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Details of endosymbiotic corpuscles (transmission electron microscopy). C corpuscles in Pomacea canaliculata (A), P. scalaris (B), and Asolene platae (C), respectively. They show an electron-lucent matrix containing many electron-dense clumps and some irregular and often concentric membrane vesicles. C corpuscles are delimited by an electron-dense wall, which seldom shows small pores (only shown in C, for A. platae. K corpuscles in P. canaliculata (D), P. scalaris (E), and Asolene platae (F), respectively. They show multiple concentric layers of a fibro-granular material. The vacuoles containing K corpuscles frequently show large globules of electron-dense material. Abbreviations: cb, host cytoplasmic band; cl, electron-dense clump; la, lamella; mc, membrane complex; vs, vesicular space; cw, corpuscular wall. Black triangles indicate zones of detachment of the wall, suggesting a plasma membrane. Scale bars represent
Source publication
We here compare morphological and molecular characters of some putative endosym-biotic elements of the digestive gland of three ampullariid species (Pomacea canaliculata, Pomacea scalaris and Asolene platae) which coexist in Lake Regatas (Palermo, Buenos Aires). The putative endosymbionts were reported in these species and were identified as C and...
Contexts in source publication
Context 1
... corpuscles of the three species ( Figs. 2A-2C) were contained within vacuoles of columnar cells and were encased in an electron-dense wall, which occasionally showed small pores. The contents showed electron-dense clumps and irregular arrangements of inner membranes in an electron-lucent matrix, but no nuclei or thylakoid structures could be recognised. Sometimes a membrane ...
Context 2
... occasionally showed small pores. The contents showed electron-dense clumps and irregular arrangements of inner membranes in an electron-lucent matrix, but no nuclei or thylakoid structures could be recognised. Sometimes a membrane appeared partly detached from the wall, suggesting the existence of a plasma membrane. C corpuscles in A. platae (Fig. 2C) showed clumps larger than those in the two Pomacea species and were dispersed in a more abundant matrix. Also, pores in the wall occurred more frequently in A. ...
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... gland exposed to the digoxigenin-labelled CYA361 probe (Fig. 3) showed fluorescence in most C and K symbiotic corpuscles. However, the cores of some K corpuscles were detached and lost during the hybridisation procedure. Sections exposed to probes that were not labelled with digoxigenin (negative controls) showed only some background fluorescence (Fig. ...
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... species, together with small vesicles and irregularly arranged membrane stacks, but lacking organelles and typical thylakoid structures. Furthermore, an electron-dense wall delimited the C corpuscles in the three species. Intriguingly, this wall occasionally showed small pores in some corpuscles of the three species (only shown for A. platae in Fig. 2C). In some cases ( Fig. 2A), a membrane appear detached from the external wall, suggesting the existence of a plasma membrane, as it was shown in a previous study of laboratory-raised P. canaliculata (Koch et al., 2006). No nuclei were observed in C corpuscles of any of the species ...
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... vesicles and irregularly arranged membrane stacks, but lacking organelles and typical thylakoid structures. Furthermore, an electron-dense wall delimited the C corpuscles in the three species. Intriguingly, this wall occasionally showed small pores in some corpuscles of the three species (only shown for A. platae in Fig. 2C). In some cases ( Fig. 2A), a membrane appear detached from the external wall, suggesting the existence of a plasma membrane, as it was shown in a previous study of laboratory-raised P. canaliculata (Koch et al., 2006). No nuclei were observed in C corpuscles of any of the species ...
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Citations
... Sections were stained with haematoxylin-eosin and a trichrome stain (Alcian Blue, Nuclear Fast Red and eosin) as reported previously (Dellagnola et al., 2017). Digestive epithelial cells, intracellular symbiotic corpuscles and storage cells were morphologically identified as reported previously for Neotropical (Castro-Vazquez et al., 2002;Vega et al., 2005Vega et al., , 2007Giraud-Billoud et al., 2008;Dellagnola et al., 2019b) and Indomalayan apple snails (Meenakshi, 1955;Takebayashi, 2013). ...
The adult fluke Stomylotrema vicarium (Stomylotrematidae, Microphalloidea) was described for the first time in Theristicus caerulescens in 1901, but the complete life cycle has remained unknown to date. Here, we found a stomylotrematid trematode in the digestive gland of the endemic apple snail Pomacea americanista. The digestive gland´s tubuloacini were compressed by the trematode larvae placed on connective tissues and haemocoel spaces. Non-virgulate, stylet-bearing cercariae showed three pairs of penetration glands with a body, oral sucker, and stylet morphometrically similar to those of stylet-bearing, unencysted young metacercariae of S. vicarium found in the aquatic coleopteran Megadytes glaucus, and at a lesser extent with cercariae of S. gratiosus found in the apple snail Pomacea maculata. The larvae molecular phylogeny was inferred using the markers rRNA 28S and ITS1, being these sequences grouped with sequences of S. vicarium obtained from adult flukes. Together, these findings indicate that the life cycle of Stomylotrema vicarium begins in P. americanista, thus supporting the hypothesis that the ampullariid snails act as a first intermediate host.
... Firmicutes was one of the most abundant bacterial phyla in the gut content of P. canaliculata, which may play an important role in protein degradation [36]. P. canaliculata has a putative symbiont (plausibly a cyanobacterium) in the digestive gland, which travels from the stomach to the coiled gut [37][38][39]. The cyanobacterium produces a protease of 30 kDa that participates in the digestion of proteins [27]. ...
Background
The apple snail, Pomacea canaliculata, is one of the world’s 100 worst invasive alien species and vector of some pathogens relevant to human health.
Methods
On account of the importance of gut microbiota to the host animals, we compared the communities of the intestinal microbiota from P. canaliculata collected at different developmental stages (juvenile and adult) and different sexes by using high-throughput sequencing.
Results
The core bacteria phyla of P. canaliculata gut microbiota included Tenericutes (at an average relative abundance of 45.7 %), Firmicutes (27.85 %), Proteobacteria (11.86 %), Actinobacteria (4.45 %), and Cyanobacteria (3.61 %). The female group possessed the highest richness values, whereas the male group possessed the lowest bacterial richness and diversity compared with the female and juvenile group. Both the developmental stages and sexes had important effects on the composition of the intestinal microbiota of P. canaliculata. By LEfSe analysis, microbes from the phyla Proteobacteria and Actinobacteria were enriched in the female group, phylum Bacteroidetes was enriched in the male group, family Mycoplasmataceae and genus Leuconostoc were enriched in the juvenile group. PICRUSt analysis predicted twenty-four metabolic functions in all samples, including general function prediction, amino acid transport and metabolism, transcription, replication, recombination and repair, carbohydrate transport and metabolism, etc.
Conclusions
This study provided a general understanding of the diversity characteristics of intestinal microbial communities of P. canaliculata, and indicated that developmental stage and gender could both influence the intestinal microbes of P. canaliculata. Further study may focus on the interaction between the gut microbiota and their host.
... The authors have hypothesized that the intracellular corpuscles are endosymbionts, based on two findings on C corpuscles: an electrondense cell wall and a DNA/protein ratio similar to those in prokaryotic cells. Furthermore, morphological and molecular studies have shown that both corpuscle types relate to Cyanobacteria or chloroplasts (Dellagnola et al. 2019;Koch et al. 2006Koch et al. , 2017Vega et al. 2005Vega et al. , 2012b, while physiological studies have shown that they have an ancillary role in protein digestion, and also in the accumulation and depuration of metals Godoy et al. 2013;Vega et al. 2012a). In all the snail populations sampled so far, endosymbionts occupy from a quarter to a fifth of the area of the glandular tissue and are released continuously from the digestive gland into the intestinal lumen and then expelled in the feces (Andrews 1965;Castro-Vazquez et al. 2002). ...
... The bioconcentration of Cd in tissues and symbiotic corpuscles of P. canaliculata suggests this symbiosis may be used as a bioindicator of Cd pollution in freshwater bodies. The ability to concentrate Cd might extend to other ampullariid species since pigmented intracellular corpuscles are present in the major clades of the family (Dellagnola et al. 2019;Devi et al. 1981;Meenakshi 1955). Also, field studies have shown that Cd from aquatic ecosystems can be accumulated in by the apple snails Lanistes (48.2 μg/g dry weight; Adewunmi et al. 1996) and P. canaliculata (head/foot = 0.4-2.5; ...
The vulnerability of aquatic ecosystems due to the entry of cadmium (Cd) is a concern of public and environmental health. This work explores the ability of tissues and symbiotic corpuscles of Pomacea canaliculata to concentrate and depurate Cd. From hatching to adulthood (4 months), snails were cultured in reconstituted water, which was a saline solution in ASTM Type I water. Then, adult snails were exposed for 8 weeks (exposure phase) to Cd (5 μg/L) and then returned to reconstituted water for other 8 weeks (depuration phase). Cadmium concentration in the digestive gland, kidney, head/foot and viscera (remaining of the snail body), symbiotic corpuscles, and particulate excreta was determined by electrothermal atomic absorption spectrometry. After exposure, the digestive gland showed the highest concentration of Cd (BCF = 5335). Symbiotic corpuscles bioaccumulated Cd at a concentration higher than that present in the water (BCF = 231 for C symbiotic corpuscles, BCF = 8 for K symbiotic corpuscles). No tissues or symbiotic corpuscles showed a significant change in the Cd levels at different time points of the depuration phase (weeks 8, 9, 10, 12, and 16). The symbiotic depuration through particulate excreta was faster between weeks 8 and 10, and then slower after on. Our findings show that epithelial cells of the digestive gland of P. canaliculata and their symbiotic C corpuscles are sensitive places for the bioindication of Cd in freshwater bodies.
In this work, we aimed at investigating cell and tissue responses of the apple snail Pomacea canaliculata, following the inoculation of the zoonotic pathogen Mycobacterium marinum. Different doses were tested (10, 20, 65, and 100 M CFU) and the mortality rate was negligible. The histopathogenesis was followed at 4, 9, and 28 days after inoculation. Overt histopathological lesions were consistently observed after the two largest doses only. In the lung, marked hemocyte aggregations, including intravascular nodule formation, were observed within the large blood veins that run along the floor and roof of this organ. Hemocyte aggregations were found occluding many of the radial sinuses supplying the respiratory lamina. Acid-fast bacilli were contained in the different hemocyte aggregations. In addition, hemocytes were observed infiltrating the storage tissue, which makes up most of the lung wall, and the connective tissue of the mantle edge. Additionally, signs of degradation in the storage tissue were observed in the lung wall on day 28. In the kidney, nodules were formed associated with the constitutive hemocyte islets and with the subpallial hemocoelic space, in whose hemocytes the acid-fast structures were found. Electron microscopy analysis revealed the presence of bacteria-containing phagosomes within hemocytes located in the surface zone of the islets. Additionally, electron-dense spheroidal structures, which are likely remnants of digested mycobacteria, were observed in close proximity to the hemocytes’ nuclei. The size attained by the hemocyte nodules varied during the observation period, but there was no clear dependence on dose or time after inoculation. Nodules were also formed subpallially. Some of these nodules showed 2–3 layers with different cellular composition, suggesting they may also form through successive waves of circulating cells reaching them. Nodular cores, including those formed intravascularly in the lung, would exhibit signs of hemocyte dedifferentiation, possibly proliferation, and death. Hemocyte congestion was observed in the hemocoelic spaces surrounding the pallial ends of the renal crypts, and the renal crypts themselves showed de-epithelization, particularly on day 28. The diverse cellular responses of P. canaliculata to M. marinum inoculation and the high resilience of this snail to the pathogen make it a suitable species for studying mycobacterial infections and their effects on cellular and physiological processes.
Background
Limnoperna fortunei is a freshwater bivalve mollusc originally from southern Asia that invaded South America in the 1990’s. Due to its highly efficient water pumping and filtering, and its capacity to form strong adhesions to a variety of substrates by byssus thread, this invasive species has been able to adapt to several environments across South America, causing significant ecological and economic damages. By gaining a deeper understanding of the biological and ecological aspects of L. fortunei we will be able to establish more effective strategies to manage its invasion. The gills of the mollusc are key structures responsible for several biological functions, including respiration and feeding. In this work, we characterized the ultrastructure of L. fortunei gills and its ciliary epithelium using light microscopy, transmission and scanning electron microscopies. This is the first report of the morphology of the epithelial cells and cilia of the gill of L. fortunei visualized in high resolution.
Results
The analysis showed highly organized and abundant ciliary structures (lateral cilia, laterofrontal cirri and frontal cilia) on the entire length of the branchial epithelium. Mitochondria, smooth endoplasmic reticulum and glycogen granules were abundantly found in the epithelial cells of the gills, demonstrating the energy-demanding function of these structures. Neutral mucopolysaccharides (low viscosity mucus) were observed on the frontal surface of the gill filaments and acid mucopolysaccharides (high viscosity mucus) were observed to be spread out, mainly on the lateral tract. Spherical vesicles, possibly containing mucus, could also be observed in these cells. These findings demonstrate the importance of the mucociliary processes in particle capture and selection.
Conclusions
Our data suggest that the mechanism used by this mollusc for particle capture and selection could contribute to a better understanding of key aspects of invasion and also in the establishment of more efficient and economically viable strategies of population control.
