Lateral asymmetry in signalling traits enables males to strategically exploit their best side. In many animals, both body colouration and fluctuating asymmetry are signals of male attractiveness. We demonstrated experimentally that even sexually naïve male Poecilia wingei were able to identify their most attractive side (i.e. that with a higher proportion of carotenoid pigmentation) and use it preferentially during courtship. Notably, males retained their strategic signalling in a male-biased social environment, whereas they ceased to signal strategically in a female-biased environment. The degree of asymmetry in colouration did not affect overall courtship activity. Strategic lateralization in courtship displays was strongest and most repeatable in the male-biased social environment where males competed with rivals for matings. Individual asymmetry in colouration changed considerably over a period of 3 months. This suggests that colouration is a dynamic feature during adulthood and that males are capable of tracking and strategically exploiting their lateral asymmetry in accordance with their social environment.

• Klíčová slova
• Poecilia wingei, behavioural laterality, experience, sidedness, sigmoid display, social environment,
• MeSH
• biologické modely MeSH
• karotenoidy metabolismus   MeSH
• sexuální chování zvířat fyziologie   MeSH
• sociální chování * MeSH
• živorodka fyziologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• karotenoidy MeSH

Unisexual reproduction, which generates clonal offspring, is an alternative strategy to sexual breeding and occurs even in vertebrates. A wide range of non-sexual reproductive modes have been described, and one of the least understood questions is how such pathways emerged and how they mechanistically proceed. The Amazon molly, Poecilia formosa, needs sperm from males of related species to trigger the parthenogenetic development of diploid eggs. However, the mechanism, of how the unreduced female gametes are produced, remains unclear. Cytological analyses revealed that the chromosomes of primary oocytes initiate pachytene but do not proceed to bivalent formation and meiotic crossovers. Comparing ovary transcriptomes of P. formosa and its sexual parental species revealed expression levels of meiosis-specific genes deviating from P. mexicana but not from P. latipinna. Furthermore, several meiosis genes show biased expression towards one of the two alleles from the parental genomes. We infer from our data that in the Amazon molly diploid oocytes are generated by apomixis due to a failure in the synapsis of homologous chromosomes. The fact that this failure is not reflected in the differential expression of known meiosis genes suggests the underlying molecular mechanism may be dysregulation on the protein level or misexpression of a so far unknown meiosis gene, and/or hybrid dysgenesis because of compromised interaction of proteins from diverged genomes.

• Klíčová slova
• Achiasmatic, Crossing-over, Meiosis, Oogenesis, Parthenogenesis, Recombination, Synaptonemal complex, Transcriptome,
• MeSH
• meióza MeSH
• sperma MeSH
• transkriptom MeSH
• živorodka * genetika   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Taiwan MeSH

Population variation in trophic niche is widespread among organisms and is of increasing interest given its role in both speciation and adaptation to changing environments. Trinidadian guppies (Poecilia reticulata) inhabiting stream reaches with different predation regimes have rapidly evolved divergent life history traits. Here, we investigated the effects of both predation and resource availability on guppy trophic niches by evaluating their gut contents, resource standing stocks, and δ15N and δ13C stable isotopes across five streams during the wet season. We found that guppies from low predation (LP) sites had a consistently higher trophic position and proportion of invertebrates in their guts and assimilate less epilithon than guppies from high predation (HP) sites. Higher trophic position was also associated with lower benthic invertebrate availability. Our results suggest that LP guppies could be more efficient invertebrate consumers, possibly as an evolutionary response to greater intraspecific competition for higher quality food. This may be intensified by seasonality, as wet season conditions can alter resource availability, feeding rates, and the intensity of intraspecific competition. Understanding how guppy diets vary among communities is critical to elucidating the role of niche shifts in mediating the link between environmental change and the evolution of life histories.

• MeSH
• biologická evoluce MeSH
• dieta * MeSH
• ekosystém * MeSH
• fyziologická adaptace fyziologie   MeSH
• populační dynamika MeSH
• predátorské chování fyziologie   MeSH
• řeky MeSH
• roční období MeSH
• zeměpis MeSH
• živorodka fyziologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Geografické názvy
• Západoindické souostroví MeSH

High rates of progestins consumption in the form of active ingredients in women's oral contraceptives and other hormonal preparations may lead to their increased concentrations in aquatic environments and subsequent harmful effect on fish reproduction. The objective of the present study was to assess the effect of etonogestrel, a third-generation synthetic progestin, on the reproductive behavior, fertility, gonads histology, and secondary sexual characteristics of male and female Endler's guppies (Poecilia wingei). Fish were subjected for 34 days to two concentrations of etonogestrel, including one possibly environmentally relevant (3.2 ng L-1) and one sublethal (320 ng L-1) concentration. A mating behavior study was subsequently conducted and revealed that the treatment with etonogestrel significantly reduced mating frequency in the exposed fish compared to controls. All the exposed females were unable to reproduce. In addition, female fish exposed to the highest level of etonogestrel were masculinized, as their anal fins and body coloration showed patterns similar to those of male fish. Etonogestrel-exposed females also had fewer developed oocytes. In conclusion, the low etonogestrel concentration (3.2 ng L-1) led to a reduction of mating activity in males without effect on their reproductive success, but it completely inhibited reproduction in females. Exposure to etonogestrel clearly has more severe consequences for females than males.

• Klíčová slova
• Fertility, Gonads, Mating, Sexual dimorphism, Steroid,
• MeSH
• chemické látky znečišťující vodu škodlivé účinky   MeSH
• desogestrel škodlivé účinky   MeSH
• fertilita účinky léků   MeSH
• gonády anatomie a histologie   účinky léků   MeSH
• kontraceptiva ženská škodlivé účinky   MeSH
• pohlavní dimorfismus MeSH
• rozmnožování účinky léků   MeSH
• sexuální chování zvířat účinky léků   MeSH
• živorodka anatomie a histologie   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chemické látky znečišťující vodu MeSH
• desogestrel MeSH
• etonogestrel MeSH Prohlížeč
• kontraceptiva ženská MeSH

The aim of this study is to assess the acute toxicity of silver nitrate in adult zebra fish and adult guppies and to compare the sensitivity of these species to this compound. Silver is a naturally occurring element in our environment and it combines with other elements such as sulfide, chloride, and nitrate. Silver, in the form of silver nitrate, is one of the most toxic metals affecting freshwater fish. Industry, particularly photographical and electrotechnical, is the major contributor of silver that is released into the environment. Tests of acute toxicity were performed on the most common species of aquarium fish, Danio rerio and Poecilia reticulata. Both zebra fish and guppies were exposed to progressive concentrations of silver nitrate; a semi-static method according to OECD 203 was used. In each test series, 6 tests of acute toxicity were conducted, with 10 fish used for each separate concentration and for the control group. The results (number of fish deaths in the individual test concentrations) were subjected to probit analysis (EKO-TOX 5.1 software) to determine the 96hLC(50) AgNO(3) values. The 96hLC(50) AgNO(3) value for the zebra fish was (mean±SEM) 15±0.52 µg/l and for the guppies was (mean±SEM) 17.14±5.43 µg/l. We didn't find any statistically significant difference between the sensitivity of zebra fish and guppies. The results reported in this study are in agreement with LC(50) values published in peer-reviewed literature, and conclude that AgNO(3) is one of the most toxic compounds known to fishery.

• Klíčová slova
• LC50, Zebra fish, fish, guppy, silver, susceptibility, toxicity,
• Publikační typ
• časopisecké články MeSH

Low-molecular mass proteins rich in cysteines called metallothioneins (MT) can be considered as markers for the pollution of the environment by metals. Here, we report on suggestion for an automated procedure for the isolation of MT followed by voltammetric analysis. Primarily, we optimized the automated detection of MT using an electrochemical analyser. It was found that the most sensitive and repeatable analyses are obtained at a temperature of 4 °C for the supporting electrolyte. Further, we optimized experimental conditions for the isolation of MT by using antibody-linked paramagnetic microparticles. Under the optimal conditions (4 h long interaction between the microparticles and MT), the microparticles were tested on isolation of various amounts of MT. The lowest isolated amount of MT by antibody-linked paramagnetic microparticles was 5 μg ml(-1) of MT (50 ng). The automated procedure of MT isolation was further tested on isolation of MT from guppy fish (Poecilia reticulata) treated with silver(i) ions (50 μM AgNO(3)). The whole process lasted less than five hours and was fully automated. We attempted to correlate these results with the standard method for MT isolation. The correlation coefficient is 0.9901, which confirms that results are in good agreement. Moreover, the concentration of silver ions in tissues of fish treated with Ag(i) ions was determined by high performance liquid chromatography with electrochemical detection.

• MeSH
• chemické látky znečišťující vodu toxicita   MeSH
• magnetismus MeSH
• metalothionein chemie   izolace a purifikace   metabolismus   MeSH
• monitorování životního prostředí metody   MeSH
• živorodka metabolismus   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chemické látky znečišťující vodu MeSH
• metalothionein MeSH

Neurons are the basic computational units of the brain, but brain size is the predominant surrogate measure of brain functional capacity in comparative and cognitive neuroscience. This approach is based on the assumption that larger brains harbor higher numbers of neurons and their connections, and therefore have a higher information-processing capacity. However, recent studies have shown that brain mass may be less strongly correlated with neuron counts than previously thought. Till now, no experimental test has been conducted to examine the relationship between evolutionary changes in brain size and the number of brain neurons. Here, we provide such a test by comparing neuron number in artificial selection lines of female guppies (Poecilia reticulata) with >15% difference in relative brain mass and numerous previously demonstrated cognitive differences. Using the isotropic fractionator, we demonstrate that large-brained females have a higher overall number of neurons than small-brained females, but similar neuronal densities. Importantly, this difference holds also for the telencephalon, a key region for cognition. Our study provides the first direct experimental evidence that selection for brain mass leads to matching changes in number of neurons and shows that brain size evolution is intimately linked to the evolution of neuron number and cognition.

• Klíčová slova
• Artificial selection, brain size, cognition, isotropic fractionator, number of neurons,
• MeSH
• biologická evoluce MeSH
• kognice MeSH
• modely neurologické MeSH
• mozek fyziologie   MeSH
• neurony fyziologie   MeSH
• selekce (genetika) * MeSH
• velikost orgánu MeSH
• živorodka genetika   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

OBJECTIVES: Formaldehyde, sodium chloride and potassium permanganate belong to the commonly used substances for fish treatment. The aim is to define and compare their acute toxicity and therapeutic index between two fish species - Danio rerio and Poecilia reticulata. DESIGN: To determine acute toxicity of these compounds, the semistatic method was implemented in compliance with the OECD No. 203 (Fish acute toxicity test). In each test series, 4 acute toxicity tests were performed. The results were subjected to the probit analysis to determine the 96hLC50 values. Therapeutic index (TI) was calculated with respect to short-term LC50 and effective therapeutic concentrations commonly used for fish treatment. RESULTS: The mean 96hLC50 values for sodium chloride were 21.69 +/- 0.92 g l-1 (TI = 1.4) for P. reticulata and 10.39 +/- 0.12 g l-1 (TI = 1.0) for D. rerio. The acute toxicity of formaldehyde for D. rerio expressed as 96LC50 was 0.12 +/- 0.003 ml l-1 (TI = 5.24) and for P. reticulata 0.1 +/- 0.003 ml l-1 (TI = 4.9). The acute toxicity of potassium permanganate for D. rerio expressed as 96LC50 was 1.25 +/- 0.15 mg l-1(TI = 1.5) and for P. reticulata 1.43 +/- 0.05 mg l-1 (TI = 2). CONCLUSION: P. reticulata showed significantly higher (p < 0.05) tolerance to sodium chloride than D. rerio, whereas D. rerio showed significantly higher (p < 0.05) tolerance to formaldehyde than P. reticulata. The acute toxicity of potassium permanganate was comparable for both fish species. Calculated therapeutic indexes of all tested substances were low; therefore it is important to conduct preliminary tolerance tests before application of treatment baths.

• MeSH
• časové faktory MeSH
• chlorid sodný aplikace a dávkování   toxicita   MeSH
• dánio pruhované * MeSH
• dezinficiencia aplikace a dávkování   toxicita   MeSH
• druhová specificita MeSH
• formaldehyd aplikace a dávkování   toxicita   MeSH
• manganistan draselný aplikace a dávkování   toxicita   MeSH
• testy akutní toxicity MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• živorodka * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• chlorid sodný MeSH
• dezinficiencia MeSH
• formaldehyd MeSH
• manganistan draselný MeSH

• Klíčová slova
• COLCHICINE *, FISH *,
• MeSH
• kolchicin * MeSH
• ryby * MeSH
• živorodka * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• kolchicin * MeSH

In this paper, the quantitative post-embryonic development of the Asian freshwater fish nematode Camallanus cotti Fujita, 1927, is described. Larval and adult morphometrics were obtained by following the parasite's life cycle experimentally using copepods Macrocyclops albidus (Jurine) as intermediate host and guppies Poecilia reticulata (Peters), southern platyfish Xiphophorus maculatus (Günther) and paradise fish Macropodus opercularis (L.) as definitive host. Additionally, adult worms were obtained from heavily infected paradise fish imported from Singapore. It is suggested that the gradual change in proportions of the worm's somatic body parts reflects the specific ecological role of each developmental stage. The free-living infective first-stage larva seems to be adapted for transmission, as indicated by its relatively long tail, designed to generate host-attracting movements, and its non-functional intestine. The second- and third-stage larvae from the copepod intermediate host seem mainly to invest in trophic functionality, i.e., the development of the buccal capsule and the oesophagus, which are crucial structures for the worm's successful establishment in the definitive fish host. Once in the fish intestine, the larvae enter a period of considerable growth. After the fourth (i.e., last) moult, a 72% increase in average female body length occurs. This is accompanied by doubling the average vulva-tail tip distance and the average tail length. The length of the female hind body expands in an accelerating allometric fashion, and seems to be closely linked to the posterior-wards expansion of the uterus. In the males however, growth seems to cease after the final moult. We conclude that female post-maturational body size, but especially the length of the hind body and the tail, are closely related to reproductive state, i.e., the developmental stage of the offspring in the uterus, and, probably, the worms' age. Any future taxonomical studies of camallanids in general, and C. cotti in particular, should thus be aware of the reproductive state of the females used.

• MeSH
• Copepoda parazitologie   MeSH
• hlístice anatomie a histologie   růst a vývoj   MeSH
• neparametrická statistika MeSH
• živorodka parazitologie   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Singapur MeSH