دراسة نسجية وحياتية لقوقعbengalensis Bellamya لبعض المواقع في محافظة كربلاء

Histological and Biological study of snail Bellamya bengalensis for some sites in Karbala governorate

Summery
Biological and histological study was conducted on the freshwater snail Bellamya bengalesis (Lamarck, 1882) for the period from September 2021 to August 2022, in which some physical and chemical parameters of the environment of the studied snail Bellamya bengalensis (Lamarck, 1882) were studied.
Which was in two different sites, which is the site of Al-Rashdiyah and the site of Al-Aiwij.
The results of the study showed that there were slight monthly differences in the values of physical and chemical measurements of the water of the two sites, as the average values ranged in the two sites as follows:
The air temperature was (32.85-33.65) °C, the water was (25.40-22.75) °C, the pH values were (7.2 -7.25), and the salinity values were (0.671 – 0.665) ‰, and the electrical conductivity was (1045.25 – 1232.05) microsiemens/cm. The total hardness was (853.5 – 778.5) mg/L, while the values of dissolved oxygen ranged between (8.05-8.1) mg/L, and the values of the vital oxygen requirement were (3.5-4.95) mg/L, and the values of calcium ion ranged between (81.3-91.8) mg/L. CaCoз .
The bottom sediments of the two sites (Al-Rashidia and Al- Aiwij) were also analyzed, and they were a mixture of sand, silt and clay. It was found that the type of sediments are almost equal in both sites (silty sandy).

The study dealt with the population density of the Bellamya bengalensis snail population. Monthly samples were collected from the two study sites, with 4 replications per month. The study showed the snail density (females) higher than the density of the snail itself (males), and the highest density rate for females in August 2022 was (69) individuals. While the males in the months of May and July of the same year (11) individuals.
The study also dealt with the average length of snails (males, females) by measuring the length of the shell. The study showed that the average length of females is higher than males during the study period, and the highest average length recorded for females in February 2022 was (34.2 mm) as for males. In December 2021 (30) mm.
The study of the structure of the population group, which was represented by (10 categories for females and 6 categories for males), found the length of the category (4,40) in females, the two categories are the least and the most long and frequent (respectively). In females was the most frequent, while it was found that the longest category in males (32) is the most frequent, and the least tall category was (12), noting that no category was recorded for males in February
The wet weight ,dry weight and the ash-free dry weight of the snail were calculated for the purpose of finding the annual average of the live mass in terms of their significance and it was the highest in the month of November (460) mg for females. In terms of the two weights (dry and ash-free dry weight) of snails, the annual average of live mass was calculated, and it was found that females are the largest in mass by weight, respectively.
The study of secondary productivity and in terms of the two weights of snails is an important indicator of the life of the snail and for both sexes. The productivity of females was the highest and greatest value. It was recorded in female secondary productivity in terms of dry weight 9873.01 (mg/m²/year) while it was 1546.99 (mg/m²/year) in terms of weight. Ash-free dry.
And the ratio Biomass to Secondary production in terms of snail weights showed that the average live mass of the female study snail in terms of dry weight and ash-free dry weight was higher than that of the same snail for males, estimated at( 0.954 ,0.876) Straight.
In view of the different strategy of this snail in reproduction, where it differs from other snails, it was found that this snail is fertile eggs. Large numbers of different ages and lengths were dissected to document some anatomical differences and internal structures for comparison between male and female and the ease of distinguishing between them due to the difficulty of distinguishing between them from the morphological shape.
The female was also distinguished in more than one age group through the nursery pockets (brood pouches).
Determining the four stages of the embryonic development of B. bengalensis eggs and observing the changes that occur in the eggs and recording them as categories (A, B, C, D) based on the number of turns of the snail shell, which is the most prominent sign for determining the age and completion of growth or not .
Histological sections of the male and female gonads were photographed with different focusing forces (40X, 4X) to identify the shape of the gonads and the clear differences between them. A tissue section was also taken of the brood pouches area and the abdominal foot area, which is no less important as a structure for the snail body than the rest of the body parts also for its importance in contributing to the liberation of snails young to their natural environment.