The insect immune system faces various challenges; particularly in social bees, caste system and age polyethism expose individuals to numerous environmental and working conditions. However, little is known about how cellular defenses in social bees may be organized to respond to a variety of immune challenges. Here, we describe the morphological features and the total and differential counts of hemocytes in different female classes (newly emerged workers, nurses, foragers, and virgin queens) of the eusocial stingless bee Melipona quadrifasciata. Granulocytes and prohemocytes were, respectively, the most and the least abundant cells among all classes of females. Furthermore, there were more prohemocytes in virgin queens than in foragers. The total number of hemocytes was smaller in foragers, whereas the largest number was observed in nurse workers. This reduced amount of hemocytes in foragers might allow energy savings to perform colony activities such as foraging and defense. Foragers also had the biggest hemocytes (either prohemocytes, granulocytes, or plasmatocytes) in comparison to the other classes of females, which might have arisen as a compensation for the reduction in number of these cells during aging. These results suggest that profiles of hemocytes of M. quadrifasciata vary according to the caste and age of this eusocial bee. 相似文献
The theory that fluctuating asymmetry is sensitive to both environmental and genetic stress is gaining acceptance among evolutionary
biologists. Most empirical work has focused on ornamental traits on the assumption that they are more susceptible to stress.
In tegumentary coloration is a common ornament in nature, and frequently has a hormonal basis. Earlier studies in the lizard
Psammodromus algirus indicate that testosterone induces the development of head nuptial coloration in large males and, at the same time, produces
an increase of the ectoparasite load and higher mortality. Hence, the manipulation of testosterone levels may be a way to
increase ornament expression and simultaneously create conditions that may make symmetrical development difficult. This positive
covariation between character size and symmetry is opposite to that expected in theory for sexually selected traits, so the
predicted elevation of asymmetry due to the treatment cannot be confounded by any intrinsic association between symmetry and
character size. We firstly consider the effect that testosterone supplementation has on two variables that reflect the symmetry
of bilateral throat nuptial coloration in large P. algirus males. Also, we examine whether ornament symmetry is positively associated with reproductive success, a prediction of theory
of sexually selected symmetry. Testosterone treatment did not increase the fluctuating asymmetry of throat coloration. Size
asymmetry increased with character size in individuals with a fragmented colour pattern, but changed suddenly to a highly
symmetric pattern in individuals with non-fragmented coloration. Mirror asymmetry decreased steadily with character size.
These results suggest that the development of coloration on both sides of the throat midline follows a random pattern. Asymmetry
did not correlate with variables that estimated reproductive success, suggesting that asymmetry is not affected by physiological
stress and that this trait is not a sexually selected signal in P. algirus.
Received: 1 July 1996 / Accepted after revision: 4 May 1997 相似文献
The spatial and temporal distribution of the copepodEurytemora affinis hirundoides (Nordquist, 1888) in the Gironde estuary, southwest France, was investigated in 1976, and between 1981 and 1983. The distribution pattern of the population bore a clear relationship to the patterns of water circulation and transport of particulate matter. Laboratory experiments suggested thatE. affinis hirundoides is incapable of autonomous displacement against the direction of general circulation and behaves as passive particles. A major problem faced by species living in estuaries is that of the maintenance of endemic populations. Some authors have suggested that behavioural responses may play an important role in minimising population losses. Our study indicated that hydrodynamic processes are sufficient to explain the distribution and retention ofE. affinis hirundoides, whose populations are retained in the estuary in the same manner as the suspended sediment. Since the outflow of particulate matter from the Gironde estuary to the sea is very sporadic, we hypothesize that most of the production ofE. affinis hirundoides remains within the estuary, and does not fertilize the continental shelf, at least not in the form of particulate organic matter. 相似文献
Environmental Science and Pollution Research - Groundwaters are normally consumed without previous treatment and therefore the monitoring of contaminants in order to guarantee its safety is... 相似文献
Environment, Development and Sustainability - The COVID-19 pandemic has caused a global crisis, one which also influences the ways sustainability is being taught at universities. This paper... 相似文献
Although competition is usually assumed to be the most common interaction between closely related organisms that share limiting resources, the relationships linking distant taxa that use the same nesting sites are poorly understood. In the present study, we examine the interactions among social hymenopterans (honeybees and wasps) and vertebrates in tropical ecosystems of East Africa. By analysing the preferences of these three groups for nest boxes that were empty or previously occupied by a different taxon, we try to establish whether the relationships among them are commensal, mutualistic, competitive or amensal. Vertebrates and honeybees selected nest boxes that had previously been occupied by the other, which suggests that each obtains some benefit from the other. This relationship can be considered mutualistic, although a mutual preference for each others’ nests does not exclude a competitive interaction. Vertebrates and wasps preferred nest boxes not previously occupied by the other, which suggests that they compete for tree cavities. Finally, wasps seemed to completely refuse cavities previously used by honeybees, while the bees occupied cavities regardless of whether they had been previously used by wasps, an apparently amensal relationship. These results indicate that the interdependence between distantly related taxa is stronger and more complex than previously described, which may have important implications for population dynamics and community structure.