搜索结果：Centris

Intraspecific variation in behavior is associated with variable brain resource allocation patterns: There is frequently increased tissue investment in discrete regions that support fitness-relevant cognitive abilities. However, the relationships between tissue volume and actual cell numbers have rarely been explored for insects due to methodological hurdles recently addressed via the application of isotropic fractionation. In solitary desert Centris pallida (Hymenoptera: Apidae) bees, there are two major levels of intraspecific variation: sex (males vs. females) and male morph (as a result of alternative reproductive tactics, large morph and small morph males rely on scent or sight, respectively, for mate location). Using isotropic fractionation, we separately analyzed optic lobe (OL) and central brain (CB) cell numbers of males and females to determine the impacts of sex and morph on brain cell allometry. Female bees' brains were bigger and had higher cell numbers and cell densities than males of the same size. In both sexes, total brain cell number increased with brain size, driven by increases in OL cell numbers. Between male morphs, we found that OL masses were relatively larger in small-morph males, consistent with the relationship between body size and OL volumes reported in prior studies. However, small-morph C. pallida males had fewer total cells (as represented by cell nuclei) and reduced cell density, in their OLs. Together, these data suggest that there is intraspecific and brain-region-specific variation in brain cell numbers and that variation in brain tissue volume may not match other levels of neural organization like brain cell numbers/densities.

Habitat loss and fragmentation (HLF) are among the major drivers of bee decline, yet closely related species often show contrasting responses depending on their ecological and demographic traits. The Brazilian Cerrado biodiversity hotspot experiences among the world's highest rates of HLF. Here we combined whole-genome sequencing and six decades of museum occurrence records to assess the population genomic diversity, demographic history, temporal trends and seasonal activity of two ecologically similar oil-collecting bees, Centris aenea and Centris fuscata, in the Brazilian Cerrado-a global biodiversity hotspot under intense anthropogenic pressure. Despite the occurrence in a fragmented landscape, our results revealed a high nucleotide diversity and weak population structure for both species. However, whereas C. aenea exhibited higher diversity, no inbreeding and negligible population genetic differentiation, C. fuscata displayed numerous runs of homozygosity and moderate differentiation between some populations. Demographic reconstructions revealed that both species underwent historical declines, likely linked to Holocene climatic transitions, but recent trajectories diverged: C. aenea maintained a stable effective population size, whereas C. fuscata showed strong fluctuations and a recent decline. Museum records corroborated these patterns, indicating a decline in C. fuscata but not in C. aenea. Our findings highlight how subtle differences in a species' ecology can drive divergent responses to HLF. While conserving natural vegetation is critical for both species, C. fuscata may require targeted monitoring and management to safeguard its long-term persistence in the increasingly threatened Cerrado biome.

The indiscriminate use of pesticides is one of the factors directly impacting bee populations. However, limited information is available on the pesticide effects on solitary bees, especially in Neotropical countries. In this scenario, this study evaluated the survival and histopathological effects caused by the neonicotinoid insecticide acetamiprid (7 ng/μL) and the fungicide azoxystrobin (10 ng/μL) in the midgut and parietal fat body of the solitary bee Centris analis. Female and male newly-emerged bees were orally exposed for 48 h to the pesticides, or alone or in combination, under laboratory conditions. The exposure to the insecticide reduced the survival of males, while the mixture reduced survival in both sexes. Acetamiprid promoted a reduction in the number of regenerative nests in the midgut, alterations of fat body cells by increasing carbohydrates in trophocytes, and reduction of oenocyte size, and increased the frequency of pericardial cells in the advanced activity stage. Both pesticides caused changes in HSP70 immunolabelling of midgut from males at the end of pesticide exposure. Comparatively, the effects on males were stronger than in females exposed to the same pesticides. Therefore, acetamiprid alone and in mixture with fungicide azoxystrobin can be harmful to males and females of Neotropical solitary bee C. analis showing lethal and sublethal effects at a concentration likely to be found in the environment.

Pesticide use is a major factor contributing to the global decline in bee populations. Sublethal effects, such as behavior alterations, are neglected in pesticide regulation for pollinators. However, these effects can bring important information to understanding the impacts of pesticides on bees' daily activities. In this study, we aimed to investigate the effects of the insecticide acetamiprid (7 ng/μL) and the fungicide azoxystrobin (10 ng/μL) on the behavior of the Neotropical solitary bee Centris analis. Female and male bees were exposed to these chemicals continuously for 48 h, followed by an additional 48 h without contaminated food, totaling 96 h of observation. We used five experimental groups: control, solvent control, insecticide, fungicide, and pesticide mixture (insecticide + fungicide). Behavioral alterations based on locomotion and light response were assessed by video tracking at 48 (end of pesticide exposure) and 96 h (end of bioassay). In addition, after recording bees at 96 h, the individuals were anesthetized for brain collection and histological evaluation of mushroom bodies to evaluate if pesticides can damage their neurons and impair the cognitive processes and responses of bees to sensory stimuli. Bees exposed to acetamiprid and pesticide mixture showed lethargic movements and impaired locomotion at 48 h. Notably, these behavioral effects were no longer evident after the bees consumed uncontaminated food for an additional 48 h, totaling 96 h from the start of pesticide exposure. Only fungicide exposure did not result in any behavioral or brain histological changes. Therefore, our study showed that acetamiprid at an estimated residual concentration, despite being classified as having low toxicity for bees, can cause significant initial locomotion disruption in solitary bees. These findings highlight the importance of considering sublethal effects in environmental risk assessment.

Currently, only Apis mellifera is used in environmental regulation to evaluate the hazard of pesticides to pollinators. The low representativeness of pollinators and bee diversity in this approach may result in insufficient protection for the wild species. This scenario is intensified in tropical environments, where little is known about the effects of pesticides on solitary bees. We aimed to calculate the medium lethal dose (LD50) and medium lethal concentration (LC50) of the insecticide dimethoate in the Neotropical solitary bee Centris analis, a cavity-nesting, oil-collecting bee distributed from Brazil to Mexico. Males and females of C. analis were exposed orally to dimethoate for 48 h under laboratory conditions. Lethality was assessed every 24 h until 144 h after the beginning of the test. After the LD50 calculation, we compared the value with available LD50 values in the literature of other bee species using the species sensitivity distribution curve. In 48 h of exposure, males showed an LD50 value 1.33 times lower than females (32.78 and 43.84 ng active ingredient/bee, respectively). Centris analis was more sensitive to dimethoate than the model species A. mellifera and the solitary bee from temperate zones, Osmia lignaria. However, on a body weight basis, C. analis and A. mellifera had similar LD50 values. Ours is the first study that calculated an LD50 for a Neotropical solitary bee. Besides, the results are of crucial importance for a better understanding of the effects of pesticides on the tropical bee fauna and will help to improve the risk assessment of pesticides to bees under tropical conditions, giving attention to wild species, which are commonly neglected. Environ Toxicol Chem 2023;42:2758-2767. © 2023 SETAC.

Primary types of Centris bees described by the German melittologist Heinrich Friese were studied. To stabilize the application of some names, lectotypes were designated for C. agilis abdominalis, C. americana bicincta, C. atriventris rubripes, C. bakeri, C. birkmannii, C. breviceps, C. bucephala, C. buchwaldi, C. burgdorfi paraguayensis, C. chilensis neoqueenensis, C. collaris fluviatilis, C. costaricensis erubescens, C. flavothoracica, C. labrosa, C. labrosa simplex, C. lateritia, C. lutea, C. metathoracica, C. mexicana albiceps, C. mixta, C. mocsaryi, C. muralis melanopus, C. nigripes, C. pauloensis, and C. versicolor rufiventris. Centris agilis abdominalis and C. labrosa simplex were revalidated from the synonymy of C. agilis Smith and C. analis (Fabricius), respectively, raising both varieties at species level. Centris fulvicollis is removed from C. (Ptilotopus) and transferred to C. (Melanocentris), transforming the former subgenus in a natural group. Centris fusciventris atriceps is proposed as n. syn. of C. mocsaryi, C. flavifrons rufescens as n. syn. of C. flavifrons (Fabricius), and C. xanthocnemis ardesiaca as n. syn. of C. xanthocnemis (Perty). Centris femoralis is withdrawn from the synonymy of C. lutea and proposed as n. syn. of C. rufipes. Taxonomic notes and comments of the remaining species described by Friese are also provided.

Wild bees are vital for the pollination of native plants and crops, providing essential ecosystem services. Climate change is known to impact biodiversity and species distributions, but insects adapted to desert ecosystems may exhibit unique physiological, behavioral, and evolutionary responses. The desert pallid bee (C. pallida), a solitary bee native to the arid southwestern United States and northern Mexico, primarily forages on yellow palo verde (P. microphylla), blue palo verde (P. florida), and desert ironwood (O. tesota). This study used MaxEnt to estimate the current and projected geographical overlap of suitable habitats for C. pallida and its host plants. Here, we used MaxEnt to estimate the current and forecasted overlapping geographically suitable habitat of C. pallida with all three host plants. We forecasted potential environmentally suitable areas for each species to the year 2040 using the current distribution model and climate projections with moderate CO2 levels. We found a continued spatial alignment in the suitable area of the bee and its host plants with a 70% increase in the range overlap area, though shifted to higher average altitudes and a slight northern expansion. These findings may provide insight to stakeholders on the conservation needs of desert-dwelling pollinators.

The genera Centris and Epicharis constitute the Centridini and are widely distributed in the Neotropical region. Centris is also found in the southern portion of the Neartic region, although both genera are more abundant in the humid tropical regions. To describe the structure of the male reproductive system and spermatozoa, light and transmission electron microscopy were used. The male reproductive system of Centris sp. is formed by a pair of testes, a pair of deferent ducts, a pair of seminal vesicles, a pair of accessory glands and an ejaculatory duct connected to the external genitalia, the aedeagus. In this species, testes and the pre-vesicular deferens ducts as well as the seminal vesicles are encapsulated in a single conjunctive capsule, the scrotal membrane. Each testis consists of four testicular follicles, made up of cysts with up to 64 germinative cells. Histologically, the seminal vesicles are formed by a simple cylindrical epithelium, basal membrane and muscular tunic. The spermatozoa of Centris analis, C. fuscata, C. tarsata and Centris sp. are morphologically similar. They have two easily distinguishable regions: the head and flagellum. The head is formed by the two-layer acrosome, the linear nucleus and the flagellum, the centriole adjunct, the axoneme of pattern 9+9+2 microtubules, two asymmetric mitochondrial derivatives and two accessory bodies. These Centris species share various morphological characteristics of the male reproductive system and spermatozoa with the other bees previously described, indicating that several characteristics are synapomorphic for the family Apidae. Studies on the morphology of the male reproductive system and spermatozoa in Hymenoptera have demonstrated the diversity of the information provided by these reproductive structures, which can be used in taxonomy studies and the phylogeny of this important group of insects.

Three new species of oil-collecting bees of the genus Centris (Xanthemisia) Moure are described and illustrated: C. jakalteka sp. nov., C. maya sp. nov. and C. purhepecha sp. nov. The new proposed taxa are distributed in the north of the Neotropical Region, specifically in the Mesoamerican Dominion and the Mexican Transition Zone, between the Neotropics and Nearctic. In addition, a distribution map and an identification key for the species of the subgenus occurring in the aforementioned regions are also presented.

Incoming solar radiation (wavelengths 290-2500 nm) significantly affects an organism's thermal balance via radiative heat gain. Species adapted to different environments can differ in solar reflectance profiles. We hypothesized that conspecific individuals using thermally distinct microhabitats to engage in fitness-relevant behaviors would show intraspecific differences in reflectance: we predicted individuals that use hot microclimates (where radiative heat gain represents a greater thermoregulatory challenge) would be more reflective across the entire solar spectrum than those using cooler microclimates. Differences in near-infrared (NIR) reflectance (700-2500 nm) are strongly indicative of thermoregulatory adaptation as, unlike differences in visible reflectance (400-700 nm), they are not perceived by ecological or social partners. We tested these predictions in male Centris pallida (Hymenoptera: Apidae) bees from the Sonoran Desert. Male C. pallida use alternative reproductive tactics that are associated with distinct microclimates: Large-morph males, with paler visible coloration, behave in an extremely hot microclimate close to the ground, while small-morph males, with a dark brown dorsal coloration, frequently use cooler microclimates above the ground near vegetation. We found that large-morph males had higher reflectance of solar radiation (UV through NIR) resulting in lower solar absorption coefficients. This thermoregulatory adaptation was specific to the dorsal surface, and produced by differences in hair, not cuticle, characteristics. Our results showed that intraspecific variation in behavior, particular in relation to microclimate use, can generate unique thermal adaptations that changes the reflectance of shortwave radiation among individuals within the same population.

In this paper the primary types of Centris bees described by the British entomologist Frederick Smith deposited in the Natural History Museum, London and in the Oxford University Museum of Natural History, Oxford, United Kingdom were studied. To stabilize the application of some names, lectotypes were designated for C. agilis, C. apiformis (= C. aenea Lepeletier), C. ardens (= C. varia (Erichson)), C. aterrima, C. cineraria, C. concinna (= C. dentata), C. crassipes, C. dentata, C. difformis, C. discolor, C. elegans, C. ephippium, C. festiva, C. ignita (= C. agilis), C. insignis, C. insularis, C. maculifrons, C. melanochlaena, C. mexicana, C. modesta, C. nitida, C. perforator, C. personata (= C. longimana Fabricius), C. plumipes, C. rubella (= C. ferruginea Lepeletier), C. semicaerulea, C. simillima, C. tarsata, C. thoracica (= C. domingensis Dalla Torre) and Anthophora dimidiata (= C. nigerrima (Spinola)). Centris perforator nom. rev. and C. modesta nom. rev. are withdrawn from the synonymy of C. fuscata Lepeletier and C. obsoleta Lepeletier respectively, and consequently revalidated. Centris fulviventris Cresson and C. simillima are removed from the synonymy of C. lanipes (Fabricius), proposing the revalidation of the first species and the second one as its new junior synonym. Centris insignis and C. insignis scutellaris Friese are proposed as new junior synonyms of C. laticincta (Spinola). The critical study of the primary type of C. aterrima, for a long time a misidentified species, allowed for proposing C. anomala Snelling as its new junior synonym. As result of this synonymy, C. apache new species is here described based on specimens incorrectly considered as belonging to C. aterrima. In addition, a lectotype for Centris clypeata Friese (= C. nigrocaerulea Smith) is also designated.

Centris dimidiata (Olivier) is currently considered an easily recognizable species widely distributed throughout the Amazon basin, mainly in Brazil. For much of its taxonomic history, C. atriventris Mocsáry and C. furcata (Fabricius) have been considered its junior subjective synonymies. Such interpretation was apparently due to the lack of a detailed study of the type specimens, misinterpretation of the original descriptions, and inability to study the apparently lost type specimen of C. dimidiata. In this paper, a neotype for C. dimidiata is designated, the species is placed in Centris (Ptilotopus), and C. denudans rubida Gribodo is proposed as its new junior synonymy. Simultaneously, as a result of a detailed study of the type material of C. atriventris and C. furcata, both species are revalidated and their placement in Centris (Melacentris) is confirmed. For all species, the female is redescribed and the male is described for the first time. A lectotype for C. atriventris is designated and new distribution records and a distribution map are provided.

In this paper, a complete taxonomic revision of the species of Centris (Wagenknechtia) Moure is presented for the first time. The following species are recognized: Centris cineraria Smith, C. escomeli Cockerell, C. moldenkei Toro & Chiappa, C. muralis Burmeister, C. orellanai Ruiz, C. rhodophthalma Pérez and C. vardyorum Roig-Alsina. Floral associations, distribution records, and diagnoses of both sexes based on type specimens, are given. An identification key, illustrations, along with an updated catalogue of all species of the subgenus, are also provided. In addition, a neotype for Centris orellanai is designated.

Centris analis (Fabricius, 1804) is a solitary, cavity-nesting bee that is often recorded in studies through the use of trap nests. This species is considered to be a good candidate as a manageable pollinator for some orchards. However, further studies are still needed to optimize its rational rearing. This study sought to analyze female preference for different lengths and diameters of trap nests, as well as the effects of nest dimensions on the number of constructed cells, mortality rates, parasitism rates, and sex ratio. We used compact trap nests comprised of tubes with internal diameters ranging from 0.6 to 0.8 cm, and lengths ranging from 8 to 12 cm. The results showed that females preferred the narrowest (0.6 and 0.7 cm) and two of the longest cavities (10 and 12 cm). The greatest number of cells built was observed in the most used lengths. The lengths that were tested did not affect the mortality or parasitism rates or the sex ratio. Based on our findings concerning the dimensions examined, we recommend using the narrowest and longest cavities. The combined analyses of the tested parameters (diameter and length) demonstrated new data that can help improve the rearing and maintenance techniques applied to C. analis populations.

It is plausible that specialized ecological interactions constrain geographic ranges. We address this question in neotropical bees, Centris and Epicharis, that collect oils from flowers of Calceolariaceae, Iridaceae, Krameriaceae, Malpighiaceae, Plantaginaceae, or Solanaceae, with different species exploiting between one and five of these families, which either have epithelial oil glands or hair fields. We plotted the level of oil-host specialization on a clock-dated phylogeny for 22 of the 35 species of Epicharis and 72 of the 230 species of Centris (genera that are not sister genera) and calculated geographic ranges (km(2) ) for 23 bee species based on collection data from museum specimens. Of the oil-offering plants, the Malpighiaceae date to the Upper Cretaceous, whereas the other five families are progressively younger. The stem and crown groups of the two bee genera date to the Cretaceous, Eocene, and Oligocene. Shifts between oil hosts from different families are common in Centris, but absent in Epicharis, and the direction is from flowers with epithelial oil glands to flowers with oil hairs, canalized by bees' oil-collecting apparatuses, suitable for piercing epithelia or mopping oil from hair fields. With the current data, a link between host specialization and geographic range size could not be detected.

In this paper the primary types of Centris described by Amédée Lepeletier de Saint-Fargeau in 1841 deposited at Muséum National d'Histoire Naturelle, France and Hope Entomological Collection, Oxford University Museum of Natural History, United Kingdom were studied. To stabilize the application of some names, lectotypes were designated for C. bimaculata, C. collaris, C. decolorata, C. denudans, C. dorsata, C. ferruginea, C. fuscata, C. maculata (= C. decolorata), C. obsoleta, C. picea, C. poecila, C. trigonoides, C. violacea and C. vittata. Centris picea nomen oblitum is withdrawn from the synonymy of C. lanipes (Fabricius) and proposed as new junior synonym of C. trigonoides nomen protectum. Centris nigrescens is removed from the synonymy of C. vittata and revalidated, proposing C. merrillae Cockerell and C. lanipes ogilviei Cockerell as its new junior synonymies. Lectotypes for this latter species and for C. rubella Smith (= C. ferruginea) were also designated. In addition, due to the impossibility of identifying C. thoracica and the misplacement of its type material, it is proposed to consider it nomen dubium and place it incertae sedis.