Maturity classification and growth of capelin, Mallotus villosus villosus (M), oocytes

Ovaries of female capelin, Mallotus villosus villosus (M), from the Barents Sea were sampled at various times of the year and material conserved for morphological examination. The maturity of female capelin, was assessed using low power microscopy for examination of whole oocytes. The diameters of oocytes were measured to give additional information regarding development, and to study the growth rate of the ripening oocytes. A maturity scale for use in the field is described based on the result of low power microscopy. A comparison is made between the'old'and'new'maturity scales, and the ease of use of the new scale has been tested.     

Incubation Temperature Effect on Qualitative and Quantitative Composition of Abnormalities and Mortality Rate in Embryogenesis of the Barents Sea Capelin Mallotus villosus (Osmeridae)

Journal of Ichthyology - The development of capelin Mallotus villosus from insemination to total resorption of the yolk is investigated at 5 and 8°C by the assessment of development of each...     

Purification and characterization of pepsins from the arctic fish capelin (Mallotus villosus)

Two pepsins from the stomach of the arctic fish capelin (Mallotus villosus) have been isolated and characterized. The purification was achieved by ammonium sulphate precipitation, ion exchange chromatography and gel filtration. Both pepsins resemble mammalian pepsins regarding pepstatin sensitivity, amino acid composition, stability and specific activity. The major capelin pepsin has optimum activity at significantly higher pH than is common for mammalian pepsins, and the optimum pH is different with different substrates. Both pepsins have relatively high activity at low temperatures. The pepsins have mol. wt of about 25,000 which is significantly lower than that of mammalian pepsins.     

Some aspects of the feeding and behavior of larvae of the Barents Sea capelin Mallotus villosus villosus (Salmoniformes, Osmeridae) in experimental conditions

The results of experimental investigations on the feeding and behavior of larvae of the Barents Sea capelin Mallotus villosus villosus during their transition to exogenous feeding are presented. Data concerning the passage duration of nauplii of Artemia salina along the intestine, feeding intensity, the portion of feeding larvae, swimming speed, sinking speed of non-feeding individuals, distances of responses and escape, as well as certain features of the passage of food through the intestines are given.     

Comparison of liver enzymes in osmerid fishes: key differences between a glycerol accumulating species,rainbow smelt (Osmerus mordax), and a species that does not accumulate glycerol,capelin (Mallotus villosus)

Activities of enzymes associated with glycerol synthesis were compared in the liver of two osmerid fishes, the smelt (Osmerus mordax), which can accumulate high (400 mM) levels of glycerol and capelin (Mallotus villosus) that does not accumulate glycerol. Animals were sampled at approximately the same time of year and temperature thus negating potential seasonal effects. These species are closely related, reducing interpretative issues involving comparison between unrelated species. We found that key enzyme activities were elevated in the smelt relative to the non-glycerol accumulating capelin, namely enzymes involved with glycolysis (phosphofructose kinase-1 and aldolase), amino acid metabolism (aspartate aminotransferase and alanine aminotransferase), gluconeogenesis (phosphoenolpyruvate carboxykinase) and glycerol synthesis (glycerol-3-phosphate dehydrogenase). The enzyme profiles strongly support the hypothesis that smelt can synthesize glycerol by utilizing glycogen and amino acids as the carbon source and that they have increased capacity for metabolic flux through loci required for synthesis of the three carbon intermediate dihydroxyacetone phosphate and subsequently glycerol synthesis.     

Genetic differentiation among populations of capelin Mallotus villosus from the West Coast of Greenland

Three populations of capelin, Mallotus villosus , from the west coast of Greenland were analyzed for variation among twelve proteins, determined by fifteen loci, using starch gel electrophoresis. The level of polymorphic loci at the 0.99 level varies from 0.39 to 0.62 and the heterozy gosity from 0.155 to 0.174. A significant heterogeneity among samples is demonstrated. The test values for homogeneity vary from 17.231 to 28.597 with four degrees of freedom.

Zusammenfassung

Genetische Unterschiede in Populationen der Lodde (Mallotus villosus) vor der Westküste Grönlands
In drei Populationen der Lodde, Mallotus villosus , von der Westküste Grönlands wurde die genetische Variation an zwölf Proteinen untersucht, die von fünfzehn Genorten bestimmt werden. Der Polymor-phiegrad (0.99 Kriterium) varüerte zwischen 0.39 und 0.62 und der Heterozygotiegrad zwischen 0.155 und 0.174. Bei den Populationen bestanden signifikante Unterschiede in den Genhäufigkeiten. Im Homogenitätstest mit vier Freiheitsgraden variierten die Testwerte zwischen 17.231 und 28.597.

Résumé

Différentiation génétique parmi des populations de capelans (Mallotus villosus) de la côte ouest du Greenland
L'électrophorèse sur le gel d'amidon permet d'étudier chez trois populations de capelans, Mallotus villosus , de la côte ouest du Greenland douze protéines déterminées par quinze loci. Le degré de polymorphisme au niveau 0.99 varie de 0.39 a 0.62 et le niveau d'hétérozygotie de 0.155 ä 0.174. L'hétérogénéité significative entre les populations a été trouvée.     

The distribution and biology of the cestode Eubothrium parvum in capelin, Mallotus villosus, (Pallas) in the Barents Sea, and its use as a biological tag

Samples of Eubothrium parvum were obtained from capelin Mallotus villosus at 55 stations throughout the Barents Sea and from Balsfjord, North Norway. The parasite is distributed widely throughout the Barents Sea, but both incidence and intensity of infection are higher in the regions off Murmansk and the Kola peninsula, and Spitsbergen. E. parvum exhibits a seasonal peak in maturation and probably also in acquisition of new infections. The incidence of infection is greatest in 1 + fish, whereas the intensity is more independent of host age. It is suggested that the parasite requires only a single intermediate host, a plank-tonic copepod, and its distribution in relation to age of host is a reflection of the dietary preference shown by young capelin for copepods. The frequency distribution of E. parvum in capelin was over-dispersed in Balsfjord, where infection levels of between 1 and 28 parasites per fish were encountered in all samples, but under-dispersed in the Barents Sea, where infections of more than four parasites per fish were never found and even infections with three and four parasites were very local. It is suggested that the underdispersion is due to a very low probability of infection in the open waters of the sea. Although the presence of E. parvum cannot be used as a biological tag for capelin, its abundance and frequency distribution can. The difference in frequency distribution and the failure to find any heavily infected fish in the Barents Sea confirm the suggestion that the capelin of Balsfjord form a local isolated population, which does not migrate into the Barents Sea. The differences in infection levels within the Barents Sea suggest the further possibility that there are at least two stocks of capelin there, but this requires further investigation and confirmation.     

Mitochondrial DNA variation in Pacific capelin (Mallotus villosus catervarius) from the Sea of Okhotsk, inferred from PCR-RFLP analysis

Four population samples of Pacific capelin Mallotus villosus catervarius (Pennant, 1784) from geographically distant localities in the Sea of Okhotsk, Tauy Bay and the eastern coast of the Sakhalin Island, were examined using PCR-RFLP analysis of three mitochondrial DNA regions (A8/A6/COIII/ND3, ND3/ND4L/ND4, and ND5/ND6). The nucleotide divergence of mtDNA sequences among the samples, as well as the analysis of geographic heterogeneity of the haplotype frequencies and quantitative estimation of genetic differentiation performed by means of AMOVA, showed that the samples examined belonged to one panmictic population. Genealogic analysis of the mtDNA variation structure was carried out. It was demonstrated that the high level of haplotype diversity (0.9639 +/- 0.00015) along with the low level of nucleotide diversity (0.003818 +/- 0.0000003) pointed to the exponential rate of population growth of the capelin from the Sea of Okhotsk, which rather recently in its evolutionary history faced the bottleneck effect.     

Effects of alternative prey on predation intensity from herring Clupea harengus and sandeel Ammodytes marinus on capelin Mallotus villosus larvae in the Barents Sea

Stomach contents from lesser sandeel Ammodytes marinus and herring Clupea harengus caught at one and three stations, respectively, were analysed to investigate predation intensity on capelin Mallotus villosus larvae. Most capelin larvae were found in the anterior sections of the stomachs close to the oesophagus, indicating that rapid digestion rates of larvae reduced the abundance in the posterior sections. The anterior sections of the stomachs had alternating layers of either copepods or capelin larvae and krill. This shows that the individual predators switched between feeding on either copepods or on krill and capelin larvae. A total of 549 capelin larvae was found in 440 fish stomachs. Capelin larvae were found in 20% of the sandeel stomachs, and 24, 34 and 62% of the stomachs from the three herring stations, respectively. Many of the predator stomachs contained more than five larvae, and up to 28 larvae were found in one herring stomach. The herring appeared to prey selectively on the largest capelin larvae, and the number of larvae per stomach was much higher in stomachs where krill had recently been eaten than where copepods were dominant. The predation intensity measured in this study is much higher than reported in earlier studies, and it is suggested that the predators were feeding using a searching image, and that the concentrations of alternative prey (copepods and krill) varied around a switching threshold.     

Morphometric characteristic of sex cells and seasonal changes of female gonads of Cucumaria japonica (Semper, 1868) (Echinodermata: Holothuroidea) from Peter the Great Bay, Sea of Japan

The oocytes at different stages of development were characterized morphometrically, and seasonal changes in female gonads of the Far-eastern edible holothurian Cucumaria japonica (Semper, 1868) from the Peter the Great Bay were described. Groups of oocytes and categories of sexual tubules corresponding to different stages of development of gonads were distinguished. Free laying oocytes were divided into several groups, i.e., oocytes 3, 4 and 5. The greatest size of C. japonica oocytes was 460 μm. In various seasons of the year there was greater growth of oocytes in the gonads, which reached its maximum volume during reproduction of the holothurians. The gonads developed asynchronously. All the stages of development were observable simultaneously in the gonads of each individual of this species during the reproductive cycle, and the stage of fast growth prevailed. C. japonica spawned twice a year, in May–June and from July to October. Unreleased oocytes were subjected to resorption.     

The timing of spawning in capelin (Mallotus villosus Müller) at a coastal location in eastern Newfoundland

We tested three hypotheses concerning the timing of spawning for a circumpolar species, capelin (Mallotus villosus), for which timing of larval emergence is known to be synchronized by physical conditions. The first hypothesis, developed from previous studies, was that spawning would be synchronized by upwelling events. Initial results from Middle Cove Beach in eastern Newfoundland indicated that spawning was not synchronized with upwelling. We next hypothesized that spawning was a function of several environmental variables. Results from logistic regression indicated that neither single-factor nor multi-factor models could explain the timing of spawning. Single variables could predict spawning in some years but no variable could reliably predict the time of spawning year after year. Finally, we hypothesized that the probability of spawning increased as a set of significant variables approached preferred levels. For capelin at Middle Cove, the set of variables that influence capelin spawning were identified as wave height, sea surface roughness and capelin abundance in the water. Thus only a combination of variables explained the timing of spawning for capelin. Preferred conditions for capelin spawning were wave heights less than 20 cm at the beach, a sea surface with a slight ripple, and an intermediate rank abundance of capelin in the water corresponding to hundreds to thousands of individuals. Capelin abundance alone was not a useful predictor. During the course of the study we observed a shift in the dates that capelin arrived and spawned at the beach. During 1987–1990 capelin spawned at Middle Cove Beach during June, but in more recent years (1991–1993) capelin did not arrive or spawn until July.     

Growth of the Barents Sea capelin,Mallotus villosus,in relation to climate

Synopsis In order to investigate a possible relationship between temperature and fish length growth in the Barents Sea capelin stock, estimates of environmental temperature in the feeding season were compared to estimates of length growth during the same season. The mean temperature of the capelin feeding area was calculated by averaging the temperatures in September for the depth interval 10–200 m in statistical rectangles. The estimates of capelin growth were obtained for the same rectangles using backcalculation of length from otoliths. Correlation coefficients for the relationship between water temperature and growth were 0.70 and 0.53 for two- and three-year-olds, respectively, when all the material was considered, and between 0.85 and 0.91 for within-year data. In addition, a close correspondence between feeding area and growth rates was found.     

Shrinkage correction and length conversion equations for Theragra chalcogramma, Mallotus villosus and Thaleichthys pacificus

Preservation of walleye pollock Theragra chalcogramma, capelin Mallotus villosus and eulachon Thaleichthys pacificus by freezing decreased fork length ( L _F) up to 1·8, 5·6 and 2·7% and reduced mass by up to 8·4, 3·5 and 1·1%, respectively. Shrinkage of walleye pollock standard length ( L _S) was greater for fish in 95% ethanol v . 5% formalin and for fish in 10% formalin v . frozen. Equations describing the shrinkage and loss in mass for these species are presented as well as conversions between different length measurements ( L _S, L _F and total length, L _T) for fishes that were frozen.     

Chemotaxonomic study on Thymus villosus from Portugal

The composition of the essential oils of four populations of Thymus villosus subsp. lusitanicus (Boiss.) Coutinho from Portugal was investigated by GC and GC-MS. To study the chemical polymorphism the results obtained from GC analyses of the volatile oils from individual plants from four populations were submited to Principal Component and Cluster analyses. A comparision with the essential oil of T. villosus subsp. villosus, previously studied by us was done. Important differences with regard to the major constituents in these two taxa were found. Linalool, geranyl acetate, geraniol and terpinen-4-ol were the main components of the essential oils of T. villosus subsp. lusitanicus, whereas in the oil of T. villosus subsp. villosus p-cymene, myrcene and alpha-terpineol were the major ones. Although, both taxa showed chemical polymorphism, different types of essential oils were characterized in each one: linalool; linalool/ terpinen-4-ol/trans-sabinene hydrate; linalool/1,8-cineole; geranyl acetate/geraniol; geranyl acetate/geraniol/1,8-cineole in T. villosus subsp. lusitanicus and p-cymene/camphor/linalool; p-cymene/borneol; linalool/geraniol/geranyl acetate; alpha-terpineol/camphor/myrcene in T. villosus subsp. villosus. Thus, the two subspecies of T. villosus can be easely differenciated by the composition of their essential oils.     

Mitochondrial DNA variation in Pacific capelin (<Emphasis Type="Italic">Mallotus villosus catervarius</Emphasis>) from the Sea of Okhotsk,inferred from PCR-RFLP analysis

Four population samples of Pacific capelin Mallotus villosus catervarius (Pennat, 1784) from geographically distant localities in the Sea of Okhotsk, Tauy Bay and the eastern coast of the Sakhalin Island, were examined using PCR-RFLP analysis of three mitochondrial DNA regions (A8/A6/COIII/ND3, ND3/ND4L/ND4, and ND5/ND6). The nucleotide divergence of mtDNA sequences among the samples, as well as the analysis of geographic heterogeneity of the haplotype frequencies and quantitative estimation of genetic differentiation performed by means of AMOVA, showed that the samples examined belonged to one panmictic population. Genealogic analysis of the mtDNA variation structure was carried out. It was demonstrated that the high level of haplotype diversity (0.9639 ± 0.00015) along with the low level of nucleotide diversity (0.003818 ± 0.0000003) pointed to the exponential rate of population growth of the capelin from the Sea of Okhotsk, which rather recently in its evolutionary history faced the bottleneck effect.     

Induction of maturation in small Xenopus laevis oocytes

The competence of Xenopus laevis oocytes in various stages of growth to respond to progesterone treatment was investigated. Full-grown (stage 6) oocytes undergo nuclear membrane dissolution and resume meiosis in response to progesterone exposure, while smaller oocytes (stages 3-5; less than 1100 micron in diameter) do not. The defect which prevents 750- to 1050-micron oocytes from responding to progesterone can be overcome by microinjecting cytoplasm withdrawn from a stage 6 oocyte. Germinal vesicle breakdown in these small oocytes occurs on a timetable similar to that of stage 6 oocytes exposed to progesterone and is accompanied by a twofold increase in protein synthesis as well as the activation of MPF. The results argue that a cytoplasmic factor(s) which probably first appears at late stage 5 is required for progesterone responsiveness. The identity and role of the factor(s) in the development of maturation competence and the regulation of maternal mRNA translation are discussed.     

养殖鲥鱼性腺发育的研究

经激素处理和生态调控的养殖鲥鱼,能完成性腺发育的全过程,其可分为６个时期,卵细胞发育可相应分为６个时相。与其它鱼类不同,细胞中液泡最早出现在胞质的内缘而不是外缘。大、小核仁数随卵母细胞的发育而变化。成熟卵巢成熟系数为８５４％～１２６４％。成熟期卵径为６２８５～８３５３μｍ、精子头径为０７４～１５５μｍ。达性成熟的鲥鱼,冬季卵巢为Ⅱ期、精巢为Ⅱ～Ⅲ期。精、卵巢发育呈现出明显的不同步现象。前者５月底开始进入成熟期,后者７月初进入成熟期。初级卵母细胞由Ⅱ时相发育到Ⅳ时相基本上是同步的。第Ⅳ期卵巢卵径的频率仅出现１个高峰。养殖鲥鱼属１年１次产卵类型。     

Thermohaline tolerance and embryonic development in capelin eggs (Mallotus villosus) from the Northeast Atlantic Ocean

Capelin (Mallotus villosus) displays alternative reproductive modes throughout its circumpolar distribution. This predicts divergent thermohaline tolerance of eggs because they are incubated in either a steady offshore or variable intertidal environment. We investigate herein thermohaline tolerance of eggs from the offshore spawning Barents Sea capelin. Subsequently, we compare our data with those previously published on other offshore and intertidal spawning capelin populations across the Northeast Atlantic Ocean, with the aim of determining possible patterns in the thermohaline tolerance of eggs from the alternative reproductive modes. In a 2?×?4 factorial design various combinations of salinities and temperatures had only negligible effect on the survival of eggs until first hatch. The embryonic development rate from fertilisation until first hatch across populations and between the two reproductive modes suggested non-local thermohaline tolerance towards the physical factors during development. Finally, no differences were observed in salinity tolerance from fertilisation to first hatch between populations representing different reproductive modes. The present findings demonstrate wide thermohaline tolerance of capelin eggs regardless of population origin and reproductive mode.     

KINETIC ANALYSIS OF ENTIRE OOGENESIS IN XENOPUS LAEVIS

In our breeding conditions (without artificial hormonal stimulation) two years after metamorphosis are necessary for a Xenopus laevis female to produce mature oocytes. Four periods of different growth rates can be distinguished into this first wave of oogenesis: 1) oocytes reach 120 μm in diameter (early stage I according to D umont (5)) in a few weeks after metamorphosis; 2) growth slows down and the size of 250–300 μm (late stage I) is obtained 6–7 months later; 3) a rapid growth resumes during vitellogenesis (stages II, III and IV) and a 1,000–1,100 μm diameter is reached in 2–3 months; 4) the last period spans for a year and the oocyte grows up to 1,200 μm. This phase covers many physiological changes and it should be critical to size carefully the oocytes for biochemical investigations and comparisons.
At last most of the oocytes in a young female do not proceed through this entire oogenesis, they are stopped at the end of the second growth phase (about 250 μm in diameter).     

Epigenetic modifications necessary for normal development are established during oocyte growth in mice

The ability of maternal chromatin to support full-term development is attained during oocyte growth. The aim of this study was to identify when during the growth phase the maternal chromatin developed the capacity to support term development. Mature metaphase II-arrested oocytes that contained chromatin from oocytes at different stages of oocyte growth were constructed by micromanipulation. The oocytes were fertilized in vitro, developed to the blastocyst stage in vitro, and transferred to recipients to assay developmental potential. The results demonstrate, firstly, that the origin of the maternal chromatin has no effect on the rate of oocyte maturation, fertilization, or development to the blastocyst in vitro. Secondly we demonstrate that maternal chromatin is first competent to support development to term during the latter half of oocyte growth when oocytes are 60-69 microm in diameter in juvenile mice or 50-59 microm in diameter in adult mice. These data show that epigenetic modifications necessary for postimplantation development occur during a specific phase of oocyte growth.