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.
Mediální dialog ztrácí některé rysy přirozeného dialogu tváří v tvář, který leží v jeho půdorysu, a získává rysy další, neboť komunikace tu přestupuje přes hranice primární řečové situace. Televizní dialog je dialog veřejný, který se vede před diváckým publikem a pro toto publikum. Divák je nejen svědkem, ale pravým cílem, k němuž je dialog směrován. Stať analyzuje komunikační situaci, při níž jsou ve studiu přítomni redaktor a dva hosté, představitelé různých profesí a názorových proudů (ekonom a ekoložka) i různých stanovisek k určité otázce (globalizace). Redaktor se obrací s otázkami střídavě k oběma. aby je vzájemně konfrontoval a spor vyhrotil. Dotazovaní hosté se snaží nejen odpovídat na otázky redaktora (to je jejich základní role v interview), ale i zpochybňovat či přímo vyvracet odpovědi druhého z hostí (role často neméně důležitá). Hosté komunikují nejen s redaktorem, ale komunikují i mezi sebou navzájem, ať už skrytě, či zjevně, s cílem získat diváka na svou stranu. Stať analyzuje toto interview v souvislosti s otázkou typologie debat a debat založených na konfliktu zájmů a konfliktu hodnot.
Determination of modulated chlorophyll fluorescence coupled to measurements of the net photosynthetic rate (P^) leaf water potential has heen assessed as a screening method to score a set of twenty genotypes of barley {Hordeum vulgare L.) for drought tolerance. These methods can be ušed as rapid screening tests for water stress tolerance in barley, although applied alone they are appropriate indicators for a severe water stress. For genotypes growing under a mild water stress, it is necessary to use several screening tests simultaneously. Drought tolerant genotypes show smaller variations of photochemical quenching, P^, water use efficiency and leaf temperature than the drought sensitive ones.
During a survey of the parasites of freshwater fishes from cenotes (sinkholes) of the Yucatan Peninsula the following species of monogeneans were found on cichlid, pimelodid, characid and poeciliid fishes: Sciadicleithrum mexicanum Kritsky, Vidal-Martinez et Rodriguez-Canul, 1994 from C.ichlasoma urophthalmus (Giinther) (type host), Cichlasoma friedrichsthali (Heckel), Cichlasoma octofasciatum (Regan), and Cichlasoma synspilum Hubbs, all new host records; Sciadicleithrum meekii Mcndoza-Franco, Scholz et Vidal-Martinez, 1997 from Cichlasoma meeki (Brind); Urocleidoides chavarriai (Price, 1938) and Urocleidoides travassosi (Price, 1938) from Rhamdia guatemalensis (Günther); Urocleidoides costaricensis (Price et Bussing, 1967), Urocleidoides heteroancistrium (Price et Bussing, 1968), Urocleidoides anops Kritsky et Thatcher, 1974, Anacanthocotyle anacanthocolyle Kritsky et Fritts, 1970, and Gyrodaclylus neotropicalis Kritsky et Fritts, 1970 from Aslyanax fasciatus; and Gyrodactylus sp. from Gambusia yucatana Regan. Urocleidoides chavarriai, U. travassosi, U. costaricensis, U. heteroancistrium, U. anops, Anacanthocotyle anacanthocotyle and Gyrodactylus neotropicalis are reported from North America (Mexico) for the first time. These findings support the idea about the dispersion of freshwater fishes and their monogenean parasites from South America through Central America to southeastern Mexico, following the emergence of the Panamanian isthmus between 2 and 5 million years ago.