Showing papers in "Oecologia in 1970"

Protean defence by prey animals.

Abstract: Attention is drawn to the widespread occurrence ofprotean phenomena, in which the appearance and behaviour of prey animals are rendered variable and irregular, as a weapon in the biological arms race between predators and their prey. Protean behaviour is defined as that behaviour which is sufficiently unsystematic to prevent a reactor predicting in detail the position or actions of the actor.

On the significance of dispersal power for populations of carabid-beetles (Coleoptera, Carabidae).

Abstract: By various observations on carabid populations the author attempts to give an impression of the quantitative occurrence of dispersal and of the relation between dispersal and the chance of founding populations (dispersal power). Pitfall-catches in the recently reclamed “Zuiderzee”-polder E-Flevoland demonstrate that within seven years individuals of a number of monomorphic macropterous and dimorphic species had founded populations there. From the very high frequency of full-winged individuals within the latter populations it follows that full-winged carabid individuals generally must have a much greater power of dispersal than flightless ones. Therefore, winged individuals of dimorphic species were about equally able to reach E-Flevoland as were those of monomorphic macropterous ones, whereas individuals of monomorphic brachypterous species obviously are seriously hampered. The early appearance of individuals of riparian species on the shores of an artificial lake in the dune area “Meijendel” suggests that particularly populations living in unstable environments extensively “invest” in dispersal. It appears, however, that an important “investment” in dispersal apparently is not restricted to species from unstable environments; at least some sparse populations living in more stable environments also “sacrifice” relatively great numbers of individuals for dispersal (Pterostichus strenuus). The hypothesis is proposed, that populations facing a high risk of extinction generally will have a sufficient chance of founding populations (high “turnover”) when “investing” extensively in dispersal. Not only macropterous but — at least in some populations — also brachypterous individuals participate in migration, although in the populations studied the dispersal power of flightless individuals is found to be very small (Carabus problematicus). Under certain conditions the dispersal of full-winged individuals from wing-dimorphic populations may ultimately lead to a decrease or even a loss of dispersal power by a decrease of the frequency of macropterous individuals. It is assumed, however, that under certain natural conditions also brachypterous individuals may contribute to the spreading of risk within and between populations. The dispersal power of monomorphic macropterous, dimorphic and monomorphic brachypterous populations in a cultivated countryside like Drenthe is discussed. The connection between the dispersal power of different kinds of carabid populations and the resulting chance of survival under different conditions is discussed. Some suggestions for nature preservation management are given.

Simulation experiments illustrating stabilization of animal numbers by spreading of risk

Abstract: 1. This paper discusses results of simulation studies with population models that were set up to illustrate the ideas about stabilization of population fluctuations and spreading of the risk of extinction expounded by den Boer (1968). In particular, the number of factors influencing net reproduction, the heterogeneity of the habitat and the possibility of a population's containing animals of different age classes were considered as possibly contributing to stabilization and to spreading of risk. 2. The model defined by equation (3.1.2), where r(t) denotes the net reproduction from t to t+1, f i (t) denotes the value of the i-th environmental factor in year t, and where the other symbols denote positive constants, was simulated by choosing for the f i(t) sequences of meteorological data from published tables. Such sequences may be serially correlated as well as correlated among themselves and using such real data was considered to be more realistic than working with sequences of independent random numbers, for example. Increasing the number k of factors turned out to stabilize fluctuations in the density. This fact could also be mathematically proved under not very restrictive assumptions. In a model where the logarithm of the net reproduction on the average is some-what greater than zero, and where "crashes" may occur at high densities, the population may persist for a very long time, even if the "size" of the crashes does not depend on density, and the times at which the crashes occur are chosen at random. 3. A model formulated in terms of matrices and vectors, in which a population was supposed to consist of 9 subpopulations and of several age classes was simulated. It was assumed that after a reproduction period the animals migrate between the subpopulations or emigrate from the whole population. It turned out that increasing the number of age classes may increase stability and that models where there is exchange of individuals between subpopulations by \ldmigration\rd are more stable than populations consisting of isolated subpopulations. Letting the exchange between subpopulations be \lddensity-dependent\rd had some stabilizing effect too, but not very conspicuously so.

Aerial dispersal in relation to habitat in eight wolf spider species (Pardosa, Araneae, Lycosidae)

Abstract: In the eight Pardosa species studied, aerial dispersal occurs generally in the young instars. The climatic conditions, particularly wind but also temperature and humidity, affect the occurrence of aerial dispersal. Within the different systematic groups in the genus, species with relatively high and relatively low dispersal capacities occur. These differences in dispersal capacity are discussed in relation with the abundance and stability of the habitat, in which the species are found.

Snail populations, beech litter production, and the role of snails in litter decomposition

Abstract: The population densities of snails living in beech litter were studied form March 1968 to April 1969. Litter production over one year was measured and the role of snails in litter disappearance assessed. Snails were extracted from litter using a modified Vagvolgyi (1952) flotation method, extraction efficiencies being 84%. The mean annual population density of the twenty-one species of snail recorded on the main sampling site was estimated at 489/m2. Carychium tridentatum was the most numerous species, with a mean density of 200/m2. Acanthinula aculeata, Punctum pygmaeum and Vitrea contracta also had fairly high mean densities. The mean annual biomass was 699 mg dry wt./m2 or 278 mg ash-free dry wt./m2. Hygromia striolata and Oxychilus cellarius/alliarius were the most important species in terms of biomass on the main site. Within the limits of accuracy imposed by the sampling regime the population densities of four out of five of the species (C. tridentatum, A. aculeata, V. contracta, Retinella pura) studied remained unchanged throughout the year, whereas P. pygmaeum had a significantly higher autumn population. C. tridentatum populations were highly aggregated at all times of the year, most markedly so in June. Other species were aggregated at certain times of the year only. Samples taken from other sites showed total population densities of snails ranging from 185–1082 snails/m2. A total tree litter production of 652 g/m2/annum was recorded of which 584g/m2/annum was of beech material. 72% fell in the October–December period. 58% of the beech litter-fall was leaves, 5.2% bud-scales, 27% fruits and 10% twigs and bark. Summation of appropriate field layer peak standing crops amounted to 23.3 g/m2. This was considered as potential litter and was equivalent to 3.4% of the total litter input. The litter standing on the woodland floor in Septermber 1968 was 2,700 g/m2, hence, assuming a steady state, litter turnover time was estimated as 4.5 years. It was calculated that the total snail population ingested 0.35–0.43% of the annual litter input, of which 49% was assimilated. The role of the individual species is examined in relation to concepts of “key species” in ecosystem functioning. The possible role of slugs in decomposition processes is also discussed.

Aspects of the ecology of an exposed shore population of dogwhelks Nucella lapillus (L.).

Abstract: Up to the third year of life Nucella lapillus (L.) could be aged in the laboratory and in the field using shell characters. Monthly counts along transects on an exposed rocky shore have shown that the age groups behave differently, dogwhelks in their first year migrating upshore, and returning to lower levels in the second year. Adults (three years or older) lived and laid egg capsules in the low shore. The most favourable situation for subsequent hatching of these capsules was where they were permanently submerged in sea water.

Spatial competition among porifera: Solution by epizoism.

Abstract: Sponges settling on solid substrates which are separated by sediment bottoms compete for the limited space. Some species have solved this problem by occurring as epizoans, thus avoiding the risk of being expelled from the habitat. The supporting species on the other hand, are specialized in that they possess skeletogenous ectosomal structures and aquiferous processes to maintain their integrity and to escape starvation or suffocation. Although specimens are sometimes intimately interwoven no chimaerid mixing of tissues was observed.

Food, feeding rates and assimilation in woodland snails.

Abstract: Analyses of the faeces of seven species of woodland, litterdwelling snails (Marpessa laminata, Clausilia bidentata, Oxychilus cellarius, O. alliarius, Discus rotundatus, Arianta arbustorum and Hygromia striolata), showed that all feed predominently on higher plant material, be it living or dead. H. striolata and A. arbustorum took more chlorophyll-containing plant material than the other species, D. rotundatus had a significant amount of fungus in its faeces, while the faeces of O. cellarius and O. alliarius contained significant amounts of animal material.The consumption and assimilation of a variety of foods by molluscs was studied in the laboratory using an ash-ratio technique, which had been shown to give similar results to those obtained by the standard gravimetric technique. The assimilation efficiency of the molluscs was found to be temperature independent, but ingestion rates and absolute assimilation rates were temperature dependent. The assimilation efficiency of D. rotundatus on living plant material (three field layer species) was 44.8±4.43% that of H. striolata (Urtica dioica) was 52.4±8.78% while O. cellarius and H. aspersa (on Lactuca sativa) had assimilation efficiencies of 70.2±4.40% and 53.50±6.04% respectively. The results fall within the range shown by other invertebrate groups. The assimilation efficiency of D. rotundatus on leaf litter (a mean of 49.1±1.88% on five litter types) was higher than that shown by other invertebrates, probably due to the presence of gut polysaccharidases. The assimilation on dead earthworm as animal material (86.9±2.53% with O. alliarius and 78.6±6.73% with D. rotundatus) was in the range of true carnivores. Consumption rates were more variable; Urtica dioica, amongst living material, was eaten in greatest quantity; Acer pseudoplatanus, Castanea sativa and Quercus robur litter were eaten in greater quantity than Fagus sylvatica and Carpinus betulus. Consumption was examined in terms of percentage body weight.

Influence of temperature on the population dynamics of the rotifer Brachionus calyciflorus pallas

Abstract: Experiments were designed to test the influence of temperature on the life table data of the rotifer Brachionus calyciflorus Pallas. It is examined how well the observed modifications agree with theoretical models, and how they influence the temporal changes of population densities in limited and unlimited laboratory populations. On the basis of the experimental results, the population dynamics of planktonic rotifers in several natural habitats were analysed and interpreted. Laboratory Studies at 15, 20, and 25° C. 1. In individual cultures, the duration of all developmental stages (eggs, juvenils, adults) decreased with increasing temperature (Table 1, Fig. 1). On the other hand, the rate of reproduction was positively correlated with temperature. As a result of this twofold influence of temperature, the mean number of offspring per female shows an optimum at 20° C. 2. Unlimited populations which grew exponentially were characterised by a stable age distribution. Within the temperature range under study, the intrinsic rate of natural increase of unlimited populations rose with increasing temperature. 3. In populations limited by food supply, the mean population densities as well as the type and the intensity of oscillations was determined (Table 4, Figs. 2-5). Egg ratios and proportions of immature animals were also determined. Highest mean population densities occured at low temperatures, highest maximum densities at high temperatures. The latter fact is the result of stronger oscillations at higher temperatures: at 15° C oscillations were damped, at 20° C permanent or just increasing (no extinction within 60 days), at 25° C clearly increasing (extinction within 30 days). Amplitude and frequence of the oscillations were positively correlated with temperature. 4. The optima for the population growth and abundance were apparently not at the same temperature (Table 4). 5. The mictic rate, measured as the proportion of sexual females in the population, was relatively small; in limited populations it was larger than in unlimited populations. Temperature had a positive influence at high population densities. Test of Population Models. 1. Using life table data of individuals, theoretical predictions about the growth rate and the age structure of populations during exponential growth have been made by several authors. It is shown that at all temperatures the predictive power of the well known demographic model of Lotka is about as good as that of a recent model by Edmondson (Table 2). It is suggested that both models give adequate causal descriptions of exponential growth inspite of their manifold and different simplifications. As a consequence it is concluded that the observed influences of temperature on exponential growth are the result of direct influences of temperature on the life table data. 2. When mean population densities were estimated by theoretical calculations of energy balance, a rather good agreement with the empirical data was found. 3. Determination of the animal's food efficiencies on the basis of the observed production of biomass suggest that the coefficient of efficiency is significantly larger at 15° C (37%) than at 20 and 25° C (27 and 28%, resp.). 4. According to Cook and to Ricker, the mean generation length T permits predictions about type and frequency of the oscillations. When T was calculated from the life table data, the predictions about the oscillations were in fairly good agreement with the results on limited populations. The meaning of the parameter T in species with overlapping generations is discussed. Field Observations. During 1967 measurements of temperature and population densities of Brachionus calyciflorus were carried out in 15 artificial basins (0.3-50 m3) and 7 ponds (Figs. 6-8). An analysis of these data gave the following results: 1. During sudden population explosions, the growth rates were, on the average, positively correlated with environmental temperature. The agreement with laboratory data is quite good (Fig. 9). It is concluded, that temperature co-determines this aspect of population dynamics in the field. 2. The largest maxima of population densities were found at 20-28° C. With about 105 individuals/liter they are in the same order of magnitude as the corresponding data of laboratory populations. Average population densities seem to be independent of temperature within the range of 12-28° C; outside this range they appear to decrease (Fig. 10). Average densities in the field were clearly lower (10-102 individuals/liter) than long-term means of population densities in experimental populations (about 104-105 individuals/liter). 3. Fluctuations were stronger at high than at low temperatures. The degree of temperature dependence is about the same in the laboratory and in the field. However, at all temperatures the absolute values were greater in the field than in laboratory populations of the same temperature (Fig. 11). Modifying influences of biotic factors (phytoplankton, competitors, predators) are discussed.

The factors determining temporal variation in Brachionus calyciflorus pallas (rotatoria)

Abstract: 1. Die Temporalvariation von Brachionus calyciflorus betrifft vor allem ein Paar Posterolateraldornen (PL), die in ihrer Ausbildung von vollst\:andigem Fehlen bis zu K\:orperl\:ange variieren k\:onnen. Die Bildung dieser Dornen wird durch Hunger, tiefe Temperatur und einen Stoff hervorgerufen, den das r\:auberische R\:adertier Asplanchna ins Medium abgibt. Diese drei Faktoren wurden quantitativ vergleichend auf Unterschiede in der Art ihrer Wirksamkeit und auf ihre Bedeutung f\:ur die Variation im Freiland untersucht. 2. Es besteht eine positive Korrelation zwischen der L\:ange der PL und derjenigen der anderen Dornen, die stets vorhanden sind (Abb. 1). Diese anderen Dornen variieren auch noch bei Fehlen der PL, und zwar in gleichem Sinne (Tabelle 2). 3. Hunger und tiefe Temperatur k\:onnen nur kurze PL induzieren, zur Ausbildung langer PL ist der Asplanchna-Stoff notwendig (Abb. 2). Die Effekte der drei Faktoren k\:onnen sich \:uberlagern. Hohe Temperatur scheint dabei hemmend auf die Dornenbildung einzuwirken. Die Art der Inkubation hat keinen erkennbaren Einflu\sB auf die Variation der Reaktion (Abb. 3 und 4); auch bei maximaler Reaktion ist die Streubreite nicht verringert. 4. Es gibt keine deutliche Tradierung des Variationstyps: bei allen drei Faktoren manifestiert sich die nahezu volle Reaktion auf einen induzierenden Reiz in der n\:achsten Generation (Abb. 5). 5. Die Temperatur hat einen Einflu\sB auf die K\:orpergr\:o\sBe: je tiefer die Temperatur ist, desto gr\:o\sBer sind die Tiere. Dieser Temperatureinflu\sB besteht aus einer pr\:a- und einer postnatalen Komponente (Abb. 6 und 7). 6. Die Determination der Dornenl\:ange erfolgt in allen F\:allen vor der Geburt (vgl. Abb. 5). Die dorneninduzierenden Faktoren bestimmen die Proportionen der Neonaten, nach der Geburt erfolgt das Dornenwachstum negativ allometrisch mit einer konstanten Allometrierate k=0,54, die von der Art der Dorneninduktion, der Gr\:o\sBe der Dornenanlage und den Aufzuchtbedingungen unabh\:angig ist (Tabelle 4 und Abb. 9). 7. Mit Hilfe der Allometriebeziehung wird ein Dornenindex ID definiert, der von der K\:orpergr\:o\sBe der Tiere unabh\:angig ist. Mit ihm k\:onnen die Dornenausbildungen von Populationen verglichen werden, auch wenn diese unterschiedliche Altersstruktur besitzen. Ebenso sind auf diese Weise die verschiedenen Alters- (bzw. Gr\:o\sBen-) Klassen einer Stichprobe bez\:uglich ihrer Dornenausbildung miteinander vergleichbar. Unterschiede in den Dornenindices verschiedener Altersklassen einer Stichprobe weisen darauf hin, da\sB ein dorneninduzierender Faktor (wie etwa der Asplanchna-Stoff) Schwankungen unterworfen war (Abb. 10). Auf diese Weise kann man aufgrund einer einzigen Planktonprobe Aussagen \:uber die Vorgeschichte der dorneninduzierenden Faktoren in den letzten Tagen und Wochen machen (Abb. 11 und 12). 8. Es wurde ein reproduzierbarer Test auf die dorneninduzierende Aktivit\:at eines Mediums ausgearbeitet. Mit Hilfe deses Testes lie\sB sich eine relative Einheit der Asplanchna-Stoffmenge (as) definieren. Die pro Volumen-und Zeiteinheit gebildete Stoffmenge ist der Asplanchnen-Dichte proportional und h\:angt von der Temperatur ab (im Bereich von 10\2-25\dg C: Q10=4). Ein Asplanchna produziert z.B. bei 20\dg C in 25 sec die Stoffmenge, die in 1 ml gerade erkennbare Dornenbildung bewirkt. Entsprechende Werte werden f\:ur 10, 15 und 25\dg C angegeben (Tabelle 6). Der Stoff zerf\:allt jedoch exponentiell (Abb. 14a). Diese nat\:urliche Stoffzersetzung ist ebenfalls temperaturabh\:angig (Halbwertszeit je nach Temperatur 1\2-3 Tage, Abb. 14b). Jeder Asplanchnen-Dichte kann theoretisch eine Gleichgewichtskonzentration an Stoff zugeordnet werden, die sich aus Daten der Produktion und des Zerfalls berechnen l\:a\sBt (Tabelle 6). In Populationsversuchen wie im Freiland stellten sich jedoch die theoretisch errechneten Stoffkonzentrationen nicht ein, m\:oglicherweise weil die Brachionus den Stoff inkorporieren. Eine pragmatische Korrektur der theoretischen Asplanchnastoff-Bilanz (keine Akkumulation \:uber 24 Std hinaus) ergab gute \:Ubereinstimmung zwischen den erwarteten und den beobachteten Dornenindices (in Experimental-und Freilandpopulationen). 9. Ein quantitativer Vergleich der Effektivit\:at der drei dorneninduzierenden Faktoren (Abb. 17) ergab, da\sB lange Dornen (mittl. ID>0,3) weder durch tiefe Temperatur noch durch Hunger induziert werden k\:onnen, sondern allein durch die Asplanchna-Substanz hervorgerufen werden. 10. Auch im Freiland ist der Asplanchna-Stoff das wichtigste induzierende Agens. Labortests zeigen, da\sB Wasser aus Teichen, in denen Asplanchnen vorkommen, dorneninduzierende Aktivit\:at besitzen (Tabelle 7). Dies gilt f\:ur Asplanchna sieboldi (s. 1.) und f\:ur A. priodonta. Die Dornenindices der Neonaten zeigen in ihrem zeitlichen Verlauf eine gute Korrelation mit der Asplanchnen-Dichte (Abb. 20\2-22), die der Adulten zeigen eine Phasenverschiebung, die dem Alter der Tiere entspricht. Verschwinden die Asplanchnen aus dem Biotop, so gehen die Dornenindices mit einer zeitlichen Verz\:ogerung von einigen Tagen ebenfalls zur\:uck. Der Einflus der Temperatur ist im Freiland schwacher als im Labor (Abb. 23). Die mogliche Wirksamkeit unbekannter Faktoren im Freiland wird diskutiert. 11. Mittels Labortests lie\sBen sich Unterschiede in der Reaktionsnorm zweier St\:amme von verschiedenen Fundorten nachweisen (Abb. 2). Diese betreffen (unabh\:angig von der Art des Induktionsfaktors) die mittleren Dornenindices, mit denen die Tiere auf bestimmte Induktionsreize reagieren. 12. Es werden denkbare Mechanismen der Dornenbildung besprochen und m\:ogliche Unterschiede in der physiologischen Wirkungsweise der drei dorneninduzierenden Faktoren diskutiert. Einige Aspekte, die die Funktion der zyklomorphen Dornenbildung betreffen, werden angedeutet.

[Bio-Acoustic and ecological investigations in the midwife toad, Alytes, o. obstetricans (Laur.)].

Abstract: 1. In einer Gerollhalde in der Nahe Tubingens rufen Alytes o. obstetricans von Anfang April bis Ende August. Die annuelle Ruf-Aktivitat gliedert sich in vier verschieden lange Rufperioden. Sie sind weitgehend witterungsunabhangig. 2. Der diurnalen Ruf-Aktivitat liegt ein endogener Rhythmus zugrunde, der von zwei exogenen Faktoren, der Lufttemperatur und der allgemeinhelligkeit, beeinflust wird. Die untere Temperaturschwelle der Ruf-Aktivitat liegt bei 7° C, die obere bei 26° C. Der Zeitgeber (kunstlicher Licht-Dunkel-Wechsel 12:12) vermag den endogenen Rhythmus in beliebiger Weise zu synchronisieren. Die Ruf-Aktivitat liegt innerhalb der Dunkelzeit und entspricht einem Bigeminus. 3. Mannliche Alytes erzeugen sechs funktionell verschiedene Rufe: I. Paarungsruf mit langsamer Ruffolge. II. Paarungsruf mit schneller Ruffolge. III. Einzelner Erregungsruf. IV. Wiederholter Erregungsruf. V. Befreiungsruf. VI. Schreckruf. Weibliche Alytes sind ebenfalls stimmbegabt, sie haben nur zwei Rufe: einen Paarungs- und einen Schreckruf. Die Rufe beider Geschlechter stellen mit Ausnahme des Befreiungs- und des Schreckrufes Klange dar. 4. Der Paarungsruf ist durch die Parameter, Ruffolge, Grundfrequenz, Rufdauer und Schalldruck gekennzeichnet. Sie andern sich unter dem Einflus der Lufttemperatur. Mit steigender Lufttemperatur gehorchen die Ruffolgen und die Grundfrequenz einer positiven, linearen Regression, dagegen verkurzt sich die Rufdauer logarithmisch. Der Schalldruck verstarkt sich mit zunehmender Lufttemperatur nur annahernd linear. Die Grundfrequenz, sowie die Rufdauer verandern sich auserdem mit der Tiergrose. 5. Das Kehlkopfskelet besteht aus einem Cricoid und zwei Arytaenoiden. An den Kehlkopfknorpel inserieren drei Muskelpaare: M. dilatator laryngis, M. sphincter und M. hyo-laryngeus. Sie werden von zwei Asten des N. vagus, dem R. laryngeus longus und dem R. laryngeus brevis innerviert.

Untersuchungen über den Nahrungserwerb der Waldameisen (Formica polyctena Foerster) im Eichenwald

Abstract: Die Zahl der aus- und einlaufenden Ameisen eines Waldameisennestes hangt im wesentlichen von der Temperatur ab (Maximum bei etwa 23° C), daneben in geringem Mas von der Tageszeit. Storende Faktoren sind Dunkelheit wahrend der Nachtstunden und Niederschlage.

Die Steuerung von Jahresrhythmik und Diapause bei Larval-und Imagoüberwinterern der Gattung Pterostichus (Col., Carab.).

Abstract: 1. Innerhalb der Carabidengattung Pterostichus finden sich verschiedene Typen der Jahresrhythmik. Untersucht wurden P. cupreus und P. coerulescens als Repr\:asentanten der Fr\:uhlingstiere mit Sommerlarven und Imaginal\:uberwinterung und P. vulgaris als Repr\:asentant der Herbsttiere mit Larval\:uberwinterung. 2. Die Weibchen der Fr\:uhlingstiere treten unabh\:angig von der Photoperiode in eine Dormanz ein, die durch aufeinanderfolgende Behandlung mit Kurztag und Langtag in Dauerw\:arme \:uberwunden wird (photoperiodische Parapause). Im Freiland bewirkt die steigende Tagesl\:ange die Aufhebung der Parapause. Der Prozentsatz reifer Weibchen hangt bei beiden Arten von der Dauer der Kurztag-Behandlung ab. Bei 4wochiger Kurztag-Behandlung erhalt man im folgenden Langtag die ersten reifen Weibchen. Nach 8 Wochen Kurztag steigt der Prozentsatz von Weibchen mit legereifen Eiern auf maximale Werte bis 100%. Durch erneute Behandlung mit zunachst Kurztag, dann Langtag konnen alte Weibchen zu einer zweiten Eireifung gebracht werden. Die Parapause der Weibchen kann auch bei konstanter Photoperiode (Dauer-Kurztag oder-Langtag) durch eine vorubergehende (4monatige) starke Temperatursenkung aufgehoben werden. Hierbei kommen aber weniger als 40% der Weibchen von P. coerulescens und weniger als 20% der Weibchen von P. cupreus zur Reife. Eine weitere Moglichkeit zur Uberwindung der Parapause bei Weibchen besteht in der Steigerung der Lichtintensitat bei konstantem Kurztag. Hier entwickelten sich aber nur 33% der Weibchen von P. coerulescens zur Reife. 3. Die M\:annchen der Fr\:uhlingstiere reifen in Dauerw\:arme bei Wechsel von Kurztag und langtag nur zu einem geringen Prozentsatz (maximal 25%). Sie kommen dagegen durch mit dem Kurztag verbundene K\:altebehandlung zur Reife. Dabei steigt der Prozentsatz reifer M\:annchen bei Verl\:angerung der K\:altekurztagwirkung von 2 auf 4 Monate und Senkung der Temperatur von +5\2−7\dg auf +2\2−3\dg steil an (auf \:uber 80%). Laborzuchtweibchen, die mit kaltekurztagbehandelten Mannchen gepaart werden, haben viel mehr Nachkommen als solche, die mit Mannchen gepaart werden, die in Warme mit Kurztag behandelt worden sind. Die Dormanz, in der die Mannchen von P. cupreus in Warme verharren, kann auch im Dauer-Langtag und Dauer-Kurztag durch zeitweilige Temperatursenkung zu einem hohen Prozentsatz uberwunden werden (thermische Parapause). Mannchen von P. coerulescens reifen durch Temperaturwechsel nur im Dauer-Kurztag zu einem geringen Prozentstatz, nicht im Langtag. 4. Die Entwicklung und Metamorphose l\:auft bei den untersuchten Fr\:uhlingstieren in W\:arme unter Kurztag und Langtag ab. Die Mortalit\:at ist unter beiden Photoperioden gleich. Langtag verl\:angert bei beiden Arten die Entwicklungsdauer. 5. Bei den Imagines des Herbsttieres P. vulgaris erfolgt die Reifung bei beiden Geschlechtern unabh\:angig von der Photoperiode. Eine Dormanz tritt nicht auf. 6. Die Larvalentwicklung von P. vulgaris verl\:auft unabh\:angig von der Photoperiode. Bei W\:arme verf\:allt das 2. oder 3. Larvenstadium in eine Dormanz, die als thermische Parapause der Larven bezeichnet werden soll, da sie durch zeitweilige K\:alteeinwirkung auf das 3. Stadium aufgehoben werden kann.

Plant temperatures and heat flux in a Sonoran Desert ecosystem.

Abstract: In the extreme desert environment the potential energy load is high, consequently high temperatures might be a limiting factor for plant survival. Field measurements of plant temperatures in a Sonoran Desert ecosystem were made using fine thermocouples. Temperatures of six desert species were measured: Opuntia engelmannii, Opuntia bigelovii, Opuntia acanthocarpa, Echinocereus engelmannii, Larrea tridentata and Franseria deltoidea. Daily temperature profiles were used to compare the different responses of cacti and shrubs to the desert heat load and also to compare spring and summer responses. Leaf temperature of shrubs was at or near air temperature during both the mild, spring season and the hotter dry season. The cacti, on the other hand, absorbed and stored heat, thus temperatures were often above air temperature. The energy absorbed is determined largely by plant orientation and surface area exposed to the sun. Actual energy absorbed by the plants was estimated from energy diagrams. The flat stem pads of Opuntia engelmannii plants are oriented to receive maximum sunlight without long periods of continuous heating. Opuntia bigelovii spines reflect and absorb much of the environmental energy load, thereby protecting the thick, succulent stems from overheating. The smaller stems of Opuntia acanthocarpa dissipate heat more effectively by their large surface area exposed to convective air currents. Leaves on desert shrubs remain nearer to air temperature than do succulent stems of cacti, because their very large surface to volume ratio allows them to dissipate much heat by convection.

The utility of a digital simulation language for ecological modeling

Abstract: Dynamic modeling of ecological phenomena has been greatly facilitated by the recent development of continuous system simulator programs. This paper illustrates the application of one of these programs, S/360 Continuous System Modeling Program (S/360 CSMP), to four systems of graduated complexity. The first is a two species system, with one feeding on the other, using differential equations with constant coefficients. The second and third systems involve two competing plant species in which the coefficients of the differential equations are varying with time. The final example considers the management of a postulated buffalo herd in which the dynamics of the herd population and composition by sex and age is combined with various strategies to control its size and to optimize buffalo production.

ATP as an indecator of biomass in marine sediments

Abstract: ATP was extracted from sediments with Tris buffer at 100° C. Using the luciferine-luciferase assay for the determination of ATP the lowest detectable concentration in the sediments was 5x10-8 g ATP/ml Sediment. By multiplication with the factor 50 ATP levels were converted into biomass-carbon. Comparison with total organic carbon content of the sediments led to the conclusion that, depending on the type of sediment, the organic carbon content of living matter amounts to 0.13-1.6 per cent of the total organic carbon.

Herbivore-Algal relationships on a coastal rock platform (Cape Banks, N.S.W.).

Abstract: A fifty-three metre inter-tidal transect on a headland near Sydney, New South Wales, has been studied. Its profile, fauna and flora are illustrated and described.

Zoogeography and parallel level-bottom communities of the meiobenthic harpacticoida (Crustacea, Copepoda) of Bermuda

Abstract: Twenty nine harpacticoid copepods are new to Bermuda and significant changes are noted in the distribution records of several species. Six temporary groups are organized to separate the copepods on their apparent zoogeographical ranges: (1) cosmopolitan, (2) warm temperate-tropical, (3) North Atlantic, (4) North Atlantic-Mediterranean, (5) Endemic to Bermuda and (6) uncertain. These six artificial groups do not necessarily correspond to the standard zoogeographical provinces. Endemism of the Bermudian harpacticoids is similar to the rates reported and predicted for other fauna on North Atlantic Islands. Low endemic rates probably reflect changing environmental conditions during the late Pleistocene.

Laich-Fressen durch Kaulquappen als mögliche Ursache spezifischer Biotoppräferenzen und kurzer Laichzeiten bei europäischen Froschlurchen (Amphibia, Anura)

Abstract: Tadpoles of Rana temporaria which have been raised in an artificial pond prey in the experimental situation shown in Fig. 1 upon the spawn of the following sympatric European Anura species: Rana temporaria (cannibalism), Rana esculenta, Rana ridibunda, Bufo bufo, Bufo calamita, Bombina variegata and Hyla arborea (predation). - Rana temporaria is an early breeder. Thus selection pressure acts in the following ways: Rana temporaria establishes for itself an explosive breeding pattern. Species which breed later in the year in shallow water are suppressed in the biotope of Rana temporaria and develop other biotope preferences (Bombina variegata, Bufo calamita, Hyla arborea). Rana esculenta, Rana ridibunda and Bufo bufo spawn in deeper water. Therefore they are scarcely exposed to the tadpoles of Rana temporaria. Moreover Bufo bufo, too, is an early breeder. Alytes obstetricans laying no spawn in the water is not endangered. - An analysis of biotope preferences and breeding times of the species involved confirms these interpretations.

Comparability of Cartesian Diver, Gilson, Warburg and Winkler methods of measuring the respiratory rates of aquatic invertebrates in ecological studies.

Abstract: Comparison of Cartesian Diver-Winkler measurements of respiratory rates in larvae of the damselfly Pyrrhosoma nymphula, and Cartesian Diver-Gilson comparisons in the snail Potamopyrgus jenkinsi are descibed. Measurements of oxygen uptake using these different methods do not differ significantly for the same species of animal at the same temperature. Published data likewise suggest that Warburg and Winkler measurements can give similar results. All these methods, therefore, appear to be equally suitable for ecological work, providing they are used carefully and with a sound knowledge of the biology of the animal under investigation.

Differential susceptibility of species of slugs to metaldehyde/bran and to methiocarb baits.

Abstract: Laboratory experiments were designed to study differential susceptibility of nine species of slugs to metaldehyde/bran and to methiocarb baits. Differential susceptibility was found between some of the species for each type of bait, both immediately after baiting and also after a 48 h recovery period. Thus neither type of bait is suitable for use in ecological investigations. This conclusion was supported by evidence that interspecific behavioural interactions occurred when metaldehyde, but not methiocarb, baits were used.At the same time the relative efficiency of the two types of baits as molluscicides was estimated. Methiocarb was shown to be a better molluscicide because, not only did it initially poison more slugs than did metaldehyde, but also a number of the slugs initially poisoned by metaldehyde recovered during the following 48 h period, whereas this did not happen with methiocarb. The similarity between these results and those obtained from field experiments by other workers is discussed.

Population dynamics and salinity tolerance of Hyadesia fusca (Lohman) (Acarina, Sarcoptiformes) from brackish water rockpools, with notes on the microenvironment inside Enteromorpha tubes.

Abstract: The salt water mite Hyadesia fusca has been recorded from Scandinavia for the first time. It is entirely restricted to the green alga Enteromorpha spp. in the littoral zone or in rockpools. The algae serve as substratum, food and breeding room but they also give rise to violent fluctuations in abiotic environmental parameters. However, oxygen availability and hydrogen-ion activities do not differ very much inside and outside the algal thalli. The fluctuations recorded are between 2 and 12 g O2·10-7 cm-2 min-1 and between pH 8.5 and 10.1.

Relation between habitat structure and development of the glandulae ampullaceae in eight wolf spider species (Pardosa, Araneae, Lycosidae).

Abstract: In eight Pardosa species studied there is a correlation between the structure of the habitat in which the species live, the quantity of silk (drag-lines) produced, the plane in which the silk is spun and the degree of development of the silk glands (the gl. ampullaceae). In general, species living in field-type vegetation have large gl. ampullaceae, produce large quantities of silk and spin proportionally more silk in the vertical plane, while the converse is true for species from open-ground type vegetation.

Upstream migration of Philopotamus montanus (Trichoptera)

Abstract: Imagines of Philopotamus montanus were sampled by light-traps and by hand at four sites along the Kaltisjokk in Swedish-Lappland. The samples were quantitatively and qualitatively analysed and compared. They differed in the following points: 1. There were many more imagines at the mouth of the stream than in the upper reaches. 2. At the mouth of the stream the percentage of the females was about one third compared with the samples from the upper reaches. Most of these females were immature, whereas most of the females from the upper parts had already laid their eggs. Mature females, which were ready for the first oviposition were distributed uniformly along the stream. 3. The proportion of mature females caught in the light-traps was twice that caught by hand. Immature females and females which had already laid their eggs were less numerous in the light-traps than in the hand-catches. 4. During the ten-day period of the investigation the differences between the samples from the four sites decreased. 5. With the light-traps most of the insects were caught during the day-time (6-22h). The sex ratio changed with the time of day. In the morning males dominated the catch, and in the afternoon females. 6. The reliability of the methods is discussed and the hypothesis is put forward that mature, egg-bearing females migrate upstream.

Monoxenic cultivation of the rotifer Brachionus calyciflorus in a defined medium

Abstract: Techniques are described for the initiation and maintenance of axenic cultures of Euglena gracilis strain Z and monoxenic cultures of Brachionus calyciflorus variety pala with the Euglena, using in both the same defined, buffered medium. The medium, which is inorganic—except for the citrate chelating agent, the buffer, and vitamins B1 and B12 — has been used for the axenic cultuvation of the Euglena for more than 13 months. The monoxenic Brachionus cultures, established by inoculating rotifers into Euglena cultures, have been maintained for more than 8 months. Contamination tests on the rotifer cultures were performed frequently in three different test media.

The structure of tick-borne encephalitis (TBE) foci in Central Europe

Abstract: The investigations on the structure of TBE foci were carried out in the localities Jivova (northern Moravia), Topolcianky and Žirany (Tribec Mountains), and environs of Debreczen (Pannonian lowland, Hungary). The biphasic activity curve of Ixodes ricinus, characteristic for the central European conditions was confirmed in all three types.

The acoustical behavior of Acheta domesticus L. (Orthoptera: Gryllidae) following sublethal doses of parathion, Dieldrin and Sevin.

Abstract: Studies were conducted on the effects of sublethal doses of an organophosphate, Parathion, a chlorinated hydrocarbon, Dieldrin, and a carbamate, Sevin, on the acoustical and sexual behavior of Acheta domesticus L. The LD10 of orally administered Parathion was 0.100 μg/g, that of Dieldrin was 0.066 μg/g, and that of Sevin was 0.330 μg/g. Parathion treated crickets were unable to emit pure calling, threat, or courtship songs. As a result of these changes in acoustic behavior, treated male crickets were unable to complete copulation. Oral administration of both Dieldrin and Sevin resulted in complete cessation of singing in all specimens for 3 to 6 hours. Once singing resumed there was a significant increase in chirp rate and pulse rate of the calling song. It is suggested that sublethal doses of Parathion act primaily on the peripheral neuromuscular system and the thoracic ganglia, whereas both Dieldrin and Sevin appear to act upon components of the brain, first in an inhibitory capacity and subsequently as excitants.

Die ökologische Spezialisierung der Eidechse Cryptoblepharus boutoni cognatus (Boettger) auf das Leben in der Gezeitenzone (Reptilia, Skinkidae)

Abstract: Auf Madagaskar lauft die EidechseCryptoblepharus boutoni cognatus einmal am Tag bei Einsetzen der Ebbe in die langsam trockenfallende Gezeitenzone, wo sie nach Insekten, Krebsen und Fischen (jungePeriophtalmus kohlreuteri) jagt. Die gezeitenanhangige Aktivitat, definiert als die Anzahl der frei umherlaufenden Tiere, wurde gemessen. Die Eidechse ist ortstreu und wandert auf erlernten Wegen zwischen den Ruheplatzen an Land und den Jagdgrunden in der Gezeitenzone. Bei Verfrachtung uber ca. 200 m auserhalb ihres Aktionsraumes (home range) kehrt sie in ihr Heimatareal zuruck. Ortstreue, gezeitenperiodische Wanderungen und Heimfinde-Verhalten werden als Anpassung fur das Leben in der Gezeitenzone diskutiert. Die Eidechse ist ein Gezeitenzonen-Spezialist, die ohne Aufgabe ihrer terrestrischen Lebensweise in diese neue okologische Nische eingedrungen ist.