Szexuális szelekció a barna varangynál (Bufo bufo). - A párválasztás evolúciós okai és következményei. = Sexual selection in the common toad (Bufo bufo). - Evolutionary causes and consequences of mate choice.

(1) Barna varangy (Bufo bufo) nőstényeknél nem találtunk közvetlen párválasztásra utaló jelet. (2) Barna varangy hímek limitált spermiumkészleteik miatt csak kis számú sikeres párzásra képesek egy nászidőszakon belül. A nagyobb, így több párzásra esélyes hímek ugyanakkor nem rendelkeztek több spermiummal a nászidőszak elején. (3) Barna varangy ebihalak érzékelték a ragadozók (szitakötőlárvák) jelenlétét, fenotípusos válaszuk azonban a vizsgált ragadozóval szemben hatástalannak bizonyult. (4) Közvetett nőstényválaszt az erdei békánál (Rana dalmatina) vizsgálva azt tapasztaltuk, hogy ha a nőstényekkel alkalmatlan hím állt párba, a nőstények késleltették a peterakást, kevesebb petét raktak, vagy ismételt peterakással biztosították legalább petéik egy részének megtermékenyítését. (5) Erdei békáknál a hímek párbaállási sebessége független volt a testmérettől, ugyanakkor a nagyobb hímek sikeresebbek voltak a párzási partnerek megszerzésében és megtartásában. (6) Ragadozó-specifikus, adaptív, több külső és belső tényező által befolyásolt indukált védekezést mutattunk ki erdei béka ebihalaknál. (7) Mocsári békáknál (R. arvalis) az intenzívebb színezetű hímeknek nagyobb volt a párzási sikere természetes populációkban, ugyanakkor a színezet és a hímek rendelkezésére álló spermiumok száma között nem találtunk összefüggést. (8) Adaptáltuk a mesterséges megtermékenyítés módszerét petezsinórt rakó kétéltűekre. (9) A párválasztás közvetett előnyeiről elméleti összefoglaló cikket írtunk. | (1) We did not observe direct female choice in common toad (Bufo bufo) females. (2) Common toad males were able to participate in only a few successful matings within a breeding season due to limited sperm stocks. Larger males, that are more likely to obtain matings repeatedly, however, did not dispose over more sperm at the beginning of the breeding season. (3) Common toad tadpoles could sense the presence of predators (dragonfly nymphs), but their phenotypic response was not efficient against the predator. (4) When investigating indirect female choice in agile frogs (Rana dalmatina), we observed that when mated with a non-matching male, females delayed egg-deposition, laid fewer eggs or released eggs repeatedly to obtain at least some fertilizations. (5) Mating speed of agile frog males was not related to their body size, but larger males were more successful in performing take-overs and in fending off take-over attempts of other males. (6) We found predator-specific and adaptive induced defenses that seemed to be fine-tuned based on several external and internal factors in agile frog tadpoles. (7) Moor frog (R. arvalis) males exhibiting a more conspicuous nuptial coloration had a higher mating success in natural populations, but we found no relationship between male coloration and the number of sperm stored in the testes. (8) We adapted the method of artificial fertilization to amphibians laying egg-strings. (9) We wrote a review about indirect benefits of mate choice

Social environment and reproductive interference affect reproductive success in the frog Rana latastei

Variation in the social environment produces selection on morphological and behavioral traits. It is less clear how the social environment generates variation in demography through behavioral mechanisms. Theory suggests that one aspect of social environment, relative abundance of heterospecifics, influences the intensity of reproductive interference and its demographic effects. These effects are countered by species recognition and female preferences. We studied the effects of social environment on reproductive success in replicated, mixed breeding populations of two ranid frogs, Rana latastei and Rana dalmatina, the former being of international conservation concern. We manipulated the social environment of female R. latastei experimentally by varying the relative abundance of potential conspecific and heterospecific sexual partners. We measured amplexus frequency and recorded the reproductive success of R. latastei females. When conspecific males were relatively uncommon, (1) the absolute and relative frequencies of conspecific amplexus decreased, indicating a breakdown of sexual isolation, (2) oviposition was less frequent, and (3) the percentage of viable embryos in deposited clutches decreased. R. latastei females in an environment of low relative conspecific abundance (1:5, R. Latastei:R. dalmatina) demonstrated 6.8% the reproductive success of females in an environment exclusively with conspecifics. We present a model for the dependence of conspecific amplexus on the social environment. We discuss several mechanisms that may influence reproduction by R. latastei, and we support conservation of the species' preferred habitat to reduce opportunities for reproductive interference that occur at shared breeding site

Kétéltűeket sujtó járvány, a kitridiomikózis: A kórokozó Achilles-sarka

Az állat- és növényvilágban is megtalálhatók a járványokat okozó kórokozók, amelyek ugyanúgy viselkednek, mint az embereket fertőző patogének. Ám míg az emberekre is átterjedő járványokról a fejlett orvosi hálózatnak és a médiának köszönhetően hamar értesülünk, különösen, ha nagy a halálos áldozatok száma, addig az állatok ezreit vagy akár millióit elpusztító ragályos betegségekről gyakran megkésve vagy csak utólag, populációk, netán egész fajok kipusztulása után szerzünk tudomást. A kitridiomikózis az elmúlt 50 év alatt 500 faj hanyatlásához vezetett, közülük 90 faj véglegesen eltűnt, és további sok száz faj létét fenyegeti világszerte

Responses in the diet composition of the Common frog (Rana temporaria) to the stochastic gradation of Autumnal moth (Epirrita autumnata) larvae

We studied the feeding ecology of the common frog Rana temporaria in a population located at the subarctic taiga-tundra frontier in Finland over two consecutive years (2002, 2003). In the summer of 2003, an unexpected gradation of autumnal moth (Epirrita autumnata) larvae occurred at our study site. This situation allowed us to study the changes in the diet composition of the same common frog population between a presumably average and an extraordinary year with respect to the gradation of one of the prey species. We found clear evidence for the opportunistic feeding behaviour of common frogs in a natural population, as reflected by the mass appearance of Epirrita autumnata larvae in the frogs’ stomach content in 2003. Further, our results draw attention to the fact that a one-year study on the feeding ecology of an opportunistic species can result in flawed conclusions

Variation in fertilisation abilities between hemiclonal hybrid and sexual parental males of sympatric water frogs ( Rana lessonae , R. esculenta , R. ridibunda )

In many species, males and females mate with multiple partners, which gives rise to sperm competition and multiple paternity. The experiments on water frogs presented here demonstrate that such sperm competition can affect the structure and dynamics of mixed-species communities. The hybrid frog Rana esculenta (LR) mates with one of its parental species, usually R. lessonae (LL), although in some areas R. ridibunda (RR), to regain the premeiotically eliminated parental genome ("hybridogenesis"). Mixed LL/LR-populations are stable although hybrid numbers should continuously increase at the expense of parental animals, because of differences in female fecundity and other factors. This would finally lead to the extinction of the sexual host, followed by that of the sexual parasite, unless the reproductive superiority of R. esculenta is reduced by other factors, such as lower hybrid male fertility. Eggs from LL- and LR-females were fertilised in vitro by single- and multi-male sperm suspensions of LL-, LR- and RR-males. In all experiments, the proportion of offspring sired by R. esculenta sperm was significantly lower than that sired by R. lessonae or R. ridibunda sperm. Gonad mass, sperm morphology, sperm swimming velocity, and sperm survival did not explain these differences in fertilisation success; nor did gamete recognition and compatibility. Sperm density was the only trait that paralleled fertilisation success, but it offers no explanation either, because densities were equalised for the in-vitro fertilisations. In natural LL/LR populations, the significantly smaller amount, poorer competitive ability and lower long-term survival of R. esculenta compared to R. lessonae sperm will reduce the initial reproductive superiority of hybrids and contribute to the stabilisation of mixed water-frog populations. Differences in fertilisation ability are also likely to be relevant for the structure and dynamics of several other systems with encounters between eggs and sperm from different genotypes, ecotypes, ploidy levels and/or specie

Post-Meiotic Intra-Testicular Sperm Senescence in a Wild Vertebrate

There is growing interest in sperm senescence, both in its underlying mechanisms and evolutionary consequences, because it can impact the evolution of numerous life history traits. Previous studies have documented various types of sperm senescence, but evidence of post-meiotic intra-testicular sperm senescence in wild animals is lacking. To assess such senescence, we studied within-season changes in sperm motility in the common toad (Bufo bufo), where males produce all sperm prior to the breeding season. We found that males exposed to experimentally induced re-hibernation at the start of the breeding season, that is to experimentally lowered metabolic rates, stored sperm of significantly higher motility than males that were kept under seminatural conditions without females throughout the breeding season. This finding indicates that re-hibernation slows normal rates of sperm ageing and constitutes the first evidence to our knowledge of post-meiotic intra-testicular sperm senescence in a wild vertebrate. We also found that in males kept in seminatural conditions, sperm motility was positively related to the number of matings a male achieved. Thus, our results suggest that post-meiotic intratesticular sperm senescence does not have a genetically fixed rate and may be modulated by temperature and possibly by mating opportunities

Efficiency against the Two-spotted spider mite Tetranychus urticae and prey-age-related choice of three predatory mites

Specialist and generalist predator mites have been recommended against the Two-spotted spider mite (Tetranycus urticae) as biological control agents, but their effectiveness in population regulation has been rarely examined under circumstances when prey had the opportunity to express antipredatory responses. We tested the efficiency and preference for prey life stages of three predator mites, one specialist (Phytoseiulus persimilis) and two generalists (Amblyseius swirskii and Iphiseius degenerans). We used two predator densities and performed the experiment under ‘seminatural’ conditions. We found that significantly less eggs and adult spider mites survived in the presence of P. persimilis compared to the control group, and this predator mite consumed more eggs at high density than the other predators. In the presence of A. swirskii fewer adult spider mites survived at low density compared to the control, whereas egg survival was lower than in the control group at both densities. In the presence of I. degenerans, only the survival of eggs was lower than in the control group and only at high density. Our results suggest that the generalist A. swirskii, but not I. degenerans, may be efficient in regulating prey populations through egg consumption, and, thus, represents an alternative to the effective specialist predator

How to disinfect anuran eggs? Sensitivity of anuran embryos to chemicals widely used for the disinfection of larval and post‐metamorphic amphibians

Emerging infectious diseases are major drivers of global and local amphibian biodiversity loss. Developing effective disinfection methods to manage the impact of diseases in wild and captive ‘ark’ populations is therefore an important goal in amphibian conservation. While chemical disinfectants have been used safely and effectively in larval and adult amphibians infected with pathogenic microbes, their applicability to amphibian egg masses has remained untested. To bridge this gap, we experimentally exposed embryos of the common toad (Bufo bufo) and agile frog (Rana dalmatina) to three widely used disinfectants: voriconazole, chloramphenicol and chlorogen-sesquihydrate. For three days we exposed portions of egg masses to these disinfectants at 1×, 2×, 5× and 10× of the concentration recommended for the disinfection of tadpoles and adults. Subsequently, we recorded embryonic and larval survival, as well as larval body mass and the incidence of abnormalities twelve days after hatching. Application of voriconazole had species and concentration-dependent negative impacts on survival and body mass and caused marked malformations in the viscerocranial structure of B. bufo tadpoles. Exposure to chlorogen-sesquihydrate also resulted in significant mortality in B. bufo embryos and negatively affected body mass of R. dalmatina larvae. Chloramphenicol had little negative effects on embryos or larvae in either species. Based on these results, the application of voriconazole and chlorogen-sesquihydrate cannot be recommended for the disinfection of amphibian eggs, whereas treatment with chloramphenicol appears to be a safe method for eliminating potential pathogens from anuran egg masses and their immediate aquatic environment

Experimental evidence for beneficial effects of projected climate change on hibernating amphibians

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