Ecology and Species Composition of Fresh Water Snails in Amassoma Community and Niger Delta University Campuses, Bayelsa State, Nigeria

The knowledge about the population dynamics of freshwater snail intermediate host and their roles in disease transmission is little known in Bayelsa State. This study investigated the species composition of fresh water snail intermediate host in Amassoma community and the Niger Delta University Campuses during August 2019-October 2019 across five locations (Main campus Hostel, E.T.F Building, Ogboebi-Ama, Efeke-Ama, Ogbopina). Snails were collected from the water bodies with the aid of a scooping net and hand picking. The morphological identification of the snail intermediate host followed standard procedures. From the result, five hundred and seventy-one freshwater snails belonging to four genera and five species were recorded. The presence of Lymnae and Bulinus in the locations highlights foci for fascioliasis and schistosomiasis. The presence of Melanoides spp. is novel in Bayelsa State. The public health implications of these snails have called for timely control intervention.

Molluscicidal activity of chlorophyll extraction against the freshwater snails

Objective:To evaluate the molluscicidal activity of chlorophyll extract as a photodynamic substance against the snails Lymnaea stagnalis,Biomphalaria spp.and Physa marmorata.Methods:Chlorophyllin was extracted from deep-frozen spinach.Snails were incubated in chlorophyllin containing water with 2.5,5.0,10.0 and 15.0μg/mL.All samples were kept in darkness overnight for incubation.After incubation,three samples were irradiated with simulated solar radiation for 3 h.After irradiation,the vitality of the organisms was determined.Results:The photodynamically active chlorophyllin,at low concentrations,was able to kill snails within a few hours under exposure of solar radiation.Besides,it had a killing effect by about 70%and 100%on the snails’eggs and the newly hatched snails,respectively,after 3 h exposure to solar radiation.Conclusion:The derivates of chlorophyll was a very interesting substance for photodynamic freshwater snail control.Hence,it might be a promising and cheap new strategy which probably had the potential to replace the synthetic molluscicides for snail control.

Mechanistic Analysis and Bio-inspired Applications for a Bidirectional Stiffness of a Water Snail Operculum

The water snail Pomacea canaliculata retracts the discoidal and multi-layered operculum to protect the soft body from being attacked by predators,and releases it when threats lifted.However,the duration of the operculum retraction is usually less than that of the operculum protraction.In this paper,we elucidate the biological compliant mechanism of the operculum.By using confocal laser scanning microscopy,we find that the operculum has compliant sandwiched layers between hard layers.The layered structure results in a compliant mechanism with a bidirectional stiffness for the locking and unlocking processes of the operculum.A mathematical model is derived to rationalize the bidirectional stiffness mechanism of the operculum.In addition,we carry out the experiments on the locking and unlocking processes.The experimental results show that the locking tension is about two-fifths of the unlocking tension of the operculum.Moreover,based on the mechanical properties of the operculum with the layered structure,we designed an operculum-inspired structure,which may have a variety of potential applications in combined driving patterns.

Operculum of a Water Snail is a Hydrodynamic Lubrication Sheet

Water snails developed a distinct appendage, the operculum, to better protect the body against predators. When the animal is active and crawling, part of the underside of the shell rests on the outer surface of the operculum. We observed the water snails （Pomacea canaliculata） spend -3 hours per day foraging, and the relative angular velocity between the shell and operculum can reach up to 10°·s^-1, which might inevitably lead to abrasion on the shell and operculum interface. However, by electron microscopy images, we found that the underside of the shell and outer surface of the operculum is not severely worn, which indicates that this animal might have a strategy to reduce wear. We discovered the superimposed rings distributed concentrically on the surface, which can generate micro-grooves for a hydrodynamic lubrication. We theoretically and experimentally revealed the mechanism of drag reduction combing the groove geometry and hydrodynamics. This textured operculum surface might provide a friction coefficient up to 0.012 as a stability-resilience, which protects the structure of the snail＇s shell and operculum. This mechanism might open up new paths for studies of micro-anti-wear structures used in liquid media.

Enzyme inhibition by molluscicidal agents of Bauhinia variegata and Mimusops elengi in the nervous tissue of Lymnaea acuminata

Objective:To evaluate the effect of enzymatic activity in the nervous tissue of snail Lymnaea acuminata(L.acuminata)by Bauhinia variegata(B.variegata)and Mimusops elengi(M.elengi)and their active molluscicidal components quercetin and saponin.Methods:Treatment of sublethal concentration(40%and 80%of 96-h LC_(50))in vivo of column-purified fraction of B.variegata leaf and M.elengi bark and their molluscicidal agents quercetin and saponin inhibit the acetylcholinesterase(AChE),acid and alkaline phosphatase(ACP and ALP)activities in the nervous tissue of L.acuminata.Results:AChE activity was more inhibited than ACP and ALP in snail exposed to column-purified fraction of M.elengi bark and saponin.Among all the treatments the highest inhibition in AChE activity(27.77%)was noted in snail L.acuminata exposed to 80%of 96-h LC_(50)of saponin at 96-h exposure period.Conclusions:It can be concluded from the present study that inhibition of AChE,ACP and ALP by B.variegata leaf(quercetin)and M.elengi bark(saponin)in snail L.acuminata could be the cause of snail mortality.