Organization, evolution and transcriptional profile of hexamerin genes of the parasitic wasp Nasonia vitripennis (Hymenoptera: Pteromalidae)

Hexamerins and prophenoloxidases (PPOs) proteins are members of the arthropod-haemocyanin superfamily. In contrast to haemocyanin and PPO, hexamerins do not bind oxygen, but mainly play a role as storage proteins that supply amino acids for insect metamorphosis. We identified seven genes encoding hexamerins, three encoding PPOs, and one hexamerin pseudogene in the genome of the parasitoid wasp Nasonia vitripennis. A phylogenetic analysis of hexamerins and PPOs from this wasp and related proteins from other insect orders suggests an essentially order-specific radiation of hexamerins. Temporal and spatial transcriptional profiles of N. vitripennis hexamerins suggest that they have physiological functions other than metamorphosis, which are arguably coupled with its lifestyle.

Unique features of odorant-binding proteins of the parasitoid wasp Nasonia vitripennis revealed by genome annotation and comparative analyses

Insects are the most diverse group of animals on the planet, comprising over 90% of all metazoan life forms, and have adapted to a wide diversity of ecosystems in nearly all environments. They have evolved highly sensitive chemical senses that are central to their interaction with their environment and to communication between individuals. Understanding the molecular bases of insect olfaction is therefore of great importance from both a basic and applied perspective. Odorant binding proteins (OBPs) are some of most abundant proteins found in insect olfactory organs, where they are the first component of the olfactory transduction cascade, carrying odorant molecules to the olfactory receptors. We carried out a search for OBPs in the genome of the parasitoid wasp Nasonia vitripennis and identified 90 sequences encoding putative OBPs. This is the largest OBP family so far reported in insects. We report unique features of the N. vitripennis OBPs, including the presence and evolutionary origin of a new subfamily of double-domain OBPs (consisting of two concatenated OBP domains), the loss of conserved cysteine residues and the expression of pseudogenes. This study also demonstrates the extremely dynamic evolution of the insect OBP family: (i) the number of different OBPs can vary greatly between species; (ii) the sequences are highly diverse, sometimes as a result of positive selection pressure with even the canonical cysteines being lost; (iii) new lineage specific domain arrangements can arise, such as the double domain OBP subfamily of wasps and mosquitoes.

Functional and Evolutionary Insights from the Genomes of Three Parasitoid Nasonia Species

We report here genome sequences and comparative analyses of three closely related parasitoid wasps: Nasonia vitripennis, N. giraulti, and N. longicornis. Parasitoids are important regulators of arthropod populations, including major agricultural pests and disease vectors, and Nasonia is an emerging genetic model, particularly for evolutionary and developmental genetics. Key findings include the identification of a functional DNA methylation tool kit; hymenopteran-specific genes including diverse venoms; lateral gene transfers among Pox viruses, Wolbachia, and Nasonia; and the rapid evolution of genes involved in nuclear-mitochondrial interactions that are implicated in speciation. Newly developed genome resources advance Nasonia for genetic research, accelerate mapping and cloning of quantitative trait loci, and will ultimately provide tools and knowledge for further increasing the utility of parasitoids as pest insect-control agents.

Researches on the insect metamorphosis ...

"From Transactions of the Royal Society of South Australia, vol. xlvi., 1922."

Unsuccessful attacks dominate a drone-preying wasp's hunting performance near stingless bee nests

Bee males (drones) of stingless bees tend to congregate near entrances of conspecific nests, where they wait for virgin queens that initiate their nuptial flight. We observed that the Neotropical solitary wasp Trachypus boharti (Hymenoptera, Cabronidae) specifically preys on males of the stingless bee Scaptotrigona postica (Hymenoptera, Apidae); these wasps captured up to 50 males per day near the entrance of a single hive. Over 90% of the wasp attacks were unsuccessful; such erroneous attacks often involved conspecific wasps and worker bees. After the capture of non-male prey, wasps almost immediately released these individuals unharmed and continued hunting. A simple behavioral experiment showed that at short distances wasps were not specifically attracted to S. postica males nor were they repelled by workers of the same species. Likely, short-range prey detection near the bees' nest is achieved mainly by vision whereas close-range prey recognition is based principally on chemical and/or mechanical cues. We argue that the dependence on the wasp's visual perception during attack and the crowded and dynamic hunting conditions caused wasps to make many preying attempts that failed. Two wasp-density-related factors, wasp-prey distance and wasp-wasp encounters, may account for the fact that the highest male capture and unsuccessful wasp bee encounter rates occurred at intermediate wasp numbers.

Anatomy of the mouthparts and digestive tract during feeding in larvae of the parasitoid wasp Trichogramma australicum Girault (Hymenoptera : Trichogrammatidae)

To aid in the development of artificial diets for mass rearing parasitioids, we investigated the anatomical changes in the digestive tract during feeding behaviour of larval Trichogramma australicum (Hymenoptera: Trichogrammatidae). Larvae begin to feed immediately upon eclosion and feed continuously for 4 h until replete. Feeding is characterised by rhythmic muscle contractions (ca 1 per s) of the pharynx. Contractions of the pharyngeal dilator muscles lift the roof of the lobe-shaped pharynx away from the floor of the chamber, opening the mouth and pumping food into the pharyngeal cavity. Another muscle contraction occurs about 0.5 s later, forcing the bolus of food through the oesophagus and into the midgut. The junction of fore- and midgut is marked by a cardiac valve. The midgut occupies most of the body cavity and is lined with highly vacuolated, flattened cells and a dispersed layer of muscle cells. In the centre of the midgut, food has the appearance of host egg contents. Food near the midgut epithelial cells has a finer, more homogeneous appearance. This change in the physical properties of the gut contents is indicative of the digestion process. In the prepupa, where digestion is complete, the entire gut contents have this appearance. After eclosion, the vitelline membrane remains attached to the posterior end of the larva. We believe this attachment to be adaptive in two ways: (1) to anchor the larva against the movements of its anterior portion, thereby increasing the efficiency of foraging within the egg, and (2) to prevent a free-floating membrane from clogging the mouthparts during ingestion. 1998 Elsevier Science Ltd. All rights reserved.

Sequence analysis and expression of a virus-like particle protein,VLP2, from the parasitic wasp Venturia canescens

Endoparasitoid wasps produce maternal protein secretions, which are transported into the body of insect hosts at oviposition to regulate host physiology for successful development of their offspring. Venturia canescens calyx fluid contains so-called virus-like particles (VLPs) that are essential for immune evasion of the developing parasitoid inside the host. VLPs consist of four major proteins. In this paper, we describe the isolation and molecular cloning of a gene (vlp2) that is a constituent of VLPs and discuss its possible role in VLP structure and function.

Virus or not? Phylogenetics of polydnaviruses and their wasp carriers

Our current, still limited, understanding of the comparative biology and evolution of polydnaviruses (PDVs) is reviewed, especially in the context of the possible origins of these parasitoid viruses and of their coevolution with carrier wasps. A hypothetical scenario of evolution of PDVs from ascovirus (or ascovirus-like) ancestors is presented, with examples of apparent extant transitional forms. PDVs appear, in the case of bracoviruses, to show phylogenetic relationships that mirror those of their wasp carriers: with ichno-viruses, the picture is less clear. Ongoing sequencing studies of entire PDV genomes from diverse wasp species are likely to greatly contribute to our understanding of PDV evolution. (C) 2003 Elsevier Science Ltd. All rights reserved.

A serine proteinase homolog venom protein from an endoparasitoid wasp inhibits melanization of the host hemolymph

Activation of prophenoloxidase (proPO) in insects is a defense mechanism against intruding microorganisms and parasites. Pattern recognition molecules induce activation of an enzymatic cascade involving serine proteinases, which leads to the conversion of proPO to active phenoloxidase (PO). Phenolic compounds produced by pPO-activation are toxic to invaders. Here, we describe the isolation of a venom protein from the parasitoid, Cotesia rubecula, injected into the host, Pieris rapae, which is homologous to serine proteinase homologs (SPH). The data presented here indicate that the protein interferes with the proteolytic cascade, which under normal circumstances leads to the activation of proPO and melanin formation. (C) 2003 Elsevier Ltd. All rights reserved.

Nestmate recognition in a Neotropical swarm-founding wasp: no effect of seasonality on tolerance of alien conspecifics

Previous study revealed that the swarm-founding wasp Polybia paulista is accurately able to distinguish nestmates from non-nestmates in the summer. However, the risk of accepting alien intruders is considered to be low in winter colonies, and additionally brood production is limited in 30-40% of colonies during the winter in this species. Thus, it is expected that colonies might lower their acceptance threshold and accept some conspecific wasps from alien colonies in winter. We conducted field experiments to examine tolerance of conspecific (nestmate and non-nestmate) females in winter. In contrast to our prediction, our colonies did not accept any individuals from alien colonies. We suggest that P. paulista exhibits the colony-specific acceptance threshold in winter, and colonies that produced brood in their nests may have raised the acceptance threshold even if the risk of accepting alien intruders is low in winter.

Co-occurrence of three types of egg policing in the Norwegian wasp Dolichovespula norwegica

In insect societies, workers often try to challenge the reproductive monopoly of the queen by laying their own eggs. Successful worker reproduction, however, is frequently prevented by queen policing or worker policing, whereby either the mother queen or non-reproductive workers selectively kill worker-laid eggs. Recently, a third mechanism-""selfish"" worker policing-has also been described in which the workers selectively police worker-laid eggs but also lay eggs themselves. Here, we present results from the monogynous wasp Dolichovespula norwegica, which show that all three kinds of policing-queen policing, worker policing and ""selfish"" worker policing-co-occur. The net effect of these three kinds of policing collectively favoured the queen`s reproduction, as within 1 day 44% of the worker-laid eggs versus only 8% of the queen-laid eggs were eaten. Of the worker-laid eggs that were killed by workers, approximately two thirds were eaten by the reproductive workers even though these made up only a small proportion, 8%, of the work force. This means that policing workers obtained both direct fitness benefits as well as indirect (inclusive) fitness. In addition, we show that worker policing was carried out by a limited, specialised set of workers that was estimated to constitute approximately one quarter of the whole colony and of which 66% were non-reproductive.

Sperm morphology: A novel way to associate female-males of highly sexual dimorphic fig wasp species

Males of pollinating and some non-pollinating fig wasps are wingless and quite dissimilar to their co-specific females. Due to the accentuated sexual dimorphism, males and females of some fig wasp species were described in different genera. We used morphological sperm features obtained from male seminal vesicles and female spermathecas to associate sexes in three non-pollinating fig wasp species, genus Idarnes, that are associated with Ficus citrifolia in Brazil. Sperm obtained from each female morph species presented diagnostic features that led to the association with sperm obtained from males. This method can potentially be used to help enlighten taxonomic problems in other wasp species with sexual di- or polymorphism.

Worker demography in a large-colony, swarm-founding wasp

Neotropical swarm-founding wasps build nests enclosed in a covering envelope, which makes it difficult to count individual births and deaths. Thus, knowledge of worker demography is very limited for swarm-founding species compared with that for independent-founding species. In this study, we explored the worker demography of the swarm-founding wasp Polybia paulista, the colony size of which usually exceeds several thousand adults. We considered each wasp colony as an open-population and estimated the survival probability, recruitment rate, and population size of workers using the developments of the Cormack-Jolly-Seber model. We found that capture probability varied considerably among the workers, probably due to age polyethism and/or task specialization. The daily survival rate of workers was high (around 0.97) throughout the season and was not related to the phase of colony development. On the other hand, the recruitment rate ranged from 0 to 0.37, suggesting that worker production was substantially less important than worker survival in determining worker population fluctuations. When we compared survival rates among worker groups of one colony, the mean daily survival rate was lower for founding workers than for progeny workers and tended to be higher in progeny workers that emerged in winter. These differences in survivorship patterns among worker cohorts would be related to worker foraging activity and/or level of parasitism.

Nest site selection by a neotropical swarm-founding wasp: seasonal alternation of nest orientation

Nest orientation in social insects has been intensively studied in warmer and cooler climates, particularly in the northern hemisphere. Previous studies have consistently shown that species subjected to these climatic conditions prefer to select mostly southern locations where the nests can gain direct sunlight. However, very little is known on nest orientation in tropical and subtropical social insects. We studied nest orientations initiated by swarms throughout a year in a Brazilian swarm-founding wasp, Polybia paulista von Ihering (Hymenoptera: Polistinae). Swarms selected various orientations as nest sites, but there was a particular trend in that swarms in the winter period (May-August) preferred to build northward-facing nests. This preference is opposite from that of social wasps observed in the northern hemisphere. Colonies of this species can potentially last for many years with continuous nesting, but nesting activities of colonies during the winter are severely limited due to cool temperature and a shortened day length. Northward-facing nests are warmer through the gain of direct solar heat during the winter period; consequently, choosing northward-facing sites may be advantageous for swarms in terms of a shortened brood development and shortened time needed to increase metabolic rates during warm-up for flight.

Thermal Characteristics of the Mud Nests of the Social Wasp Polybia spinifex (Hymenoptera; Vespidae)

The thermal characteristics of mud nests of Polybia spinifex were investigated by measuring internal and surface temperatures of the nests. The nests had a layer of mud envelope and consisted of mud with fine sand particles. The envelope had a vertically long slit-like entrance hole. The mud nests had high thermal conductivities (0.51-0.67 W/(m degrees C)) comparable to brick, rather than insulation materials of wasps` nests such as paper and wood. It was revealed that the long entrance radiated more heat from the thereto-image. The rate of thermal radiation (emissivity) of the nest surface was 0.80, and the value was similar to that of sand. The internal temperatures of the nests were high from top (T(n1), temperature difference between ambient temperature (T(a)) was 10 degrees C) to bottom (T(n3), difference, 5 degrees C) at noon. On the other hand, the temperature distributions were reversed during the night. Temperature T(n1) was lower by 1 degrees C than T(a), possibly from nightly dew on the top surface, whereas, at the middle point (T(n2),) and T(n3), temperatures were higher by 1 degrees C compared to T(a). Temperature fluctuations (ranges between maximum and minimum temperature) at T(n2) and T(n3) were similar to that of T(a), whereas the values at T(n1) and T(s) were higher than that of T(a).