Samples of fresh adults of two sympatric species, Orchestia montagui and Orchestia gammarellus, from the supralittoral zone of Bizerte lagoon (Northern of Tunisia) at Menzel Jmil (37813 0 8 00 N 09855 0 1 00 E) were housed in a controlled environment cabinet. Locomotor activity rhythms were recorded in individual animals in spring, at a constant temperature of 18 + 18C; firstly, under light-dark (LD) cycle and constant darkness (DD), and secondly, under continuous light with high (140 lux) and low (5 lux) luminous intensities during the first and second week, respectively. Results showed that whatever the regimen imposed and species studied, periodogram analysis indicated a circadian rhythm with the presence of ultradian component close to 12 h. Double plotted actograms and wave forms highlighted two different locomotor behaviors; in fact, individuals of O. montagui are active during photophase when placed under LD cycle whereas, individuals of O. gammarellus concentrated their activity during the scotophase. The comparison of rhythm characteristics showed that the highest rhythmicity was observed under entraining condition both for O. montagui and O. gammarellus with 77% and 60%, respectively. Moreover, the most important stability and activity time were better defined under continuous light with high luminous intensity for O. montagui and entraining conditions for O. gammarellus. On the other hand, results showed a highly standard deviation explaining the important intraspecific variation. We concluded thus the presence of diurnal and nocturnal trends adopted by these two talitrids. This strategy allowed these concurrent species to minimize their interactions. These two sympatric species, which have the same food preferences, do not share the same temporal niche. This is a strategy to allow the diminution of interspecific competition intensity. This result is discussed in this paper.
In the current study, the difference between the sex‐sorted and non‐sex‐sorted frozen semen of Holstein Friesian breed cattle was investigated. Significant variation (p < .05) was found in the semen quality parameters such as motility; vitality; acrosome integrity rate; the anti‐oxidative enzyme activity including GSH (glutathione); SOD (superoxide dismutase); CAT (catalase); GSH‐Px (glutathione peroxidase) and the rate of fertilization. The results showed that the sperm acrosome integrity and motility of the non‐sorted sperm were higher compared to sex‐sorted sperm (p < .05). The linearity index and mean coefficient analysis revealed that the percentage of ‘grade a’ in sex‐sorted sperm were significantly (p < .05) lower than non‐sorted sperm. Interestingly, low SOD level and high CAT level was found in the non‐sexed semen than in the sexed semen (p < .05). Furthermore, the GSH and GSH‐Px activity in the sexed semen was found lower than the non‐sexed semen (p < .05). In conclusion, sperm motility characteristics were lower in sex‐sorted semen than in non‐sex‐sorted semen. This might be related to the complex process of sexed semen production, which could reduce sperm motility and movement characteristics, acrosomal integrity, CAT, SOD, GSH and GSH‐Px, and finally lead to the decline in the fertilization rate.
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