of apple snail for a green synthesis of small size AgNPs exhibiting the antibacterial activity.

Economic and environmental impacts of harmful non-indigenous species in southeast Asia

Harmful non-indigenous species (NIS) impose great economic and environmental impacts globally, but little is known about their impacts in Southeast Asia. Lack of knowledge of the magnitude of the problem hinders the allocation of appropriate resources for NIS prevention and management. We used benefit-cost analysis embedded in a Monte-Carlo simulation model and analysed economic and environmental impacts of NIS in the region to estimate the total burden of NIS in Southeast Asia. The total annual loss caused by NIS to agriculture, human health and the environment in Southeast Asia is estimated to be US$33.5 billion (5^th and 95^th percentile US$25.8–39.8 billion). Losses and costs to the agricultural sector are estimated to be nearly 90% of the total (US$23.4–33.9 billion), while the annual costs associated with human health and the environment are US$1.85 billion (US$1.4–2.5 billion) and US$2.1 billion (US$0.9–3.3 billion), respectively, although these estimates are based on conservative assumptions. We demonstrate that the economic and environmental impacts of NIS in low and middle-income regions can be considerable and that further measures, such as the adoption of regional risk assessment protocols to inform decisions on prevention and control of NIS in Southeast Asia, could be beneficial.