Distribution and habitats of the alien invader freshwater snail <i>Physa acuta</i> in South Africa

An account is given of all invasive alien freshwater snail species samples found in the Kruger National Park currently on record in the National Freshwater Snail Collection(NFSC) database. This report mainly focuses on samples collected during surveys of selected water bodies in the Kruger National Park (KNP) during 1964, 1995, 2001 and 2006. The progress made by four alien invasive freshwater snail species, Lymnaea columella, Physa acuta, Aplexa marmorata and Tarebia granifera, in colonising water bodies since first being recorded in the KNP is addressed. The results clearly show that all four species are in the process of becoming more widespread than they were when first recorded. However, T. granifera is the only one of these species of which exceptionally dense populations were encountered in several water bodies. All indications are that this species could already have had a negative impact on the species diversity of molluscs in these water bodies, and it is recommended that the situation be closely monitored.

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Angucycline-like Aromatic Polyketide from a Novel Streptomyces Species Reveals Freshwater Snail Physa acuta as Underexplored Reservoir for Antibiotic-Producing Actinomycetes

Antibiotics ◽

10.3390/antibiotics10010022 ◽

2020 ◽

Vol 10 (1) ◽

pp. 22

Author(s):

Nasim Safaei ◽

Yvonne Mast ◽

Michael Steinert ◽

Katharina Huber ◽

Boyke Bunk ◽

...

Keyword(s):

High Throughput Sequencing ◽

Genome Mining ◽

Freshwater Snail ◽

Whole Genome Sequence ◽

Phylogenomic Analysis ◽

Ionization Mass ◽

Gram Positive ◽

Streptomyces Species ◽

Genus Streptomyces ◽

Physa Acuta

Antibiotic producers have mainly been isolated from soil, which often has led to the rediscovery of known compounds. In this study, we identified the freshwater snail Physa acuta as an unexplored source for new antibiotic producers. The bacterial diversity associated with the snail was characterized by a metagenomic approach using cultivation-independent high-throughput sequencing. Although Actinobacteria represented only 2% of the bacterial community, the focus was laid on the isolation of the genus Streptomyces due to its potential to produce antibiotics. Three Streptomyces strains (7NS1, 7NS2 and 7NS3) were isolated from P. acuta, and the antimicrobial activity of the crude extracts were tested against a selection of Gram-positive and Gram-negative bacteria and fungi. 7NS3 showed the strongest activity against Gram-positive bacteria and, thus, was selected for genome sequencing and a phylogenomic analysis. 7NS3 represents a novel Streptomyces species, which was deposited as Streptomyces sp. DSM 110735 at the Leibniz Institute-German Collection of Microorganisms and Cell Cultures (DSMZ). Bioassay-guided high-performance liquid chromatography (HPLC) and high-resolution electrospray ionization-mass spectrometry (HR-ESI-MS) analyses of crude extract fractions resulted in the detection of four compounds, one of which matched the compound characteristics of emycin A, an angucycline-like aromatic polyketide. Genome mining studies based on the whole-genome sequence of 7NS3 resulted in the identification of a gene cluster potentially coding for emycin A biosynthesis. Our study demonstrates that freshwater snails like P. acuta can represent promising reservoirs for the isolation of new antibiotic-producing actinobacterial species.

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Distribution and habitats of Lymnaea natalensis, snail intermediate host of the liver fluke Fasciola gigantica, in South Africa

Suid-Afrikaanse Tydskrif vir Natuurwetenskap en Tegnologie ◽

10.4102/satnt.v20i2.253 ◽

2001 ◽

Vol 20 (2) ◽

pp. 56-71

Author(s):

Editorial Office

Keyword(s):

South Africa ◽

Intermediate Host ◽

Geographical Distribution ◽

Liver Fluke ◽

Economic Factor ◽

Freshwater Snail ◽

Fasciola Gigantica ◽

Snail Intermediate Host ◽

Planning And Construction ◽

Lymnaea Natalensis

This paper focuses on the geographical distribution and the habitats of Lymnaea natalensis, the snail intermediate host of the liver fluke, Fasciola gigantica, as reflected by the collection sites of its 4 552 samples currently on record in the National Freshwater Snail Collection (NFSC) of South Africa. Although this species was represented in a variety of waterbodies, the majority of samples(±70%)came from rivers, brooks and dams and in 70.8% of the cases the water was described as permanent and in 71.8% as slow flowing or standing. The results of life-table studies conducted by various authors indicated that temperature should be a relatively unimportant factor in determining its geographical distribution, but that the availability of permanent water should be decisive for its presence in a given habitat. These results are in agreement with the finding that only 7.5% of the samples of this species in the NFSC were collected in habitats which were described as seasonal. Furthermore, it gives a logical explanation for the sporadic occurrence, or total absence of this species in the more arid regions of South Africa. Water impoundments and irrigation networks contribute to a large extent towards creating perennial habitats which would be suitable for L. natalensis. As intermediate host for one of the liver fluke species which already is an economic factor in South Africa, this certainly is an aspect which ought to be reckoned within the planning and construction of new irrigation schemes.

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Effect of cadmium on the embryos and juveniles of a tropical freshwater snail, Physa acuta (Draparnaud, 1805)

Water Science & Technology ◽

10.2166/wst.1998.0300 ◽

1998 ◽

Vol 38 (7) ◽

pp. 263-270 ◽

Cited By ~ 14

Author(s):

C. C. C. Cheung ◽

P. K. S. Lam

Keyword(s):

Early Life ◽

Freshwater Snail ◽

Toxicity Tests ◽

Life Stages ◽

Early Life Stages ◽

Physa Acuta ◽

Ecotoxicological Tests ◽

Embryonic Growth ◽

Potential Use ◽

Tropical Freshwater

The effects of cadmium on early life stages of a freshwater snail, Physa acuta (Draparnaud), were investigated. The 24- and 48-hour LC50 for embryos were 1.27 mg/l (95% confidence interval: 1.13 - 1.42) and 0.85 mg/l (0.71 - 1.01), respectively. The 24- and 48-hour LC50 for juveniles were 1.32 mg/l (1.13 - 1.54) and 1.05 mg/l (0.81 - 1.36), respectively. An increase in cadmium concentrations at sublethal levels resulted in a significant reduction in embryo growth rate and embryo hatchability. Developmental deformities of the embryos were also observed. The NOEC and LOEC for embryonic growth were 0.32 and 0.50 mg/l, respectively, and the LOEC for hatchability was 0.13 mg/l. These results suggest that embryonic growth and hatchability are useful endpoints in chronic toxicity tests. In addition, the potential use of early life stages of pulmonate snails in ecotoxicological tests is discussed.

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