Status of the Nightingale Luscinia megarhynchos in Britain at the end of the 20th Century with particular reference to climate change

Capsule The population level may be unchanged but the range has contracted.

Aims To establish the current status of the Nightingale in Britain and explore causes for any changes.

Methods Over 3000 sites where Nightingales were known to have occurred since 1980 were surveyed by volunteers between mid-April and early June 1999. A selection of 135 random tetrads were also surveyed to gauge the efficiency of the volunteer survey in locating Nightingales.

Results The survey located 4565 singing male Nightingales while the random tetrad surveys suggest that c. 32% of birds occur away from known sites, increasing the estimate for the British Nightingale population to 6700 males (95% confidence limits 5600–9350) in 1999. A higher proportion of Nightingales was found in scrub (46.7%) than in 1976 (28.4%), suggesting a recent shift in habitat use.

Conclusion There is little evidence of a change in the size of the British Nightingale population, probably because earlier surveys underestimated numbers. The range has contracted markedly over the last few decades and numbers outside the core areas in southeast England are now low. Changes in habitat quality and increasing deer populations have caused decreases on a local scale. Changes in climate on the breeding grounds and general changes in climate or habitat suitability on the African winter quarters are likely to be important in influencing the distribution within England. Models of the effects of future climate change on Nightingale distribution in Britain predict that numbers and range should increase over the next few decades.     

Experimental evidence that deer browsing reduces habitat suitability for breeding Common Nightingales Luscinia megarhynchos

The ecological impacts of increasing populations of deer (Cervidae) in Europe and North America are becoming more widespread and pronounced. Within Britain, it has been suggested that declines in several woodland bird species, particularly those dependent on dense understorey vegetation, may be at least partly due to these effects. Here we present experimental evidence of the effects of deer browsing on the fine‐scale habitat selection and habitat use by a bird species in Europe. The study was conducted in a wood in eastern England where a decrease in Common Nightingale Luscinia megarhynchos numbers has coincided with a large increase in deer numbers. Eight woodland plots were cut to produce young coppice regrowth (a favoured habitat for Nightingales). Deer were excluded from half of each plot using steel fences, thus creating eight experimental pairs of exclosures (unbrowsed) and controls (browsed). Radiotelemetry and territory mapping of male Nightingales showed strong selection of exclosures. The density of territories was 15 times greater in the exclosures than in grazed controls. Selection for exclosures was significant for the minimum convex polygon, 95% kernel and 50% core home‐ranges used by seven radiotracked males. Tracked birds spent 69% of their time in the 6% of the study area protected from deer. Intensified browsing by deer influenced local settlement patterns of Nightingales, supporting the conclusion that increased deer populations are likely to have contributed to declines of Nightingales in Britain, and potentially those of other bird species dependent on dense understorey.     

新疆鸟类环志与回收

2001年8月与14－26日在新疆阿勒泰,吐鲁番的8个环志地点进行了秋际鸟类环志工作。环志鸟类233只,约33种,多以莺亚科（Sylviinae)和鸫亚科（Turdinae)的种类为主。其中的新疆歌鸲（Luscinia sp.)等17种鸟类均属于中国首次环志种类,占环志种数的53％。     

Nightingales Luscinia megarhynchos in scrub habitats in the southern fens of East Anglia, England: associations with soil type and vegetation structure

The southeast corner of the East Anglian Fens supports a large concentration of Nightingale Luscinia megarhynchos territories. A total of 382 territories were located in extensive surveys in 1999 and 2000, probably representing over 5% of the English population. Transect counts revealed that the Fenland population is restricted in distribution and is associated with localized thickets of scrub. The highest densities are found on humus‐rich soils, suggesting that soil type, in addition to habitat availability, may have a strong influence on the Nightingale's distribution in this region. This paper provides the first assessment of habitat requirements of the Nightingale in scrub, which now forms a principal habitat for the species in England. Detailed studies of the attributes of over 100 Nightingale territories revealed subtle differences in the vegetation structure of these thickets when compared with paired, unoccupied, but apparently similar thickets. The Nightingale territories tended to have a higher proportion of bare ground or short vegetation in the field layer under the canopy, whereas paired sites were more likely to have low field layer vegetation beneath the canopy. The bare ground within the thickets is a feature of shading beneath very dense foliage cover. Within Nightingale territories, low field layer volume and shrub twig volume at the thicket edges was higher than in unoccupied thickets. The differences detected in vegetation structure suggest that a dense and continuous canopy forming a shell over bare ground but with dense low foliage at thicket edges provides the ideal vegetation structure for Nightingales in scrub habitats. Our study suggests that Nightingales occupy scrub of a very specific structure, and specific stage in vegetation succession. This structure probably provides an optimal combination of foraging habitat, microclimate and cover from predators. It is suggested that humus‐rich soils may be preferred because they may support a particularly rich source of invertebrate food, but this remains to be tested empirically.     

Seasonal changes in the nocturnal singing routines of Common Nightingales Luscinia megarhynchos

Male Common Nightingales Luscinia megarhynchos famously sing at night. There are two distinct types of nocturnal singing routine (the dusk-to-dawn pattern of variation in song rate): (1) dusk and dawn choruses, with little or no song during the middle of the night; (2) a rapid increase in song rate after dusk, reaching a broad peak in the middle of the night, declining towards dawn, and followed by a dawn chorus. Males sing different nocturnal singing routines at different times in the breeding season. Earlier in the breeding season, most males sing Type 2 routines. Later in the breeding season, most males sing Type 1 routines, as do birds on the wintering grounds. At least some individuals may also sing Type 1 routines during the first few days after their arrival on their breeding territories, before the arrival of females. The main function of nocturnal song appears to be mate attraction. The patterns of variation in song rate over the course of the night are qualitatively similar to those predicted by stochastic dynamic programming (SDP) models of daily singing and foraging routines, for birds that do not forage at night, in circumstances when birds can pair at night (Type 2 routines), and when they cannot (Type 1 routines). The observed seasonal changes in the types of routine sung are also consistent with the predictions of these models.     

First-Year Common Nightingales (Luscinia megarhynchos) Have Smaller Song-Type Repertoire Sizes Than Older Males

Based on the assumptions that birdsong indicates male quality and that quality is related to age, one might expect older birds to signal their age. That is, in addition to actual body condition, at least some song features should vary with age, presumably towards more complexity. We investigated this issue by comparing repertoire sizes of free‐ranging common nightingale males in their first breeding season with those of older males. Nightingales are a good model species as they are open‐ended learners, where song acquisition is not confined to an early sensitive period of learning. Moreover, nightingales develop an extraordinarily large song‐type repertoire (approx. 180 different song types per male), and differences in repertoire size among males are pronounced. We analysed repertoire characteristics of the nocturnal song of nine nightingales in their first breeding season and compared them with the songs of nine older males. The repertoire size of older males was on average 53% larger than that of yearlings. When analysing two song categories of nightingales, whistle and non‐whistle songs separately, we found similar results. Our findings show marked differences in repertoire size between age categories, suggesting that this song feature may reflect a male's age. We discuss those mechanisms that may constrain the development of larger repertoires in first‐year males. Whether repertoire sizes are crucial for female mate choice or in vocal interactions among conspecific males remains open to further investigations.     

The costs of singing in nightingales

The costs of singing in birds are poorly understood. One potential type of cost is a metabolic cost of singing. Previous studies have measured short-term changes in oxygen consumption associated with bouts of vocalizations, with equivocal results. In this study, I used an alternative approach to measuring the metabolic cost of singing, by measuring overnight loss of body mass, in male common nightingales, Luscinia megarhynchos, singing at night at different rates. Nightingales were shown not to forage at night. They reached a higher mass at dusk prior to singing more at night, and lost more mass overnight when dusk mass and overnight song rate were high. These results show that singing at night is associated with increased overnight consumption of body reserves, which represents a significant metabolic cost of singing at night. However, the correlation between dusk mass and overnight song rate makes it impossible to determine whether these costs arise from the energetic costs of the singing itself, or from the metabolic costs of the additional body reserves laid down at dusk on nights when song rate was high. There are also likely to be costs associated with accumulating and carrying these extra body reserves during daylight, as well as other potential costs of singing such as an increased risk of predation. These results are consistent with those models of signalling in biology that predict or assume that honest signals are costly. Copyright 2002 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.     

The predictive value of trill performance in a large repertoire songbird,the nightingale Luscinia megarhynchos

In animal communication, elaborate signals have been shown to be under sexual selection and often to reliably indicate a signaler's quality, condition, or motivation. For instance, the performance of physically challenging signals such as trills – i.e. rapidly repeated elements of broad frequency bandwidth – is considered to reflect signaler quality. Nightingales Luscinia megarhynchos are renowned for their outstanding song repertoire sizes, and most songs include a variety of complex trills. In the present study, we examined whether performance of trills can reliably reflect male quality. We show that vocal performance of trills predicts the age of a male. Older males sang trills that were closer to the performance limit than did younger males. Moreover, males with narrower beaks sang more consistent trills than did males with wider beaks. Vocal performance of trills, however, did not significantly predict other measures of biometric quality such as body size or body condition of the males. The findings suggest that receivers could benefit from the predictive value of physically demanding song traits in assessing age as an important quality component of potential mates or rivals. Particularly in species with high singing versatility, signaler assessment based on readily assessable structures may be adaptive, as this will allow receivers to quickly gather relevant information about the singer without attending to the full song repertoire.     

Art- und Mischgesang von Nachtigall und Sprosser (Luscinia megarhynchos, L. luscinia)

Zusammenfassung Die Gesänge beider Arten unterscheiden sich in der Strophenlänge [Nachtigall (Ng) im Mittel 3,1 s, Sprosser (Sp) etwa 6 s], im Strophenaufbau (Gesamtzahl der Phrasen, Anzahl und Lage von echten Phrasen) und in einer beim Sp hörbar langsameren Vortragsweise (Silben·s^–1), sowie im Auftreten von jeweils artcharakteristischen Phrasen. Die hier untersuchten Sp weichen in den Silbentypen ihrer Kastagnetten- und Schnatter-Phrasen stark von einer finnischen Population ab (Dialektbildung beim Sp). Mischsänger trugen in unterschiedlichen Anteilen arteigene Strophen, solche der Zwillingsart und Mischstrophen vor. Während ihre Artstrophen weitgehend denen normal singender Artgenossen entsprachen, waren die Fremdstrophen in allen untersuchten Parametern sehr ähnlich denen des Vorbildes. Eine geringe gegenseitige Beeinflussung beider Gesangsformen kann jedoch nicht ausgeschlossen werden. Von 239 untersuchten Sp- waren 67 (28%) Mischsänger. Ihr Anteil blieb über neun Jahre gleich. Wahrscheinlich gab es weitere Individuen mit einem unerkannten geringen Anteil fremder Lautmuster. Unter mehr als 200 Ng fand sich ein Mischsänger; dies ist der erste Nachweis bei dieser Art. Der Mischgesang ist wahrscheinlich auf Fehler beim Gesangslernen zurückzuführen. Die Kopierfehler werden innerhalb der Sp-Population tradiert. Sp-Mischsänger waren in 12 Fällen erfolgreich konspezifisch verpaart. Möglicherweise wird der Mischgesang beim Sp durch einen Selektionsdruck auf die Ausbildung interspezifischer Reviere begünstigt (character convergence). Sechsmal kam es zur Bastardierung mit der Zwillingsart, wobei der Mischgesang der beteiligten als hauptsächliche Ursache angesehen wird. Dennoch ist gegen Sp-Mischsänger wahrscheinlich keine Selektion wirksam. Mischgesang verschafft ihnen möglicherweise einen von der Populationsdichte abhängigen Selektionsvorteil.

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Species-specific song and mixed singing of Nightingale and Thrush Nightingale (Luscinia megarhynchos, L. luscinia)

Summary In Schleswig-Holstein (northern FRG), the sibling species Nightingale (Ng) and Thrush Nightingale (Sprosser, Sp) are sympatric. Here their respective ranges form the most northwestern part of the zone of overlap. In 1976–1984, the song of both species was investigated. Species-specific songs (Strophen) differ in length (Ng mean 3,1 s, Sp about 6 s), structure (total number of phrases, number and position of real phrases built up by repeated syllables), and by a slower speed (syllables·s^–1) in the Thrush Nightingale's songs. Both species dispose of species-characteristic phrases. In the castanet phrases and in the rattling phrases the Thrush Nightingales showed a quite different syllable type repertoire compared with a Finnish population (song dialect in this species). Mixed singers performed species-specific songs as well as songs which were heterospecific or mixed up of vocal patterns of both species. Their species-specific songs were highly equivalent to those of normal singing conspecifics, whereas all investigated parameters of the heterospecific songs were very similar to those of the imitated model. A possible slight mutual influence of both forms on each other can, however, not be excluded. Out of 239 Thrush Nightingales examined 67 (28 %) were mixed singers. The annual proportion in the population remained more or less constant during nine years. Presumably there were further individuals having only a small unrecognized amount of alien song patterns in their repertoire. In the Nightingale, only one out of more than 200 studied was a mixed singer. This is the first proof for mixed song in this species.Mixed singing is most probably due to misdirected song learning. The copying errors are transmitted within the Thrush Nightingale population by cultural tradition. In 12 cases mixed singing paired successfully with conspecific . Mixed song is here possibly favoured by a selective pressure on the development of interspecific territories (character convergence). In 6 cases, however, where hybridisation with the sibling species was observed, these mixed breedings could mainly be attributed to mixed singing of the involved. Nevertheless, there is probably no selection against mixed singing Thrush Nightingales. Dependent on population density it might even be advantageous for the birds to exhibit mixed song.

     

Temporal patterns of territory settlement and detectability in mated and unmated Nightingales Luscinia megarhynchos

In many bird species the sex ratio of adults is male-biased, which is likely to have consequences for the ecology as well as for the conservation of a species. For example, when some males remain unpaired in a population, there should be strong selection on behavioural traits that enhance pairing success. A surplus of males is also likely to have important implications for the interpretation of breeding bird survey data. In our study population of Nightingales Luscinia megarhynchos , about half of the males stayed unpaired, suggesting that the number of males encountered singing was greater than the number of breeding pairs. Furthermore, the detectability (the probability of encountering a male singing) of mated males was only two-thirds that of unmated males when censused in the morning or late in the breeding season. The relative detectability was more similar early in the season and during the twilight periods before sunrise and after sunset. Males that arrived earlier on the breeding grounds were more successful in attracting a mate than males arriving later. Some of the unmated males deserted their territories and prospected areas up to 4000 m distant, whereas others settled on the study site only late in the season and may actually have changed territories. We suggest that adult sex ratios and the time of the census should be taken into account when interpreting the results of breeding bird surveys.     

The Causes and Evolutionary Consequences of Mixed Singing in Two Hybridizing Songbird Species (Luscinia spp.)

Bird song plays an important role in the establishment and maintenance of prezygotic reproductive barriers. When two closely related species come into secondary contact, song convergence caused by acquisition of heterospecific songs into the birds’ repertoires is often observed. The proximate mechanisms responsible for such mixed singing, and its effect on the speciation process, are poorly understood. We used a combination of genetic and bioacoustic analyses to test whether mixed singing observed in the secondary contact zone of two passerine birds, the Thrush Nightingale (Luscinia luscinia) and the Common Nightingale (L. megarhynchos), is caused by introgressive hybridization. We analysed song recordings of both species from allopatric and sympatric populations together with genotype data from one mitochondrial and seven nuclear loci. Semi-automated comparisons of our recordings with an extensive catalogue of Common Nightingale song types confirmed that most of the analysed sympatric Thrush Nightingale males were ‘mixed singers’ that use heterospecific song types in their repertoires. None of these ‘mixed singers’ possessed any alleles introgressed from the Common Nightingale, suggesting that they were not backcross hybrids. We also analysed songs of five individuals with intermediate phenotype, which were identified as F₁ hybrids between the Thrush Nightingale female and the Common Nightingale male by genetic analysis. Songs of three of these hybrids corresponded to the paternal species (Common Nightingale) but the remaining two sung a mixed song. Our results suggest that although hybridization might increase the tendency for learning songs from both parental species, interspecific cultural transmission is the major proximate mechanism explaining the occurrence of mixed singers among the sympatric Thrush Nightingales. We also provide evidence that mixed singing does not substantially increase the rate of interspecific hybridization and discuss the possible adaptive value of this phenomenon in nightingales.     

Egg Discrimination in an Open Nesting Passerine Under Dim Light Conditions

Many hosts of avian brood parasites such as the common cuckoo (Cuculus canorus) show refined egg discrimination behaviour. Egg recognition in most open‐nesting hosts seems to be based entirely on differences in colour. However, hole‐ and dome‐nesting hosts may rely largely on luminance contrasts. Here, we studied egg rejection behaviour in nightingales (Luscinia megarhynchos), an open‐nesting species that nests in deeply shadowed positions and lays very specific dark olive‐green eggs. Although being theoretically suitable as hosts of the cuckoo, nightingales are very rarely parasitized and no cuckoo egg morph mimicking nightingale eggs is known. Thus, we predicted high rejection rate of foreign eggs, but because of the dim nesting environments, luminance contrasts would be an important cue in egg rejection decisions, similar to cavity‐ or dome‐nesting species. We experimentally parasitized nightingale nests with two groups of model egg types: ‘bright eggs’ and ‘dark eggs’. Within each group, one of the egg types was an effective match while the other type was a poor colour match (whitish vs. pale blue and olive‐green vs. black).We used a discrimination visual model to quantify host‐model egg similarity and compared egg rejection predicted by the model with the observed rejection pattern. Consistent with a scenario of largely luminance‐based egg recognition, blue and white eggs, which had larger achromatic mismatching, were rejected at a higher relative rate than the better achromatic matching black and green eggs. Nightingales showed strong aggression to a cuckoo dummy, suggesting that they were involved in coevolutionary interactions with the cuckoo in the past. However, because of the highly distinct appearance of nightingale eggs relative to the other sympatrically breeding passerines, and the largely luminance‐based egg recognition, this arms race was likely terminated at an early stage.     

Vergleich des Strophenaufbaus und der Strophenabfolge an Ges?ngen von Sprosser (Luscinia luscinia) und Blaukehlchen (Luscinia svecica)

Zusammenfassung Ziel der Studie war es, die Elementabfolge sowie die Strophenabfolge des Gesanges von Sprosser und Blaukehlchen vergleichend zu untersuchen. Zur sonagraphischen Analyse wurden die Gesänge im Freiland aufgezeichnet. Der Abfolge (Syntax) der Strophenelemente lag bei beiden Arten ein hierarchisch organisiertes Verzweigungsschema zu Grunde. Bei beiden Arten konnten die Strophen anhand definierter Strukturparameter klar in drei Abschnitte gegliedert werden. Die Gesänge der Sprosser wurden von Serien aus Strophen gebildet, die jeweils in ihren beiden Anfangselementtypen übereinstimmten (gleiche Strophenklasse). Die Abfolge von Strophen verschiedenen Typs war durch bevorzugte Übergänge und ein gruppiertes Auftreten bestimmter Strophentypen charakterisiert. Beim Blaukehlchen traten Strophen, die in allen Abschnitten strukturell gleich waren, seltener im Gesang wieder auf. Die Blaukehlchen wechselten häufiger die Strophenklasse, wodurch es nur seltener zu einer Serienbildung von gleichklassigen Strophen kam. Die auffälligen Gemeinsamkeiten in der Gesangsorganisation zwischen Sprosser und Nachtigall sowie Blaukehlchen und Gartenrotschwanz liefern Hinweise auf Zusammenhänge zwischen der syntaktischen Organisation von Strophen und der Organisation der Strophenabfolge.

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Comparison of the song structure and song succession in the Thrush Nightingale (Luscinia luscinia) and the Blue Throat (Luscinia svecica)

Summary Songs of three Thrush Nightingales and three Blue Throats were recorded in the field and analyzed by visual inspection of frequency spectrograms. An analysis of the succession of elements within a song as well as the succession of songs in a song bout revealed the following results in both species: a) the succession of elements within songs was organized as a hierarchical branching structure, b) three structurally different sections could be found in all songs, c) songs were initialized by specific element types. A termination of songs by specific element types was only found in the thrush nightingale.Songs ot the Thrush Nightingale were organized as series of songs which corresponded in their first two element types (same song class). These series consisted of different song types, which succeeded with a high constancy. Different song types were sung in close sequential association and recurred preferably after intervals of 8–10 songs.In song bouts of the Blue Throat however songs which corresponded in all sections were rarely found. Those songs corresponding in the first two element types were often repeated immediately, but in comparison to the Thrush Nightingale series of these songs were rare.Besides many similarities in the song organization in both species the song of the Thrush Nightingale was more similar to the closely related Nightingale (Luscinia megarhynchos) — with regard to the syntactical organization of song and the organization of consecutive songs. The song organization of the Blue Throat showed more similarities to the European Redstart (Phoenicurus phoenicurus).These results indicate a relation between the syntactical organization of song and the sequential organisation of consecutive songs.

     

Nightingales in space: song and extra-territorial forays of radio tagged song birds

Summary Most temperate zone passerines defend territories during the breeding season. Commonly the size of these territories is estimated by plotting the singing locations of the males. However, an individual's activities need not be restricted to the area used for singing. So far, only little quantitative information has been available to determine how the singing territory relates to the activity range of male songbirds. Here, we present a study in which we used radio-tracking techniques to collect quantitative data on the spatial behaviour of 11 male territorial Nightingales (Luscinia megarhynchos). The results show that the singing territories made up only about 50% of the activity ranges. Nevertheless, males spent over 90% of the time within the singing territory. Singing territories almost never overlapped but activity ranges overlapped in all cases with the activity range of at least one neighbour. Males intruded into neighbouring territories throughout the season but the longest excursions were made before and during the female fertile period. The time spent for forays correlated significantly with song rate and territories of males with higher song rates in turn were less frequently the object of forays by other males. Song rate can be indicative of male quality, so that our findings strongly suggest that foray behaviour is related to male quality in nightingales.

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Das Raum- und Gesangsverhalten von männlichen Nachtigallen in der Brutsaison: radiotelemetrische Untersuchungen

Zusammenfassung Männliche Singvögel markieren mit ihrem Gesang ein Revier. Empirische Studien zeigen allerdings, dass Männchen und Weibchen das Revier verlassen und in Reviere von Nachbarn eindringen. Solche Ausflüge sind vor allem in dichteren Habitaten schwierig zu beobachten, so dass für die meisten Vogelarten kaum Datenmaterial für die Raumnutzung außerhalb der Gesangsreviere vorliegt. In dieser Studie haben wir über den Verlauf der Brutsaison 11 männliche territoriale Nachtigallen telemetriert. Die Ergebnisse zeigen, dass die Aktionstradien im Mittel doppelt so groß waren, wie die Gesangsreviere und dass die Männchen ca. 8% der Zeit außerhalb der Gesangsreviere verbracht haben. Dabei überlappten die Aktionsräume benachbarter Männchen deutlich. Die Männchen drangen vor allem vor und während der fertilen Phasen der Weibchen in Nachbarreviere vor. Darüber hinaus drangen Männchen mit höherer Gesangsaktivität signifikant länger in Nachbarreviere ein, als Männchen mit geringerer Gesangsaktivität. Reviere von Männchen mit höherer Gesangsaktivität wurden dabei auch signifikant seltener von anderen Männchen besucht. Da die Gesangsaktivität mit der Qualität eines Männchens zusammenhängen kann, weisen die Ergebnisse darauf hin, dass qualitativ bessere Männchen mehr in Nachbarreviere eindringen als qualitativ schlechtere Männchen und die Reviere der qualitativ besseren Männchen auch weniger häufig von Rivalen besucht werden. Dass solche Ausflüge von Männchen für Versuche zu außerpaarlichen Kopulationen genutzt werden, ist anzunehmen, muss aber noch geklärt werden. Die räumlichen Beziehungen territorialer Männchen reflektieren darüber hinaus vermutlich Aspekte der sozialen Beziehungen.

     

Somatic aberration induction in Tradescantia occidentalis by neutrons, x- and gamma-radiations. II. Biological results, r.b.e. and o.e.r.

Biological results, including statistical features, are described for the irradiation of Tradescantia occidentalis with 250 kVp X-rays, cobalt-60 gamma-radiation and monoenergetic neutrons with energies between 0-08 and 15 MeV. The effect studied was that of the induction of pink sectors in the otherwise blue staminal hairs of the flowers at low doses of radiation. Statistical aspects of the results suggest that a fraction of the asynchronous cell population in the hairs is very sensitive to neutron radiation, but not necessarily to lower LET radiations. All the results were fitted by a least-squares method by polynomials of different degrees. Best fits to X- and gamma-ray data were provided by second-degree polynomials, and to the neutron data by either second- or third-degree polynomials. Limiting r.b.e. and o.e.r. values at low doses are derived. Some computed microdosimetric parameters are presented in comparison with the r.b.e. values. It is concluded that the effect studied is complex and may not provide a critical test of bio-physical theories of radiation effects.     

Proteinases of Streptomyces fradiae. II. Specificity.

It has been shown that extracellular proteinases synthesized by a keratinolytic strain of S. fradiae are characterized by diversified activity in the decomposition of both proteins and synthetic substrates. Among the six proteinases isolated, apart from the ones dominating and having relatively low specificity, there are two enzymes characterized by narrow catalytic abilities--extremely similar to those of trypsin. These proteinases intensively degraded all the trypsin substrates studied, but they were inactive or showed slight activity toward others. They were also highly sensitive to such specific inhibitors of trypsin as TLCK, SBTI and TIO.     

Radical formation in salts of pyrimidines. I. 1-methyluracil. HBr crystals.

Radicals produced by X-irradiation at 77 K of 1-methyluracil. HBr crystals have been analysed by electron spin resonance spectroscopy. The results are compared with those obtained on 1-methyluracil crystals. Four radicals have been identified, two of which are present only in 1-methyluracil. HBr crystals: the C6-addition radical and the pyrimidine--anion radical. Warming-up experiments have been performed in order to study the secondary radical reactions. The different mechanisms proposed for the radiolysis of DNA constituents in the solid state are discussed in connection with these findings.     

Ascaridoid nematodes of amphibians and reptiles: Gedoelstascaris n.g. and Ortleppascaris n.g.

Two new genera, Gedoelstascaris and Orleppascaris, are proposed for species of ascaridoid nematodes occurring in crocodilians and previously included in Dujardinascaris. Species included in Gedoelstascaris are vandenbrandeni Baylis, 1929 as type species and australiensis Baylis, 1931 (= salomonis Kreis, 1940). These species occur in Crocodylus spp. in Africa and Australia respectively and are characterised by lips with a rostral plate, without interlocking processes or dentigerous ridges, with well-developed interlabia, lobulated ventriculus, and excetory pore in front of the nerve ring. Species included in Ortleppascaris are: nigra Gedoelst, 1916 (= tasmani Ortlepp, 1932) as type species; alata Baylis, 1947: antipini Mozgovoy, 1950. These species occur in Crocodylus, Caiman and Alligator and are characterized by flat lips with alate margins, without anterior rostral plate, interlocking processes or dentigerous ridges, with weakly developed interlabia, by an irregular-shaped ventriculus, excretory pore behind or between the subventral lips, and by the presence of lateral alae or cuticular thickenings in the oesophageal region. The significance of this proposal is discussed in relation to the radiation and dispersal of ascaridoids of crocodilians.     

There is a difference between scientific hypothesis and the "phylogenetic presumption" by Rasnitsyn (concerning the paper by I.Ia. Pavlinov, 2005. J. Gen. Biology. V. 66. No 5)

The arguments by Pavlinov against my critical analysis of the concept of the "phylogenetic presumptions" proposed by Rasnitsyn are briefly discussed. It is proved that these arguments are invalid because they are based on the substitution of terms. Instead of the term "phylogenetic presumption" introduced by Rasnitsyn just as an analogue of the presumption of innocence in jurisprudence, Pavlinov considers the presumption in the wider understanding, i.e. as a "preliminary statement".