Effects of temperature and salinity on larval development ofElminius modestus (Crustacea,Cirripedia) from Helgoland (North Sea) and New Zealand

Larvae ofElminius modestus (Darwin) from four different populations (Portobello, Leigh, Doubtless Bay [New Zealand] and Helgoland [North Sea]) were reared at different salinity and temperature combinations. The larvae ofE. modestus from Helgoland developed successfully at a wide range of temperature (6° to 24 °C) and salinity (20 to 50 S). Mortality was highest at 10 S; only at 12° and 18 °C did a small percentage develop to the cypris. The larvae from New Zealand were reared at a temperature range of 12°–24 °C at 20, 30 and 40 S; mortality increased in all populations at all salinities with decreasing temperature and was extremely high at 12 °C and 40 S. The temperature influence on larval duration could be described in all cases by a power function. No significant differences in temperature influences on developmental times between the tested salinities were found, except for the Portobello population at 20 S. Significant differences were found in the temperature influence on larval development between the populations from Helgoland and the North Island of New Zealand (Leigh, Doubtless Bay). No differences were found between the Helgoland and Portobello population. The pooled data for the temperature influence on the larval development of the three tested New Zealand populations at 20, 30 and 40 S and the pooled Helgoland data at 20, 30 and 40 S show highly significant differences.Larval size (stage VI) was influenced by experimental conditions. The larvae grew bigger at low temperatures and attained their maximum size at 30 S (Helgoland). There was a strong reduction in larval size at temperatures from 18° to 24 °C. The larvae of the New Zealand populations were smaller than those from Helgoland. The greatest difference in size existed between the larvae from Portobello and Helgoland.     

Growth and reproduction as a function of temperature and salinity inClava multicornis (Cnidaria,Hydrozoa)

Summary 1. Rates of growth (length increase of stolons) and of asexual reproduction (increase in number of polyps) were determined in secondaryClava multicornis colonies of a clone exposed to 12 different combinations of water temperature and salinity (12°, 17°, 22° C; 16 , 24 , 32 , 40 S). Sexual reproduction (via gonophores) has been observed only at 12° and 17° C; temperature and salinity ranges are narrower for sexual than for asexual reproduction.2. The data obtained are insufficient for a detailed analysis; they provide, however, interesting insights into the variability of growth and reproduction ofC. multicornis caused by different intensities of temperature and salinity.3. It appears that temperature requirements for maximum colony increase are reduced as the colony grows older.4. One feeding period per 24 hours seems insufficient for maximum growth and reproduction at the higher temperature levels, especially at 22° C.5. The different degrees of environmental stress endured during the initial period of transfer into the test combinations of temperature and salinity have affected the resulting colony size at least up to an age of 39 days. More appropriate criteria for assessment of rates of growth and reproduction are therefore the doubling times (number of days within which stolon length and polyp numbers taken 20 days after initiation of experiments have doubled).6. On the basis of doubling time values, increase in stolon length is progressively reduced with increasing water temperature (12°, 17°, 22° C). At 12° and 17° C stolons grow fastest in 32 , followed by 24 , 16 and 40 S; at 22° C stolon growth rates are identical in 32 and 24 S.7. Doubling times of polyp numbers per colony show a less obvious trend. In 56-day-old colonies, however, stolon length and polyp number are modified to similar degrees by the various temperatures and salinities offered. The sequence of temperatures causing fastest increase in polyp number is 12°>17°>22° C; the respective sequence of salinities reads: 24 , 32 , 16 , 40 S.8. Stolon length and polyp number per colony increase exponentially; most curves obtained exhibit undulations indicating endogenous growth rhythms.9. During the initial period of transfer into the final test media, asexual reproduction via budding seems to have been stimulated by a reduction in salinity.10. The doubling times obtained forC. multicornis are considerably longer than those found forCordylophora caspia and indicate that our culture conditions may have been suboptimal.

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Wachstum und Reproduktion als Funktion von Temperatur und Salzgehalt beiClava multicornis (Cnidaria, Hydrozoa)

Kurzfassung Einzelpolypen eines Klons vonC. multicornis Forskål wurden schrittweise in 12 verschiedene Temperatur-Salzgehalts-Kombinationen überführt und — während sie zu neuen Kolonien heranwuchsen — das Längenwachstum ihrer Stolonen, die Geschwindigkeit ihrer asexuellen Vermehrung durch Knospung neuer Hydranthen sowie die Gonophorenausbildung (sexuelle Fortpflanzung) registriert. Die erhaltenen Daten sind unzureichend für eine detaillierte Analyse, gewähren jedoch interessante Einblicke in die Bedeutung der verschiedenen Temperatur- und Salzgehaltsbedingungen für Wachstum und Vermehrung. Die anfängliche, schrittweise Überführung in die Testmedien verursacht per se Leistungsunterschiede, deren Auswirkungen sich mindestens bis zu einem Alter von 39 Tagen verfolgen lassen. Doubling times stellen daher objektivere Kriterien dar als absolute Zuwachswerte. Die doubling times von Kolonien, welche länger als 20 Tage in den Testmedien gewachsen waren, zeigen eine Verringerung der Stolonenzuwachsrate mit steigender Temperatur (12°, 17°, 22° C). Die Reihenfolge der fördernden Wirkung der einzelnen Salzgehaltsstufen ergibt sich zu 32 , 24 , 16 , 40 S. Im Prinzip ähnliche Verhältnisse liegen hinsichtlich der asexuellen Vermehrungsrate vor. Bemessen an den getesteten Kriterien scheinen die Temperaturansprüche mit zunehmendem Koloniealter abzunehmen. Die errechneten doubling times sind wesentlich länger als beiCordylophora; möglicherweise deutet dieser Unterschied auf inadäquate Kulturbedingungen (Fütterung, Wasserbewegung) hin.

     

Coelomomyces opifexi (Pillai & Smith). Coelomomycetaceae: Blastocladiales II. Experiments in sporangial germination

Summary Laboratory experiments on sporangial germination and zoospore activity in Coelomomyces opifexi which utilises a suparlittoral environment are described. Sporangial germination depends upon (a) salinity of the medium used and (b) whether the sporangia were derived from living or deceased larvae. Sporangia from living larvae germinated almost instantaneously in distilled, tap, brackish pond and sea water with a salinity of 4.2 There was only partial germination at a salinity of 17, and none at all in 35 (full sea water). Sporangia from deceased larvae required a conditioning of 7 days or more under moisture at 23°C or 28°C before germination. Sporangia from living and moribund larvae became thick-walled and darker when exposed to a salinity of 8.5 or higher. These, likewise, required a conditioning period for germination. The biological and ecological significance of these observations are discussed.

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Zusammenfassung Die in vitro-Versuche an das Keimen und die Zootätigkeit von der supralitteral lebenden spezies Coelomomyces opifexi sind hier beschrieben worden. Das sporenbeheltische Keimen ist abhängig von (a) der Salzhaltigkeit der Umgebung und (b) ob die Sporenbehalter von lebenden oder toten Puppen erhalten sind. Die von lebenden Puppen herstammenden Sporenbehalter keimen sofort in distilliertem, Leitings,- Brack- und 4.2 tigem Salzwasser, nur zum Teil in 17 tigem Salzwasser und gar nicht in Meereswasser (35). Die Wänder der von toten Puppen herstammende Sporenbehalter waren dichter und schwarzer und brauchten mindestens 7 Tage zum keimen in einer feuchten Umgebung von 23° bis zu 28°C. Wenn der Salzgehalt stieg über 8.5, so worden die Wänder beider Arten dichter und schwarzer und brauchten ebenso eine bedingte Periode zum keimen. Die biologische und ekologische Bedeutung dieser Beobachtungen sind diskutiert worden.

     

Adaptive Responses of the Larvae of Cirripede Barnacle Peltogasterella gracilis to Changes in Seawater Temperature and Salinity

The responses of the larvae of the cirripede barnacle Peltogasterella gracilis (Crustacea: Cirripedia: Rhizocephala) that parasitizes the hermit crab Pagurus pectinatus to different combinations of seawater temperature (25, 22, 20, 16, and 12°C) and salinity (from 34 to 8) were studied in a laboratory. The nauplii of P. gracilis completed the entire cycle of development at 22 to 12°C in a narrow range of salinity (from 34 to 28), which agrees well with the environmental conditions of the crab hosts' habitat. At favorable temperatures (22–20°C) and salinity (34–28), the nauplii reached the cypris stage in 88 ± 2 h, while at 12°C and 34–30, the naupliar development took 156 ± 5 h. The cypris larvae appeared more resistant compared with the nauplii, in terms of changes in both the temperature and salinity of seawater. They actively swam at all experimental temperatures and in the salinity range of 34–18. At temperatures (22–16°C) and salinities (34–24) favorable for the cyprids, their longevity in plankton equaled 6–10 days. Thus, the nauplii of P. gracilis is the more vulnerable stage of development in the life cycle of this parasitic barnacle. The tolerance against changes in environmental factors is due to the adaptive capabilities of parasitic larvae and the environmental conditions in the habitats of its host, a typical marine crustacean. The insignificant parasitization rate of the hermit crab by its rhizocephalan parasite may be explained by the death of the nauplii of P. gracilis, which occurs when they enter to the surface water layer.     

Growth rates and the salinity response of an Antarctic ice microflora community

Summary An ice microflora community collected from the bottom of seasonal pack-ice off the Amery Ice Shelf, Antarctica, was grown at salinities which varied from 11.5 to 34. The response exhibited by the community and by individual species was characterized by an initial lag phase-adaptation period followed by a short period of exponential growth. Doubling rates based on changes in chlorophyll a had a range from 0.05 to 0.23 day^-1 during the time required to reach maximum chlorophyll a concentration and a range of 0.04 to 0.42 day^-1 during a period of exponential growth. Exponential growth rates of individual species ranged from 0.2 to 1.0 doublings day^-1. Growth occurred at all salinities above 11.5. Community growth rates increased with increasing salinity, and the growth-salinity response of most species was shifted toward higher salinities suggesting that this Antarctic ice microalgal community was adapted to the ambient salinity regime: 34.     

Combined Effects of Seawater Temperature and Salinity on Development of the Larvae of the Rhizocephalan Peltogaster reticulatus (Crustacea: Cirripedia)

The effects of seawater temperature (12, 16, 20, 22, and 25°C) and salinity (of 8 to 34) in different combinations on the larvae of the rhizocephalan Peltogaster reticulatus (Crustacea: Cirripedia), a parasite of the hermit crab Pagurus proximus, were examined. The development of P. reticulatus is comprised of five naupliar stages and one cypris stage. Nauplii have a specific structure, the flotation collar encircling the dorsal side of the larval body. Larvae lack the pigmented nauplius eye, and they show no positive phototaxis. Successful naupliar development occurred in temperature and salinity ranges of 16–25°C and 20 to 34, respectively; but all nauplii died at 12°C and 16. The duration of each naupliar stage increased under lowering of the seawater temperature. At 22–25°C and 26–28, the entire development cycle was completed in 72–80 h; and at 16°C and 20 it lasted 153 h. The cypris larvae showed a greater resistance to decreased salinity in comparison with the nauplii. At temperatures of 16–25°C and salinities of 14 to 34, the lifespan of cyprids was 6 to 12 days, and it decreased at increasing temperature.     

Effects of short-term storage of gametes on fertilization of Pacific herring eggs

A method is described whereby arrays of samples ofClupea pallasi eggs may be stored during their preparation. The high fertilization potential retained by the eggs during short-term storage allows them to be fertilized synchronously when sample preparation is complete. A variation of the dry method of storage retained maximum fertilization potential (80–85%) of the eggs for about 1 hr, and of milt dilution (18 with 17 S sea water), about 7 hr. Following dry storage, eggs fertilized in salinities of 0–45 showed maximum rates of fertilization in salinities of 10–20, and fertilization rates 50% in salinities of 4.5–42. Salinities of fertilization influenced egg diameter, median hatching time, and larval length at hatching in egg samples transferred 21/2 hr after fertilization to an incubation salinity of 17 at 7°C. Fertilization rates were higher (90–95%) for eggs stored in 17 S at 7°C prior to fertilization. Under such wet storage conditions, maximum fertilization pontential was retained for about 2 hr. Highest fertilization rates (95–96%) were obtained for eggs stored and fertilized in salinities of 12–15. For the species and the area of origin considered (British Columbia), wet storage of eggs should result in maximum fertilization when the eggs are stored at 4°C for a period not greater than 2 hr prior to fertilization in the 12–15 S storage medium.Prepared under the auspices of the Canadian-German Scientific and Technical Cooperation Agreement.     

Microbial autotrophy explains large-scale soil CO2 fixation

Microbial communities play critical roles in fixing carbon from the atmosphere and fixing it in the soils. However, the large-scale variations and drivers of these microbial communities remain poorly understood. Here, we conducted a large-scale survey across China and found that soil autotrophic organisms are critical for explaining CO₂ fluxes from the atmosphere to soils. In particular, we showed that large-scale variations in CO₂ fixation rates are highly correlated to those in autotrophic bacteria and phototrophic protists. Paddy soils, supporting a larger proportion of obligate bacterial and protist autotrophs, display four-fold of CO₂ fixation rates over upland and forest soils. Precipitation and pH, together with key ecological clusters of autotrophic microbes, also played important roles in controlling CO₂ fixation. Our work provides a novel quantification on the contribution of terrestrial autotrophic microbes to soil CO₂ fixation processes at a large scale, with implications for global carbon regulation under climate change.     

Stable sulfur isotopic biogeochemistry of the Hubbard Brook Experimental Forest, New Hampshire

In natural ecosystems, differences often exist in the relative abundanceof stable S isotopes (°³⁴S) that can provide clues as tothe source, nature, and cycling of S. Values of °³⁴S inprecipitation, throughfall, soils, soil solution, and stream waters weremeasured at the Hubbard Brook Experimental Forest (HBEF), New Hampshire.Values of °³⁴S in precipitation and throughfall weresimilar to each other but differed seasonally. Precipitation°³⁴S values were higher in the dormant season[°³⁴S = 5.9±0.6 (17)][Mean + SE(N)]than in the growing season [°³⁴S = 5.0±0.6(40)] but throughfall growing-season values were higher[°³⁴S = 5.6±0.6(68)] than for the dormantseason [°³⁴S = 4.9±0.7 (9)]. Different treespecies did not affect throughfall °³⁴S values. In soilsolution, °³⁴S values were higher in the growing season(°³⁴S = 8.9±2.8; 8.8±1.7;and 4.0±0.6 for Oa, Bh, and Bs horizons, respectively) thanin the dormant season (°³⁴S = 5.6±1.5;3.7±2.4; and 3.4±1.2 for Oa, Bh, and Bshorizons, respectively). These seasonal differences in°³⁴S were probably caused by biological isotopicfractionation. The °³⁴S values in streams were generally2 lower and more variable than those in precipitation andthroughfall, suggesting fractionation and/or different isotopic sources inthe soil.     

Erbrütung der Eier von Dorsch(Gadus morhua), Flunder(Pleuronectes flesus) und Scholle(Pleuronectes platessa) unter kombinierten Temperatur- und Salzgehaltsbedingungen

Zusammenfassung 1. Die Eier von Dorsch (Gadus morhua L.), Flunder (Pleuronectes flesus L.) und Scholle (Pleuronectes platessa L.) der westlichen Ostsee wurden unter kombinierten Salzgehalts-Temperaturbedingungen (0°–16° C, 7–42 S) erbrütet. Es wurde untersucht, inwieweit die Embryonalentwicklung durch das Zusammenwirken von Temperatur und Salzgehalt beeinflußt wird.2. Die optimalen Temperatur- und Salzgehaltsbereiche für die Erbrütung von Dorsch, Flunder und Scholle wurden festgestellt. Für den Dorsch konnten drei Versuche mit unterschiedlichem Material durchgeführt werden. Die optimalen Temperaturund Salzgehaltskombinationen für die Erbrütung von Dorscheiern betrugen: (a) 6°–8° C bei 25–30 S, (b) 4° C bei 20–33 S und (c) 4°–6° C bei 33 S. Für die Flundereier wurde als optimale Temperatur-Salzgehaltskombination 4° C und 33 S gefunden. Die untersuchten Scholleneier entwickelten sich bei 6° C und 20 S am besten.3. In nicht-optimalen Temperatur- und Salzgehaltsbereichen war ein Absinken der Überlebensrate und verstärktes Auftreten morphologischer Anomalien an Embryonen und Larven zu verzeichnen. Als charakteristische Schädigungen traten Verkrümmungen der caudalen Körperregion auf. Larven, die in schwach salzigem Wasser gehalten wurden (20 und 15 S), litten an Dottersackquellung, was bei den Flunderlarven zu Kieferdeformationen führte.4. Als wahrscheinliche Ursache für die Verkrümmungen und Verwachsungen des Schwanzes wurde ein durch extreme Temperaturen allgemein gestörtes Zusammenwirken der Enzyme diskutiert.5. Die Wirkung hoher und niedriger Salzgehalte wurde in der Diskussion auf eine Störung im embryonalen Stoffwechsel zurückgeführt, die durch Änderung im Ionenmilieu der Zelle hervorgerufen wird.6. Mit zunehmender Aussüßung des Erbrütungswassers konnte bei allen untersuchten Eiern Entwicklungsverlangsamung beobachtet werden. Bei hohen Erbrütungstemperaturen wurden die Unterschiede in der Entwicklungsgeschwindigkeit geringer.7. Der für die Erbrütung optimale Salzgehalt änderte sich in Abhängigkeit von der Inkubationstemperatur. Ebenfalls war die optimale Erbrütungstemperatur in Abhängigkeit vom Salzgehalt des Erbrütungsmediums veränderlich. Extrem niedrige Salzgehalte (15 und 20 S) wurden im Bereich der Optimaltemperaturen oder bei niedrigen Temperaturen besser ertragen.8. Bei allen drei untersuchten Fischarten wurde das Auftreten von Brackwasserrassen in der Ostsee erörtert und für wahrscheinlich gehalten.

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Rearing the eggs of cod(Gadus morhua), flounder(Pleuronectes flesus) and plaice(Pleuronectes platessa) under combined temperature and salinity conditions

Eggs of Baltic cod (Gadus morhua L.), flounder (Pleuronectes flesus L.) and plaice (Pleuronectes platessa L.) have been reared under combined temperature and salinity conditions (0°–16° C, 7–42 S). Combined temperature and salinity influences on embryonic development were investigated. Optimum temperatures for the rearing of cod eggs range from 4° to 8° C, and optimum salinities from 20 to 33 S. Flounder eggs develop best at 4° C and in 33 S, and plaice eggs at 6° C and in 20 S. Suboptimum conditions result in lower percentages of larval hatching and survival, and increased morphological anomalies such as curvature of tail and body. Low salinities (20 and 15 S) cause swollen yolk sacs which, in experiments with flounder eggs, lead to jaw deformities. Rearing at low salinity decreases speed of development. Optimum salinity varies as a function of incubation temperature and influences variations in optimum rearing temperature. Extremely low salinities (20 and 15 S) are tolerated best at optimum or lower temperatures. From the results of these experiments it can be concluded that brackish water races of these fishes are likely to exist in the Baltic Sea.

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Diese Arbeit wurde als Dissertation unter der Leitung von Herrn Prof. Dr.K. Lillelund am Institut für Hydrobiologie und Fischereiwissenschaft der Universität Hamburg angefertigt. Für die Drucklegung wurde die Arbeit geringfügig gekürzt und in ihrem Wortlaut abgeändert.     

Life cycles of marine nematodes

Summary Monhystera denticulata Timm, a free-living nematode present in the aufwuchs assemblages of several marine macrophytes located in North Sea Harbor, Southampton, New York, was isolated from Zostera marina and established in laboratory culture in order to study the influences of temperature and salinity on its life history. Under experimental conditions, M. denticulata has a generation time (Measured as the time elapsing between the first egg depositions of consecutive generations) of 10–12 days at 25° C and 26 S, which represent optimal growth conditions in the laboratory. The organism has a generation time of 20 days at 25° C and 13, 17 days at 25° C and 39, 18 days at 15° C and 26, 36 days at 15° C and 13 and 34 days at 15° C and 39. As conditions vary from the optimum of 25° C and 26 S, a decrease in temperature of 10° C and an increase or decrease in salinity of 13 results in a doubling of the generation time. At 5° C the generation time is about 180–197 days.Assuming optimum conditions and average generation time, about 15 generations of M. denticulata could occur in North Sea Harbor during the year. The number of generations occurring in reality is probably less, however, due to the fact that the females deposit their eggs over a period of several days.This work was supported by National Science Foundation Grant GB-19245.Contribution No. 04 from the Institute of Oceanography, City University of New York.     

Ecology of a tidal marsh corixid,Trichocorixa verticalis (Insecta,Hemiptera)

The high marsh panne ecosystem at Adam's Point, N. H. provides a particular opportunity for holistic, yet autecological approach to the natural history of Trichocorixa verticalis var. sellaris (Corixidae). This area was dominated by physical and chemical factors associated with highly variable salinities (1 to 160) and temperatures (–1 to 40°C) caused by irregular tidal flooding and neap tidal dry periods. Trichocorixa verticalis reach a maximum density of 26,914/m² (x = 3,909.6/m²) in open shallow pannes, where eggs hatch in staggered sequence, allowing population replenishment after drought and reflooding. Winter eggs hatched between salinities of 0 to 30 at 20°C and 0 to 20 at 10°C. Summer eggs hatched between salinities of 0 to 55 at variable temperatures (20 to 36°C). All instars showed a similar higher summer and lower fall tolerance; immatures were more tolerant than adults. Body molt measurements of the 6 instars are given here.Aside from being herbivores and detritivores, T, verticalis feed on chironomid larvae and oligochaetes. They are food for invertebrates and vertebrates, and provide substantial food for migratory shorebirds.The experimental work was based on a thesis submitted to the Graduate School of the University of New Hampshire in partial fulfillment of the requirements for the degree of Doctor of Philosophy.     

Acclimation of Antarctic bottom-ice algal communities to lowered salinities during melting

Sea-ice brine algal communities were exposed to salinities between 30 and 10 during melting. There was a progressive decline in maximum quantum yield, relative electron transfer rate (rETR_max) and photosynthetic efficiency () with decreasing salinity of the final melted sample. While all species showed a drop in these parameters, Fragilariopsis curta and Entomoneis kjellmannii showed the least inhibition. There was a steady increase in rETR_max and over 5 days after melting, especially in the samples melted into the highest salinities. In addition, the samples melted from the ice without added filtered seawater showed no photosynthetic activity after 2 days. Our results suggest that for experimental work using sea-ice microalgae, the final salinity of the melted sample should be greater than 28 (i.e. the ratio of sea ice to filtered seawater should be at least 1:2).     

The effects of various temperature-salinity combinations on the body form of newly hatchedCyprinodon macularius (Teleostei)

Summary 1. Spawning groups of the teleostCyprinodon macularius kept at 28° C in air-saturated water of 35 salinity were allowed to spawn at intervals of 3 to 4 days. Their eggs were transferred 4 hours after fertilization into a variety of temperature-salinity combinations and the newly hatched young fixed within 60 minutes. The body form of these young was then examined by measuring 13 different length, depth and width dimensions.2. All 13 dimensions vary as a function of the temperature and salinity conditions effective during incubation. The dimension versus temperature plot results in differently shaped curves in the three test salinities.3. In fresh water, body length decreases above and below 32° to 33° C, while the various depth and width measurements increase. Maximum total length values are therefore correlated with minimum depth and width values; the body tends to become deeper and wider in the lowest and highest temperatures tested.4. In 35 body length decreases progressively with increasing temperature, especially near the upper critical temperature (34°, 35° C). All depth and width dimensions measured tend to decrease more or less harmoniously; hence there is little change in body form (isometry).5. In 70 body length decreases rapidly from 26° to 28° C but changes little in the next higher temperature level (31° C). All depth and width dimensions measured tend to change proportionally (often not quite as harmoniously as in 35 ).6. It seems possible that the increasing degree of disharmony in the order 35 < 70 < fresh water is related to the fact that(a) all eggs tested were laid and fertilized in 35 and remained there for 4 hours before being transferred into the test salinities and(b) 35 affords near optimum conditions for growth and reproduction. It seems possible that the structural consequences of exposure to the different incubation media may be different if spawning took place in fresh water or 70 instead of in 35 .7. Body depth and width tend to increase with decreasing salinity, resulting in rounder fish in fresh water with less surface area per unit volume.8. Body dimensions (length as well as depth and width) are significantly smaller in 70 than in fresh water or 35 .9. Changes in body dimensions of hatching fry may be related to the concomittant changes in the amounts of dissolved gases, especially O₂, in the various temperature and salinity combinations employed.10. Environmental effects during very early ontogeny are of paramount importance for the functional and structural properties of the individual and may modify its ecological capacities.

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Die Wirkungen verschiedener Temperatur-Salzgehalts Kombinationen auf die Körperform frischgeschlüpftercyprinodon macularius (Teleostei)

Kurzfassung Eier des KnochenfischesCyprinodon macularius wurden 4 Stunden nach dem Laichakt in verschiedene Temperatur-Salzgehalts Kombinationen überführt und unter kontrollierten Bedingungen erbrütet. Alle zum Laichen angesetzten Elterntiere besaßen einen ähnlichen genetischen Hintergrund (Nachkommen eines einzigen Ausgangspaares) und waren während ihres ganzen Lebens bei 28° C und 35 S gehalten worden. Die frischgeschlüpften Jungfische wurden möglichst rasch fixiert und 13 ihrer Körperdimensionen vermessen. — Alle vermessenen Dimensionen werden durch Temperatur und Salzgehalt des Inkubationsmediums beeinflußt. Trägt man die Dimensionen gegen die Inkubationstemperatur auf, so ergeben sich in den drei Testsalzgehalten unterschiedliche Kurvenzüge. In Süßwasser nimmt die Körperlänge von 28° bis 33° C zu, verringert sich aber merkbar bei 34° C; Körpertiefe und -breite verhalten sich praktisch umgekehrt; die größte Länge wird also bei einer intermediären Temperaturstufe erreicht und ist korreliert mit Minimalwerten für Tiefe und Breite (v-förmige Kurven); die größte Tiefe und Breite wird in den niedrigsten (28° C) und in den höchsten (34° C) Testtemperaturen erreicht. In 35 verringert sich die Körperlänge mit abnehmender Temperatur und sowohl die Tiefe als auch die Breite des Körpers verändern sich nahezu direkt proportional (weitgehend isometrisches Wachstum). In 70 nimmt die Körperlänge von 26° nach 28° C rapide ab, zeigt aber bei 31° C nur geringfügige Veränderungen; Tiefe und Breite verändern sich harmonisch; das Ausmaß der Isometrie ist jedoch zumeist geringer als in 35 . Mit abnehmendem Salzgehalt verringert sich der Oberflächen/Volumen-Quotient des Körpers. Die Befunde werden im Lichte früherer Untersuchungen anC. macularius und ähnlicher Studien an anderen aquatischen Organismen eingehend erörtert. Zweifellos kommt dem Einfluß der Umwelt — insbesondere während der sehr frühen Ontogenie — eine hervorragende Bedeutung zu für die funktionellen und strukturellen Eigenschaften und damit für die ökologische Potenz des aufwachsenden Individuums.

     

A pond for edible Spirulina production and its hydraulic studies

Morphometric variation in three clones of Brachionus plicatilis cultured at 20°C, 25°C and 30°C, and 9, 12 and 24 salinity was analysed. Size appeared to be largely under genetic control and this defined the narrow limits within which variation due to abiotic factors could occur. Temperature had a significant effect on size, but affected the three clones differently. The most general effect of temperature was a reduction in size which levelled off as the temperature rose. Of the measurements taken, only distance between the median spines was affected by salinity. An important inter-relationship between the effects of temperature and salinity was also detected.     

Salinity-temperature tolerance of two closely related triclad species,Dugesia lugubris and D. polychroa (Turbellaria), in relation to their distribution in The Netherlands

The tolerance of adult specimens of Dugesia lugubris and D. polychroa for 13 different chlorinities ranging from 15.0–3.8 and for two temperatures, viz. 4 and 23 °C, was tested.At chlorinities of 7.5 and lower, the survival time of both species was considerably longer than at higher chlorinities (a few hours at 7.5, one to several days at 6.6 and lower concentrations). It is assumed that this is determined by the osmoregulatory capacity of the planarians.It was found that at low chlorinities combined with a high temperature D. polychroa survived longer than D. lugubris, while at the same chlorinities the opposite was true for a low temperature. The effect of temperature on survival at low chlorinities was more drastic for D. lugubris than for D. polychroa.The results correlate with data on the distribution of both species in The Netherlands. Outside areas with an average chlorinity below 2 the two species were rarely found.     

Polar bears make little use of terrestrial food webs: evidence from stable-carbon isotope analysis

Summary The mean stable-carbon isotope ratios (¹³C) for polar bear (Ursus maritimus) tissues (bone collagen –15.7, muscle –17.7, fat –24.7) were close to those of the same tissues from ringed seals (Phoca hispida) (–16.2, –18.1, and –26.1, respectively), which feed exclusively from the marine food chain. The ¹³C values for 4 species of fruits to which polar bears have access when on land in summer ranged from –27.8 to –26.2, typical of terrestrial plants in the Arctic. An animal's ¹³C signature reflects closely the ¹³C signature of it's food. Accordingly, the amount of food that polar bears consume from terrestrial food webs appears negligible, even though some bears spend 1/3 or more of each year on land during the seasons of greatest primary productivity.     

Changes in Resistance to Salinity and Temperature in Some Species of Polychaetes from the White Sea in Early Ontogenesis

We studied the effects of different salinities on plankton larvae of some polychaetes in the White Sea. It has been found that the salinity resistance of Alitta virens (Nereidae) increases during ontogenesis. Successful fertilization and further larval development in this species occur at the salinity of 22 to 34; embryos taken into the experiment at the stage of 32 blastomeres, trochophores, and early nektochaetes could survive and normally develop at the salinity of 16–32, 14–45, and 12–45 respectively. The rate of settling and metamorphosis in late nektochaetes of A. virens at normal or lowered (down to 14) salinity is dependent on temperature in the range of 5 to 23°C. It is found that the larvae of Harmothoe imbricata (Polynoidae) show the greatest salinity resistance at the stage of nektochaeta, whose lower limit of salinity is 14. Later larval stages of these species can survive in a wide range of salinity due to the development of a provisory nephridial system. The eurybionty of larvae of Spirorbis spirorbis ready for metamorphosis was higher than that in the larvae of Circeus spirillum (Spirorbidae). Under salinity reduced down to 10 the larvae of S. spirorbis die in 8–14 days, whereas more stenohaline larvae of C. spirillum die by the 3-rd day of the experiment. At water temperatures under 5°C the survival of S. spirorbis was the highest at three examined values of salinity, whereas C. spirillum showed the highest survival only under normal salinity.     

Growth and productivity of the psychrophilic marine diatoms Thalassiosira antarctica Comber and Nitzschia frigida Grunow in batch cultures at temperatures below the freezing point of sea water

Summary The diatoms Nitzschia frigida and Thalassiosira antarctica grow exponentially even at temperatures between-4 and -6°C and a salinity between 73 and 100 Under these conditions the light saturation of growth is reached in continuous light at a scalar quantum irradiance of between 7 mol·m^–2·s^–1 and 10 mol · m^–2 · s^–1. The increase in salinity retards growth more than a decrease in temperature. For N. frigida the limit of growth is at -8°C (S = 145%.). At increasing quantum irradiance, the chlorophyll content per unit cell volume decreases, whereas there is a significant increase in the carbon content of the exponentially growing cells. In addition, there is hardly any change in the protein content. The results show that both species of diatom can survive in ice without forming resting spores and even grow at extremely low temperatures.     

Mutualism between autotrophic ammonia-oxidizing bacteria (AOB) and heterotrophs present in an ammonia-oxidizing colony

Coexistence of an autotrophic ammonia-oxidizing bacterium (Nitrosomonas sp. RA) and heterotrophic bacteria was consistently observed when cultured in an inorganic medium without any external supply of organic carbon. The present study was undertaken to understand the association between autotrophs and the associated heterotrophs for which a system containing active autotrophs and heterotrophs controlled by Hg²⁺ addition was developed. The study revealed interdependence of heterotrophs and Nitrosomonas sp. RA for growth under iron-limited condition. Growth of Nitrosomonas sp. RA was supported by siderophores produced by the associated heterotroph, Pusillimonas sp., thereby complementing its high iron requirement while the organics (such as pyruvate) excreted by Nitrosomonas sp. RA during its autotrophic growth supported the survival of heterotrophs in the inorganic medium. The study thus sheds light on the nature of the mutual interactions between heterotrophs and autotrophs that play a role in the ammonia-oxidizing system involved in wastewater treatment.