摘要: In social groups, competition for individual advantage is balanced with cooperation, for the collective benefit. Selection against aggression has favored cooperation and non-aggressive competitive strategies. Because social play is a behavioral system that fluctuates between cooperation and competition, selection against aggression might have especially influenced this behavior. African savannah elephants (Loxodonta africana) are a low aggressive species, therefore suitable to investigate this aspect. We collected all occurrences observational audio-video data on social play, aggression/threats, and affiliation on an African elephant colony housed in a 25-ha open space at Parque de la Naturaleza de Cabarceno (Cantabria, Spain) and composed of 4 family groups (3 immature males, 3 immature females, and 7 adult females) and 2 adult males. Anticipating the influence of reduced aggression, we found that social play decreased with age, persisting in adults, and that it was highest in males. Social play was associated with affiliation (informing cooperation). Indeed, individuals that were central in the social play network were also central in the affiliation network. For immature subjects, we found a correlation between social play and affiliation sociomatrices. However, such correlation was absent in adults and social play mostly occurred between families. Despite the limitations related to dealing with a small captive group, this study largely supports the idea that the features of social play in African savannah elephants may be related to low aggression. This investigation hints toward a non-purely cooperative use of play, possibly as a non-aggressive interaction that accommodates different levels of cooperation and competition.

摘要: Captive breeding and stocking are commonly employed strategies for enhancing fisheries and conserving endangered fish species. However, hatchery-raised fish often exhibit reduced performance in the wild, displaying alterations in physiological, morphological, and behavioral traits. We tested for differences in swimming capacity and metabolic traits between wild and hatchery-reared individuals of the Spanish toothcarp (Aphanius iberus) from 2 different populations. Furthermore, we experimentally tested if these changes translated into fitness differences after their stocking into the wild. There were significant differences in swimming capacity and metabolic traits between wild and hatchery-reared individuals and also between the 2 populations. Captive-bred individuals displayed consistently lower metabolic rates than wild individuals from the same population (30-76% lower). Critical swimming speed rather differed between the 2 populations. Sex-specific differences were observed in maximum and standard metabolic rates, with wild individuals and females generally exhibiting higher values but with some exceptions. During a 3-month experiment, survival rates did not significantly differ between wild and captive-bred fish. Captive-bred individuals started smaller but exhibited rapid growth during the experiment. Initially, larger captive-bred fish had lower body conditions than their wild counterparts, but these differences progressively diminished. In summary, captive-bred individuals of this fish species showed lower metabolic rates, although the differences with wild individuals slightly depended on sex and size.

摘要: Maternal care in crayfish has been extensively studied, but little is known of its response to environmental factors. We studied the duration of maternal care and its association with the juvenile development of marbled crayfish Procambarus virginalis in adverse environmental conditions. We exposed females with developmental stage 3 juveniles to environments of low water volume (LW) with food provided, low water volume with no feed (starvation) (LWS), and low water volume without feeding plus an intruder (red swamp crayfish male) (LWSI). A control group with standard water level/feed conditions was included for comparison. Groups were monitored for up to 90 days. The LWS group showed significantly prolonged maternal care (similar to 65 days) as indicated by an extended attachment phase, delayed moulting of mothers (similar to 53 days), and retarded juvenile development. In the LWSI group, conflict precluded extended maternal care. Low use of shelter and feeding was evident under all stress conditions. The results showed that crayfish females modify maternal care in accordance with conditions, providing a longer period of safety for offspring under adverse circumstances. It is possible that the expression of maternal pheromones can manipulate the developmental rate in juveniles, a topic for future research.

摘要: Maternal care is critically important for the survival of offspring in various animals. Spiders in the family Lycosidae are known for their hunting ability and maternal care behaviors. Predation on newly hatched spiderlings (pulli) by mother spiders decreases when they come into contact, and they carry the pulli on their dorsal surface. However, the factors inducing maternal care in lycosid spiders have not been elucidated. In this study, we investigated maternal care in Pardosa pseudoannulata (Araneae, Lycosidae) females. We proposed that the physical interaction between pulli and mother spiders induces maternal care via m-aminophenylacetylene (m-A), a novel regulator of maternal care. The presence of pulli on the dorsal abdomen of non-mother spiders suppressed pulli predation and increased the pulli-carrying rate, and the absence of pulli on the mother spiders increased pulli predation and decreased the pulli-carrying rate. The compound m-A was abundant in mother spiders, and it could be induced in non-mother spiders when they carried pulli. The topical application of m-A to non-mother spiders and m-A injection decreased pulli predation and increased the pulli-carrying rate, respectively; these findings indicate that m-A in both internal tissues and the integument is required for the induction of maternal care behavior, and the interaction between pulli and females induces the production of m-A. In-depth study of the regulatory mechanism of maternal care will enhance our understanding of spider biology and behavior.

摘要: Behavior and fitness are important ecological traits frequently measured in insect bioassays. A common method to measure them in soft-bodied herbivorous insects involves confining individuals to plant leaves using clip cages. Although studies have previously highlighted the negative effects of clip cages on leaf physiology, little is known about the impact that using this confinement method has on insect fitness. The responses of different aphid genotypes/clones to different containment methods have not previously been investigated. Here we measured key fitness traits (intrinsic rate of natural increase, mean relative growth rate, time to reach reproductive adulthood and population doubling time) in the potato aphid, Macrosiphum euphorbiae Thomas (Hemiptera: Aphididae), when confined to plants using two methods: (1) clip cages to confine aphids to individual strawberry leaves and (2) a mesh bag to confine aphids to whole strawberry plants. Our study identified a strong negative impact on all the measured aphid fitness traits when using clip cages instead of mesh bags. We also identified genotype-specific differences in response to confinement method, where clip cage confinement differentially affected the fitness of a given aphid genotype compared to the same genotype on whole plants. These results suggest that clip cage use should be carefully considered when experiments seek to quantify insect fitness and that whole plants should be used wherever possible. Given the prevalence of clip cage use in insect bioassays, our results highlight the need for caution when interpreting the existing literature as confinement method significantly impacts aphid fitness depending on their genotype. Confinement method has an important effect on aphid fitness, with clip cages negatively impacting the parameters. Aphid genotype also modulates the extent of the confinement method's impact on aphid fitness. The results herein presented suggest that the results obtained with (the widely used method of) clip cages should be interpreted with caution.image