Resting Eggs Research Articles

Impact of anoxia and sulfide on the viability of eggs of three planktonic copepods

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 146:291-295 (1997) - doi:10.3354/meps146291 Impact of anoxia and sulfide on the viability of eggs of three planktonic copepods Marcus NH, Lutz RV, Chanton JP Eggs of 3 calanoid copepods Acartia tonsa, Centropages hamatus and Labidocera aestiva were exposed to either anoxia or anoxia/sulfide. Mean sulfide concentrations ranged from 283 to 352 M. Viability, determined at 4 d intervals for 32 d and judged as hatching success under normoxia was variable, but generally declined with increasing time of exposure. Values for hatching success were transformed to probits to determine the median lethal times of exposure to anoxia and anoxia/sulfide and 95% confidence limits. We observed no significant difference in the mortality of eggs exposed to anoxia/sulfide compared to anoxia alone and suggest that eggs switch to anaerobic metabolism when exposed to anoxia. Copepods · Resting eggs · Anoxia · Sulfide Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 146. Publication date: January 30, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

Behavioural response in plants: adjustment in algal recruitment induced by herbivores

Behavioural responses to chemical cues are common among animals, whereas there is still intense debate as to whether plants are able to detect environmental information and adjust their behaviour accordingly. Here, I report that several freshwater algal species respond to the presence or absence of grazers in the water column by regulating their recruitment rate from sediment to water. In lakes, as well as in controlled laboratory experiments with low abundances of grazers, recruitment of certain flagellated algal species was high, whereas recruitment was negligible when grazer abundances were high. Hence, certain plants equipped with locomotion organelles can use cues released from herbivores to adjust the timing of recruitment from the 'seed-bank', thereby reducing the exposure to grazing. Such an adaptation may have important consequences for dominance and temporal succession in algal communities. In an evolutionary context, this study shows that consumer-avoidance behaviour is not an adaptation exclusive to animals.

Resting eggs of zooplankton (Copepoda and Cladocera) from the Kiel Bay and adjacent waters (southwestern Baltic)

Resting eggs of four species of calanoid copepods and three species of cladocerans were collected from sediments up to 5cm depth from the Kiel Bay and adjacent waters in the southwestern Baltic Sea during April–May 1994. All but one species of cladoceran was successfully hatched/reared in the laboratory. In the Kiel Bay, egg abundances varied from 1.8x105 to 7.4x105 m-2. Hatching success of copepod eggs collected from all depths was high (49 to 94%), but was 0 to 79% for cladoceran eggs. Darkness did not seem to affect hatching. Eggs found in the 4 to 5 cm layer of sediment were estimated to be about 15 yr old, showing the presence of an “egg bank” in the Baltic. Formation of resting eggs may be a genetic trait acquired during the ice ages.

Biometrics and Fatty Acid Composition of the Resting Eggs of Thamnocephalus Platyurus (Anostraca) in View of an Eventual Use as Fish Feed

AbstractFairy shrimps have recently been considered for use in larval fish rearing, because of their size and their nutritional value. This study presents the results obtained for Thamnocephalus platyurus, a species from Central and South America, which was already mass cultured successfully in the United States in a flow-through system. Cysts and instar I nauplii have an unfavourably large size: mean diameter 278 μm and 240 μm for untreated and decapsulated cysts, respectively; mean naupliar length 436 μm. However, the species shows an interesting pattern in its fatty acid methyl ester (FAME) profile, especially with regard to polyunsaturated fatty acids (PUFA). In particular, T. platyurus cysts are characterized by significant levels of the 18:2 and the 20:5w3, and by the presence of the 22:6w3, which are normally absent in Artemia cysts.

Biometrics and Fatty Acid Composition of the Resting Eggs of Thamnocephalus Platyurus (Anostraca) in View of an Eventual Use as Fish Feed

Biometrics and Fatty Acid Composition of the Resting Eggs of Thamnocephalus Platyurus (Anostraca) in View of an Eventual Use as Fish Feed

Calanoid copepod resting eggs can be surface-disinfected

Resting eggs of the two calanoid copepods, Eurytemora affinis and Acartia clausi, were exposed to the surface disinfectants Buffodine TM, FAM-30 TM and glutardialdehyde. Eggs were placed individually in wells of multiwell dishes and checked for hatching success and nauplii survival at Day 5 after hatching. To verify sterilization, eggs were incubated individually with two different media for six weeks, allowing bacterial growth to occur. Buffodine had no significant effect on hatching rate and survival, but indications of non-complete disinfection were found. FAM-30 seemed to be harmless to Acartia eggs, but caused very low hatching percentages of Eurytemora eggs and nearly instaneous mortality of the hatched nauplii. Glutardialdehyde treatment of Acartia eggs had no significant effect on hatching rate, but all nauplii died shortly after hatching. This disinfectant had no significant effect on hatching of Eurytemora eggs compared with the control group, although a small negative tendency in hatching rate and survival could be detected. FAM-30 and glutardialdehyde were most successful in obtaining surface-sterile eggs. This study shows that resting eggs collected from sediments can survive disinfection, making them attractive as sterile inoculum for live feed cultures in aquaculture.

Studies on the Formation and Hatching of Fertilized Eggs of the Rotifer Brachionus plicatilis-VIII. Dietary Value of Neonates from Rotifer Brachionus plicatilis Resting Eggs for Red Sea Bream Larvae.

The dietary value of hatched neonates from the marine rotifer Brachionus plicatilis resting eggs was investigated through larval rearing trials of red sea bream Pagrus major and chemical analysis. Rotifer resting eggs were mass-produced in 50m3 tanks by feeding Nannochloropsis oculata and baker's yeast. Eggs were preserved at 5°C under total darkness for 1-2 years and hatched at 23°C under continuous light. After nutritional enrichment with the use of N. oculata and squid oil, hatched neonates or commonly mass-cultured rotifers (control) were fed to fish larvae. Newly hatched fish larvae were stocked in 100l (80l in water volume) polycarbonate tanks at 15 or 30/l. No significant differences in larval growth (notochord length and dry weight) were found on Day 20 between groups fed on neonates from resting eggs and those fed on control rotifers. The survival rate of fish larvae fed on neonates (38%) were, however, significantly lower than the group fed on control diets (69%). This may be due to the fact that the uniform lorica size and synchronous growth of neonates during the enrichment culture after simultaneous resting egg hatching did not fit the mouth size of the fish larvae. The amount and composition of fatty acids of neonates were the same as those of the control rotifers.

Studies on the Formation and Hatching of Fertilized Eggs of the Rotifer Brachionus plicatilis-VI. Use of Preserved Diet for Rotifer Brachionus plicatilis Resting Egg Formation.

The reduction of environmental water exchange and the supply of an ample amount of diet are required for inducing rotifer resting egg formation. The use of a preserved diet is essential for conducting trials of mass formation of resting eggs in a large scale tank. The potential for applying preserved diets for L-and S-type rotifer Brachionus plicatilis resting egg production was investigated in the laboratory. Dietary values of frozen or refrigerated diets (baker's yeast, Chlorella vulgaris, Euglena gracilis, and Nannochloropsis oculata) in condensed forms were compared with fresh N. oculata diet (control).Frequencies of rotifer mastax movement when fed most of the preserved diets were equal with the control. In the individual culture experiment, growth and mixis rates obtained by feeding preserved diets were much less than the control. Growth rates increased to the level of the control, however, when tested diets were fed to batch-cultured rotifers in a 20l medium. The remarkable increase of mixis rates in batch cultures was observed when preserved diets were fed to S-type rotifers. The number of resting eggs formed from 1g dry weight preserved diet was 7.8-112.0 (×103) and 2.1-5.0 (×103) for L-and S-type rotifers, respectively. Meanwhile, it was 138.0 for L-type and 15.4 for S-type with the control diet.

Calanoid resting eggs in the Baltic Sea: implications for the population dynamics of Acartia bifilosa (Copepoda)

Resting eggs of Acartia spp. (presumably A. bifilosa Giesbr.) at densities between 65 and 125 eggs cm-2 were found in sediment off the southern coast of Finland and represent the first observations of dormant calanoid eggs in the Baltic Sea. The highest egg densities were found at sediment depths between 4 and 8 cm. The hatching percentage varied between 0 and 90% in the different sediment layers and at different experimental temperatures (13, 16 and 19°C). Some nauplii emerged from the eggs extracted from sediment layers 9 to 10 cm beneath the surface layer and other nauplii emerged from eggs after 82 d of dark storage at 3°C. Light was not needed to trigger hatching; the nauplii were able to hatch in darkness when the eggs were resuspended in filtered seawater. Indirect evidence suggests that the marked spring peak of Acartia spp. nauplii seen in a monitoring data from the years 1973 to 1984 was derived from benthic eggs and not from spawning. The possible mechanisms for induction of hatching and the adaptive benefits of resting egg production for A. bifilosa are discussed.

Sem Morphology of Resting Eggs in the Species of the Genus Branchinecta From North America

ABSTRACT Cyst morphology of the 13 species of Branchinecta thus far recorded in North America is described by means of scanning electron microscopy. Differences in morphology are emphasized to determine whether egg ornamentation could be an easy and useful means to distinguish species even in the absence of water. The eggs of Branchinecta are compared with data from previous studies on other anostracan genera.

Calanoid copepod, cladoceran, and rotifer eggs in sea-bottom sediments of northern Californian coastal waters: Identification, occurrence and hatching

Resting eggs of copepods, cladocerans, and a rotifer were found in sediments from water depths of 60 to 120 m off the northern coast of California in February and April 1989. Eggs occurred as deep as 10 cm in the sediment. These eggs were viable, as evidenced by their hatching (41 to 58%) at 14°C in the laboratory.

Studies on the formation and hatching of fertilized eggs of the rotifer Brachionus plicatilis - III. Comparison of resting egg formation among five Japanese stocks of the rotifer Brachionus plicatilis.

Resting egg formation was compared among five stocks of the marine rotifer Brachionus plicatilis. The three large type (L-type) and two small type (S-type) stocks were collected in Japan. The number of resting eggs produced by 10, 000 rotifers at 25°C and 8‰ Cl', was: 3680 (L-type University of Tokyo stock), 2270 (S-type Mie Prefecture stock), 1480 (L-type Mie Prefecture stock), 1.7 (S-type Lake Hamana stock) and 0 (L-type Yashima stock). These results were supported by data on the appearance rate of mictic females and the fecundity of resting egg producing females. Results of the current study suggest that the selection of rotifer stock is crucial to mass production of resting eggs.

松阪産シオミズツボワムシ2型の耐久卵携帯様式の差異

松阪産シオミズツボワムシ2型の耐久卵携帯様式の差異

Reproduction and sexual development in a freshwater gastrotrich

Post-embryonic development of parthenogenic eggs of Lepidodermella squammata was studied by light and electron microscopy in animals of known age and reproductive history. Each bilateral gonad initially contains eight cells. No mitotic proliferation occurs during parthenogenic egg development. Germ cells are tightly clustered, have smooth plasma membranes with no interconnections, and are uninucleate. There is no surrounding ovary or oviduct. At hatching, two cells in each gonad are identifiable as parthenogenic eggs. The enlarged nucleolus of the most mature egg has already attained the morphology that persists throughout vitellogenesis, with intertwined granular and fibrillar threads. Less mature eggs have earlier stages of nucleolar development, and lack indications of meiotic events. Parthenogenic eggs enter vitellogenesis singly, with formation of RER and active Golgi complexes, and the accumulation of lipid, yolk, and various granules. The shell is formed in situ, whereas the spines elongate after egg deposition. Most animals produce four parthenogenic eggs, which undergo immediate development (tachyblastic eggs). Resting (opsiblastic) eggs are rare in isolation culture. Both types of eggs are produced only prior to the formation of sperm and primary oocytes. The absence of synaptonemal complexes, which would indicate synapsis of homologous chromosomes in prophase of meiosis I, implies that parthenogenesis is by apomixis in L. squammata.

Size and Distribution of Resting Eggs in a Natural Population of the Rotifer Brachionus plicatilis

Resting eggs of the rotifer Brachionus plicatilis were collected from the sediments of a brackish-water pond near Tampa, Florida. These core samples were examined for resting egg density and size. Resting egg density decreased exponentially from the surface down to 7 cm in the sediments at all stations, with depth in the sediments accounting for 42.3% of the total variance. The maximum resting egg density recorded was 194 RE/cm3 with no significant differences in density among stations. Resting eggs were found to be significantly larger in the top 2 cm of sediment than resting eggs from deeper in the sediments. These data are discussed with regard to other work on resting egg densities in natural populations. Hypotheses are offered to explain the observed decrease in resting egg size with depth in sediments.

Seasonal Cycle in Abundance of Resting Eggs of Acartia Steueri Smirnov (Copepoda, Calanoida) in Sea-Bottom Mud of Onagawa Bay, Japan

Seasonal Cycle in Abundance of Resting Eggs of Acartia Steueri Smirnov (Copepoda, Calanoida) in Sea-Bottom Mud of Onagawa Bay, Japan

Species-Specific Morphology of Resting Eggs in the Rotifer Asplanchna

Species-Specific Morphology of Resting Eggs in the Rotifer Asplanchna

Addendum to: Fine Structure of the Resting Eggs of the Rotifers Brachionus calyciflorus and Asplanchna sieboldi

Addendum to: Fine Structure of the Resting Eggs of the Rotifers Brachionus calyciflorus and Asplanchna sieboldi

蔗糖液による底土中からの海産枝角類・橈脚類耐久卵の分離法

蔗糖液による底土中からの海産枝角類・橈脚類耐久卵の分離法

伊勢湾・浦神湾の底土中の海産枝角類耐久卵の分布

伊勢湾・浦神湾の底土中の海産枝角類耐久卵の分布