Influence of the degree of homozygosity of STR-loci on the fertility of thoroughbred horses

Purpose: to study the effect of the level of homozygosity and inbreeding on the fecundity of thoroughbred mares.Materials and methods. A total of 3662 heads of breeding sows from leading stud farms of the Russian Federation were selected for the analysis. The influence of the homozygosity level on 17 microsatellite DNA loci on the main indices of reproduction of thoroughbred mares, such as the safe yield of foals and the number of fetal years, was analyzed in the article. All mares in the experimental sample had at least three years of breeding use. Individual fecundity rates and the number of homozygous loci in the STR profile were calculated for each horse.Results. The highest live foal yields (75.92%) had sows with homozygosity levels of 62.78-69.02%, and the lowest foal yields (45.73%) were recorded in mares with the highest homozygosity levels (75.28-76.92%). The maximum foal yield (65.85%) was determined in sows with an inbreeding rate of 4.1% or more, with a productive longevity of 6.26 fetal years on average. Analysis of the data showed that the level of inbreeding had almost no effect on the yield of live foals (R=0.010 at P>0.05), but had a negative correlation with the number of fruiting years (R=-0.092 at P<0.005).Conclusion. Estimation of homozygosity level of thoroughbred horses is especially relevant, as this breed has been perfected by purebred breeding method only for more than thirty years. In the thoroughbred horse breed, it is necessary to create a system of maintaining heterozygosity as well as the diversity of genotypes through the organization of breeding work.

CONDITIONS FOR THE FORMATION OF THE ARTEMIA CRUSTACEAN POPULATION AND THEIR PRODUCTION INDICATORS IN DIFFERENT TYPES OF HYPERHALINE LAKES OF THE ALTAI TERRITORY

Long-term data (2002–2019) on the conditions of the formation of Artemia populations in different types of hyperhaline lakes of the Altai Territory are analyzed. The boundaries of individual fecundity and average fecundity were calculated, the influence of abiotic factors on the quality content of ovisak was shown. The peculiarities of their changes at different levels of water salinity during the growing season have been investigated. The average number of litters (clutches) for Altai populations was calculated, the influence of environmental factors on this indicator was analyzed.

Comparative characteristics of growth of the scales from pink salmon in returns to Sakhalin Island (southeast coast) and Iturup Island in 2017 and 2018

Iturup Island (in southern Kuril Islands) and southeastern Sakhalin Island are known by the highest catches of salmons within the Sakhalin-Kuril region. The timing of pink salmon mass return to Iturup is 5–10 days later than to Sakhalin, and the females returned to Iturup have higher relative individual fecundity, on average. In 2014, an unexpected increase of pink salmon catches occurred on southeastern Sakhalin Island, with a simultaneous sharp decrease of the catches on Iturup Island. Assumption on appearance of Kuril pink salmon in the Sakhalin waters was confirmed by analysis of the scale parameters (number of sclerites and intercirculi distance in the first-year scale zone), dynamics of catches, and individual fecundity of females. Sharp opposite changes of the pink salmon catch dynamics were noted again for these areas in 2017 and 2018. Such changes of pink salmon abundance could be reasoned by environmental conditions of reproduction in these areas or new redistribution between two areas. To clarify the issue, complex analysis (same as for 2014) was applied for pink salmon at southeastern Sakhalin and Iturup in 2017 and 2018 (187 and 215 fish samples from Sakhalin and 194 and 152 fish samples from Iturup in these two years, respectively). The results were interpreted following the hypothesis of fluctuating stocks. Taking into account the complex of traits, there is concluded that the assumption about redistribution of pink salmon between southeastern Sakhalin and Iturup Island in 2017 and 2018 is untenable.

REPRODUCTIVE BIOLOGY IN GREEN SPINY LOBSTER, PANULIRUS REGIUS (DE BRITO CAPELLO 1864), FROM THE PETITE COTE OF SENEGAL, WEST AFRICA

Green spiny lobster is one of the highest economically valued fisheries resources in Senegal. However, knowledge on this species are relatively old and insufficient. To realize this study on reproductive biology of Panulirusregius, sampling has been carried out between April and September 2017 from small-scale fisheries landed catches at the Petite Cote, Senegal. The length at first sexual maturity computed from the body allometric relationship according to the cephalothorax length (CL) was 67.95 mm in females and 67.51 mm in males. The CL at which 50% of the females were mature during the breeding season (CL50) was 94.50 mm. Individual fecundity was between 229,860 and 638,775 eggs depending on CL of individuals. In the catches surveyed, 64% of landed individuals had a total length (TL) less than 200 mm, which is the minimum landing length in accordance with the Senegalese fisheries law. This result indicates the difficulties to apply management measures relative to this fishery, which could compromise its sustainability in Senegalese Petite Cote.

Comparative Analysis of Fecundity in Related Amphimictic Aporrectodea сaliginosa and Apomictic A. trapezoides Earthworms, and the Problem of Reproductive Advantages of Parthenogenetic Animals

The comparative analysis of fecundity and fertility was studied experimentally for the amphimictic Aporrectodea caliginosa diploid earthworms and the close parthenogenetic A. trapezoides triploid earthworms during two seasons. The individual fecundity of cocoons at is significantly higher in the parthenogenetic species than in amphimictic one. Fertility is in contrast lower in the parthenogenetic species, which results in leveled parameters of the reproductive potential. A generalization and analysis of the available data on the comparative fecundity of representatives of different animal groups shows that the automatic increase in fecundity in same-sex organisms due to the exclusion of males cannot be considered a universal rule providing biological progress and the ecological advantage of parthenogenetic organisms. This explanation is not suitable for hermaphroditic organisms. In addition, in some cases, parthenogenetic reproduction is accompanied by reduced fertility and even reduced fecundity.

Modern state of the reproductive potential of Black Sea sprat Sprattus sprattus phalericus (Risso, 1826) (Pisces: Clupeidae) in Crimean region and conditions for its formation

Black Sea sprat Sprattus sprattus phalericus (Risso, 1826) is one of the abundant species of fish in the Sea of Azov – Black Sea basin. Due to its large number sprat plays an extremely important role in the ecosystem of the sea, being an intermediate link between zooplankton and representatives of the highest trophic level – large predatory fish, dolphins, and birds. At the same time sprat is one of the important commercial fish in all the Black Sea countries, steadily being on the second place of catch volume in recent decades (after anchovy). The total catch reaches 100 thousand tons. Turkey and Ukraine are the main producing countries. Monitoring and forecast of biological state of sprat population with rising fishing intensity and climate changes are urgent tasks. The research subject of this article is the long-term (2000–2016) dynamics of biological (qualitative) parameters determining the population fecundity of Black Sea sprat in Crimean region, the current state of reproductive potential, and the conditions for its formation. The article is based on the results of own research. Parameters determining the population fecundity – the length-age structure of the spawning part population, the absolute individual fecundity, and the sex structure population (ratio between females and males) – were studied. In the long-term plan (in 2011–2016 compared with 2000–2004) the average length of spawning females decreased by 1.22 times (from 7.36 to 6.03 cm). It was accompanied by a decrease in the absolute individual fecundity by 2.39 times (from 13 625 to 5690 eggs). The numerical ratio between females and males decreased by 1.23 times (from 1.95 to 1.59). Simultaneously the sprat stock in the northern part of the Black Sea was reduced by more than 2.5 times (from > 500 thousand tons to < 200 thousand tons). As a result, the population fecundity of sprat in Crimean region decreased by more than 7 times (2.39 × 1.23 × 2.5). The conditions of sprat fishing in the northern part of the Black Sea (from the mouth of the Danube River to the Kerch Strait) were studied. They showed 2-fold decrease (from 251.9 thousand tons in 2000–2004 to 129.1 thousand tons in 2011–2016) in the total catch and more than 2.3-fold decrease (from 50.4 to 21.4 thousand tons) in average annual catch in this region. On the contrary, in the Crimean shelf the total catch at that time increased by 1.2 times (from 76.9 to 92.2 thousand tons), and its average annual value remained constant (15.4 thousand tons). While reducing the stock by 2.5 times, this means that the fishing pressure on the Crimean population increased 2.5 times. This fact suggests considering the factor of fishing as the main cause of its degradation. Validity of this version is confirmed by the fact of conjugacy (inverse connection) of interannual fluctuations between the catch and the length-age parameters of sprat in Crimean region in 2003–2013 previously found: catches over 15–16 thousand tons were accompanied by a next year decrease in the fish average length. Regulation of fishing is a necessary condition for preventing further degradation, for restoring and maintaining sustainable state of sprat population in Crimean region and its reproductive potential. The negative impact of natural (climatic and trophic) factors on the state of the population should be recognized as a secondary one. Local overfishing indicates indirectly the structuring of the commercial stock of Black Sea sprat, its division into a number of geographical aggregations (stock units), i. e. the presence of intraspecific differentiation.

A first fecundity study of the female snow crab Chionoecetes opilio Fabricius, 1788 (Decapoda: Brachyura: Oregoniidae) of the newly established population in the Barents Sea

The snow crab Chionoecetes opilioFabricius, 1788 is a newly established species in the Barents Sea. Since the first individuals were recorded in 1996, the population has increased and a fishery was initiated in 2012. Mature female snow crab caught in the central Barents Sea were investigated with regards to fecundity. Ovigerous females (N = 185) ranged from 48 to 100 mm carapace width (CW). Fecundity was 15,000–184,000 eggs per female with 100% clutch fullness, and was positively related to body size (fecundity = 0.233 * CW2.944) consistent with relationships described for other snow crab populations. Eight females had less than 100% clutch fullness, two of which had only 10% clutch fullness along with an old shell, indicating senescence. Dry egg weight was on average 0.065 mg and was hardly affected by CW. Females across all sizes invest similarly in individual eggs, and potential size-dependent differences in fitness are more related to the number of eggs produced than to the investment into individual eggs. We conclude that the fecundity-at-size of females is overall comparable to that of other populations, although the presence of large females results in high maximum individual fecundity estimates.

BIOLOGY OF NORTH CASPIAN ROACH RUTILUS RUTILUS CASPICUS (JAKOWLEW, 1870) OF THE NORTHERN DAGHESTAN CASPIAN COAST

The article is devoted to the study of biological characteristics of the north Caspian roach of the Daghestan coast of the Caspian Sea. Discussed are size and weight, fatness, passing the stage of gonad maturity, the absolute individual fecundity and feeding habits. The degree of occurrence of organisms in the food lumps with identification of dominant groups is determined.

Reproductive Homeostasis and Senescence in Drosophila melanogaster

The homeostatic properties of reproduction in aging female Drosophila melanogaster are investigated. Classic studies based on cohort analysis suggest that homeostatic capacity declines gradually as daily oviposition rates decline in aging flies. Analysis at the level of individuals gives a very different picture: reproductive homeostasis remains relatively constant for most of adult life until a critical point when oviposition either ceases entirely or continues in dysregulated fashion. The collapse of homeostatic capacity is abrupt. Enhanced homeostasis is associated with increased lifetime fecundity and improved prospects for survival. The fractal concept of lacunarity can be used to parameterize the “roughness” of individual fecundity trajectories and is inversely related to homeostatic capacity.

Oviplate: A Convenient and Space-Saving Method to Perform Individual Oviposition Assays in Aedes aegypti

Aedes aegypti is the principal vector of the urban arboviruses and the blood ingestion is important to produce the eggs in this species. To analyze the egg production in Ae. aegypti, researchers frequently use small cages or Drosophila vials to collect eggs from gravid females. Although it is affordable, the setup is time- and space-consuming, mainly when many mosquitoes need to be individually analyzed. This study presents an easy, cheap, and space-saving method to perform individual oviposition assays in Ae. aegypti using cell culture plates. This new method to access fecundity rate was named “oviplate”. The oviplates are setup with 12- or 24-well plates, distilled water and filter paper and they are 78 to 88% cheaper than the traditional Drosophila vial assay, respectively. Furthermore, to allocate 72 vitellogenic females in an insectary using Drosophila vial is necessary 4100 cm3 against 1400 cm3 and 700 cm3 when using 12- and 24-well plates, respectively. No statistical differences were found between the number of eggs laid in Drosophila vials and the oviplates, validating the method. The oviplate method is an affordable, and time- and space-efficient device, and it is simpler to perform individual fecundity analyses in Ae. aegypti.