The study of the influence of selenium on the regeneration and fecundity of the crab Sesarma boulengeri Calman has been conducted. The results demonstrated: The effect of selenium on the regeneration of walking legs of S. boulengeri Calman. Morphology of the regenerated appendage was different from control specimen. The speed of growth in the regenerated bud was lower than the control and it was depended on the size class of the crab. Regeneration index (R) was higher in the small crabs than in the large ones and in single autotomy than in double autotomy. Fecundity varied, when females exposed to selenium (0.27, 1.35, 2.7 ppm). It showed a decrease with all stages, especially in the first and second stage. The eggs in the last stage suffered more teratogens with exposure time and the concentration of selenium. 3

No abstract

The present study was conducted on the gills structure and the gill surface area of 40 individuals of the Blue swimming crabs, Portunus pelagicus, and 40 Chinese mitten crabs, Eriocheir sinensis, specimens of the species were collected from the  different regions of Shatt Al- Arab and North-west Arabian gulf. Both species were having eight phyllobranchiatesas of the same structure but different in length and surface area. The second gill in P. pelagicus shows major difference in shape from the other gills with missing platelets from one side of the filament. The results showed there were positive relationships between dry body weight with gill surface area, total number of platelets and number of platelets surface area in each gill. The gill surface area had no significant difference (p>0.05) with dry weight in the two species.

The current study was conducted on N. indica in three stations for the period from December 2017 to November 2018 (Al-Sharsh, Al-Salhiya and Al-Dweab), as samples were collected monthly. Some environmental factors were calculated, such as water temperature. The lowest water temperature was 12 °C during January and the highest temperature was 33 °C during July, both in Al-Salhiya station. The lowest value of salinity was 0.5‰ reached in April and November in Al-Sharsh station, while reached highest value ‰ 39.3 were recorded during July for Al-Dweab station, the light transmittance values ranged between (63-18) cm, recorded during July and November for Al-Salhiya and Al-Sharsh stations, respectively. As for the values of dissolved oxygen, it ranged between (12.1-5.1) mg/liter during August and May in the two stations. Al- Salhiya and Al-Sharsh, respectively. As for the bottom sediments of all the stations, they were alluvial with few and different percentages of sand and clay. The study showed that the studied environmental factors have an impact on the distribution and spread of this species within the horizontal and vertical sections in the tidal zone. The total density and density were measured within the horizontal distribution pattern in each station and the monthly total density ranges were 592-32 individuals/m2. The density of the three species was calculated within the horizontal distribution after dividing the area into three sections for each station. The results of the study indicated that there were significant differences at the level of P<0.05 for densities between the first and second different sections of N. indica, and there were significant differences between the first and third sections and between the second and third sections.