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Item An abdominal stridulation organ in Cyphoderris (Prophalangopsidae) and concerning the systematic classification of the Ensifera (Saltatoria)(2021-01-11) Ander, Kjell; Sander, Barbara; Judge, Kevin; translated.comEnsiferan insects (crickets, katydids, grigs and allies) are well known for rubbing parts of their cuticle together to produce sound: a process called stridulation. In this article Swedish entomologist Kjell Ander describes a novel (at the time) stridulatory apparatus in the great grig, Cyphoderris monstrosa (Prophalangopsidae), a relict ensiferan found in the mountainous regions of western North America. Ander used preserved specimens to predict the sound-producing function of a pair of abdominal file-scraper apparatuses, although he was never able to directly test his proposed mechanism nor did he speculate as to the adaptive significance of the structures. The article concludes with a review of the systematic placement of various higher level taxa within the order Orthoptera, of which Ensifera is one suborder.Item Abundance of the parasitic copepod Caligus elongatus on wild pollock near commercial salmonid net-pens(1996) Shaw, Ross; Opitz, M.Between July and December 1993, wild pollock Pollachius virens collected near salmonid net‐pens on the Atlantic coast of Maine in the United States were examined for parasitic copepods of the family Caligidae to determine the role of pollock as host reservoirs. Only Caligus elongatus was detected on 1,456 pollock sampled. Most pollock (97.39%) had two or fewer sea lice per fish. A maximum prevalence (percent of fish infested) of 50%, an abundance (average number per fish) of 0.9, and an intensity (average number per infested fish) of L79 were recorded. Only one larval C. elongatus was found. No seasonal or geographic trends in infestation statistics were observed.Item Ancient hybridization patterns between bighorn and thinhorn sheep(2021) Santos, Sarah H. D.; Peery, Rhiannon M.; Miller, Joshua M.; Dao, Anh; Lyu, Feng-Hua; Li, Xin; Li, Meng-Hua; Coltman, David W.Whole-genome sequencing has advanced the study of species evolution, including the detection of genealogical discordant events such as ancient hybridization and incomplete lineage sorting (ILS). The evolutionary history of bighorn (Ovis canadensis) and thinhorn (Ovis dalli) sheep present an ideal system to investigate evolutionary discordance due to their recent and rapid radiation and putative secondary contact between bighorn and thinhorn sheep subspecies, specifically the dark pelage Stone sheep (O. dalli stonei) and predominately white Dall sheep (O. dalli dalli), during the last ice age. Here, we used multiple genomes of bighorn and thinhorn sheep, together with snow (O. nivicola) and the domestic sheep (O. aries) as outgroups, to assess their phylogenomic history, potential introgression patterns and their adaptive consequences. Among the Pachyceriforms (snow, bighorn and thinhorn sheep) a consistent monophyletic species tree was retrieved; however, many genealogical discordance patterns were observed. Alternative phylogenies frequently placed Stone and bighorn as sister clades. This relationship occurred more often and was less divergent than that between Dall and bighorn. We also observed many blocks containing introgression signal between Stone and bighorn genomes in which coat colour genes were present. Introgression signals observed between Dall and bighorn were more random and less frequent, and therefore probably due to ILS or intermediary secondary contact. These results strongly suggest that Stone sheep originated from a complex series of events, characterized by multiple, ancient periods of secondary contact with bighorn sheep.Item The Ander's organ: a mechanism for anti-predator ultrasound in a relict orthopteran(2021) Woodrow, C.; Judge, Kevin; Pulver, C.; Jonsson, T.; Montealegre-Z, F.The use of acoustics in predator evasion is a widely reported phenomenon amongst invertebrate taxa, but the study of ultrasonic anti-predator acoustics is often limited to the prey of bats. Here, we describe the acoustic function and morphology of a unique stridulatory structure – the Ander's organ – in the relict orthopteran Cyphoderris monstrosa (Ensifera, Hagloidea). This species is one of just eight remaining members of the family Prophalangopsidae, a group with a fossil record of over 90 extinct species widespread during the Jurassic period. We reveal that the sound produced by this organ has the characteristics of a broadband ultrasonic anti-predator defence, with a peak frequency of 58±15.5 kHz and a bandwidth of 50 kHz (at 10 dB below peak). Evidence from sexual dimorphism, knowledge on hearing capabilities and assessment of local predators, suggests that the signal likely targets ground-dwelling predators. Additionally, we reveal a previously undescribed series of cavities underneath the organ that probably function as a mechanism for ultrasound amplification. Morphological structures homologous in both appearance and anatomical location to the Ander's organ are observed to varying degrees in 4 of the 7 other extant members of this family, with the remaining 3 yet to be assessed. Therefore, we suggest that such structures may either be more widely present in this ancient family than previously assumed, or have evolved to serve a key function in the long-term survival of these few species, allowing them to outlive their extinct counterparts.Item Are the alarm calls of North American red squirrels (Tamiasciurus hudsonicus) functionally referential?(2009) Digweed, Shannon; Rendall, DrewNorth American red squirrels are a small-bodied and solitary-living species that faces a diversity of predators and produces two different variants of alarm calls in response to them. Recent studies have yielded conflicting interpretations of the predator-specific and functionally referential nature of these alarm call variants. We undertook a systematic set of playback experiments to quantify the responses of red squirrels to alarm calls produced by other squirrels during encounters with different predators. The experiment was designed to test a core requirement of functionally referential alarm calls, namely that different alarm call types induce distinct and functionally appropriate escape responses in listeners. Results indicated that squirrels registered and responded to alarm calls produced by others; however, their responses were not differentiated according to the type of alarm call they heard and thus did not provide evidence that the different alarm call variants hold any predator-specific, referential value. These outcomes are discussed in light of complementary work on alarm call production in red squirrels and broader aspects of this species’ life history in an effort to better understand the necessary and sufficient pressures promoting the evolution of referential call systems in animals.Item BldG and SCO3548 interact antagonistically to control key developmental processes in streptomyces coelicolor(2009) Parashar, Archana; Bignell, Dawn R. D.; Leskiw, Brenda K.; Harcombe, KimberleyThe similarity of BldG and the downstream coexpressed protein SCO3548 to anti-anti-sigma and anti-sigma factors, respectively, together with the phenotype of a bldG mutant, suggests that BldG and SCO3548 interact as part of a regulatory system to control both antibiotic production and morphological differentiation in Streptomyces coelicolor. A combination of bacterial two-hybrid, affinity purification, and far-Western analyses demonstrated that there was self-interaction of both BldG and SCO3548, as well as a direct interaction between the two proteins. Furthermore, a genetic complementation experiment demonstrated that SCO3548 antagonizes the function of BldG, similar to other anti-anti-sigma/anti-sigma factor pairs. It is therefore proposed that BldG and SCO3548 form a partner-switching pair that regulates the function of one or more sigma factors in S. coelicolor. The conservation of bldG and sco3548 in other streptomycetes demonstrates that this system is likely a key regulatory switch controlling developmental processes throughout the genus Streptomyces.Item BMP3 is a novel locus involved in the causality of ocular coloboma(2022) Fox, Sabrina C.; Widen, Sonya A.; Asai-Coakwell, Mika; Havrylov, Serhiy; Benson, Matthew; Prichard, Lisa; Baddam, Pranidhi; Graf, Daniel; Lehmann, Ordan J.; Waskiewicz, Andrew J.Coloboma, a congenital disorder characterized by gaps in ocular tissues, is caused when the choroid fissure fails to close during embryonic development. Several loci have been associated with coloboma, but these represent less than 40% of those that are involved with this disease. Here, we describe a novel coloboma-causing locus, BMP3. Whole exome sequencing and Sanger sequencing of patients with coloboma identified three variants in BMP3, two of which are predicted to be disease causing. Consistent with this, bmp3 mutant zebrafish have aberrant fissure closure. bmp3 is expressed in the ventral head mesenchyme and regulates phosphorylated Smad3 in a population of cells adjacent to the choroid fissure. Furthermore, mutations in bmp3 sensitize embryos to Smad3 inhibitor treatment resulting in open choroid fissures. Micro CT scans and Alcian blue staining of zebrafish demonstrate that mutations in bmp3 cause midface hypoplasia, suggesting that bmp3 regulates cranial neural crest cells. Consistent with this, we see active Smad3 in a population of periocular neural crest cells, and bmp3 mutant zebrafish have reduced neural crest cells in the choroid fissure. Taken together, these data suggest that Bmp3 controls Smad3 phosphorylation in neural crest cells to regulate early craniofacial and ocular development.Item Body size and lifespan are condition dependent in the mealworm beetle, Tenebrio molitor, but not sexually-selected traits(2018) McConnell, Murray; Judge, KevinTraits under strong directional selection are predicted to be condition dependent, and thus increase in development when an organism acquires more resources. This prediction has been tested for a variety of traits, particularly those under precopulatory sexual selection. However, few studies compare the condition dependence of a variety of phenotypic traits, potentially subject to different selective forces. Here we examine the condition dependence of several important life history traits, including those under both pre- and postcopulatory sexual selection, in the mealworm beetle, Tenebrio molitor. We manipulated condition by randomly assigning larvae to one of: high-, medium- or low-quality diets. For males reared on the three diets we measured: a) adult body size and lifespan, b) pheromone attractiveness, c) weight of their ejaculate transferred to females, and d) fecundity of their female mates. Males raised on a high-diet were larger and lived longer than males raised on medium- and low-diets. Although females were significantly attracted to male pheromones, there were no significant differences amongst condition treatments in male attractiveness, nor ejaculate transfer. Furthermore, mates’ fecundity was also not affected by male condition. We discuss these results considering previous work on trade-offs and condition dependence of life history traits.Item Boreal peatlands and plant diversity: what’s there and why it matters(2010) Locky, DavidShould plant conservation in western Canadian peatlands be an integral part of forest management activities? This research note introduces the concepts of plant diversity (richness and rarity) in a variety of peatland types from the perspective of forest management.Item Characterization of microplastics and anthropogenic fibers in surface waters of the North Saskatchewan River, Alberta, Canada(2021) Bujaczek, Taylor; Kolter, Sheldon; Locky, David; Ross, Matthew S.Microplastics are globally ubiquitous contaminants, but quantitative data on their presence in freshwater environments are sparse. This study investigates the occurrence, composition, and spatial trends of microplastic contamination in the North Saskatchewan River flowing through Edmonton, Alberta, the fifth largest city in Canada. Surface water samples were collected from seven sites throughout the city, upstream and downstream of the city, and near potential point sources (i.e., a wastewater treatment plant). Samples were spiked with fluorescent microbeads as internal standards and extracted by wet peroxide oxidation and density floatation. Microplastics were found in all samples, ranging in concentration from 4.6 to 88.3 particles·m−3 (mean = 26.2 ± 18.4 particles·m−3). Fibers were the dominant morphology recovered, and most were of anthropogenic origin and chemically identified as dyed cotton or polyester by Raman microspectroscopy. The majority of fragments were identified as polyethylene or polypropylene. No upstream to downstream differences were found in concentration, size distribution, or morphological composition suggesting nonpoint sources of microplastics to the river. This study represents one of the first investigations into the occurrence of microplastics in the freshwater environment in western Canada and will provide a baseline for future studies.Item Condition dependence of male lifespan and calling effort in a field cricket(2008) Judge, Kevin; Ting, Janice J.; Gwynne, Darryl T.Sexually selected traits are thought to impose survival costs on showy males. Recent empirical work found a negative relationship between male display and survival in a field cricket species (Orthoptera, Gryllidae, Gryllinae) where there is no evidence of a mating bias towards older males. In most species, however, male survival and ornamentation are positively correlated, and older males often have a mating success advantage over younger males. These findings suggest that male quality and survival are positively correlated, but more tests of this hypothesis are needed. We measured the condition dependence of male survival and mating investment (calling effort) in another grylline, Gryllus pennsylvanicus, where older males have previously been shown to have greater mating success. We varied condition by manipulating diet, and measured male lifespan and calling effort to assess the relative condition dependence of these traits. High and medium condition males survived longer than low condition males, and high condition males called more than medium and low condition males. Differences in calling effort among the condition treatments were not apparent early in life, but emerged as males aged. We discuss possible explanations for the differences between our study and contrasting results such as the previous grylline work.Item Condition- and parasite-dependent expression of a male-like trait in a female bird(2011) Martinez-Padilla, J.; Vergara, P.; Perez-Rodriguez, L.; Mougeot, F.; Casas, F.; Ludwig, S. C.; Haines, Jessica A.; Ludwig, S. C.; Redpath, S. M.In many species, females display brightly coloured and elaborate traits similar to those that males use in intra- and inter-sexual selection processes. These female characters are sometimes related to fitness, and might function as secondary sexual characteristics that have evolved through sexual selection. Here, we used descriptive data from 674 females in 10 populations and an experimental removal of Trichostrongylus tenuis parasites in four populations, to examine the effects of season, age, condition, and parasites on the size of supra-orbital combs displayed by female red grouse Lagopus lagopus scoticus. We found that comb size (i) was greater during the breeding than the non-breeding season, (ii) was greater in adult than in young females, (iii) was positively correlated with body condition, and (iv) negatively correlated with parasite abundance. Experimentally, we showed that comb size increased proportionally to the number of worms removed after parasite dosing. Our findings provide a better understanding of proximate mechanisms behind the expression of a male-like trait in females, and we discuss its possible function as a female ornament.Item Conservation triage at the trailing edge of climate envelopes(2020) Gilbert, Sophie L.; Broadley, Kate; Doran-Myers, Darcy; Droghini, Amanda; Haines, Jessica A.; Hämäläinen, Anni; Lamb, Clayton T.; Neilson, Eric W.; Boutin, StanSpecies protection via geographically fixed conservation actions is a primary tool for maintenance of biodiversity worldwide (Pimm et al. 2014). Yet, for many species, the assumption that currently suitable sites will remain so is undermined by climate change (Urban 2015; Wiens 2016). Climate-change-associated range shifts (Chen et al. 2011), a process driven by populations at the trailing edge of the climate envelope going extinct or moving and those at the leading edge becoming established, are becoming widespread around the world (Wiens 2016). We argue that conservation of populations of at-risk species should be prioritized across each species’ range based on future climatic suitability of an area with the goal of maintaining or increasing the number of viable populations range wide. Such range-wide prioritization could help conserve species in a changing climate when resources are limited; effort would be reallocated to viable populations (Oliver et al. 2012; Alagador & Cerdeira 2016). Promisingly, resistance to this approach (Oliver et al. 2016) may be waning. Many nongovernment organizations (e.g., International Panel on Climate Change, World Wildlife Fund) now use climate-informed range-wide approaches, as do some national and state agencies (e.g., Association of Fish & Wildlife Agencies 2018; Cornwall 2018). We aimed to advance discussion and implementation of climate-informed prioritization across species’ ranges and considered when populations behind the trailing edge of climate change should be deprioritized.Item The crucial role of genome-wide genetic variation in conservation(2021) Kardos, Marty; Armstrong, Ellie E.; Fitzpatrick, Sarah; Hauser, Samantha; Hedrick, Philip W.; Miller, Joshua M.; Tallmon, David A.; Funk, W. ChrisThe unprecedented rate of extinction calls for efficient use of genetics to help conserve biodiversity. Several recent genomic and simulation-based studies have argued that the field of conservation biology has placed too much focus on conserving genome-wide genetic variation, and that the field should instead focus on managing the subset of functional genetic variation that is thought to affect fitness. Here, we critically evaluate the feasibility and likely benefits of this approach in conservation. We find that population genetics theory and empirical results show that conserving genome-wide genetic variation is generally the best approach to prevent inbreeding depression and loss of adaptive potential from driving populations towards extinction. Focusing conservation efforts on presumably functional genetic variation will only be feasible occasionally, often misleading, and counterproductive when prioritized over genome-wide genetic variation. Given the increasing rate of habitat loss and other environmental changes, failure to recognize the detrimental effects of lost genome-wide genetic variation on long-term population viability will only worsen the biodiversity crisis.Item Cypermethrin inhibits egg development in the ixodid tick, Amblyomma hebraeum(2003) Friesen, Kevin; Kaufman, ReubenThe pyrethroid insecticide, cypermethrin (CyM), stimulates vitellogenesis in Ornithodoros moubata (an argasid tick) by stimulating the release of the normal vitellogenesis-inducing factor (a neuropeptide) and subsequent release of the vitellogenic hormone [19]. Here we examine the effects of CyM on egg development in the ixodid tick, Amblyomma hebraeum. Ovary weight, oocyte size, and vitellin content of the ovary were measured after CyM treatment; in partially fed ticks, none of these parameters were affected significantly. However, CyM treatment caused an inhibition of ovary development, as well as reduction of both hemolymph 20-hydroxyecdysone (20E; the vitellogenic hormone in this species) and vitellogenin (Vg)-concentrations in engorged ticks. In addition, the degree of salivary gland degeneration (which is triggered by 20E) was slightly reduced in CyM-treated engorged ticks. These results indicate that CyM acts differently in Amblyomma compared to Ornithodoros. Instead of stimulating vitellogenesis, CyM inhibits egg development perhaps in part as a result of inhibiting release of 20E.Item Does hunger lead to hybridization in a genus of sexually cannibalistic insects (Orthoptera: Prophalangopsidae)?(2020) Dupuis, Julian R.; Judge, Kevin; Brunet, Bryan M. T.; Ohlmann Chan, Shawna; Sperling, Felix A. H.Allochronic isolation can be a strong mechanism for reproductive isolation and speciation. However, imperfect allochrony and the expression of phenological plasticity can erode temporal barriers to gene flow and result in hybridization between divergent lineages. Here, we combine behavioural ecology and genomics to investigate this scenario in two closely related species of grigs in the genus Cyphoderris. These species exhibit a unique mating system whereby females feed on the fleshy hind wings of the male during copulation, and copulation with conspecific males is more likely in food-restricted females than in well-fed females. In western Canada, Cyphoderris buckelli and Cyphoderris monstrosa are sympatric but largely allochronically separated, with C. buckelli breeding earlier. However, their breeding seasons can overlap, leading to potential for older C. buckelli females to mate with young C. monstrosa males to obtain resources via sexual cannibalism. We used behavioural assays to test whether female feeding status affects the propensity for interspecific mating between C. buckelli females and C. monstrosa males. We then tested for hybridization and gene exchange in wild populations of both species, using morphology, mitochondrial DNA and genome-wide nuclear markers. We found that interspecific courtship and mating can occur, but the relationship between food restriction and increased propensity for hybridization was not significant. Although we observed intraspecific population genetic structure in both species, we found no signatures of hybridization in the morphological or genetic datasets, which suggests that postmating reproductive barriers might be preventing successful hybridization in the wild.Item Early stand-level assessment of forest harvesting in western boreal peatlands(2009) Locky, DavidApproximately 20% of Canada’s boreal region is covered by wetlands. Most of these are peatlands, which are defined as wetlands with at least 40 cm of moss and sedge-dominated organic soil. Commonly known as ‘muskeg’, boreal peatlands are comprised of bogs, fens, and conifer swamps. Recent studies in Canada’s western boreal region have shown that the greatest overall species diversity and number of rare bryophytes (mosses, liverworts, and hornworts) and vascular plants occurs in wooded peatlands. This is particularly true for wooded moderate-rich fens and black spruce swamps. Most species of rare vascular plants in peatlands are orchids or sedges. Less is known of rare bryophytes.Item The ecological significance of secondary seed dispersal by carnivores(2017) Hämäläinen, Anni; Broadley, Kate; Droghini, Amanda; Haines, Jessica A.; Lamb, Clayton T.; Boutin, Stan; Gilbert, Sophie L.Animals play an important role in the seed dispersal of many plants. It is increasingly recognized, however, that the actions of a single disperser rarely determine a seed's fate and final location; rather, multiple abiotic or animal dispersal vectors are involved. Some carnivores act as secondary dispersers by preying on primary seed dispersers or seed predators, inadvertently consuming seeds contained in their prey's digestive tracts and later depositing viable seeds, a process known as diploendozoochory. Carnivores occupy an array of ecological niches and thus range broadly on the landscape. Consequently, secondary seed dispersal by carnivores could have important consequences for plant dispersal outcomes, with implications for ecosystem functioning under a changing climate and across disturbed landscapes where dispersal may be otherwise limited. For example, trophic downgrading through the loss of carnivores may reduce or eliminate diploendozoochory and thus compromise population connectivity for lower trophic levels. We review the literature on diploendozoochory and conclude that the ecological impact of a secondary vs. primary seed disperser depends on the relative dispersal distances, germination success, and the proportion of seeds exposed to secondary dispersal by carnivores. None of the studies up to present day have been able to rigorously assess the ecological significance of this process. We provide a framework of the components that determine the significance of diploendozoochory across systems and identify the components that must be addressed in future studies attempting to assess the ecological importance of diploendozoochory.Item Ecomorph or endangered coral? DNA and microstructure reveal Hawaiian species complexes: montipora dilatata/ flabellata/turgescens & M. patula/verrilli(2010) Forsman, Z. H.; Concepcion, G. T.; Haverkort, R. D.; Shaw, Ross; Maragos, J. E.; Toonen, R. J.M. dilatata, M. flabellata, and M. patula and 80 other scleractinian corals were petitioned to be listed under the US Endangered Species Act (ESA), which would have major conservation implications. One of the difficulties with this evaluation is that reproductive boundaries between morphologically defined coral species are often permeable, and morphology can be wildly variable. We examined genetic and morphological variation in Hawaiian Montipora with a suite of molecular markers (mitochondrial: COI, CR, Cyt-B, 16S, ATP6; nuclear: ATPsβ, ITS) and microscopic skeletal measurements. Mitochondrial markers and the ITS region revealed four distinct clades: I) M. patula/M. verrilli, II) M. cf. incrassata, III) M. capitata, IV) M. dilatata/M. flabellata/M. cf. turgescens. These clades are likely to occur outside of Hawai'i according to mitochondrial control region haplotypes from previous studies. The ATPsβ intron data showed a pattern often interpreted as resulting from hybridization and introgression; however, incomplete lineage sorting may be more likely since the multicopy nuclear ITS region was consistent with the mitochondrial data. Furthermore, principal components analysis (PCA) of skeletal microstructure was concordant with the mitochondrial clades, while nominal taxa overlapped. The size and shape of verrucae or papillae contributed most to identifying groups, while colony-level morphology was highly variable. It is not yet clear if these species complexes represent population-level variation or incipient speciation (CA<1MYA), two alternatives that have very different conservation implications. This study highlights the difficulty in understanding the scale of genetic and morphological variation that corresponds to species as opposed to population-level variation, information that is essential for conservation and for understanding coral biodiversity.Item Effect of 20-hydroxyecdysone and haemolymph on oogenesis in the ixodid tick Amblyomma hebraeum(2008) Seixas, Adriana; Friesen, Kevin; Kaufman, ReubenEarlier work from our laboratory indicated that injection of 20-hydroxyecdysone (20E) into non-vitellogenic female Amblyomma hebraeum ticks stimulates the synthesis of vitellogenin (Vg), but not its uptake into oocytes [Friesen, K., Kaufman, W.R., 2004. Effects of 20-hydroxyecdysone and other hormones on egg development, and identification of a vitellin-binding protein in the ovary of the tick, Amblyomma hebraeum. Journal of Insect Physiology 50, 519–529]. In contrast, Thompson et al. [Thompson, D.M., Khalil, S.M.S., Jeffers, L.A., Ananthapadmanaban, U., Sonenshine, D.E., Mitchell, R.D., Osgood, C.J., Apperson, C.S., Roe, M.R., 2005. In vivo role of 20-hydroxyecdysone in the regulation of the vitellogenin mRNA and egg development in the American dog tick, Dermacentor variabilis (Say). Journal of Insect Physiology 51, 1105–1116] demonstrated that injection of 20E into virgin female Dermacentor variabilis ticks stimulated both vitellogenesis and Vg uptake into oocytes. In addition to the species difference in the two studies there were substantially different methods for injecting 20E. In our earlier work we injected small partially fed ticks after removing them from the host. Thompson et al. injected the females while they remained attached to the host. So in this study we repeated our earlier experiments on A. hebraeum using on-host injection. We also injected 20E into off-host ticks with or without haemolymph collected from engorged ticks (days 2–10 post-engorgement), or from large partially fed mated ticks in the rapid phase of engorgement, to see whether we might detect a ‘vitellogenin uptake factor’ (VUF) in haemolymph. Off-host injection of 20E (0.45 μg/g body weight (bw)) did not induce ovary development beyond that of vehicle-injected controls. But ticks in this study, receiving 20E plus haemolymph from engorged ticks, showed a significant increase in ovary weight beyond that of 20E alone (1.31 ± 0.05% bw; 34 for 20E plus haemolymph and 1.03 ± 0.05% bw; 25 for 20E alone). However, in normal engorged A. hebraeum, the ovary exceeds 7% bw at the onset of oviposition. As in our earlier work, in this study 20E stimulated Vg-synthesis (3.9 ± 0.5 mg Vt-equivalents/ml) beyond that occurring in vehicle-injected ticks (0.76 ± 0.14 mg Vt-equivalents/ml), and there was a further increase in ticks injected with 20E plus haemolymph from engorged ticks (8.9 ± 1.0 mg Vt-equivalents/ml). On-host injection of 20E alone (6 μg 20E/g bw) did not produce a statistically significant increase in oocyte length over that of vehicle-injected controls, whereas on-host injection of 20E plus engorged haemolymph resulted in significantly larger oocytes (261 ± 57 μm) compared to vehicle-injected controls (132 ± 11 μm), compared to 20E alone (131 ± 12 μm), or haemolymph alone (124 ± 24 μm). There was a marked stimulation of Vg-synthesis by 31 μg 20E/g bw (6.0 ± 1.5 mg Vt-equivalents/ml) compared to vehicle-injected controls (1.02 ± 33 mg Vt-equivalents/ml). Vt accumulation by ovaries was significantly greater in ticks treated with haemolymph (12 ± 3 μg Vt/mg ovary) or 20E plus haemolymph (56 ± 26 μg Vt/mg ovary) compared to vehicle-injected controls (5.1 ± 1.5 μg Vt/mg ovary). There was also a significant effect of 6 μg 20E/g bw plus engorged haemolymph on ovary weight (1.74 ± 0.29% bw) compared to vehicle-injected ticks (0.95 ± 0.10% bw), but not compared to ticks injected with 20E alone (1.25 ± 0.19% bw). We conclude that at least some of the differences observed between the two laboratories relate to the species difference, and that there is some evidence that the engorged haemolymph of A. hebraeum contains a VUF.