Condition-dependent survival and movement behavior in an endangered endemic damselfly

Movement is essential for the maintenance of populations in their natural habitats, particularly for threatened species living in fluctuating environments. Empirical evidence suggests that the probability and distance of movement in territorial species are context-dependent, often depending on population density and sex. Here, we investigate the movement behavior of the spring cohort of an endangered endemic damselfly Calopteryx exul in a lotic habitat of Northeast Algeria using capture-mark-recapture (CMR) of adults. By sampling 10 gridded river stretches across a 2 km section of the watercourse, we were able to estimate the distance of movement throughout individual lifespans and estimate movement probability for both males and females. We used multistate models to examine whether individual density and sex ratio influence survival and movement probability. We found that males and females had similar movement kernels with most individuals moving short distances (83% performing movements of < 100 m and only 1% > 1000 m). Of the 547 marked individuals, 63% were residents, and 37% were movers (moved at least 50 m from one sampling occasion to another). Survival probability showed higher estimates for females and was slightly density-dependent (i.e., lower survival probabilities were associated with high male densities). Survival probability did not show a marked difference between residents and movers. Movement probability and distances were positively correlated with individual density, but were not or slightly correlated with sex ratio, respectively. These results are not in line with the hypotheses of sex-biased movement and survival costs of movement. Our results suggest that the species performs mostly short-distance movements that are dependent on intraspecific interactions.

Determination of Heavy Metal Levels and Health Risk Assessment of Raw Cow Milk in Guelma Region, Algeria

During the recent decades, adverse effects of unexpected contaminants, such as heavy metals on raw cow milk quality, have threatened human health. The objective of this study was to determine heavy metal levels in raw milk collected from autochthonous bovine breeds in the eastern region of Algeria. Eighty-eight pooled milk samples were analyzed using atomic absorption spectrometry for Pb, Cd, Cr, Cu, Ni, Fe, and Zn, and dietary risks were estimated for infants, children, and adults with minimum, average, and maximum milk consumption scenarios. Results revealed that Pb (0.94 ± 0.49 mg/kg), Cd (0.03 ± 0.01 mg/kg), and Cu (0.14 ± 0.08 mg/kg) levels in all analyzed samples were higher than their corresponding maximum residue levels (MRLs). The task hazard quotient (THQ) values suggest potential risk for infants in the three scenarios from Pb, Cd, and Cr; for children in the three scenarios from Pb and in the high scenario from Cr; and for adults in the medium and high scenarios from Pb. The hazard index (HI) values were higher than 1, and the contributions of each metal to the overall HI followed a descending order of Pb, Cr, Cd, Ni, Zn, Cu, and Fe with values of 68.19%, 15.39%, 6.91%, 4.94%, 3.42%, 0.88%, and 0.28%, respectively. Our results indicated that there may be a potential risk of heavy metals, especially Pb, for infants through raw cow milk consumption. Moreover, data actualization and continuous monitoring are necessary and recommended to evaluate heavy metal effects in future studies.

Field estimates of fitness costs of the pace-of-life in an endangered damselfly

Theory predicts that within-population differences in the pace-of-life can lead to cohort splitting and produce marked intraspecific variation in body size. Although many studies showed that body size is positively correlated with fitness, many argue that selection for the larger body is counterbalanced by opposing physiological and ecological selective mechanisms that favour smaller body. When a population split into cohorts with different paces of life (slow or fast cohort), one would expect to detect the fitness-size relationship among and within cohorts, that is, (a) slower-developing cohort has larger body size and higher fitness than faster-developing cohort, and (b) larger individuals within each cohort show higher fitness than smaller individuals. Here, we test these hypotheses in capture-mark-recapture field surveys that assess body size, lifespan, survival and lifetime mating success in two consecutive generations of a partially bivoltine aquatic insect, Coenagrion mercuriale, where the spring cohort is slower-developing than the autumn cohort. As expected, body size was larger in the slow-developing cohort, which is consistent with the temperature-size rule and also with the duration of development. Body size seasonal variation was greater in slow-developing cohort most likely because of the higher variation in age at maturity. Concordant with theory, survival probability, lifespan and lifetime mating success were higher in the slow-developing cohort. Moreover, individual body size was positively correlated with survival and mating success in both cohorts. Our study confirms the fitness costs of fast pace-of-life and the benefits of larger body size to adult fitness.

Niche partitioning in three sympatric congeneric species of dragonfly, Orthetrum chrysostigma, O. coerulescens anceps, and O. nitidinerve: the importance of microhabitat

Habitat heterogeneity has been shown to promote co-existence of closely related species. Based on this concept, a field study was conducted on the niche partitioning of three territorial congeneric species of skimmers (Anisoptera: Libellulidae) in Northeast Algeria during the breeding season of 2011. According to their size, there is a descending hierarchy between Orthetrum nitidinerve Sélys, O. chrysostigma (Burmeister), and O. coerulescens anceps (Schneider). After being marked and surveyed, the two latter species had the same breeding behavior sequence. Knowing that they had almost the same size, such species could not co-occur in the same habitat according to the competitive exclusion principle. The spatial distribution of the three species was investigated at two different microhabitats, and it was found that these two species were actually isolated at this scale. O. chrysostigma and O. nitidinerve preferred open areas, while O. c. anceps occurred in highly vegetated waters. This study highlights the role of microhabitat in community structure as an important niche axis that maintains closely related species in the same habitat.