First-stadium juveniles of Polydesmus angustus born each month from May to September were reared throughout their life cycle under controlled seasonal conditions. At maturity, the reproductive patterns of 62 females were studied individually. It was confirmed that females born from May to August have a 1-year life cycle and those born from late August onwards a 2-year life cycle (cohort-splitting). A third type of life cycle - interseasonal iteroparity - was observed in a few females born late in the season. On average, annual females started to reproduce when 11.4 months old and produced 3.6 broods per female over 1.8 months; the later they were born from May to August, the later they reproduced the following year. Biennial females started to reproduce when 19.9 months old and produced 3.8 broods per female over 2.2 months; all reproduced early in the breeding season. These results indicate that only annual females can produce an appreciable proportion of biennial offspring from late August onwards, which rules out direct genetic determination of life-cycle duration. The reproductive characteristics of P. angustus suggest a non-genetic mechanism that can drive cohort-splitting. Because individual females reproduce for about 2 months on average, this automatically results in cyclic variation in life-cycle duration (annual/biennial/annual) in the long-term progeny of any female.
The distribution of Alisma gramineum in the Czech Republic was determined using herbarium specimens, data in the literature and the authors’ own records. Comparison of records from four periods (before 1900, 1901–1945, 1946–1970, 1971–2001) revealed that the total number of localities has not decreased, but the occurrence changed considerably both in terms of the localities and regions where the species is found. Abundant populations were observed on exposed shores of water reservoirs. It has colonized the Třeboň Basin, S Bohemia, over the last few decades. Effect of water regime, light/darkness regime and temperature on germination and dormancy was studied. A. gramineum is adapted to germinate in water and in the dark; germination occurs in late spring, i.e. a period of high temperature. The high variation in the germination response to particular environmental factors may be accounted for the irregular occurrence of A. gramineum at certain localities. Best conditions for seed production are shallow water and recently exposed shores of water reservoirs, where plants can grow and set seed within one growing season. The ability to survive in a vegetative stage is more important in deep water, but seed banks in the mud at the bottom of reservoirs is the only way the species can persist when adult plants die.
Laboratory work was conducted to elucidate the life cycle of the South African gnathiid isopod, Gnathia africana Barnard, 1914. The natural fish hosts of this temporary parasite, the super klipfish Clinus superciliosus (Linnaeus, 1758), were exposed to gnathiid larvae in the laboratory. It was found that G. africana has three larval stages, consisting of three unfed (zuphea) and three fed (praniza) stages. First-, second- and third-stage zuphea larvae took an average of 2 h 18 min, 2 h 43 min and 10 h 8 min respectively to complete their feeding and the first- and second-stage praniza moulted at 8 and 10 days respectively into the next zuphea stage. Three to six days after its last blood meal, the sex of the third and final praniza stage could be determined by the presence of either a testis or two ovaries in the dorsal pereon. Male larvae moulted into adult males between 8 and 10 days post feeding. Female larvae moulted at approximately 17 days into adult females. Fertilisation of the eggs by the male took place within 24 hours of completion of the female moult. The development of the embryos and subsequent release of the young larvae between 15 and 23 days post fertilisation completed the cycle. This entire cycle took approximately 62 days in water temperatures of 20-25°C.
Selected life-history traits of an oonopid spider, Triaeris stenaspis Simon, which has been introduced into greenhouses in Europe, were investigated. Spiders were reared in the laboratory under constant physical and dietary conditions, and followed from egg to death. The spiders passed through 3 juvenile instars, each lasting approximately a month. The adult stage lasted on average 6 months, which is 54% of the entire life cycle. The mortality in each juvenile instar was similar. Five morphological characters were recorded for each instar, which provided a reliable means of identifying the developmental stages. All spiders developed into females and although kept isolated they laid fertile eggs, which indicates thelytokous parthenogenesis. Eggs were always enclosed in a disc-shaped egg-sac, each containing 2 eggs. Total fecundity was on average 27 eggs and rate of laying eggs decreased with age. Fecundity was positively correlated with adult longevity. Fertility was rather low, approximately 59%. It was negatively correlated with fecundity but not related to longevity. Low fertility appears to be the only cost of parthenogenetic reproduction. There was considerable genotypic variation in all traits studied compared to that in sexually reproducing spiders. There were no apparent maternal effects on all the traits studied. Using molecular methods proved that parthenogenesis in T. stenaspis is not induced by the endosymbiotic bacteria, Wolbachia sp. or Cardinium sp.
When in vitro growth of Vittaforma comeae was tested using MDCK, MRC-5, XEN, L-929 and FHM cell lines, propagation occurred only in MDCK, MRC-5 and XEN cells. The intervals required for the various stages of the life cycle to develop were the same in all the cell lines tested. The MDCK cell line was selected to support the growth of V. comeae in vitro and provide the system for in vitro testing of drugs. The weekly output of V. comeae spores from the MDCK cell monolayer was monitored over a 61-week period during which there were fluctuations but no definite increase or decrease in output. Albendazole at 2.1 or 4.2 pg/ml in MEM was tested against V. comeae in MDCK cell monolayers and showed antimicrosporidial activity. The percentage of infected cells was reduced in the presence of the drug and there were ultrastmctural abnormalities in all stages of the life cycle. The drug prevents parasite division.
Experimental infection of the pulmonate snails Arianta arbustorum L. and Helix pomatia L. with first-stage larvae of protostrongylid nematode Elaphostrongylus cervi Cameron, 1931 was performed in order to determine modes of larval entry into the body of the snail intermediate host. Groups by four individuals of both snail species were examined histologically 30, 60, 90, and 120 minutes after the beginning of exposure and 1, 2, 4, and 7 days post infection. All 64 snails examined were found to be successfully infected. The superficial furrows of the sole were recognized as the most important site of larval entry into the snail organism. Larval penetration was observed to be accompanied by destruction of the superficial epithelium. The number of larvae found in the subepithelial connective tissue of the headfoot was significantly higher than that found in other tissues and organs. Larval counts in individual parts of the body of snails examined from 0 to 7 days p.i. did not fluctuate significantly. The present results indicate that only those protostrongylid larvae which actively penetrated the superficial epithelium of the snail sole play an important role in the life cycle.
Cercariae and metacercariae of three species of the Microphallidae Travassos, 1920 were found in snails and crustaceans from tributaries of the Brisbane River, Queensland, Australia. Specimens of Maritrema brevisacciferum Shimazu et Pearson, 1991 and Microphallus minutus Johnston, 1948, which have previously been reported in Queensland, were found as cercariae in the tateid gastropod Posticobia brazieri (Smith) and as metacercariae of M. brevisacciferum in the atyid shrimp Caridina indistincta Calman and of M. minutus in the parastacid crayfish Cherax dispar Reik. Combined analysis of morphological and molecular data, based on newly generated ITS2 and partial 28S rDNA data, linked cercariae and metacercariae for both species. This is the first report of the first intermediate hosts of M. brevisacciferum and M. minutus. Infections of another unidentified microphallid metacercariae, Microphallidae gen. sp., were found in P. brazieri and C. indistincta. The sequences of metacercarial isolates from both hosts were identical. The data on the Microphallidae from Australia and species that develop in freshwater invertebrates were examined in detail., Olena Kudlai, Scott C. Cutmore, Thomas H. Cribb., and Obsahuje bibliografii
Seven species of fishes, Catostomus commersonii (Lacépède), Etheostoma nigrum Rafinesque, Micropterus dolomieu Lacépède, Notemigonus crysoleucas (Mitchill), Notropis hudsonius (Clinton), Perca flavescens (Mitchill), and Percina caprodes (Rafinesque) from the St. Lawrence River, Quebec, Canada, were found infected with progenetic specimens of Neochasmus spp. in the orbits and/or the body musculature. Worms displayed varying degrees of maturation. Eggs occupied the entirety of the worm in late stages of development and persisted as distinct clusters in situ after worm death. Populations of parasites were studied monthly in E. nigrum from one site between May and October in order to follow parasite recruitment, development and maturation. Recruitment of parasites was observed in young-of-the-year fish primarily in July and continued through October. Worms matured rapidly, displaying egg production within a month. Later developmental stages, in which eggs occupied most of the worm, and clusters of eggs became abundant by September. Infections in overwintered fish collected in May consisted mainly of worms in early stages of egg production and of clusters of eggs. When hatched artificially, eggs from the clusters released viable miracidia, indicating that they survive beyond the lifespan of the adult worm. It is suggested that progenesis is a fixed characteristic of the life cycle of these species, that egg dispersal requires the death of the host and that it is facilitated by predation. All prior records of Neochasmus spp. are examined, leading us to conclude that the role of the putative definitive host (primarily basses) has been reduced to that of a dispersal agent. Current hypotheses concerning the evolution and maintenance of progenesis are considered, but it is concluded that they do not apply to this host-parasite system.
The nematode parasite Huffmanela huffmani Moravec, 1987 (Trichosomoididae) infects swimbladders of fishes in the family Centrarchidae. Only fish collected from the upper San Marcos River (Texas) have been found infected with H. huffmani eggs with a prevalence of 90%. Hundreds of thousands of H. huffmani eggs have been observed in these fish but only a few specimens of adult worms have ever been found. The San Marcos River arises from springs along the Balcones Fault Zone in San Marcos, Hays County, Texas. The restriction of the parasite to the upper San Marcos River and the high prevalence of the parasite eggs in centrarchids would seem to enable one to solve the life cycle of H. huffmani but this has proved false. Here, the insights and experiments used to help define some of the aspects concerning the life cycle of this enigmatic parasite are described. This study of H. huffmani includes a description of the habitat, the known limits of geographic distribution of the parasite, possible dispersal processes, egg characteristics, the testing of a possible intermediate host, Palaemonetes antrorum (Benedict) (Decapoda: Palaemonidae), and the effects of the digestion process on H. huffmani eggs.
The developmental stages and life cycle of the nematode Camallanus anabantis Pcarse, 1933 an intestinal parasite of Anabas testudineus (Bloch) arc described. The copepod Mesocyclops leuckarti (Claus) was used as experimental intermediate host. After being ingested by the copepods the nematode first-stage larvae enter its haemocoel, where they moult twice, 4 d.p.i. and 11 d.p.i., at 21-26°C, respectively to become the infective third-stage larvae. The definitive fish hosts become infected when feeding on copcpods harbouring infective larvae. In the fish host’s intestine the larvae undergo two more moults, the third on day 15 p.i. The fourth moult of “male” larvae occurred on day 68 p.i. and that of “female” larvae on day 86 pi. at water temperatures 24-36°C- A female with eggs and few larvae in the uteri was first observed on day 187 p.i.