Showing papers in "Oecologia in 1969"

The ecology of Mytilus edulis L. (Lamellibranchiata) on exposed rocky shores : II. Growth and mortality.

Abstract: Growth studies in M. edulis L. have shown that rates vary considerably according to age, size and environmental conditions. This may in part be attributed to its sessile habit, being unable to move away from the variable external conditions.The use of modal length frequency distributions is somewhat limited, since with three or more year groups represented, the growth of the majority of the population is so slow that individual year classes lose their identity. Growth boxes, containing marked animals of different ages, and set out in a variety of habitats gave information regarding local and seasonal growth rates. Disturbance rings were shown to be annual, and from them growth curves have been constructed.Growth is particularly seasonal, little or none occurring during the winter. Growth rates varied considerably with a variety of environmental factors (both biotic and physical) and some of these are discussed. Variable individual growth rates, together with slow growth of the majority of animals in mixed populations, are perhaps the major factors in producing population structures typical of this species on open shores.Survivorship curves for mussels in a variety of habitats have been constructed by following the survival of groups of marked animals. Whilst high mortalities occurred in the mid and low shore, survival in the upper shore in the absence of major predators, was greatly enhanced, resulting in established populations of considerable age. Periods of maximum mortality during spring and summer could be correlated with the abundance of major predators.The almost cosmopolitan distribution of M. edulis in the N. hemisphere has been made possible by virtue of its high reproductive capacity, successful larval dispersion and wide tolerance of environmental conditions, Its patchy and apparently erratic distribution both from one shore to annother and even on the same shore, is greatly influenced by the local and seasonal abundance of major predators. Whilst the upward extension of mussels is prevented, ultimately, by physical factors (e.g. temperature, dessication), its lower limits (and absence from the shallow sub littoral on many shores) are governed essentially by predators. The upward extension of many predators such as crabs or starfish, resulting in locally intense predation, may in turn be partly influenced by the actual topography of the shore itself.

The ecology of Mytilus edulis L. (Lamellibranchiata) on exposed rocky shores : I. Breeding and settlement.

Abstract: The population structure and apparently erratic distribution patterns exhibited by M. edulis on many open exposed coasts, are discussed in the light of findings relating to the breeding and settlement of this species. In the absence of previous literature concerning open coast mussels, the reproductive cycle has been described in some detail. These mussels do contribute to the spawning stock, and in the three years from October 1964-December 1967, the period of spawning was shown to be particularly extended. Spawning occurred mainly from early spring to late summer, though individuals could be found in the spawning condition more or less throughout the year. No marked or consistent differences in the spawning periods of mussels from different local habitats or amongst animals of different size (=age) were recorded. Sexual maturity was attained in the first year of life.The appearance of larvae in plankton samples confirmed the times of major spawnings recorded from histological preparations of the gonad. Settlement of young mussels (=plantigrades) on existing beds was not direct, there being a period of temporary attachment spent especially upon filamentous substrates. This occurred after about 3-5 weeks of planktonic existence. The majority of plantigrades remained on these primary sites for a period of 4 weeks (i.e. until they measured from 1-2 mm in length), although those settling later in the year often remained there overwinter before migrating on to adult beds. The stimulus to migrate is due to changes in the thigmotactic requirements of small mussels. Whilst filamentous substrates were ideally suitable to early plantigrades, somewhat older individuals preferred the niches and crevices provided on adult beds (especially amongst the byssus threads) and by the small cracks and pits in the rock surface. Since the thigmotactic requirements of all plantigrades were not satisfied at exactly the same time, some migration to adult beds occurred throughout the year, though periods of maximum settlement occurred from 8-10 weeks after spawning. Migration from these extensive "reservoirs" of temporary attachment could account for the sporadic outbursts of settlement recorded on many shores at certain times of the year and which often could not necessarily be predicted on a knowledge of the breeding cycle alone.Although the extended settlement period is an important contributory factor, it is not thought that this alone could account for the distinctive population structure in this species. At settlement, mussels are particularly gregarious, attraction of plantigrades to adult beds being essentially a thigmotactic response, aided by their ability to attach and detach themselves until favourable situations are encountered. Settlement is favoured by roughened, scarred or pitted surfaces and the distribution patterns on many shores could partly be attributed both to the surface texture or topography of the shore (smooth, rapidly draining shores being particularly unsuitable) or the amount of local wave splash.In a subsequent publication, the population structure and distribution patterns will be examined in the light of growth and mortality rates of this species on exposed shores.

The ecology of shallow water meiofauna in two New England estuaries.

Abstract: The distribution and abundance of shallow subtidal meiofauna in four habitats in the Niantic and Pettaquamscutt estuaries in southeastern New England were studied from October 1964 through October 1965. Numbers of individuals ranged from 1,184 to 5,163/10 cm2, and wet weights from 8.5 to 62.5 mg/10 cm2. Nematodes were the dominant group, averaging 83% of the total numbers and 64% of the total biomass. Among the nematodes, epigrowth-feeding species were dominant at all four stations; in addition, deposit-feeding species were abundant at three stations where the amount of detritus was high relative to the fourth station. At these three stations ostracods and deposit-feeding polychaetes were also abundant.Nematodes showed marked seasonal changes i their species composition, with epigrowth-feeding species reaching maximum densities in spring and summer (coincident with observed increases in benthic microflora production), and deposit and omnivorous-feeding species in fall and winter (coincident with observed increases in organic detritus). Increases in the epigrowth feeders were responsible for significant increases in the total nematode populations in spring and summer.Ostracods were most abundant in late summer, fall and winter in association with the increases in detritus. Polychaetes, amphipods and lamellibranchs were most abundant in summer, the first-named in association with elevated water temperatures. Harpactacoid copepods were inconsistent in their seasonal distributions.Approximately 80% of the meiofauna occurred in the upper 3 cm of sediment. Copepods and ostracods were virtually limited to the upper 3 cm, while amphipods and lamellibranchs were limited to the upper 2 cm of sediment. Nematodes and polychaetes extended down to 5 cm (the lowest depth studied), although usually in significantly reduced numbers.

Growth rates and longevity of some gastropod mollusks on the coral reef at Heron Island

Abstract: Information on growth, gained from individually marked animals, is provided for at least one species of each of the families Trochidae, Neritidae, Strombidae, Cypraeidae, Thaisidae, Fasciolariidae, Vasidae and Conidae. Except in the cowries and strombs, which have determinate growth, shell growth is adequately described by a von Bertalanffy curve only to a certain point. Beyond this, growth continues slowly and at a rate that is independent of size. Size frequency distributions are characteristically negatively skew, mainly because early growth is fast relative to the total life span. Longevities seem to indicate that turnover rates are comparable to those of Prosobranch mollusks from colder seas.

Die relative Wirksamkeit von Zeitgebern.

Abstract: 1. External cycles may influence biological functions by entraining their endogenous circadian oscillation or by directly influencing the function measured. In order to distinguish between these two possible effects it is necessary to record the free-running period of the circadian oscillation under constant conditions, before and after the exposure to an external cycle (Fig. 4) since otherwise the results might be obscured by masking effects (Figs. 1-3). Here only synchronization of the circadian cycle is called a Zeitgeber effect. 2. Whether the circadian oscillation is entrained by a Zeitgeber depends on the difference between the spontaneous circadian period and the period of the Zeitgeber, and the strength of the Zeitgeber (Fig. 5). The strength of the Zeitgeber also influences the duration of resynchronization after a phase shift of the Zeitgeber oscillation, and the phase relation between circadian cycle and Zeitgeber cycle during entrainment. These conclusions, which are derived from the assumption that the circadian periodicity is a self-sustained oscillation in the technical sense, have been experimentally verified for biological circadian oscillations (Figs. 6 and 7). 3. The statement that certain types of factors act as Zeitgebers and others do not, is not meaningful in such general terms, as shown by the experimental evidence. There are only different strengths of Zeitgeber modalities. However, in this respect one would expect large interspecific and even intraspecific differences, depending on organization and biology of the different organisms. An example for interspecific differences in Zeitgeber strength of light cycles is given (Fig. 9). 4. Light, temperature (Table 1 and 2), acoustical signals (Table 3) and electrical fields have so far been demonstrated to act as Zeitgebers. It is suposed that many other Zeitgeber modalities will be found, which will be different for different groups of organisms. The only valid generalization so far seems to be that temperature cycles are strong Zeitgebers in poikilothermic organisms, but only very weak ones in homoiotherms (Table 1 and 2). 5. It is mentioned that Zeitgeber effects may also contribute to the internal synchronization of different circadian oscillations within the organism.

Field experiments on the movements of Apodemus sylvaticus L. using trapping and tracking techniques

Abstract: The movements of Apodemus sylvaticus were studied by trapping, tracking and direct observations in a woodland of newly planted conifers. Apodemus lived in groups or “super-families” with a dominant male (23–28g) in control. The dominant of each superfamily patrolled its territory (up to 6.4 acres) exploring it sector by sector, or more generally. Unfamiliar objects were carefully examined and labelled by urination. One dominant appeared to know when a neighboring dominant was absent and might then extend his area of movement. The other Apodemus mostly remained within the territory of their accepted dominant. Groups of subordinates moved together to preferred feeding grounds within the general territory, but outside their own individual home sites. The female Apodemus maintained compact ranges (average 0.2 acres), using one group of runways for a time and then disregarding them for another group. Females moved to new sites when populations were low (April to July) but had overlapping ranges in late summer when populations were high. Small monopolized zones were established by pregnant females. Factors influencing behavior and population control are discussed. There was no evidence of a year of peak population for Apodemus from 1963–1966.

[Comparative bio-acoustic investigations in the fire-bellied toad and the yellow-bellied toad, bombina bombina (L.) and bombina v. variegata (L.)].

Abstract: 1. During their annual activity period the toads have 2 or 3 separated calling seasons. The calling activity depends upon the water temperature. The lower limit of the calling activity of the fire-bellied toad is 12.5-13.5°C, the upper limit 30-34°C. The limits of the calling activity of the yellow-bellied toad are lower, the lower limit being 11.5-12° C and the upper limit 26-30° C. 2. According to the fluctuations of the water temperature, the toads demonstrate three different types of calling activity in the course of the year. During the first calling season they croak predominantly in the daytime, whereas they exhibit calling activity in the morning and in the evening or only in the evening during the following calling seasons. 3. Male calling toads occupy circular teritories. The territories of fire-bellied toads have a radius of 1-1.5 meters, whereas those of the yellow-bellied toads have a radius of only 0.5-0.75 meters. In both species the mating calls are territorial in function. 4. The fire-bellied toad has 5 different calls, the normal mating call, the modified mating call, the clasping call and the release calls of first and second order. Not having the release call of first order, the yellow-bellied toad has only 4 calls. The calls consist of harmonically related frequencies and are produced by forcing the air out of the oral cavity through the larynx and into the lungs. In toads the lungs are functional vocal sacs. 5. The mating calls of both species are related to environmental temperature. The repetition rate of calls of both species and the fundamental frequency of the calls of the fire-bellied toad are directly proportional to increasing water temperature. The duration of calls, however, decreases logarithmically with rising temperature. The increasing basic frequency of the yellow-bellied toad's call follows none of the above described patterns. 6. The mating calls of both species also change when the toads grow. Larger animals have a lower fundamental frequency and a longer duration of calls than smaller ones. On the other hand, the number of calls does not depend on the size of the toad and represents the most reliable differential characteristic of toad species.

Phasenlage der Tagesperiodik in Abhängigkeit von Jahreszeit und Breitengrad.

Abstract: Es wird die Hypothese vertreten, das die regelhaften jahreszeitlichen Anderungen der Phasenbeziehung zwischen Aktivitatsrhythmik und naturlichem Licht-Dunkel-Wechsel auf der Grundlage spezieller Synchronisations-mechanismen erklart werden konnen. Im Teil 1.1 werden die endogenen und exogenen Faktoren besprochen, die theoretisch die Phase zu beeinflussen vermogen. Die Uberlegungen fuhren zu dem Schlus, das das Licht-Dunkel-Verhaltnis und die Dauer der Dammerung im wesentlichen die Phase bestimmen. Experimentelle Belege sind in Teil 1.2 enthalten. In Teil 2 werden Freilandbeobachtungen uber Beginn und Ende der Aktivitat von Vogeln neu ausgewertet. Diese Ergebnisse, wie auch Meswerte der Aktivitat von Tieren in Innenraumen (Teil 3), stutzen die Hypothese. Sie zeigen alle maximal voreilende Phasen im Mittsommer bei tagaktiven Arten bzw. im Mittwinter bei einer nachtaktiven Art. Einige, in Teil 4 erwahnte Ausnahmen von dieser Regel, werfen die Frage auf, in welchem Ausmas die Ergebnisse verallgemeinert werden durfen. In der Arbeit werden auch die einheitlichen jahreszeitlichen Anderungen der Aktivitatszeit erortert.

[Bio-acoustic investigations in the green frog, rana esculenta (L.)].

Abstract: 1. An einem Teich in der Nahe Tubingens dauert die Rufperiode des Wasserfrosches von Mitte/Ende April bis Anfang/Mitte Juli; sie ist aufgrund einer zweimaligen Umstimmung im Rufverhalten und der wechselnden Zahl der Rufgruppen in Vorlaichzeit, Laichzeit und Nachlaichzeit unterteilt. 2. Wasserfroschmannchen sammeln sich zu Rufgruppen an. Die Gruppentiere lassen ein gemeinschaftliches, rhythmisches Chorrufen horen. 3. Die Rufaktivitat wird von 3 exogenen Faktoren beeinflust, dem Wetter, der Wassertemperatur und der Lufttemperatur. Die Abhangigkeit der Rufaktivitat von diesen Faktoren ist nicht linear. Im Verlauf einer Schonwetterperiode nimmt die Rufaktivitat von Tag zu Tag zu, wahrend einer Schlechtwetterperiode von Tag zu Tag ab. An Tagen, an denen die Sonne scheint, ist die Rufaktivitat bei 17,5 bis 22±1°C Wassertemperature am grosten. Von diesem Bereich aus fallt sie mit sinkender oder steigender Wassertemperatur asymptotisch gegen Null. Die untere Grenze der Rufaktivitat liegt bei 10–12°C, die obere bei 36,5±0,5°C. Bei zunehmender Erhohung der Lufttemperatur sinkt die Zahl der Rufe/Zeiteinheit asymptotisch gegen Null. 4. Der mannliche Wasserfrosch gibt 6 Rufe ab: einen Paarungsruf, 2 Revierrufe, 2 Befreiungsrufe und einen Schreckruf. Die Rufe bestehen aus Impulsen, die beim Paarungsruf zu charakteristischen Impulsgruppen angeordnet sind. Der weibliche Wasserfrosch gibt ebenfalls Rufe ab, jedoch keine Paarungsrufe. 5. Die Parameter der Paarung- und Revierrufe unterliegen dem Einflus der Wassertemperatur. Mit steigender Wassertemperatur nimmt die Rufdauer linear ab, die Impulsfolge und die Wiederholungsrate der Impulsgruppen weisen dagegen eine positive lineare Regression auf. Auch die Tiergrose beeinflust die Rufparameter. Mit zunehmender Korperlange nimmt bei Paarungs- und Revierrufen die Dauer ab und die Impulsfolge zu, bei den Paarungsrufe verringert sich auch die Wiederholungsrate der Impulsgruppen. 6. Der Kehlkopf des Wasserfrosches besteht aus 3 Knorpelelementen, der unpaaren Cartilago cricotrachealis und den 2 Cartilagines arytaenoideae. Vorhanden sind auserdem 4 Muskelpaare. Die Muskeln werden uber 2 Aste des N. vagus, den N. laryngeus longus und den N. laryngeus brevis, innerviert. Der Kehlkopf ist bei beiden Geschlechtern gleich gebaut, bei den Mannchen aber groser als bei den Weibchen. Der Kehlkopf des Seefrosches (Rana ridibunda ridibunda Pallas) unterscheidet sich nur unwesentlich von dem des Wasserfrosches. Auch bei dieser Art ist der mannliche Kehlkopf groser als der weibliche. 7. Die Ausdifferenzierung der Kehlkopfstrukturen ist beim Wasserfrosch nach vollendeter Metamorphose abgeschlossen. Die Jungtiere erzeugen Rufe, die den Revierrufen adulter Mannchen ahneln.

Photoperiod acclimation and 24-hour variations in the critical thermal maxima of a tropical and a temperate frog.

Abstract: The effect of photoperiod on the upper thermal tolerance of two species of frogs was studied by using the critical thermal maximum (CTM) as the end point Both species are heliotropic and from temperate climates, but Hyla labialis lives under a near constant tropical photoperiod while Rana pipiens lives under a varying temperatezone photoperiod The CTM of both species was studied over a 24-hour period to determine if a rhythm of temperature tolerance exists In all but one of the acclimatization conditions used, the CTM of R pipiens was higher than that of H labialis This agrees with what is known of their thermal ecology Photoperiod significantly affects the CTM of both species For Rana pipiens long (LD 16:8) photoperiods result in significantly higher thermal tolerance than short (LD 8:16) or moderate (LD 12:12) photoperiods at both 15 and 25° C H labialis shows a different pattern, having highest CTM at 25°C, LD 12:12 and lowest at 15°C, LD 12:12 When acclimated to a short (LD 8:16) photoperiod certain aspects of the frogs' tolerance of high temperatures are altered At the same acclimatization the CTM of R pipiens is higher than that of H labialis, except under a combination short light regime and low temperature, and H labialis at LD 8:16 shows no thermal acclimation between 15 and 25°C Significant variation in the CTM over a 24-hour period occurred in H labialis acclimatized at 25°C, LD 12:12 and R pipiens at 25°C, LD 8:16 and 15°C, LD 12:12 For both species the 24-hour rhythm of temperature tolerance, when it occurs at LD 12:12, might be of adaptive value Times of highest thermal tolerance are in the late morning or early afternoon and lowest tolerance is during the dark period For R pipiens under the unnatural combination of 25°C, LD 8:16, the pattern is reversed When all three significant cycles are phase shifted so that the times of highest tolerance coincide, the pattern of the curves is very similar

Patterns in the release of gaseous ammonia by terrestrial isopods.

Abstract: In the fall and in early spring P. scaber and O. asellus released gaseous ammonia in the form of more or less regularly spaced bursts. In the spring about twice as much ammonia was released by O. asellus than in the fall. In late spring and summer, however, both species released ammonia in a rhythmic fashion, with a maximum at noon and early in the afternoon, and a minimum early at night. Sometimes a second maximum occurred late at night.

The control of larval hibernation and of adult aestivation in the Carabid beetlesNebria brevicollis F. andPatrobus atrorufus stroem

Abstract: 1. Nebria brevicollis andPatrobus atrorufus have hibernating larvae and adults that breed in autumn. The young adults hatch in spring and early summer and undergo an aestivation diapause before maturation and reproduction. 2. N. brevicollis hatches earlier and breeds later in the year thanP. atrorufus, so that it shows a summer diapause of about 3.5 months. The aestivation diapause ofP. atrorufus lasts only 1.5 months. 3. In the laboratory the larvae of both species need cold for their development. While cold (+2–4° C) is obligatory forN. brevicollis from the first instar onwards,P. atrorufus larvae tolerate higher temperatures (15° C) except for the third instar. Low temperatures seem to stimulate the development of this species, too, if applied from the first instar onwards. The duration of development ofN. brevicollis is about 1.5 months shorter than that ofP. atrorufus. Metamorphosis again demands higher temperatures at the end of the third instar in both species. 4. The aestivation diapause of the adults is dependent upon the photoperiod. Long-day prevents maturation of the ovaries in the females. Ovarian maturation needs about 1 month short-day inP. atrorufus and 2–3 months inN. brevicollis. In agreement with these resultsP. atrorufus breeds about 1 month andN. brevicollis 2.5 months after summer solstice. 5. Females ofP. atrorufus mature after short-day treatment at 20° C, while those ofN. brevicollis need a decline of temperature in addition. 6. A shift from 20 to 15° C in continuous long-day yields no mature females ofN. brevicollis after 2 months. A small number ofP. atrorufus females (19%) mature after 5 weeks under continuous long-day treatment at 15° C. 7. The males of both species ripen nearly independently of the applied photoperiod.

Die kombination verschiedener endogener Rhythmen bei der zeitlichen Programmierung von Entwicklung und Verhalten

Abstract: Zahlreiche Periodizitatsphanomene in Entwicklung oder Verhalten sind nicht allein auf den Tag-Nacht-Zyklus abgestimmt, sondern gleichzeitig auf den Gezeitenzyklus oder auf den Spring-Nipptiden-Zyklus oder auf den Jahreszeitenzyklus. Die bisher vorliegenden Befunde uber die bei diesen Zeitmesvorgangen genutzte Kombination von endogenen Rhythmen verschiedener Periodendauer werden diskutiert. Hierbei werden die Kombinationen zwischen circadianen und circatidalen, zwischen circadianen und circasyzygischen (=endogenen semilunaren) und zwischen circadianen und circannualen Rhythmen besprochen. Hinsichtlich des Kombinationsmodus werden 5 Typen unterschieden, bei denen jeweils zwei endogene Rhythmen entweder simultan (nach Art einer Superposition) oder sukzessiv auf physiologische Vorgange einwirken und die geforderte zeitliche Programmierung ermoglichen.

Diurnal rhythms in Lapland Simuliidae (Diptera)

Abstract: 1. Es werden neue Methoden beschrieben, die es erlauben, Hautungs-, Verpuppungs- und Schlupfrhythmus der Simuliiden im naturlichen Milieu und unter experimentell veranderten Bedingungen zu untersuchen. 2. Die Larven fressen zu allen Tageszeiten. Tagesperiodische Unteschiede im Verhalten wurden nicht beobachtet. 3. Unter ungestorten Bedingungen ist die Driftrate der mittleren und grosen Larven sehr gering (0,05% pro Tag;n=5500). Junglarven driften wesentlich starker, konnten aber nicht quantitativ erfast werden. Eine Driftperiodik erlaubt noch keine Aussagen uber den Tagesrhythmus der Larven. 4. Die Larven hauten und verpuppen sich zu allen Tageszeiten. Die Zahl der Hautungen und Verpuppungen erreicht jedoch im Freiland nachmittags ein Maximum. 5. Die Dauer des Puppenstadiums ist von der Temperatur und der Tageszeit der Verpuppung abhangig. Sie schwankt im Kaltisjokk um 6–7 Tage. 6. Die Schlupfsaison von 9 Arten wird in zwei einander folgenden Jahren verglichen. 7. Alle untersuchten Arten (10) schlupfen am Tage. Der Schlupfrhythmus bleibt im Dauerlicht des nordischen Sommers sowie im kunstlichen LL und DD erhalten. 8. Das Schlupfen wird vom Licht-Dunkel-Wechsel und von der Temperatur gesteuert. Innerhalb okologischer Grenzen ist das Licht der dominierende Zeitgeber. 9. Im LL und DD folgt einem Anstieg der Temperatur nach 2 Std ein Schlupfschub. 10. Im Naturtag wird bei tiefen Temperaturen das Schlupfen auf die Mittagszeit konzentriert, bei hohen ist seine tageszeitliche Verteilung breiter und kann zweigipflig werden. Artspezifische Unterschiede wurden nicht gefunden. Die Geschlechter verhalten sich gleich. 11. Simuliiden fliegen eine CO2-Falle vorwiegend morgens und abends an.Helodon ferrugineus wurde nur nachts in Lichtfallen gefangen.

Adaptations of the intertidal midge Clunio to arctic conditions

Abstract: 1. The arctic population of Clunio marinus in Tromso (Norway) (69°39′N) shows a tidal periodicity of emergence (period: 12.4 hours). Emergence occurs between the times of high and low tide. 2. A semilunar periodicity of pupation could not be detected. 3. In accordance with the tidal periodicity of emergence and reproduction, the habitat is situated in the midlittoral zone (area between the high and low water levels of neap tides). High densities of pupation are found in a sandy mud flat. 4. The Tromso population is compared with European populations in temperate latitudes, which are characterized by a semilunar periodicity of emergence, and a habitat around the infralittoral fringe of the midlittoral zone. The different adaptations of the populations in biological rhythms and preferred habitat are discussed with regard to the geographic differences in photoperiodic conditions.

On the biology and ecology of halacarus basteri basteri Johnson 1836

Abstract: The carnivorous marine mite Halacarus basteri was reared on blotting paper in artificial sea water of different salinities. The mites find their food by aid of chemically working sense organs which are situated on the tarsi of the first pair of the legs and perhaps at the top of the pedipalpi. All stages of development straddle with their legs when in open water. Thus the legs become gliding filaments which reduce the sinking speed. Development from egg to the propagating mite takes one year. Sperm transmission is carried out indirectly by spermatophores (Fig. 2).In their normal range of life (salinity from 8 to 25‰) the mites behave poikilosmotic and hyperosmotic. Between 25 and 45‰ they show a hypertonic-hypotonic regulation (Fig. 3). In extreme salinities the mites swell or shrink; they recover in normal salinity (Fig. 4). The mites stand extremely low temperature without damage (Fig. 5).

[The development of the mycetome in the embryo of Euscelis plebejus Fall. (Homoptera-Cicadina)].

Abstract: 1. Anhand von histologischen Befunden wird die embryonale Entwieklung der symbiontenfuhrenden Organe der Kleinzikade Euscelis plebejus Fall. beschrieben. Daran schliest sich ein Uberblick uber die Architektur des larvalen und imaginalen Mycetoms an. 2. Die Entwicklung der symbiontischen Einrichtungen ist zeitlich korreliert mit der Embryonalentwicklung des Wirtsorganismus. 3. Die annahernd runde Infektionsmasse (Symbiontenball) aus regellos durcheinanderliegenden a- und t-Bakterien wird durch das Periplasma gegen den Dotter des frisch abgelegten Eies abgegrenzt. Gleichzeitig mit der Blastodermbildung legen sich Furchungszellen (Furchungsenergiden) als Epithel um den Symbiontenball. 4. Die Sonderung der beiden Symbiontentypen geschieht durch Aufnahme des Hauptsymbionten (a-) in die epithelialen Furchungszellen, wahrend der Symbiontenball am caudalen Ende der einrollenden Keimanlage durch den zentralen Dotter bewegt wird. 5. Im gleichen Entwicklungsabschnitt vermehren sich beide Symbiontentypen, so das der Symbiontenball etwa das 6fache Ausgangsvolumen erreicht. 6. Die Einrollung des Keimstreifs ist von einer Plasmastrahlung im Dottersystem begleitet. 7. Die Urgeschlechtszellen verbinden den Symbiontenball wahrend der Caudalkrummung des Keimstreifs mit dem V. und VI. Abdominalsegment. 8. Gegen Ende der Caudalkrummung differenzieren sich aus der visceralen Coelomwand des II. Abdomensegments polyploide Zellen, welche mit der Verkurzung des Keimstreifs an den Symbiontenball gelangen und dort die t-Symbionten aufnehmen, wodurch median ein transitorisches Mycetom entsteht. 9. Die Zellen, die bei der Einrollung die a-Symbionten aufgenommen haben, werden wahrend der Verkurzung des Keimstreifs wahrscheinlich gegen zweikernige mesodermale Zellen aus der Genitalleiste des IV.-VI. Abdominalsegments ausgetauscht. 10. Die typischen Lateralmycetome, die in getrennten Bezirken a- und t-Mycetocyten beherbergen, entstehen aus dem unpaaren transitorischen Mycetom durch Umlagern der a- und t-Mycetocyten wahrend und nach der Ausrollung des Keimstreifs. 11. Im larvalen und imaginalen Mycetom wird das a-Organ von einem hohen Epithel umgeben, dessen Zellen Ahnlichkeit mit nicht ausdifferenzierten Fettkorperzellen haben. Das t-Organ ist von einer dunnen kernarmen Membran bedeckt. Die polyploiden t-Mycetocyten vermehren sich in den Larvenstadien und in der Imago durch Mitosen. Am caudalen Ende des Mycetoms weiblicher Imagines befindet sich der Infektionshugel, in dem die Infektionsformen der a-Bakterien entstehen. 12. Die an Euscelis plebejus gewonnenen Ergebnisse werden mit der embryonalen Entwicklung symbiontischer Einrichtungen bei anderen Zikadenarten verglichen. Abschliesend gilt die Diskussion moglichen Kausalbeziehungen bei den Ortsveranderungen von Symbionten und Mycetocyten sowie phylogenetischen Gesichtspunkten der embryonalen Mycetomentwicklung.

Der Vitaminbedarf normaler und aposymbiontischer Lasioderma serricorne F. (Coleoptera, Anobiidae) und die Bedeutung der symbiontischen Pilze als Vitaminquelle für ihre Wirte

Abstract: Die Aufzucht normaler Lasioderma serricorne gelang in voll definierten, vitaminfreien Diaten uber 4 Generationen. Im Vergleich mit einer Diat, die alle von aposymbiontischen Larven benotigten B-Vitamine und ein Sterin enthielt, war die Entwicklung deutlich verzogert. Durch Aufzucht normaler und aposymbiontischer Tiere in Diaten, denen jeweils eines der benotigten Vitamine fehlte, konnte eine Lieferung von Thiamin, Lactoflavin, Pyridoxin, Nicotinsaure, Pantothensaure, Cholin und von einem Sterin durch die Symbionten nachgewiesen werden. Der Nachweis einer Biotinlieferung gelang, indem aposymbiontische Larven in einer biotinfreien Diat aufgezogen wurden. Ein Teil ihrer Nachkommen wurde mit den Symbionten reinfiziert und ihr Wachstum in einer biotinfreien Diat verglichen. Normale Larven benotigen 2 mg, aposymbiontische 8 mg Cholinchlorid pro g Diat fur optimales Wachstum. Zusatze von meso-Inosit, Carnitin, Ribo- und Desoxyribonucleinsaure blieben in einer kompletten Diat unwirksam. Heliosan-Bierhefe (Cenovis) enthalt einen wachstumsfordernden Faktor, der nach Extraktion mit Chloroform, Methanol und Wasser im unloslichen Ruckstand verbleibt.

Saugverhalten und Nahrungsaufnahme von Oncopeltus fasciatus Dallas (Heteroptera, Lygaeidae).

Abstract: The feeding behaviour of Oncopeltus fasciatus has been investigated. Exploration of food materials is performed by means of watery saliva which is secreted onto surfaces of substrates and sucked back again. Histological tests indicate that the animal preferably pierces the conducting system of the Vicia faba plant. Oncopeltus fasciatus secretes sheath material which coagulates and forms a lining to the path of the stylets during plant feeding. Feeding on seeds (Asclepias syriaca and Helianthus annuus) is not accompanied by stylet sheath formation. The function of this stylet sheath is discussed. Under extreme conditions the phytophagous animal shows cannibalism in spite of its marked subsocial behaviour. Penetration of the cuticle seems to be effected mainly by mechanical forces. No chitin-splitting enzyme could be detected in the saliva. The feeding activity over a photoperiod of 12 hrs on plants (uptake of water) and seeds (uptake of nutritive materials) is determined. It is suggested that on a green plant the animal is saturated more rapidly than on dehydrated seeds. The considerable amounts of watery saliva emulsify and suspend the contents of the seeds. Into seeds of Asclepias syriaca saliva is injected at a rate of approximately 1.14 mg/animal/hr.

Experimentelle Untersuchungen über den Einfluß von Tageslänge und Temperatur auf die Gonadenreifung beim Dreistachligen Stichling (Gasterosteus aculeatus).

Abstract: 1. Experimental investigations on the influence of photoperiod and temperature on gonad development in Gasterosteus aculeatus were carried out between October 1967 and January 1968. 2. A combination of long photoperiod and high temperature has proved to stimulate gametogenesis while a combination of short photoperiod and high temperature leads to a complete cessation. Low temperature leads to a slight gonadal development, irrespective of day length. There seem to be no sexual differences in the reaction to these environmental factors. 3. The secondary sex characteristics of the male may appear despite total absence of interstitial tissue. This indicates that either testosterone may be produced outside the Leydig cells, or other hormones may be responsible for the appearance of the secondary sex characteristics. 4. Very high population density (1 fish/4 l) prevents the appearance of the secondary sex characteristics even in the presence of Leydig cells. The females are incapable of completing gonad development if the males do not exhibit secondary sex characteristics.

Freilebende Nematoden als Nahrung der SandgarneleCrangon crangon

Abstract: Sandgarnelen (Crangon crangon) verschiedener Grosenklassen konnten unter Laboratoriumsbedingungen mit freilebenden Nematoden als einzige Nahrung bis zu 210 Tagen am Leben erhalten werden. Fur diese Experimente wurde der saprobe NematodePanagrellus redivivus benutzt, der etwa gleichgros ist wie marine freilebende Nematoden (0,0003–0,0015 mg Trockengewicht), und der ebensogern wie diese von den Garnelen als Nahrung angenommen wird. Die Garnelen konnen bis zu 5 Nematoden pro Minute aus dem Luckensystem des Sandes herausfangen, doch halten sie dieses Tempo nur etwa 1/2 Std durch und legen nach der Erbeutung von etwa 300 Nematoden (0,2 mg Trockengewicht) eine Frespause ein. Deshalb wird sehr viel weniger Nahrung aufgenommen als bei der Erbeutung von Makrofauna-Vertretern, denn ein 1,5 mg schweres Stuck des PolychaetenLanice fullt den Magen. Die groste Nahrungsaufnahme bei Nematodenernahrung war bei 20 mm langenCrangon nur 1,5 mg am Tag. Hierdurch wird verstandlich, das bei den Experimenten nur ein sehr geringer Zuwachs beobachtet wurde (1 mm in 25–74 Tagen) oder ein Wachstumsstillstand eintrat. Ohne Nahrung sterbenCrangon unter den Versuchsbedingungen in 27–47 Tagen ab. Auch wenn es sicher ist, das insbesondere grosere Garnelen nicht gut mit einer ausschlieslichen Nematoden-Ernahrung gedeihen konnen, so ist doch nicht von der Hand zu weisen, das Meiofauna-Populationen in Ermangelung besserer NahrungsquellenCrangon auch in freier Natur vor dem Verhungern bewahren konnen.

[The vitamin requirements of normal and aposymbiotic lasioderma serricorne F. (Coleoptera, Anobiidae) and the role of symbiotic fungi as vitamin sources for their hosts].

Abstract: Normal Lasioderma serricorne were reared on a totally synthetic, vitamin-free diet for 4 subsequent generations, though development was substantially retarded when compared with that in a diet containing all B-vitamins and a sterol necessary for growth of aposymbiotic larvae Comparing growth in the presence or absence of the symbionts on diets with a single vitamin omitted it was demonstrated that the microorganisms are able to supply thiamin, lactoflavin, pyridoxine, nicotinic acid, pantothenic acid, choline and a sterol The importance of symbionts for the production of biotin was shown with aposymbiotic larvae whose parents had been reared on a biotin-free diet, and part of whom had been reinfected with their symbionts Normal larvae need a concentration of 2 mgs, aposymbiotic of 8 mgs, of choline chloride per g diet for optimal growth Mesoinositol, carnitine, ribo- and desoxyribonucleic acid did not influence growth on a complete diet Heliosan beer yeast (Cenovis) contains a growth promoting factor remaining in the insoluble residue after extraction with water, methanol and chloroform

Zusammenhänge zwischen Tagesrhythmik, Jahresrhythmik und Habitatbindung bei Carabiden.

Abstract: Carabid beetles of forest habitats are mostly hygrophilous and darkpreferring species. Nearly all of them are nocturnal, and the majority are autumn breeders. Most carabids from open field habitats are xerophilous, light-preferring and diurnal species, or they are indifferent to humidity and light and can be active by day and night. This group includes markedly more spring breeders than the forest species. The adaptative value of the observed correlations is discussed.

Tageszeitliche Verzahnung der Aktivität verschiedener Organismen.

Abstract: Synchrony of diurnal activity patterns seems to have evolved entirely between groups of species. No well established case of synchrony is known which involves only two species. The interdependence of activity patterns based on diurnal rhythms is a phenomenon well known in autecology, e.g. between flowers and their pollinators, parasites and their hosts, predators and their prey.At different daytimes there are completely different food chains in one and the same biotope.The few existing quantitative investigations reveal that 1. strong selective pressure can limit the diurnal activity of a species; 2. the productivity in a biotope may reach a maximum when the daily feeding time of its predators is restricted. This seems to hold, e.g., for the marine plancton.

Tages- und jahresperiodische Driftaktivität der Wassermilben (Hydrachnellae, Acari).

Abstract: 1. Von April 1963 bis Marz 1964 wurde die Driftaktivitat in 2-Std-Intervallen von 5 Arten der Hydrachnellae im Breitenbach, einem Fuldazuflus, untersucht. 2. Sperchon glandulosus, Sperchon setiger und Atractides nodipalpis sind tagaktiv, Lebertia glabra ist nachtaktiv und Lebertia salebrosa ist dammerungsaktiv. 3. Das Muster der Jahresperiodik der Driftaktivitat von Lebertia glabra, Lebertia salebrosa und Atractides nodipalpis ist eingipflig. 4. Die beiden Lebertia-Arten haben zu verschiedenen Tageszeiten ihre taglichen Driftmaxima, haben aber zur gleichen Zeit ihre jahrlichen Driftmaxima. Die beiden Sperchon-Arten haben zur gleichen Tageszeit ihre taglichen Driftmaxima, ihre jahrlichen Driftmaxima haben einen Abstand von 2 Monaten. 5. Wahrend der jahrlichen Driftmaxima treten in groser Zahl eiertragende Weibchen auf. Die Drift wird im Zusammenhang mit der Eiablage gesehen und ein moglicher Besiedlungskreislauf fur die Hydrachnellae diskutiert.

[Free-living nematodes as food of the sand shrimp, Crangon crangon : Experiments on the role of meiofauna as food of the marine macrobenthos].

Abstract: Under laboratory conditions,Crangon crangon of different size classes survived periods of up to 210 days if fed exclusively with free-living nematodes. Experiments were performed with the saprobic nematode speciesPanagrellus redivivus which is of similar size (0.0003-0.0015 mg dry weight) as marine freeliving species and which is in the same way accepted as food by the shrimps. The shrimps are able to catch nematodes out of a sandy substratum at a rate of 5 nematodes/min, but they do so for only about 30 minutes, stopping after ingesting approximately 0.2 mg dry weight of nematodes. Thus the food intake is much less than with macrofauna prey, e.g. with the polychaeteLanice of which a shrimp may ingest 1.5 mg at one sitting. 20 mm long specimens ofCrangon feeding on nematodes had a maximum food intake of 1.5 mg dry weight per day only which explains why growth was insignificant (1 mm in 25-74 days) or non-existent.Shrimps left without food died within 27-47 days. Even if these animals, especially the larger ones, could not prosper on an exclusive diet of nematodes, in the absence of better food natural meiofauna populations may preventCrangon crangon from starving to death.

Bionomische und ökologische Studien an österreichischen Populationen der Gelbhalsmaus (Apodemus flavicollis, Melchior 1834) durch Markierungsfang.

Abstract: 1. Bionomical and ecological investigations on the yellownecked fieldmouse were carried out in forest habitats of four phytosociologically different areas in the Southeast of Lower Austria and in northern Burgenland between 1963 and 1966. A total of 418 individuals of A. flavicollis were marked and registered by 1226 trappings. 2. In two species, A. flavicollis and A. sylvaticus, winter breeding was observed in a young coniferous forest in the Gfieder area in 1963/64. From the population dynamics it can be concluded that winter breeding had also occurred in 1962/63. 3. Comparing the different areas in different years no regularity was found in the start and end of reproduction period. 4. Maximum weights of males of A. flavicollis were different in the four areas (see Table 5). The following percentages of weights over 35 g were found: 5% (Gfieder), 13% (Strelzhof), 7% (Hernstein) and 28% (Neusiedler Wald). 5. During an investigation period from spring to autumn of the next year an average life time of 3,57 (Gfieder), 3,94 (Strelzhof) and 3,53 (Hernstein) months was determined for A. flavicollis. 6. In all areas the yellow-necked fieldmouse was a typical forest species prefering dense and covered habitats, while the long-tailed fieldmouse, which has a broader ecological spectrum, showed different population densities in the course of a year which can only be explained by a change of habitat. 7. Due to the constantly high infestation with larvae of Ixodes ricinus, the yellow-necked fieldmouse can be regarded as one of the most important hosts of this tick species.

Die Brutzeiten einiger Gänsearten und ihrer Bastarde in identischen Bedingungen.

Abstract: An Hand von 229 Brutbeginn-Daten von freilebenden Gansen, die wahrend der Jahre 1956–1966 in Seewiesen (Obb.) (48°N, 11°11′E) bruteten, wurden die mittleren Brutbeginn-Daten von 5 Gansearten und von Artbastarden bestimmt. Es zeigte sich, das die untersuchten Arten unter diesen Bedingungen in derselben Reihenfolge bruteten, wie ihre Artgenossen in freier Wildbahn. Die mittleren Brutbeginn-Termine wurden allerdings um so mehr vorverlegt, je spater die Art normalerweise brutet (Abb. 1). ♀♀, die mit artfremden ♂♂ verpaart waren, bruteten zur selben Zeit wie ihre Artgenossen, die mit artgleichen ♂♂ verpaart waren (Abb. 1). GraugansxSchneegans-Bastard-♀♀, die mit Schneegantern verpaart waren, begannen meist nach den Graugansen, aber stets vor den Schneegansen zu bruten (Abb. 1, 2). Das intermediare Bruten dieser ♀♀ wird als starkes Argument fur die Richtigkeit der Hypothese gewertet, nach welcher die artspezifisch verschiedenen Brutzeiten wenigstens zum Teil genetisch bedingt sind. In der Diskussion wird die Frage kritisch erortert, wie weit schon allein die Tatsache, das die verschiedenen Arten uber Generationen hinweg in derselben Reihenfolge wie ihre wildlebenden Artgenossen zu bruten beginnen, als Beweis fur derartige genetische Unterschiede angesehen werden kann.

[Studies on the Iguanidae of Madagascar : II. Remarks on the ecology of Chalarodon madagascariensis Peters, 1854].

Abstract: The detailed comments that we made on the repartition map of Chalarodon madagascariensis enable us to define, in the climatological study, the factors limiting the extension of this species. These number two, namely rainfall and sunning. The Chalarodons live in that region of Malagasy where solar heat is strongest and rainfall lowest, and where hot climatological conditions range from subarid to semiarid (the maximum temperature is one of the highest in the island). They live in full sunlight. They are typically xerophilous and heliophilous lizards.They are adapted to life in sandy grounds, over which they move about most swiftly and out of which they dig their holes. The manner these sandy grounds are distributed accounts for the varying density within the area.The most characteristic vegetation is xerophilous bush, sparse enough to afford sufficient sunlight to the ground.These lizards do not undergo real hibernation, but only a marked slackening in their activity during winter in the southern hemisphere (dry and cool season).Lastly this study of the factors of environment allows us to describe some aspects of their biology in relation to their ecology (cycles of activity, nutrition, etc.).