Novel microsatellite markers suggest the mechanism of parthenogenesis in Extatosoma tiaratum is automixis with terminal fusion

Parthenogenetic reproduction is taxonomically widespread and occurs through various cytological mechanisms, which have different impact on the genetic variation of the offspring. Extatosoma tiaratum is a facultatively parthenogenetic Australian insect (Phasmatodea), in which females oviposit continuously throughout their adult lifespan irrespective of mating. Fertilized eggs produce sons and daughters through sexual reproduction and unfertilized eggs produce female offspring via parthenogenesis. Here, we developed novel microsatellite markers for E. tiaratum and characterized them by genotyping individuals from a natural population. We then used the microsatellite markers to infer the cytological mechanism of parthenogenesis in this species. We found evidence suggesting parthenogenesis in E. tiaratum occurs through automixis with terminal fusion, resulting in substantial loss of microsatellite heterozygosity in the offspring. Loss of microsatellite heterozygosity may be associated with loss of heterozygosity in fitness related loci. The mechanism of parthenogenetic reproduction can therefore affect fitness outcomes and needs to be considered when comparing costs and benefits of sex versus parthenogenesis.     

Male Mating Success and the Effect of Mating History on Ejaculate Traits in a Facultatively Parthenogenic Insect (Extatosoma tiaratum)

Males can typically increase their lifetime reproductive success by mating with multiple females. However, recent studies across a broad range of species have demonstrated physiological constraints on male multiple mating. In this study, we investigate male mating capacity in Extatosoma tiaratum, a facultative parthenogenetic phasmatid. Sperm limitation is thought to be one factor favouring the evolution and maintenance of parthenogenetic reproduction, but studies on male mating ability in facultative parthenogenetic species are extremely rare. To explore whether male mating success varies with mating history, we provided males with weekly mating opportunities with different females throughout their lives. We then observed mating success, and the variation in ejaculate size and quality within each mating. We showed that most, but not all, males can mate multiply, however the amount of ejaculate produced is variable and depends upon male body mass and mating history.     

The binding of lectins to carbohydrate moieties on haemocytes of the insects,Blaberus craniifer (Dictyoptera) and Extatosoma tiaratum (Phasmida)

Summary The specificity and distribution of carbohydrate moieties, which act as receptors for lectins on the haemocytes of two insect species, Blaberus craniifer and Extatosoma tiaratum, were investigated. Four peroxidase-labelled lectins were utilised as probes: wheat-germ agglutinin, Ricinus communis (120) agglutinin, concanavalin A and Lens culinaris agglutinin, and binding visualised by reaction with DAB/H₂O₂. The lectin-binding studies indicated that Blaberus and Extatosoma plasmatocytes, and Extatosoma spreading granular cells possess surface N-acetyl-D-glucosamine, D-galactose and mannose moieties; Extatosoma cystocytes have D-galactose and mannose; whilst Blaberus granular cells/cystocytes and Extatosoma fine granular cells have mannose determinants.     

Water vapour uptake by diapausing eggs of a tropical walking stick

Abstract. This study is the first to demonstrate the capacity of an arthropod egg, that of a tropical walking stick Extatosoma tiaratum (Macleuy), to absorb water vapour from the air. This species diapauses both as an early embryo and then again as a pharate first instar larva, and both stages are capable of absorbing water vapour. Water vapour absorption occurs at lower humidities and at a lower rate for an egg in early embryonic diapause (c. a_v 0.30, 0.516 mg h^-1δ_v^-1) than in the diapausing pharate first instar (c. a_v 0.60, 0.725 mgh^-1δa_v^-1) at 25C. In addition to having the capacity to gain water at very low vapour activities, water is efficiently conserved as indicated by the low rate of water loss (0.015% h^-1 in the early embryo and 0.046% h^-1 in the pharate larva at 25C). Eggs that have been killed lose water when held at a hydrating vapour activity, thus implying that active uptake contributes to net absorption. Wax block experiments suggest that water is absorbed over the entire chorionic surface. Eggs of five other insect species that were examined [Lymantria dispar (L.), Bombyx mori (L.), Antheraea polyphemus (Cram.), Oncopeltus fasciatus (Dallas) and Diaferomera femorata (Say)] lacked the ability to absorb atmospheric water.