Influence of temperature on survival, growth and fecundity of the freshwater snail Indoplanorbis exustus (Deshayes)

To note the effect of temperature on survival, growth and fecundity, newly hatched (zero day old) snails Indoplanorbis exustus were cultured at 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees and 35 degreescentigrades constant temperatures and room temperature (17.5 degrees - 32.5 degrees centigrades). Individuals exposed to 10 degrees centigrades died within 3 days while those reared at 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees centigrades and room temperature survived for a period of 6, 27, 18, 16, 12 and 17 weeks respectively. An individual added on an average 0.21 mm and 0.45 mg, 0.35 mm and 7.94 mg, 0.63 mm and 15.5 mg, 0.81 mm and 27.18 mg, 1.07 mm and 41.48 mg and 0.78 mm and 31.2 mg to the shell diameter and body weight respectively at those temperatures per week. The snails cultured at 15 degrees centigrades died prior to attainment of sexual maturity. On an average, an individual produced 31.9 and 582.77, 54.86 and 902.18, 56.01 and 968.45, 49.32 and 798.68 and 62.34 and 1143.97 capsules and eggs respectively at 20 degrees, 25 degrees, 30 degrees, 35 degrees centigrades and room temperature (17.5 degrees - 32.5 degrees centigrades).

Fecundity of Biomphalaria straminea and B. glabrata in the laboratory: a twelve-month comparative study

In the present comparative study a Biomphalaria straminea sample from Picos (Piauí) showed expressive advantages related to fecundity over a B. glabrata sample from Belo Horizonte (Minas Gerais) such as: higher egg-mass production in 10 out of 12 months of study; higher egg production in all months of study; higher egg per egg-mass ratio in 11 out of 12 months of study; 66% of the egg-masses containing more than 20 eggs while in B. glabrata 70% of the egg-masses showed less than 20 eggs; three times less empty egg capsules than B. glabrata; attainning maximum fecundity in half the time required by B. glabrata. Mortality however was higher and sooner in B. straminea, suggesting higher semelparity in this species than in B. glabrata, a possibility that requires confirmation through long-term studies with other samples of both species. This first finding of a B. straminea sample more fecund than B. glabrata is discussed in relation to other data from the literature, and some recommendations are made on the quantification of fecundity of planorbid snails.

The susceptibility of adult schistosomes to immune attrition

Mouse infection models are described that demonstrate reduction of egg production in Schistosoma haematobium infections and both worm loss and reduced fecundity in S. bovis infections. Neither phenomenum could be shown in S. mansoni infected mice. The immunological basis for these anti-adult responses was inferred by comparison with infections in T-cell deprived mice and by the serum transfer of the ability to reduce a S. bovis worm burden into immunocompromised hosts. Vaccination with irradiation attenuated parasites was also shown to have consequences for the adults of a challenge infections of S. haematobium and S. bovis specifically. Prior vaccination resulted in an abrogation of the anti-fecundity and adult worm elimination that occurred in non-vaccinated similary infected mice. hese models are being used to define the targets and mechanisms involved in anti-adult attrition. A serological assay, quantitation of a circulating antigen (CAA) has been assessed for its ability to measure worm burdens of different species of schistosome in mice. This assay will be used to question whether anti-adult immunity contributes to the pattern of infection with S. mansoni and S. haematobium in man.

Raillietina (Raillietina) guaricana n. sp. (Cestoda-Davaineidae), parasite of wild rats from the environmental protection area of Guaricana, Paraná, Brazil

Raillietina (Raillietina) guaricanae n. sp. is described from the wild rats Oryzomys intermedius, O. nigripes and O. ratticeps, captured in the Environmental Protection Area of Guaricana, from November 1988 to December 1989. Raillietina (Railietina) guaricanae n. sp. is closely related to the Neotropical mammalian Raillietina, however it differs by the fewer number of rostellar hooks, and tests different number of eggs capsules and host species. The number of known species of Raillietina (Raillietina), parasites of mammals in the Neotropical Region, is increased to four.

Egg-laying induced by insemination in Biomphalaria snails

Contrasting with many populations of Biomphalaria glabrata and B. straminea previously dealt with in this laboratory, which when reared in isolation deposit self-fertilized eggs without apparent restraint, isolated individuals of the former species from São Sebastião do Passé, Bahia state, and of the latter from Porto Alegre, Rio Grande do Sul state, show a high degree of self-sterility, laying egg capsules with a few usually abortive, rarely viable egg cells, or just jellylike masses without egg cells. When two individuals are paired they readily copulate, usually withing 24 hr deposit one of more egg capsules containing many eggs, and egg-laying continues up to exhaustion of stored allosperm. So far this aspect of reproductive biology has been only observed in a number of populations of the planorbid species Helisoma duryi, and should be viewed as a populational rather than specific characteristic. Since sterility is not overcome by courtship, copulation and insemination by individuals of a different species, the stimulating factor that causes ovulation in the studied self-sterile individuals is considered to be present in the conspecific allosperm.

Limnaea peregrina Clessin, 1882, Synonym of Lymnaea columella Say, 1817 (Gastropoda: Lymnaeidae)

A description is given of the shell, radula, renal region, reproductive system and egg capsules of topotypic specimens of limnaea peregrina Clessin, 1882. This investigation intends contributing to define the specific identity of that nominal species. A close anatomical comparison with Lymnaea columella Say, 1817 from Michigan, USA, shows that both forms are indistinguishable, giving support to previous inferences from some authors. Data on egg hatching are presented.

Myxobolus absonus sp. n. (Myxozoa: Myxosporea) Parasitizing Pimelodus maculatus (Siluriformes: Pimelodidae), a South American Freshwater Fish

A new myxoporean species is described from a freshwater fish in Brazil. Myxobolus absonus sp. n. was found infecting Pimelodus maculatus captured in the river Piracicaba, State of São Paulo, Brazil. Cysts were found free in the opercular cavity. The spores are large (length-15.7 ± 1.5 µm, width-10.2 ± 0.7 µm; mean ± S.D.) and oval in shape, with the anterior end slightly pointed. The spore valves are relatively thin, smooth, and asymmetrical in a frontal view. The polar capsules are pyriform in shape, and unequal in size; the largest are 6.4 ± 0.7 µm long and 3.6 ± 0.5 µm wide, while the smallest are 4.2 ± 0.6 µm long and 2.5 ± 0.5 µm wide.

Effect of gamma radiation on the activity of hemocytes and on the course of Schistosoma mansoni infection in resistant Biomphalaria tenagophila snails

High doses of gamma radiation (10 Krad) in Biomphalaria tenagophila snails (Taim strain), which have been found to be resistant to Schistosoma mansoni, were not sufficient to impair their resistance to the parasite. The number of hemocytes, as well as their phagocytic activity, were not affected by irradiation, thus showing resemblance with mammal macrophages, which are resistant to gamma irradiation also.

A new species of Henneguya, a gill parasite of Astyanax altiparanae (Pisces: Characidae) from Brazil, with comments on histopathology and seasonality

A new species of Myxosporea, Henneguya chydadea, is described parasitizing the gills of Astyanax altiparanae collected from a lake on Rio das Pedras farm near Campinas, state of São Paulo, Brazil. Of the fish examined, 88.3% had gills parasitized by myxosporeans. The prevalence of the parasite ranged from 80% in the spring and fall, 93% in the summer and 100% in the winter. The parasite induced the formation of white, oval-shaped cysts measuring 40-64 µm x 64-80 µm which deformed the gill lamellae, compressed the capillaries, and caused retraction of the neighboring lamellae. The mature spores were elongated and had two identical, parallel elongate polar capsules. Each capsule contained a polar filament with 9-10 turns. There was no mucous envelope or iodinophilous vacuole. Morphometric differences between this parasite and other species of the genus Henneguya indicated, that he parasite observed in A. altiparanae is a new species. This is the first report of a myxosporeanparasitizing A. altiparanae.

Histophatology and ultrastructure of Henneguya caudalongula sp. n. infecting Prochilodus lineatus (Pisces: Prochilodontidae) cultivated in the state of São Paulo, Brazil

The histological and ultrastructural characteristics of a new species of Henneguya and the host reactions to infection by this species are reported. Henneguya caudalongula sp. n. was found in the inter and intralamellar regions of the gills of Prochilodus lineatus (Valenciennes, 1836) cultivated at Center for the Research and Management of Continental Fishing Resources located in the municipality of Pirassununga, state of São Paulo, Brazil. The plasmodia were white and round or ellipsoidal and measured 0.2 to 1 mm in length. The development of the parasite was asynchronous and the mature spores were fusiform, with a total length 71 ± 1.4 µm, body length of 16.6 ± 0.54 µm and width 4.6 ± 0.2 µm. The caudal process was 52.6 ± 1.5 µm long. The polar capsules were elongate (length 6.1 ± 0.19 µm, width 1.6 ± 0.15 µm) and of equal size. The polar filament was coiled in 10-11 turns. The prevalence of the parasite was 48.3% and did not vary significantly with the season or host size.

Myxobolus insignis sp. n. (Myxozoa, Myxosporea, Myxobolidae), a parasite of the Amazonian teleost fish Semaprochilodus insignis (Osteichthyes, Prochilodontidae)

A new myxosporean species is described from the fish Semaprochilodus insignis captured from the Amazon River, near Manaus. Myxobolus insignis sp. n. was located in the gills of the host forming plasmodia inside the secondary gill lamellae. The spores had a thick wall (1.5-2 µm) all around their body, and the valves were symmetrical and smooth. The spores were a little longer than wide, with rounded extremities, in frontal view, and oval in lateral view. They were 14.5 (14-15) µm long by 11.3 (11-12) µm wide and 7.8 (7-8) µm thick. Some spores showed the presence of a triangular thickening of the internal face of the wall near the posterior end of the polar capsules. This thickening could occur in one of the sides of the spore or in both sides. The polar capsules were large and equal in size surpassing the midlength of the spore. They were oval with the posterior extremity rounded, and converging anteriorly with tapered ends. They were 7.6 (7-8) µm long by 4.2 (3-5) µm wide, and the polar filament formed 6 coils slightly obliquely to the axis of the polar capsule. An intercapsular appendix was present. There was no mucous envelope or distinct iodinophilous vacuole.

Resistance to reinfection in rats induced by irradiated metacercariae of Clonorchis sinensis

A study was made to observe the association between the resistance to reinfection induced by irradiated metacercariae (MC) of Clonorchis sinensis and antigen specific Th1- and Th2-type cytokine productions in rats. Rats were infected with 20 MC of C. sinensis, previously exposed to a single dose of gamma irradiation, which varied from 0 to 100 Gy. All of them, single dose of 12 Gy showed higher IgG antibody titer with lowest worm recovery. Thus, 50 MC were used to challenge infection in rats previously infected with 20 MC irradiated at 12 Gy and the highest resistance to challenge infection was observed. The results of lymphocyte proliferation with specific antigen, ES Ag were shown no difference of proliferative responses as compared with primary and challenge infection at 12 Gy irradiation dose. In the case of cytokines production were observed that interferon (IFN-gamma) and interlukin (IL-2) were significantly enhanced, while IL-4 and IL-10 was almost unchanged to make comparison between primary and secondary infection at 12 Gy irradiation dose. In conclusion, the single dose of 12 Gy could be adopted for induction of the highest resistance to challenge infection. Up-regulation of Th1 type cytokines, IFN-gamma and IL-2 may be affected to develop vaccine by irradiated MC.

Studies on antimicrobial activity, in vitro, of Physalis angulata L. (Solanaceae) fraction and physalin B bringing out the importance of assay determination

Complex physalin metabolites present in the capsules of the fruit of Physalis angulata L. have been isolated and submitted to a series of assays of antimicrobial activity against Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213, S. aureus ATCC 25923, S. aureus ATCC 6538P, Neisseria gonorrhoeae ATCC 49226, Escherichia coli ATCC 8739; E. coli ATCC 25922, Candida albicans ATCC 10231 applying different methodologies such as: bioautography, dilution broth, dilution agar, and agar diffusion techniques. A mixture of physalins (pool) containing physalins B, D, F, G inhibit S. aureus ATCC 29213, S. aureus ATCC 25923, S. aureus ATCC 6538P, and N. gonorrhoeae ATCC 49226 at a concentration of 200 mg/µl, using agar dilution assays. The mixture was inactive against P. aeruginosa ATCC27853, E. coli ATCC 8739; E. coli ATCC 25922, C. albicans ATCC 10231 when applying bioautography assays. Physalin B (200 µg/ml) by the agar diffusion assay inhibited S. aureus ATCC 6538P by ± 85%; and may be considered responsible for the antimicrobial activity.

Fine structure of Henneguya hemiodopsis sp. n. (Myxozoa), a parasite of the gills of the Brazilian teleostean fish Hemiodopsis microlepes (Hemiodontidae)

A fish-infecting myxosporean, Henneguya hemiodopsis sp. n., found infecting the gills of Hemiodopsis microlepis and collected from the Poty River near the city of Teresina, Brazil, was described based on ultrastructural studies. The parasite occurred within large whitish polysporic plasmodia (up to 200 μm in diameter) containing asynchronous developmental sporogonic stages, mainly mature spores. The spores measured 19.7 ± 0.9 μm in total length (n = 30) and the ellipsoidal spore body was 10.8 ± 0.5 μm long, 3.3 ± 0.4 μm wide and 2.5 ± 0.5 μm thick. The spores were composed of two equal shell valves adhering together along the straight suture line, with each valve having equal-sized caudal tapering tails measuring 8.7 ± 0.6 μm in length. The spores were surrounded by a thin anastomosed network of microfibrils, more evident on the tails. There were two symmetric elongated bottle-like polar capsules 3.5 ± 0.3 μm long and 1.0 ± 0.2 μm wide, each with a polar filament with five to six coils. Given the morphological and ultrastructural differences from previously described parasites and the specificity of the host species, we propose a new species, named H. hemiodopsis sp. n.

Light and electron microscopy of Myxobolus sciades n. sp. (Myxozoa), a parasite of the gills of the Brazilian fish Sciades herzbergii (Block, 1794) (Teleostei: Ariidae)

A myxosporean parasite in the gill lamellae of the freshwater teleost fish, Sciades herzbergii (Ariidae) (Block, 1794), from the Poti River (Northeast of Brazil) was described by light and electron microscopy studies. Polysporic histozoic cyst-like plasmodia containing several life-cycle stages, including mature spores, were observed. The spores were pyriform and uninucleate, measuring 9.15 ± 0.39 μm (n = 50) long, 4.36 ± 0.23 μm (n = 25) wide and 2.61 ± 0.31 μm (n = 25) thick. Elongated pyriform polar capsules (PC) were of equal size (4.44 ± 0.41 μm long and 1.41 ± 0.42 μm in diameter) and each contained a polar filament with 9-10 coils obliquely arranged in relation to the axis of PC. The PC wall was composed of two layers of different electron densities. Histological analysis revealed the close contact of the cyst-like plasmodia with the basal portion of the epithelial gill layer, which exhibited some alterations in the capillary vessels. Based on the morphological and ultrastructural differences, the similarity of the spore features to those of the genus Myxobolus and the specificity of this host to previously described species, we describe a new species named Myxobolus sciades n. sp. in this study.