Journal of experimental zoology. Part A, Ecological and integrative physiology最新文献

Pomacea canaliculata (Lamarck 1822), a freshwater gastropod indigenous to lower Del Plata Basin of Argentina, has become the most destructive and invasive rice pests in south China since its introduction in the 1980s. In Guangdong, the main production areas for double rice, most of P. canaliculata overwinter in paddy field ditches after late-rice harvesting in mid-November and diapause to temporarily to avoid the damaging effects of extreme low temperatures. This pest aroused from diapause and migrated to the paddy field after early-rice reviving in next late March. Overwintering and cold tolerance of natural P. canaliculata have a non-negligible impact on population dynamics and distribution in the following year. We tested the supercooling capability, levels of cryoprotectant synthesis, activity of antioxidant defense system (antioxidant enzymes and reduced glutathione), and degree of oxidative damage (concentration of malondialdehyde as an index of lipid peroxidation) monthly, using natural P. canaliculata samples with a size-gender structure (i.e., juveniles, female, and male adults) from experimental ponds during the period of mid-November to the following April. P. canaliculata survived the winter with a monthly death rate of 7%–16.5% in coldest January. The supercooling point (SCP) of overwintering P. canaliculata decreased initially before increasing subsequently with monthly changes in water temperature. P. canaliculata accumulated a high glycogen content before December, which depleted towards the end of January, while lipid content reached peak in January and depleted since February. Activity of antioxidant defense system of P. canaliculata exhibited significant monthly differences and showed relatively higher size heterogeneity than monthly variations. The results contribute to the knowledge of adaptability in overwintering P. canaliculata and help to understand the mechanism of the invasive success of this species.

Bivalve mollusks frequently experience salinity fluctuations that may drive oxidative stress (OS) in the organism. Here we investigated OS markers and histopathological changes in gills and hemolymph of Mediterranean mussels Mytilus galloprovincialis Lamarck, 1819 exposed to a wide range of salinities (6, 10, 14, 24, and 30 ppt). Mussels were captured at the shellfish farm with the salinity 18 ppt and then exposed to hypo- and hypersaline conditions in the laboratory. Indicators of redox balance in hemocytes (intracellular reactive oxygen species (ROS) levels, DNA damage) and gills (thiobarbituric acid reactive substances (TBARS), protein carbonyls (PC), activity of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) were measured. The effect of salinity stress on microstructure of gills has been evaluated as well. The results revealed induction of OS in tissues and cells of mussels for both experimental increase and decrease salinity modelings. Hemocytes showed higher sensitivity to osmotic stress compared to gills. In gills TBARS were stable in all experimental groups and PC increased only at salinity 6 ppt. The activity of SOD, CAT and GPx in gills decreased only in mussels acclimated to salinity 24 ppt and further salinisation up to 30 ppt was associated with the recovery of the activity of all enzymes. Major histopathological changes in gills upon salinity fluctuations included inflammatory reactions, circulatory alterations, regressive and progressive changes. Our findings clearly indicate that salinity fluctuations promote OS at cellular and tissue level and also affect microstructure of gills in mussels. The results provide new insights into the mechanisms of osmotic stress in bivalves.

The continuous requirement to substitute safe and affordable alternatives for helminth medications, as well as address the resistance of some used drug classes, introduced bioactive products derived from marine animals into the field of competition; however, almost all the previous research only focused on their impact on bacterial and protozoal infection. In the present work, we investigated the potential in vitro nematocidal effect of the aqueous extract of defense secretions for four species of marine mollusks: two cephalopods, namely the cuttlefish Sepia pharaonis and the common Octopus Octopus vulagris and two gastropods, the sea hare Aplysia argus and the sea slug Berthillina citrina, against the adult murine pinworm Syphacia obvelata. Data showed dose and time efficacy in all examined extracts. The sea slug's skin acid secretion has the highest impact, causing death in the cultivated worms, followed by the ink of the sea hare, the common octopus and the cuttlefish, where LC90 after 10 h of exposure were 250, 290, 316, and 391 µg/mL, respectively. Comparatively with the control and albendazole-treated groups, the skin acid secretion of the sea slug caused the highest levels of the antioxidant enzymes SOD, Cat and GSH-PX; however, albendazole prompted the highest level of GSH-PX enzyme in all experimental groups.

There is insufficient information about the migratory Eurasian teal, Anas crecca. The study provides the first anatomical description of lingual adaptations and their relationship with the species-specific feeding behavior of A. crecca collected near Egyptian Lake Nasser. Our investigation was applied with the help of gross, scanning electron microscopy (SEM), and morphometric analysis. The study focused on the feeding filtering apparatus that depends on eight lingual papillae. The spatula-shaped nail is adapted for food particle pecking, while the lingual combs, rostral border of the prominence, unique papillary crest, median groove, and papillary system aid in intra-oral transportation. The feeding apparatus is formed by the lateral and dorsal papillary systems. The lateral papillary system had conical papillae with numerous long filiform and hair-like filiform papillae to constitute the food filtration apparatus, while the dorsal papillary system had ridged-like and rod-like papillae in addition to the small papillae of the papillary crest and spinated border of the root to help in moving the food particles with water to the lateral sides of the prominence. The laryngeal region exhibited papillary (pre-glottic) and non-papillary (glottic) areas. The papillary area had two lateral papillary portions and a median smooth portion, while the non-papillary area had an ovoid laryngeal mound with a median glottic opening that was bordered by a papillary border. The papillary portion had three slightly oblique longitudinal papillary rows.

Diving beetles (Coleoptera: Dytiscidae) are general predators that feed primarily on mosquito larvae and can control their populations, but the evidence for such an assumption remains weak. Rhantus elevatus is an important predator of this group distributed in Egypt with both larval and adult stages preying on immature mosquito. For determine predator effectiveness, it is requisite to identify the functional response (a = rate of attack and T_h= time of handling) and searching efficacy (a_t= area of discovery and m = mutual interference) as both correlate with biocontrol efficacy. This study assessed the density-dependent mortality of Culex pipiens larvae by eliciting functional responses of third-instar and adult predators at prey density ranging from 100 to 500 larvae per arena. By contrast, a searching efficacy for the same predator stages was examined at densities ranging from one to five predators per 500 prey. Predation rates of third-instar and adult of R. elevatus were fitted by a model of Type II response with coefficients were: third-instar (a = 0.208 h⁻¹ and T_h = 2413 h) and adult (a = 0.1191 h⁻¹ and T_h = 3723 h). The maximum number of mosquitoes which can be devoured by an individual larva and adult of R. elevatus within 24 h was 99.46 and 64.46 prey, respectively. The area of discovery for the larval stage declined more steeply than the adult stage of the predator as their density increased from one to five individuals, indicating more interference estimated for the larval stage. Considering these characteristics, larvae would seem to be the most effective stage against low mosquito populations due to low predation risk compared to that generated at high predator densities in the same arena from intra-specific interference. Eventually, we suggested a ratio of 1:100 (predator per prey) must be considered in biocontrol plans for mosquitoes.

Crayfish are emerging as model organisms for various disciplines. Moreover, decapod crustaceans also exhibit pain-like reactions and heightened anxiety when exposed to harmful stimuli, leading to short-term or persistent behavioral shifts. Awareness of decapod crustacean sentience and thus, suffering calls for refinement of current laboratory protocols. This study aims to enhance the standard methodology for injecting substances into crayfish by minimizing stress-inducing manipulation. We examined the impacts of various administration routes on the persistence of injected chemicals in marbled crayfish, its excretion, and animal survival. Fluorescein dye was used as a visual marker. It was administered via three alternative injection routes—intracoelomic (IC), intrapericardial administration through areola (IP-A), and intrapericardial administration through arthrodial membrane (IP-AM). Continuous video observations were made for a 4-h period under UV light, followed by intermittent observations at 12-h intervals over 48 h. The highest mortality (20%) was observed in IP-A administration. The IP-A method also provided the fastest systemic distribution of the dye in the body. Results indicated visibly higher urination frequency in IP-AM compared to IP-A. IC mirrored IP-AM outcomes without any observed mortality. We conclude that IC administration proved superior to intrapericardial methods, offering the least harmful but effective approach for crayfish injections.

Seasonal changes in sleep/wake cycles and behaviors related to reproduction often co-occur with seasonal fluctuations in sex hormones. Experimental studies have established that fluctuations in circulating testosterone mediate circadian rhythms. However, most studies are performed under constant lighting conditions and fail to investigate the effects of testosterone on the phenotypic output of circadian rhythms, that is, chronotype (daily activity patterns under light:dark cycles). Here, we experimentally elevated testosterone with implants during short nonbreeding daylengths in male house sparrows (Passer domesticus) to test if observed seasonal changes in chronotype are directly in response to photoperiod or to testosterone. We fitted individuals with accelerometers to track activity across treatment periods. Birds experienced three treatments periods: short day photoperiods before manipulation (SD), followed by testosterone implants while still on short days (SD + T). Implants were then removed. After a decrease in cloacal protuberance size, an indicator of low testosterone levels, birds were then photostimulated on long days (LD). Blood samples were collected at night, when testosterone peaks, to compare testosterone levels to daily onset/offset activity for experimental periods. Our results indicate that experimentally elevated testosterone under short nonbreeding photoperiods significantly advanced daily onset of activity and total daily activity relative to daylength. This suggests that testosterone, independent of photoperiod, is responsible for seasonal shifts in chronotypes and daily activity rhythms. These findings suggest that sex steroid hormone actions regulate timing of daily behaviors, likely coordinating expression of reproductive behaviors to appropriate times of the day.