Independent cytoplasmic incompatibility induced by Cardinium and Wolbachia maintains endosymbiont coinfections in haplodiploid thrips populations

Cardinium and Wolbachia are common maternally inherited reproductive parasites that can coinfect arthropods, yet interactions between both bacterial endosymbionts are rarely studied. For the first time, we report their independent expression of complete cytoplasmic incompatibility (CI) in a coinfected host, and CI in a species of the haplodiploid insect order Thysanoptera. In Pezothrips kellyanus, Cardinium‐induced CI resulted in a combination of male development (MD) and embryonic female mortality (FM) of fertilized eggs. In contrast, Wolbachia‐induced CI resulted in FM together with postembryonic mortality not previously reported as a CI outcome. Both endosymbionts appeared to not influence fecundity but virgins produced more offspring than mated females. In coinfected individuals, Wolbachia density was higher than Cardinium. Wolbachia removal did not impact Cardinium density, suggesting a lack of competition within hosts. Maternal transmission was complete for Wolbachia and high for Cardinium. Our data support theoretical predictions and empirical detection of high endosymbiont prevalence in field populations of the native range of this pest thrips. However, previous findings of more frequent loss of Wolbachia than Cardinium, particularly in field populations of the host's invasive range, suggest that genetic diversity or varying environmental factors between field populations also play a role in shaping host‐endosymbiont dynamics.     

Interspecific interference competition between Encarsia formosa and Encarsia sophia (Hymenoptera: Aphelinidae) in parasitizing Bemisia tabaci (Hemiptera: Aleyrodidae) on five tomato varieties

Abstract Interspecific competition between Encarsia formosa and Encarsia sophia, two major parasitoids of Bemisia tabaci, and the influence of five tomato varieties on competition outcome were investigated under laboratory conditions. E. formosa parasitized more B. tabaci than E. sophia when in single wasp assays on any of the tomato varieties investigated. When B. tabaci nymphs were exposed to both wasp species (either simultaneously or sequentially), the number of B. tabaci nymphs parasitized by either wasp species was significantly decreased compared to the sole access condition. Total mortality of B. tabaci was increased when B. tabaci nymphs were exposed to both wasp species compared to only one wasp species. Thus competition between E. formosa and E. sophia apparently reduced parasitoid offspring numbers, but not the efficiency of biological control. In fact, control efficiency was enhanced in some cases, particularly on tomato variety Huangtuoyuan (HTY). When wasps were allowed sequential access to hosts, interference occurred through host feeding by the second wasp, especially if it was E. sophia. The effect of different tomato varieties was not significant.     

Growth and development of Encarsia formosa (Hymenoptera: Aphelinidae) in the greenhouse whitefly, Trialeurodes vaporariorum (Homoptera: Aleyrodidae): effect of host age

The tiny parasitoid wasp, Encarsia formosa, has been used successfully to control greenhouse whiteflies (GHWFs) in greenhouses in many countries throughout the world. Therefore, there has been considerable interest in developing methods for artificially rearing this wasp. However, little information is available concerning the regulation of its development including the host-parasitoid interactions that are required for the parasitoid to complete its life cycle. Here we confirm that parasitoid developmental rates differ significantly based upon the host instar parasitized. Development was faster when 3rd and 4th instar GHWFs were offered for parasitization than when 1st or 2nd instars were used. Our results show that it is primarily the embryo and the first two parasitoid instars that exhibit prolonged developmental times when 1st and 2nd instar whiteflies are parasitized. Although percent emergence was not affected by host age at the time of parasitization, adult longevity as well as adult emergence pattern varied greatly depending upon the instar parasitized. When 3rd and 4th instar GHWFs were selected for oviposition, adult wasps lived significantly longer than when 1st or 2nd instars were used; also, there was a sharp emergence peak on the 2nd day after emergence was first observed (reduced or absent when 1st or 2nd instar GHWFs were parasitized) and the emergence period was reduced from between 8 and 11 days to 5 days. In general, the younger the host instar parasitized, the less synchronous was parasitoid development. Previous reports that E. formosa will not molt to the 2nd instar until the host has reached its 4th instar were not confirmed. When 1st instar host nymphs were parasitized, 2nd instar parasitoids were detected in 3rd instar hosts. Importantly, however, no matter which instar was parasitized, the parasitoid never molted to its last instar until the host had reached Stage 5 of its last instar, a stage in which host pharate adult formation has been initiated. It appears, then, that a condition(s) associated with host pharate adult formation is required for the parasitoid's final larval molt. Results reported here should facilitate the development of in vitro rearing systems for E. formosa.     

Bemisia tabaci (Homoptera: Aleyrodidae) instar effects on rate of parasitism by Eretmocerus mundus and Encarsia pergandiella (Hymenoptera: Aphelinidae)

Studies were conducted to compare preference among Bemisia tabaci Gennadius, biotype B instars for parasitization by Eretmocerus mundus Mercet and Encarsia pergandiella Howard when provided one instar only, two different instars, and four different instars simultaneously. In the single‐instar no choice treatment, Er. mundus was more successful in parasitizing the younger host instars, while En. pergandiella parasitized a greater proportion of the older instars. Similar results were observed when parasitoids were provided a choice of two instars in six different pair combinations. When all four instars were provided simultaneously, the numbers of first, second, and third instars parasitized by Er. mundus were not significantly different from each other (range 10.3–16.4%), but all were significantly higher than parasitism of fourth instar nymphs (2.1%). The highest percentage parasitization by En. pergandiella was in third instar (17.2%), and the lowest in first instar (2.8%).     

The accumulation of reproductive barriers during speciation: postmating barriers in two behaviorally isolated species of darters (Percidae: Etheostoma)

Identifying the manner in which reproductive barriers accumulate during lineage divergence is central to establishing general principles of species formation. One outstanding question is which isolating mechanisms form the first complete barrier to gene flow in a given lineage or under a particular set of conditions. To identify these initial reproductive barriers requires examining lineages in very early stages of divergence, before multiple reproductive barriers have evolved to completion. We quantified the strength of three postmating barriers in a pair of darter species and compared these estimates to each other and to the strength of behavioral isolation (BI) reported in a previous study. Results reveal no evidence of gametic incompatibility but intermediate levels of conspecific sperm precedence and hybrid inviability. As BI is nearly complete, our analysis comparing the strength of multiple reproductive barriers implicates the evolution of mate choice as central to both the origin and maintenance of these species. Further examination of ecological isolation and hybrid sterility is necessary to determine the role of these barriers in darter speciation.     

“Environmental stress” and reproductive success in the common marmoset (Callithrix jacchus jacchus)

The present report documents the breeding success of a new colony of common marmosets (Callithrix jacchus jacchus) and demonstrates a correlation between environmental stress and reproductive success. Environmental conditions ranged chronologically over 40 months, through four periods: I) the initial period, when the colony was formed; II) a phase of relative environmental stability; III) a stage of “environmental stress” (when the colony was disrupted by nearby construction); and IV) a return to a stable environment. Examination of reproductive status during each period indicated that the colony exhibited severe reproductive suppression during the time of the environmental disruption. Parity and the number of live births decreased and the number of spontaneous abortions increased during this period. Reproductive success remained low during period IV. More triplets than twins were born during the period of relative environmental stability.     

“Stepping-sticks” and “seat-sticks”: New types of tools used by wild chimpanzees (Pan troglodytes) in Sierra Leone

In Tenkere, Sierra Leone, a community of wild chimpanzees (Pan troglodytes verus) spent long hours eating the fruits and flowers of the Kapok (Ceiba pentandra) tree. The branches of this species are covered in sharp thorns which make movement in their high canopies problematic for the chimpanzees. In an apparent attempt to increase their mobility and to ease the discomfort of lengthy bouts of eating in these trees, some of the Tenkere chimpanzees have been observed using stick tools as foot (“stepping-sticks”) and body (“seat-sticks”) protection against the painful thorns. This form of tool-using is culturally unique to the Tenkere chimpanzees, as at other sites where these apes have been observed eating parts of kapok trees, there are no published records of this tool technology. In three of the stepping-stick tool use incidents, the chimpanzee used the tool(s), held between their greater and lesser toes, in locomotion. This form of tool use is the first recorded case of habitually used tools that can be justifiably categorized as being “worn” by any known wild population of Pan troglodytes. Am J Primatol 41:45–52, 1997. © 1997 Wiley-Liss, Inc.     

Incipient speciation revealed in Anastrepha fraterculus (Diptera; Tephritidae) by studies on mating compatibility, sex pheromones, hybridization, and cytology

It has long been proposed that the nominal species Anastrepha fraterculus is a species complex and earlier studies showed high levels of pre-zygotic isolation between two laboratory strains from Argentina and Peru. Further experiments were carried out on the same populations and on their reciprocal hybrids, including pre- and post-zygotic isolation studies, pheromone analysis, and mitotic and polytene chromosome analysis. A high level of pre-zygotic isolation had been maintained between the parental strains despite 3 years of laboratory rearing under identical conditions. The level of pre-zygotic isolation was reduced in matings with hybrids. There were also differences in other components of mating behaviour. There were quantitative and qualitative differences in the sex pheromone of the two strains with the hybrids producing a mixture. The pre-zygotic isolation barriers were complemented by high levels of post-zygotic inviability and sex ratio distortion, most likely not due to Wolbachia , although there was evidence of some cytoplasmic factor involved in sex ratio distortion. Analysis of polytene chromosomes revealed a high level of asynapsis in the hybrids, together with karyotypic differences between the parental strains. The combined results of the present study indicate that these two strains belong to different biological entities within the proposed A. fraterculus complex.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 152–165.     

Suitability of Bemisia tabaci (Hemiptera: Aleyrodidae) instars for the parasitization by Encarsia bimaculata and Eretmocerus sp. nr. furuhashii (Hymenoptera: Aphelinidae) on glabrous and hirsute host plants

The host instar preferences of Encarsia bimaculata and Eretmocerus sp. nr. furuhashii parasitizing Bemisia tabaci and their development on four host plants, collard, eggplant, cucumber and tomato, were studied in the laboratory. Both of the parasitoids accepted all nymphal stages of B. tabaci, but E. bimaculata preferred third and fourth instars while Er. sp. nr. furuhashii preferred second and third instars under both choice and no choice conditions. Regardless of host stage parasitized, adults of parasitoids emerged only from fourth instars. When given the simultaneous choice of all instars, E. bimaculata reduced parasitization of first and second instars (3.73 and 4.76%, respectively) while increasing parasitization of third and fourth instars (5.44 and 6.93%, respectively), in contrast Er. sp. nr. furuhashii increased its parasitization of second and third instar nymphs (1.27 and 3.17%, respectively) and decreased that of first and fourth instars (7.0 and 3.06%, respectively). Host plants did not significantly influence instar preference for either parasitoid. Developmental periods of both the parasitoids from egg to adult emergence were longest when first instars were parasitized and shortest when fourth instars were selected. Parasitoid developmental time was generally shorter on glabrous plants than on hirsute plants.     

Impact of Two Accidentally Introduced Encarsia Species (Hymenoptera: Aphelinidae) and Other Biotic and Abiotic Factors on the Spiralling Whitefly Aleurodicus dispersus (Russell) (Homoptera: Aleyrodidae), in Benin, West Africa

In early 1993, the spiralling whitefly, Aleurodicus dispersus (Russell), was observed in Benin for the first time, inflicting damage to ornamental and shade trees and cassava. The parasitoids Encarsia ?haitiensis Dozier and E. guadeloupae Viggiani were observed in the second half of 1993. They were known to have the same host in the Pacific region, and were thought to have been introduced accidentally. The impact of these parasitoids was quantified using four surveys from 1993 to 1995 (on 2541 trees in 537 localities) and by population studies on guava. In 1993, A. dispersus occurred mostly in towns in the southern part of Benin; penetration into farmland was observed later. E. ?haitiensis was more abundant and widespread than E. guadeloupae , and by 1995 it had been recovered from most (84%) of the infested localities. On guava trees, the annual peaks of A. dispersus population declined by ca. 80% between 1993 and 1996. During the same period parasitism rates increased. Econometric multiple regression analyses based on 996 infested trees demonstrated that A. dispersus population densities, the proportion of infested trees and damage scores all declined significantly with increasing duration of the presence of the parasitoids, indicating their impact. Other variables were also significantly related to A. dispersus levels.     

Triadic interactions in captive Barbary macaques (Macaca sylvanus,Linnaeus, 1758): “Agonistic buffering”?

This study presents data on the expression of male-immature triadic interactions, previously termed agonistic buffering, in a captive Macaca sylvanus group. Agonistic buffering has been hypothesized as inhibiting or modifying the expression of aggression. This was tested by examining (1) the dominance ranks of the animals involved in the triadic interactions, (2) the events preceding and following the triadic interactions, and (3) the presence of an infant in nonagonistic encounters between juvenile, subadult, and adult males. The results obtained do not support the hypothesis of agonistic buffering as the single explanation for triadic interactions, but emphasize the contextual variability in the expression of these triadic interactions.     

“INTERNAL THECAE” OF EUNOTIA SOLEIROLII (BACILLARIOPHYCEAE): DEVELOPMENT,STRUCTURE AND FUNCTION AS RESTING SPORES1

The “double thecae” or “internal septa” of Eunotia soleirolii (Kütz.) Rabenh, are shown to represent the thecae of resting spores, as characterized by their physiology, as well as morphology. They differ from all resting spores of centric diatoms by the formation of both their valves as a result of unequal cell divisions; and, from the majority of centric spores by the presence of several girdle bands in both their thecae. Spore formation can be induced by high or low pH, high temperature (24 C), and iron, silica, phosphate or nitrate deficiencies, whereas low temperatures defer it. Spores do not germinate directly, but dormancy can be removed by dark treatments (–2 to 15 C) for a minimum of 4–5 wk. Longer dark treatments result in higher germination rates. At 15 C, a minimum of 2 mo is required and 4 mo is better. Heat treatments (27–42 C) are ineffective, but may shorten the dormancy-breaking subsequent cold period. Instances of secondary dormancy, as well as relative dormancy, were observed. Germination usually occurs in the light between 2 and 21 C. An equal division of the spore is followed by unequal divisions of both new cells with only the two resulting large cells being viable. The experiences in the laboratory aided the discovery of stages of spore germination in nature.     

DNA “fingerprints” and paternity ascertainment in chimpanzees (Pan troglodytes)

Highly variable regions of DNA are found in a wide diversity of organisms and are typically composed of alleles consisting of a variable number of tandem repeats (VNTRs) of a short core sequence. DNA fingerprinting probes are VNTR probes that simultaneously detect a large number of similar VNTRs in the target DNA. The highly polymorphic pattern observed in a DNA fingerprint allows resolution of questions concerning individual identification. M13 phage was used to fingerprint captive chimpanzees for paternity ascertainment. Although the probability of band sharing among captive chimps appears to be higher than among some other reported captive and feral animal populations, the probe is highly useful and can be expected to become more widely used in the genetic management of captive populations.     

Depletion interactions and modulation of DNA‐intercalators binding: Opposite behavior of the “neutral” polymer poly(ethylene‐glycol)

In this work we have investigated the role of high molecular weight poly(ethylene‐glycol) 8000 (PEG 8000) in modulating the interactions of the DNA molecule with two hydrophobic compounds: Ethidium Bromide (EtBr) and GelRed (GR). Both compounds are DNA intercalators and are used here to mimic the behavior of more complex DNA ligands such as chemotherapeutic drugs and proteins whose domains intercalate DNA. By means of single‐molecule stretching experiments, we have been able to show that PEG 8000 strongly shifts the binding equilibrium between the intercalators and the DNA even at very low concentrations (1% in mass). Additionally, microcalorimetry experiments were performed to estimate the strength of the interaction between PEG and the DNA ligands. Our results suggest that PEG, depending on the system under study, may act as an “inert polymer” with no enthalpic contribution in some processes but, on the other hand, it may as well be an active (non‐neutral) osmolyte in the context of modulating the activity of the reactants and products involved in DNA‐ligand interactions. © 2015 Wiley Periodicals, Inc. Biopolymers 105: 227–233, 2016.     

A biochemical approach toward the systematics of the Leptothorax “muscorum”Group in North America (Hymenoptera: Formicidae)

Enzyme patterns have been used to distinguish among a number of morphologically very similar ant species belonging to the Leptothorax “muscoru” group in North America. Not counting the already described species L. retractus, L. sphagnicolus and L. crassipilis, the complex apparently consists of at least three or four more different taxa.     

Adaptation of Bathynellacea (Crustacea,Syncarida) to Life in the Interstitial (“Zoea Theory”)

This study aims at demonstrating that the Bathynellacea arose by neoteny from a zoea-like ancestor (“Zoea Theory”). Bathynellacea basically have a larval morphology. Their post-embryonic development passes through phases which are directly comparable with some in the development of primitive Eucarida. These phases are called the parazoeal and bathynellid phase, and correspond to the protozoeal and zoeal phase of Penaeidea, respectively. Running initially parallel to that of Penaeidea, the development of the Bathynellacea breaks off precociously. They reach sexual maturity at a stage which, in the Penaeidea, is followed by metamorphosis. There are reasons to assume that the development of all Syncarida originally passed through a series of free-living larval stages and underwent metamorphosis. The bathynellaceans reach adulthood at a stage which corresponds to the last larval stage of their ancestor. The ecological path to interstitial life of the Bathynellacea and the bearing of the “Zoea Theory” upon views as to their phylogenetic position are discussed. The classical example of a group of crustaceans thought to have arisen by neoteny, the Cladocera, is critically examined and found to be in need of reevaluation.     

“Pollen Buds” in Ophiorrhiza (Rubiaceae) and their Role in Pollenkitt Release

Pollen buds are apertural protrusions formed by the ectintine. In their wall unesterified and methyl-esterified pectins are detected by immunogold labeling. During pollenkitt formation pollen buds become adpressed and connected to the tapetum wall. The following expansion of the endothecium causes the mechanical rupture of the tapetum at the binding sites of the pollen buds. These events are accompanied by the release of the pollenkitt.     

“Porpicide” in California: Killing of harbor porpoises (Phocoena phocoena) by coastal bottlenose dolphins (Tursiops truncatus)

Between 2007 and 2009, we witnessed three aggressive interactions between harbor porpoises and bottlenose dolphins in Monterey Bay, California. This is the first time such aggression has been documented in the Pacific, and the first time a harbor porpoise was collected immediately after witnessing its death, inflicted by bottlenose dolphins. Of the bottlenose dolphins present, 92% were males either confirmed (61%) or putative (31%). Since 2005, 44 harbor porpoise deaths inflicted by bottlenose dolphins were documented in California. Aberrant behavior was rejected as a cause of aggression, based on widespread documentation of similar behaviors in other populations of free‐ranging bottlenose dolphins. The evidence for interspecies territoriality as a form of competition for prey was weak: there is little dietary overlap and there are differences in bottlenose dolphin and harbor porpoise distribution patterns in California. Object‐oriented play was plausible as a form of practice to maintain intraspecific infanticidal skills or a form of play to maintain fighting skills between male associates. Contributing factors could be high‐testosterone levels, as attacks occurred at the height of the breeding season, and/or a skewed operational sex ratio. Ultimately, we need more information about bottlenose dolphin social structure at the time of the aggression.