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.     

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.     

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.     

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.     

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.     

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 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.

     

Vertical distribution of zooplankton biomass and species in northeastern Baffin Bay related to temperature and salinity

Summary Vertical distributions of various species and stages of zooplankton at different times of the day were determined by stratified sampling with the BIONESS in northeastern Baffin Bay during early August. The water column was divided into an upper subarctic zone (>0° C, salinity < 32), a lower subarctic zone (< 0° C, salinity 32 to 34) and a deep zone of Atlantic water (>0° C, salinity 34). The upper subarctic zone was dominated by two species of pteropod molluscs; the lower subarctic water was dominated by the copepods, Calanus finmarchicus, C. glacialis and C. hyperboreus whose copepodite stages showed depth distributions that were different from one another, with the copepodite stage 5 and adult females generally shallower than the younger stages. All stages of all Calanus species were in the zone of primary production (10 to 50 m) while the copepods Pseudocalanus, Metridia and Oithona were generally found below this zone. Only C. finmarchicus and C. glacialis showed evidence of diurnal migration, migrating to the surface waters when the sun was at its lowest position on the horizon (i.e. at 0100 h).     

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.

     

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 cycle of Porphyra vietnamensis Tanaka & Pham-Hoang Ho from Thailand

Porphyra vietnamensis Tanaka & Pham-Hoang Ho is a tropical species of high potential for farming. Studies of the life cycle have been conducted for many years but have not been successful until recently. Mature thalli were collected from Songkhla, in the southern part of Thailand, and were used to obtain Conchocelis in the laboratory in Bangkok. Conchocelis in shells as well as free-floating filaments could be observed after one week of incubation at 25 °C, 25 salinity and 350–500 lux light intensity, and covered the culture shell surface within 2 months. Conchosporangia were formed after being incubated for 10 days at 30 °C, 20 salinity under light intensities of 350–500 lux with a photoperiod of 12 hours a day. Induction of conchospore release was achieved by lowering the temperature to 25 °C and the salinity to 10–15 and increasing the light intensity to 800–1000 lux. Liberated conchospores germinated into young thalli which became mature after 70 days.     

Physiological responses of the early zoeal stages of Palaemon pandaliformis Stimpson and Palaemon northropi (Rankin) to salinity variation

The effect of salinity variation (0, 7, 14, 21, 28 and 35S) on survival, moulting and respiratory metabolism of the early zoeal stages of the shrimps Palaemon pandaliformis and P. northropi from the northern coast of the State of São Paulo, Brazil is investigated. Freshly hatched larvae were maintained at 20 °C, in each salinity for a maximum of seven days. Oxygen consumption measurements were made at 20 °C for each salinity using Cartesian diver microrespirometers. In 0S, all P. northropi zoeae died after 24 h while 24% of the P. pandaliformis zoeae survived until 4 days. Zoeae of both species survived poorly in 7S, the best survival for the two species (90%) being registered in 28%.S. Palaemon northropi zoeae did not survive 35S while 45% survival was recorded for P. pandaliformis zoeae in this medium after seven days. Moulting did not occur in zoeae of either species in 0%.S, nor in P. northropi in 7S. The metabolism-salinity curve for P. pandaliformis zoea I is very stable over the range 0–21S while that for P. northropi exhibits complete salinity independence from 21–35 S. Thus, while the early zoeal stages, at least, are conspecific, both developing in the same environment as part of the coastal zooplankton community, they clearly maintain distinct physiological characteristics. The data presented possibly reflect genetic adaptations to the adult biotope already manifested in the first zoeae.     

Effects of temperature,salinity and agitation on byssus thread formation of zebra musselDreissena polymorpha

Byssus thread production ofD. polymorpha under different conditions of temperature, salinity and agitation were studied in the laboratory. The acclimation to salinity and temperature greatly affects the byssus production ofD. polymorpha. Byssus production of mussels was significantly reduced when temperature increased beyond 20°C and decreased below 10°C. Mussels with cut threads (for counting), produced a substantially increased number of threads. However, mussels with uncut byssus threads were comparatively more mobile. Byssus production of mussels did not vary significantly at salinities up to 3. Beyond this salinity byssus production was reduced significantly. Mussels increased their byssus production with increasing frequency of agitation.     

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.

     

Oxygen isotope fractionation during respiration for different temperatures ofT. utilis andE. coli K12

Summary The temperature dependence of the oxygen isotope fractionation factor during respiration has been examined for two different microorganisms, namelyTorulopsis utilis andEscherichia coli K12 representing a yeast and a bacterium, respectively. The investigation covered a temperature range of 18° C, that is from 16° C to 34° C forT. utilis and from 19° C to 37° C forE. coli K12. Within this temperature range the fractionation factor ofT. utilis increases by 0.18; an insignificant change ( _{10° C} = 0.063;r = 0.067), whereas withE. coli K 12 an increase of 1.12; has been observed ( _{10° C} = 0.6;r = 0.55).     

The effect of salinity and temperature on survival and metamorphosis of megalops of the blue crabCallinectes sapidus

Summary 1. Megalops of the blue crab,Callinectes sapidus Rathbun, reared from hatching through all zoeal stages at 25° C, 30 p. p. m., were maintained in 23 combinations of salinity and temperature until metamorphosis to determine the effect of salinity and temperature and the combined effect of salinity and temperature on survival and rate of development.2. Survival of the megalops stage was similar at temperatures of 20°, 25°, and 30° C with the exception of the larvae maintained at 5 and 10 p. p. m. At 15° C, survival never exceed 50 percent.3. In the lower salinities (5 and 10 p. p. m.) survival decreased with a decrease in temperature.4. The most pronounced effect of temperature in delaying the time of metamorphosis was observed in megalops maintained at 15° C. As the salinity increased from 20 to 40 p. p. m., the duration of the megalops stage was further extended at 150° C. This effect was not observed at other salinity-temperature combinations.5. Statistical analysis of factorical design was used to predict the mortality and duration of the megalops stage which might be expected under a greater number of salinity-temperature combinations than are feasible to observe in the laboratory. The results of the analysis and their possible significance are discussed.6. The hypothesis is presented that survival and duration of the megalops ofC. sapidus in the natural environment are directly associated with the time of hatching, the time at which the megalops stage is reached in relation to seasonal changes in water temperatures, and the salinity of the water in which the final zoeal molt occurs. The delay of metamorphosis in waters of high salinity and low temperature may have contributed to the distribution of this species in the estuaries along a major portion of the Atlantic and Gulf Coasts of the United States.

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Die Wirkung von Salinität und Temperatur auf das Überleben und die Metamorphose der Megalopalarven der Blauen KrabbeCallinectes sapidus

Kurzfassung Larven der Blauen Krabbe (Callinectes sapidus Rathbun) wurden bei 25° C und 30 S (= p. p. m.) gezüchtet, bis das Megalopalarvenstadium erreicht war. Die Megalopalarven wurden sodann in 6 verschiedenen Salzgehalten und 4 verschiedenen Temperaturen gehalten, um die Wirkung von Salzgehalt und Temperatur sowie von deren Kombinationen auf Überlebensrate, Entwicklung und Metamorphose festzustellen. Bei 20°, 25° und 30° C überlebten über 70 % der Megalopalarven in Medien von 10 bis 40 S. Bei 15° C betrug die Überlebensrate 10 bis 50 % in Salzgehalten von 20 bis 40 . Die Megalopalarven metamorphosierten nicht bei 15° C und 10 sowie bei 20° C und 5 . Die Dauer des Megalopastadiums schwankte von 5 Tagen bei 30° C bis zu 67 Tagen bei 15° C. Die Temperatur beeinflußte die Lebensdauer der Megalopalarven stärker als der Salzgehalt. Bei 20° und 30° C wurde die Dauer des Megalopastadiums durch veränderte Salinitätsbedingungen nicht beeinflußt. Bei 15° C bewirkte eine Erhöhung des Salzgehalts jedoch eine Verzögerung der Metamorphose des ersten Krabbenstadiums. Durch statistische Analysen sind die Wirkungen von Salzgehalt und Temperatur auf Sterblichkeit und Entwicklungsrate der Megalopalarven für eine größere Anzahl von Umweltsbedingungen, als sie im Laboratorium geprüft werden konnten, ermittelt worden, so daß die Überlebensrate der Megalopalarven innerhalb eines großen Temperatur- und Salzgehaltsbereiches mit großer Wahrscheinlichkeit vorausgesagt werden kann. Es ist anzunehmen, daß durch die zeitliche Verlängerung des Megalopastadiums und die hohe Überlebensrate in Gewässern mit niedriger Temperatur und hohem Salzgehalt ein Transport der Megalopalarven durch Meeresströmungen über weite Entfernungen ermöglicht wird. Diese Annahme würde unter anderem die Verbreitung dieser Gattung über einen großen Teil der Gewässer entlang der atlantischen Küste sowie im Golf von Mexiko erklären.

     

Larval development ofMacrophthalmus erato De Man, 1887 (Brachyura ocypodidae)

The zoeal and megalopal stage ofMacrophthalmus erato were obtained under laboratory conditions and are described and figured. Five zoeal and one megalopal stages were reared at 25; salinity and temperature of 29°C. Their features are compared with those of known species of the genus.     

Preliminary results on the effects of salinity and settling conditions on megalopal metamorphosis of fiddler crab Ilyoplax pusilla

Metamorphosis of fiddler crab Ilyoplax pusilla larvaefrom megalopal to first crab stage wasstudied in laboratory experiments under variousconditions of salinity and substratum. The hatchedzoea metamorphose through five stages before reachingmegalopal stage. The megalops were placed in a 20 mlPetri dishes (2–3 megalops/dish), with salinities of10, 20 or 30 . Each salinity level was tested eitherwith or without sandy mud substratum. Thirty to 35megalops were used in each of the six treatments. Theexperiment was carried out at a water temperature of28 ±0.5°C and with daily feeding of the diatomChaetoceros gracilis. Treatment of 20 salinity andsandy mud substratum revealed the highest metamorphicrate (87%), while in contrast no metamorphosis wasobserved at 30 salinity withoutsandy mud substratum. Duration of the metamorphosiswas about 16 days. Numerous malformed juvenile crabswere observed in treatments conductedwithout sandy mud substratum.     

Hydranth structure and digestion rate as a function of temperature and salinity inClava multicornis (Cnidaria,Hydrozoa)

Summary 1. Responses to 12 different combinations of constant levels of temperature and salinity were tested in the colonial athecate hydroidClava multicornis. Criteria measured were: (a) length and width of hydranth bodies, (b) number and length of tentacles and (c) rate of digestion.2. Test colonies were obtained by allowing single hydranths — cut off from an individual primary colony — to regenerate via asexual reproduction into new secondary colonies.3. In the resulting — genetically identical — material, all criteria tested vary as a function of the different environments offered.4. In 16, 24 and 32 S hydranth length reaches maximum values at 12°C, followed by 17° and then 22°C. With increasing salinity, hydranth length declines markedly at 12°C, while there is little or no decline at 17°C and a definite increase from 24 to 32 S at 22°C.5. Hydranth width varies less extensively; in general, it follows similar patterns as does hydranth length.6. Tentacle number per hydranth tends to be positively related to the size of the hydranth body; it decreases with increasing temperature. Salinity levels producing maximum tentacle numbers vary with temperature; maxima are found at 12°C in 16, at 17°C in 24 and at 22°C at 32 S.7. Tentacle length — although a more variable criterion — is affected similarly to tentacle number; it attains, however, relatively higher values at 17°C.8. In regard to the hydranth dimensions measured, combinations of low temperatures/low salinities and of high temperatures/high salinities tend to produce maximum values.9. Rate of digestion is taken here to be identical to the time elapsing between completed food intake and defecation. This time span is reduced with increasing temperature. In all temperature levels, digestion time is shortest in 32 S.10. The results presented above compare well with those obtained earlier under similar conditions onCordylophora caspia.11. It is assumed that the structural modifications of hydranths affect rate and efficiency of exchanges between organism and environment and may thus represent a means of metabolic adjustment.

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Hydranthenstruktur und Verdauungsrate als Funktion von Temperatur und Salzgehalt beiClava multicornis (Cnidaria, Hydrozoa)

Kurzfassung Erbgleiche Polypen vonClava multicornis Forskål wurden in 12 verschiedenen Temperatur-Salzgehalts-Kombinationen durch asexuelle Vermehrung zu neuen Kolonien herangezogen und an den adulten Hydranthen dieser erbgleichen Sekundärkolonien Länge und Breite des Hydranthenkörpers, Anzahl und Länge der Tentakel sowie die Verdauungsgeschwindigkeit ermittelt. Alle gemessenen Parameter verändern sich — zum Teil sogar erheblich — als Funktion von Temperatur und Salzgehalt. Die Veränderungen der Hydranthendimensionen führen zu Verschiebungen der Oberfläche-Volumen-Quotienten. Da der Stoffaustausch zwischen Kolonie und Umwelt primär im Bereich der Hydranthen erfolgt, kommt diesen Verschiebungen vermutlich eine Bedeutung zu im Rahmen der Stresskompensation (nicht-genetische Adaptation). Die erzielten Ergebnisse bestätigen frühere Untersuchungen vonKinne an dem naheverwandten HydroidpolypenCordylophora caspia.

     

Biology of Moina mongolica (Moinidae,Cladocera) and perspective as live food for marine fish larvae: review

Moina mongolica, 1.0-1.4 mm long and 0.8 mm wide, is an Old World euryhaline species. This paper reviewed the recent advances on its autecology, reproductive biology, feeding ecology and perspective as live food for marine fish larviculture. Salinity tolerance of this species ranges from 0.4–1.4 to 65.2–75.4. Within 2–50 salinity, Moina mongolica can complete its life cycle through parthenogenesis. The optimum temperature is between 25 °C and 28 °C, while it tolerates high temperature between 34.4 °C and 36.0 °C and lower temperature between 3.2 °C and 5.4 °C. The non-toxic level of unionised ammonia (24 h LC₅₀) for M. mongolica is <2.6 mg NH₃–N l^–1. Juvenile individuals filter 2.37 ml d^–1 and feed 9.45×10⁶ algal cells d^–1, while mature individuals filter 9.45 ml d^–1 and consume 4.94×10⁶ algal cells d^–1. At 28 °C, M. mongolica reaches sex maturity in 4 d and gives birth once a day afterward; females carry 7.3 eggs brood^–1 and spawn 2.8 times during their lifetime. A variety of food can be used for M. mongolica culture including unicellular algae, yeast and manure, but the best feeding regime is the combination of Nannochloropsis oculata and horse manure. Moina mongolica reproduces parthenogenetically during most lifetime, but resting eggs can be induced at temperature (16 °C) combined with food density at 2000–5000 N. oculata ml^–1. The tolerance to low dissolved oxygen (0.14–0.93 mg l^–1) and high ammonia makes it suitable for mass production. Biochemical analyses showed that the content of eicospantanoic acid (20:53) in M. mongolica accounts for 12.7% of total fatty acids, which is higher than other live food such as Artemia nauplii and rotifers. This cladoceran has the characteristics of wide salinity adaptation, rapid reproduction and ease of mass culture. The review highlights its potential as live food for marine fish larvae.