Journal of Zoology最新文献

Female sperm storage organs in arthropods are used as taxonomic characters since it is assumed that they do not change after maturation. However, in the Golden Silk spider, Trichonephila clavipes, the shape and sclerotization of the spermathecae change with a mating event. Moreover, mating in T. clavipes consists of several hundred copulations, but the male transfers all sperm during the first insertion of each pedipalp. Given this puzzling mating behaviour, we hypothesize that multiple copulations serve purposes other than sperm transfer and uptake, such as further altering the morphology of the storage site and/or transferring substances other than sperm. We compared virgin female T. clavipes with females after two copulations, one for each spermatheca, and after ad-libitum mating. Each treatment consisted of two sub-treatments in which the state of the sperm storage organs was inspected after a short (1–3 days) or a long (11 days) time interval after the female's final moult. The size of the spermathecae increased twofold in all mating treatments compared to virgin females. The thickness of the spermathecal wall increased significantly with time in all treatments similarly. The spermathecal epithelium, which releases secretion into the lumen of the spermathecae, seems most active in virgin females during the time when mating would normally occur and turns less active after mating and with age. The spermathecae contain secretion produced by the female before mating; and after mating, sperm and another secretion transferred by the male. The numerous sperm-less matings in the ad-libitum treatment resulted in male secretion in the copulatory ducts of the female genitalia, likely impeding sperm transfer by subsequent males. Out study shows that female genitalia can change considerably after having reached maturity and suggests that sperm-less matings evolved in the context of sperm competition.

The order Chiroptera includes 55 species in Nepal, which have been recorded within a wide range of elevation between 64 and 4154 m above sea level. Assessing the potential distribution ranges in present climatic scenarios and forecasting changes in distribution ranges in future climate have been adopted to predict likely adverse impacts on biodiversity and natural ecosystems. However, very few studies have assessed the impact of climate change on bats globally and locally. We assessed the current potential distribution ranges of six representative species of bats occurring in Nepal using species distribution models (SDMs) and predicted their responses in future climatic scenarios. The occurrences of the representative species of bats were projected with six to eight environmental variables under the different climatic scenarios; present, and socioeconomic pathways 4.5 and 8.5 for the years of 2050 and 2070 deploying maximum entropy modeling. We used Arc GIS 10.7.1 to calculate the distribution range, area, and elevation for the bat species. Among 18 uncorrelated bioclimatic variables eight variables significantly contributed to the SDMs. Among the six species, two showed a wider range of current distribution. Under the future climatic scenarios, distribution ranges and latitudinal and elevation shifting were found to be species specific. Future distribution ranges for two species are predicted to be constricted, but no significant changes are predicted for the others. Major parts of the current and future distribution ranges of the bat species lie outside the current protected areas of the country. Landscape level and species-specific conservation policies are necessary for bat conservation, and future surveys of bats should be targeted in western Nepal.

Recent advancements in stress physiology, driven by the relevance of the stress response in animal welfare and conservation, have focused on alternative techniques beyond blood sampling for measuring glucocorticoids (GC). While blood samples have been traditionally used, practical and ethical concerns have spurred exploration into minimally invasive media like saliva, feces, milk, hair, and feathers. This review addresses the dearth of research on reptile endocrinology, offering insights into measuring GC or their metabolites in reptiles through various biological tissues. It underscores the importance of considering temporal dynamics in stress response evaluation and advocates for further exploration of alternative tools to enhance our understanding of reptilian stress responses.

Age-related telomere length (TL) variation is relatively well-described for mammals, birds and other model organisms. Nevertheless, it remains largely unknown in ectotherms, especially turtles and tortoises, which are extremely long-lived species with slow or negligible senescence. In this study, we described TL dynamics in wild spur-thighed tortoises (Testudo graeca), one of the chelonian species with the lowest aging rates. By combining cross-sectional (single) and longitudinal (capture–recapture) samplings, we assessed the relationship between TL and individual characteristics (sex, age, individual growth rate, body condition index, presence of shell anomalies). We did not find any association between TL and sex, individual growth rate, or body condition. However, the relationship with age remains uncertain, likely due to the complex dynamics of TL over time. Interestingly, shorter telomeres correlated significantly with shell anomalies, which are usually assumed as a fitness proxy for reptiles. Overall, our results suggest TL as a potential indicator for ontogenetic studies on tortoises, while its utility as a marker of biological age appears limited.

Nestlings normally exhibit a mix of traits that attract parental care, such as postural and vocal begging and carotenoid-based mouth colouration. These signals are hypothesised to be signs of nestling needs (vocal begging) and quality (mouth colouration). Therefore, we hypothesised that broods, where nestlings beg for less time and display more saturated carotenoid-based mouth colouration, would have lower nestling mortality. We tested these predictions in two wild blue tit (Cyanistes caeruleus) populations. The breeding success (here defined as the proportion of eggs that produced fledglings) was related to nestling mouth flanges' carotenoid-based colour saturation. This means that blue tits that raised nestlings with more coloured flanges had a higher within-population breeding success. Time spent in vocal begging, by contrast, was not associated with breeding success. Hence, our findings reveal that some communication signals displayed by nestlings (carotenoid-based colouration) predict breeding success, in our study mostly reflecting the proportion of eggs that hatched, while begging intensity does not, probably because the former reflects a better maternal pre-laying condition and nestling physiological status in the mid-term.

Seasonal changes in environmental conditions may induce reversible physiological adjustments in organisms. We studied the acclimatization for multiple stressors in energy expenditure and water balance in Galea leucoblephara, a diurnal hystricognath rodent native to South America that experiences significant changes in temperature, precipitation, and food availability among seasons. We conducted a field study in the Monte Desert of Mendoza, Argentina, where we evaluated adult individuals' physiological status during two contrasting seasons in terms of climate and primary productivity. Reduced temperature, rainfall, and primary productivity during winter were associated with a decrease of 70% in basal metabolic rate (BMR), 30% in total evaporative water loss (TEWL), and 9% in body mass (M_b). In contrast, higher water availability, high temperature, and primary productivity during summer, induced significant increases in energy expenditure and evaporative water loss. As expected, the proportion of dietary items consumed by G. leucoblephara varied seasonally, resulting in a more diverse diet during summer. Our results illustrate how G. leucoblephara can cope with high seasonal contrasts in water availability, temperature, and food availability by modifying its physiological performance. Our data provide support for the hypothesis of physiological flexibility in energetic traits and water balance in response to the environmental challenges of the Monte Desert.

Carnivorous mammals have been reported to feed on fleshy fruits and disperse seeds, but these interactions are seldom observed and are poorly understood in hyper-arid regions. Scent may play a key role in these interactions, given that most carnivores have sensitive olfactory systems and dichromatic vision. The !nara (Acanthosicyos horridus: Cucurbitaceae) in the Namib Desert produces large (10–20 cm diameter) melons that remain green while undergoing increased volatile emissions with a changing chemical profile as they ripen. Using extensive camera trapping, we found that the fruits are consumed mainly by black-backed jackals (Canis mesomelas) and rarely also by other carnivores such as cape fox (Vulpes chama) and brown hyaena (Hyaena brunnea). We found that scent cues play a crucial role as jackals mainly sought fruits at night and easily located ripe fruits that were experimentally buried beneath the sand to remove visual cues. Seeds retrieved from jackal scat showed improved germination relative to un-ingested seeds. This study highlights the importance of fruit scent in mediating seed dispersal mutualisms involving carnivores.

Co-occurrence between species may be mediated by ecological differences or competitive interactions, but the nature of these interactions can vary across spatial scales. At coarse scales, species may appear to broadly co-occur, but at fine scales, particularly for species with small home ranges, species may utilize different aspects of the microhabitat such that co-occurrence is limited and competitive interactions are reduced or eliminated. We investigated the microhabitat use of two morphologically and ecologically similar woodland salamanders (the Red-backed Salamander, Plethodon cinereus, and the Northern Ravine Salamander, P. electromorphus) that are distributed throughout the Alleghany Plateau in eastern North America to determine whether they partition habitat at finer scales. We also tested if P. electromorphus is a specialist on habitat types that allow it to exclude P. cinereus, or if P. electromorphus uses lower quality habitat as a refuge to avoid P. cinereus. At a site of microsympatry, we repeatedly sampled plots during two seasons, each within a different area of the landscape, and used occupancy and abundance modeling to assess the extent of co-occurrence and test whether the species use different microhabitat conditions. Plethodon cinereus greatly outnumbered P. electromorphus and occupied a greater proportion of plots, most plots where we detected P. electromorphus we also detected P. cinereus. In contrast to patterns documented in some montane species pairs, in which a high-elevation habitat specialist excludes a low-elevation generalist, we found that P. electromorphus primarily used microhabitat conditions favorable for both species, such as north-facing slopes, yet did not have a negative effect on the abundances of P. cinereus. In the presence of an abundant competitor, microhabitat use of the less abundant species may narrow toward optimal conditions with sufficient resources to facilitate co-occurrence.

When captured, many prey respond by biting the predator or struggling to get free. However, one indirect escape option is death feigning (DF), in which complete immobility supposedly “tricks” the predator into abandoning its meal. But lying motionless and exposed to a predator is dangerous; therefore, individuals should optimize DF occurrence and duration. We captured colour polymorphic dice snakes (Natrix tessellata, Natricidae) (N = 271) in the field and measured two behavioural responses: (1) the occurrence and duration of immobility/DF; (2) the number of tongue-flicking sequences (TF). Tongue flicking is an essential component of a key sensory mechanism to check the safety of the environment before attempting escape. We experimentally assessed the relationship between these two behaviours and the effects of phenotypic characteristic of snakes on the occurrence and duration of immobility and of TF. Snake phenotype had multiple effects. Gravid females avoided DF and displayed more TF sequences during the tests compared to non-gravid females and males. Blotched snakes stayed immobile longer than green and melanistic snakes. Larger individuals remained in DF for longer and showed fewer TF sequences than smaller individuals. Snakes burdened with a recent meal postponed fleeing and displayed more TF sequences than snakes without food. Finally, snakes showing more TF sequences postponed fleeing, which suggests that dice snakes assessed predatory risks and adapted escape behaviour to their risk status. Future studies should examine how individuals estimate the appropriate timing to shift from immobility to escape.

Extrafloral nectaried plants and myrmecophytes offer resources to ants that engage in protective mutualisms. The role of different ant species in herbivore deterrence has long been analyzed by using insect baits, and ants are regarded as effective plant guards if they attack the insects. Here, by performing a literature review, we conducted a comparative investigation on which ants display aggression toward experimental prey, which ants are better plant guards, and which plants (extrafloral nectaried plants or myrmecophytes) are better defended by ants. Data revealed that studies evaluating ant aggression toward insect baits have been performed on 37 extrafloral nectaried plant species and 19 myrmecophytes, and have involved over 30 genera of ants. Extrafloral nectaried plants and myrmecophytes rely on specific ant fauna to defend them from herbivores. In extrafloral nectaried plants, Camponotus and Crematogaster were regarded as the best plant protectors, as they attacked insects in nearly all plants. In myrmecophytes, Azteca, Pheidole, and Pseudomyrmex were the most important insect attackers. Myrmecophytes were better protected by ants, as all insects were attacked; in extrafloral nectaried plants, some ants failed to attack the insects. Plants are patrolled by several different ants, but there is a core of ants that excel in protection, and this varies according to plant type (extrafloral nectaried plants and myrmecophytes). With this knowledge, it may be possible to label different ants as effective plant guards, to anticipate their effects on plant performance, and even to understand their potential role as biological control agents.