Investigation of stretching vibrations of glycosidic linkages in disaccharides and polysaccharides with use of IR spectra deconvolution

The results are presented for the deconvolution of IR spectra of disaccharides and polysaccharides with alpha and beta configurations of the 1 --> 4 glycosidic linkage (maltose, cellobiose, amylose, and cellulose), as well as of their corresponding monosaccharides (alpha- and beta-D-glucose) in the 1200-920 cm(-1) frequency range. It is established that a characteristic of di- and polysaccharides with 1 --> 4 glycosidic linkage is the appearance of new absorption bands in the 1175-1140 cm(-1) spectral range, as opposed to the IR spectra of monosaccharides. This can be a spectroscopic manifestation of the glycosidic linkage formation. In the 1000-970 cm(-1) frequency range, absorption bands, which are not observed in the monomer spectrum, are separated as a result of the deconvolution of the IR spectra of cellobiose and cellulose. The number of bands in this range remains unchanged for maltose and amylose, as compared to the monomer spectra. It is shown that the application of the method of deconvolution leads to a considerable enhancement in the resolution of the absorption bands in the IR spectra of mono-, di-, and polysaccharides.     

Embryonic development of the pacific cod <Emphasis Type="Italic">Gadus macrocephalus</Emphasis> (Gadidae)

Incubation of pacific cod eggs was divided into eight series, in which temperatures were set at −0.04°C to +4.03°C and warm and cold conditions alternated. The morphological changes that took place during the embryogenesis were described in detail using the results of the incubation. Twenty-two morphological characters that could be identified easily and that characterized the morphogenesis were defined in the course of development. The results of the incubation and data from the literature showed that the duration of the embryonic period in the Pacific cod’s lifecycle grew exponentially as water temperature decreased. It was found during the experiment that developing cod eggs survived low water temperatures up to freezing, as well as abrupt warming or cooling (over 3°C). According to the widely accepted Rass scale, the first stage of the Pacific cod embryogenesis takes 21% of its total duration, the second stage 23%, the third, 17%, and the fourth, 39%. However, at a temperature below 0°C, the relative duration of the stages of cleavage and embryonic shield was slightly shortened, whereas the mature embryo stage extended to almost half of the embryogenesis period. A more comprehensive analysis of temperature effects on embryogenesis revealed that the reduction of the rate of embryogenesis upon a temperature decrease occurred mostly at later stages of embryo growth. Modeling of development using defined morphological characters showed that the duration of embryogenesis grew linearly as the incubation temperature dropped in the first half of the embryogenesis and exponentially in the second half. A function was selected that described the obtained results most satisfactorily and that could be used for estimating the duration of the entire embryogenesis or any its stages within the range of water temperatures typical for Pacific cod.     

The Egg Mortality in Walleye Pollock (Gadus chalcogrammus Pallas, 1814) during Embryogenesis in Waters off the Western Kamchatka Coast

Russian Journal of Marine Biology - Five consecutive ichthyoplankton surveys were conducted during the spawning season of the walleye pollock Gadus chalcogrammus, in April and May 2019, at a...     

Spawning of walleye pollock (<Emphasis Type="Italic">Theragra chalcogramma</Emphasis>) off the Southwestern coast of Kamchatka

The results of ichthyoplankton surveys conducted in 2007–2008 showed that waters off Southwest Kamchatka and North Kuril Islands were areas of mass spawning of walleye pollock. The peak spawning occurred during the last 10 days of April and in early May, which was much later than the peak at the main spawning site off West Kamchatka. The spawning activity of walleye pollock near the southwestern shores of Kamchatka is a regular event, as the analysis of archive materials shows. This gave us grounds to suspect the existence of a southern site that coincided well with the mass spawning in the Shelikhov Gulf in its timing and scale, but was missed during standard ichthyoplankton surveys conducted in early April. After analyzing the growth rates of spawners, the assumption was made that the southern spawning was performed by the East Kamchatkan walleye pollock population, whose mass spawning usually occurs in late April-early May. According to the data of 2008, the estimated biomass of walleye pollock spawning in the area of the Ozernovskaya basin in late April was nearly 600000 tons. Regular monitoring of the southern spawning is proposed by means of additional ichthyoplankton surveys south of 53° N, including the Okhotsk Sea waters of the North Kuril Islands, in late April—early May.