Sean McCann

Age modifies the effect of body size on fecundity in Culex quinquefasciatus Say (Diptera: Culicidae)

Fecundity of mosquitoes can vary with many factors and can have a strong effect on population growth. This study reports the effects of body size, blood meal size, and age on the reproductive output of nulliparous Culex quinquefasciatus, a vector of arboviruses and other pathogens. Mated adult female mosquitoes from a colony were reared under standard conditions and fed on chickens at different ages post-eclosion. Blood meal size and wing length were recorded, as well as the number of eggs in the first-cycle egg raft. Each of these factors had a significant influence on fecundity considered in a simple regression context. Multiple regression analysis revealed a significant interaction effect between age and body size on fecundity. Up to 13 days of age, fecundity was positively correlated with body size, but in mosquitoes older than 13 days, this relationship was not significantly different from zero. These results are discussed in terms of the known physiology of this and other species.

Ontogeny-Driven rDNA Rearrangement, Methylation, and Transcription, and Paternal Influence

Gene rearrangement occurs during development in some cell types and this genome dynamics is modulated by intrinsic and extrinsic factors, including growth stimulants and nutrients. This raises a possibility that such structural change in the genome and its subsequent epigenetic modifications may also take place during mammalian ontogeny, a process undergoing finely orchestrated cell division and differentiation. We tested this hypothesis by comparing single nucleotide polymorphism-defined haplotype frequencies and DNA methylation of the rDNA multicopy gene between two mouse ontogenic stages and among three adult tissues of individual mice. Possible influences to the genetic and epigenetic dynamics by paternal exposures were also examined for Cr(III) and acid saline extrinsic factors. Variables derived from litters, individuals, and duplicate assays in large mouse populations were examined using linear mixed-effects model. We report here that active rDNA rearrangement, represented by changes of haplotype frequencies, arises during ontogenic progression from day 8 embryos to 6-week adult mice as well as in different tissue lineages and is modifiable by paternal exposures. The rDNA methylation levels were also altered in concordance with this ontogenic progression and were associated with rDNA haplotypes. Sperm showed highest level of methylation, followed by lungs and livers, and preferentially selected haplotypes that are positively associated with methylation. Livers, maintaining lower levels of rDNA methylation compared with lungs, expressed more rRNA transcript. In vitro transcription demonstrated haplotype-dependent rRNA expression. Thus, the genome is also dynamic during mammalian ontogeny and its rearrangement may trigger epigenetic changes and subsequent transcriptional controls, that are further influenced by paternal exposures.

(R)-Desmolactone Is a Sex Pheromone or Sex Attractant for the Endangered Valley Elderberry Longhorn Beetle Desmocerus californicus dimorphus and Several Congeners (Cerambycidae: Lepturinae)

We report here that (4R,9Z)-hexadec-9-en-4-olide [(R)-desmolactone] is a sex attractant or sex pheromone for multiple species and subspecies in the cerambycid genus Desmocerus. This compound was previously identified as a female-produced sex attractant pheromone of Desmocerus californicus californicus. Headspace volatiles from female Desmocerus aureipennis aureipennis contained (R)-desmolactone, and the antennae of adult males of two species responded strongly to synthetic (R)-desmolactone in coupled gas chromatography-electroantennogram analyses. In field bioassays in California, Oregon, and British Columbia, traps baited with synthetic (R)-desmolactone captured males of several Desmocerus species and subspecies. Only male beetles were captured, indicating that this compound acts as a sex-specific attractant, rather than as a signal for aggregation. In targeted field bioassays, males of the US federally threatened subspecies Desmocerus californicus dimorphus responded to the synthetic attractant in a dose dependent manner. Our results represent the first example of a “generic” sex pheromone used by multiple species in the subfamily Lepturinae, and demonstrate that pheromone-baited traps may be a sensitive and efficient method of monitoring the threatened species Desmocerus californicus dimorphus, commonly known as the valley elderberry longhorn beetle.

Nesting and Nest-Provisioning of the Red-throated Caracara (Ibycter americanus) in Central French Guiana

ANIDACION Y APROVISIONAMIENTO DE NIDOS DE IBYCTER AMERICANUS EN GUYANA FRANCESA CENTRAL Utilizamos camaras de video para estudiar un nido en cada una de dos estaciones reproductivas de un grupo de Ibycter americanus en Guyana Francesa. Encontramos que I. americanus no construyo un nido, sino que utilizo plataformas naturales, como bromelias, para anidar. Las aves adultas trajeron alimento al nido en promedio 1.77 (±0.37 DE) veces/hr en 2008 y 0.91 (±0.30 DE) veces/hr en 2009. La mayoria de los items alimenticios (58.6% en 2008; 78.6% en 2009) fueron nidos de avispas o fragmentos de estos. Con base en anillas coloridas y determinacion del sexo, por lo menos seis individuos con plumaje de adulto (dos hembras, dos machos, dos de sexo desconocido) atendieron y aprovisionaron a los polluelos en 2009.

The First Record of Aedes (Hulecoeteomyia) japonicus (Diptera: Culicidae) and Its Establishment in Western Canada.

Abstract The potential disease-carrying mosquito, Aedes japonicus (Theobald) (Diptera: Culicidae), was identified among larvae collected in suburban Vancouver, BC, in July 2014, and over 200 were found at the same site in February 2015 where it presumably had overwintered in the egg stage. In late May 2015, a female was captured taking a bloodmeal 13km east of the larval site. This population and those in the Washington and Oregon states are clearly disjunct from those in eastern North America, and their origin, probably from one or more different introductions from Asia, is discussed. Key characters of those in British Columbia are examined and match the description of subspecies japonicus, presumably like the others in North America.

Red-throated Caracara, a falconid raptor, rivals predatory impact of army ants on social wasps

Paper wasps are diverse in Neotropical rainforests but the factors that affect their abundance are poorly understood. Army ants (Ecitoninae) are generally thought to have the greatest predatory impact on populations of social wasps, but there is emerging evidence that predatory birds could also be a significant source of colony mortality. Our objectives were to (1) identify the genera of wasps preyed upon by Ibycter americanus (Falconidae), a specialist predator of Neotropical social wasps, (2) quantify wasp nest predation by I. americanus, and (3) compare wasp nest predation rates by I. americanus with calculated rates of wasp nest predation by Eciton burchellii army ants. In 2008 and 2009, we video recorded chick provisioning at I. americanus nests in French Guiana and found that adult birds brought nests of at least ten genera of mainly swarm-founding wasps (Epiponini). In 2012, we noted that three of four sympatric Eciton species raided into trees and thus potentially preyed upon the brood of paper wasps at the same site. We quantified the population density of one Eciton species, calculated its rate of wasp nest predation, and compared this predation rate to that of I. americanus. We conclude that I. americanus rivals the predatory impact of E. burchellii army ants on some populations of Neotropical social wasps. Ibycter americanus and other diurnal vertebrate predators may exert strong selection on wasp defensive behavior, resulting in defensive adaptations that include selection of specific nest sites as well as physical fortification and visual crypsis of nests.

Molecular and organismal changes in offspring of male mice treated with chemical stressors

Both gene methylation changes and genetic instability have been noted in offspring of male rodents exposed to radiation or chemicals, but few specific gene targets have been established. Previously, we identified the gene for ribosomal RNA, rDNA, as showing methylation change in sperm of mice treated with the preconceptional carcinogen, chromium(III) chloride. rDNA is a critical cell growth regulator. Here, we investigated the effects of paternal treatments on rDNA in offspring tissue. A total of 93 litters and 758 offspring were obtained, permitting rigorous mixed‐effects models statistical analysis of the results. We show that the offspring of male mice treated with Cr(III) presented increased methylation in a promoter sequence of the rDNA gene, specifically in lung. Furthermore polymorphic variants of the multi‐copy rDNA genes displayed altered frequencies indicative of structural changes, as a function of both tissue type and paternal treatments. Organismal effects also occurred: some groups of offspring of male mice treated with either Cr(III) or its vehicle, acidic saline, compared with those of untreated mice, had altered average body and liver weights and levels of serum glucose and leptin. Males treated directly with Cr(III) or acidic saline presented serum hormone changes consistent with a stress response. These results establish for the first time epigenetic and genetic instability effects in a gene of central physiological importance, in offspring of male mice exposed preconceptionally to chemicals, possibly related to a stress response in these males.

The role of silk in courtship and chemical communication of the false widow spider, Steatoda grossa (Araneae: Theridiidae)

In spiders, sex pheromones are often associated with silk produced by females, and function in mate attraction, recognition, and evaluation. Silk-bound pheromones typically elicit courtship behaviour in web-building spiders. Here we (1) describe courtship interactions of Steatoda grossa males with virgin or mated females, and (2) show that silk and methanol extracts of silk produced by virgin females trigger courtship behaviour (silk production) by males, whereas silk of mated females does not. Our results indicate that (1) virgin females produce a silk-bound sex pheromone, (2) males discriminate between virgin and mated females based on silk cues, and (3) male silk likely functions in sexual communication.

Developing a paired-target apparatus for quantitative testing of nest defense behavior by vespine wasps in response to con- or heterospecific nest defense pheromones

Social wasps commonly exhibit impressive, pheromone-mediated nest defenses with stinging attacks on potential vertebrate nest predators. Studying this type of nest defense and comparing results across studies is challenging because there is no standardized method for quantifying defense intensities. For that reason, we developed a simple, paired-target apparatus coupled with easy and inexpensive data recording and analysis technologies. Each target is formed by two conjoined black plastic weigh boats that generate distinct percussive sounds when struck by attacking wasps. A battery-powered microphone inside each target converts the sounds into electrical signals that are transferred to a digital audio recorder. These audio files are then split into left- and right-channel files, saved as 16-bit WAV files, and the strikes to each target are counted using the open-source software SoundRuler. Using this apparatus, we show that workers of Vespula pensylvanica, V. alascensis, and V. germanica strike targets that are treated with conspecific venom sac extract more frequently than paired control targets. We also show that workers of V. alascensis, V. pensylvanica and V. germanica strike targets that are treated with heterospecific extracts more frequently than paired control targets, indicating that the wasps recognize nest alarm pheromones from congeners. These data provide evidence for conserved nest defense pheromones among some Vespula wasps and proof of concept that our technology is capable of quantifying the intensity of pheromone-mediated nest defense behavior in Vespula and other large and formidable social wasps.