title: Developmental pathways of Psammotermes hybostoma (Isoptera: Rhinotermitidae): old pseudergates make up a new sterile caste.
abstract: BACKGROUND
  Ergonomic efficiency is in termites maximized by task partitioning among specialized castes. The isopteran caste systems can be classified as either (i) linear, when tasks are performed by pluripotent immatures (pseudergates), retaining the ability to develop into winged imagoes or (ii) bifurcated, with the presence of a true worker caste, which diverges early and permanently from the sexual (nymph/alate) line.
  
  
  RESULTS
  Here, we report on the ontogenetic potentialities of the highly polymorphic sand termite Psammotermes hybostoma. Beside numerous pluripotent pseudergates, constituting the main work force, some larger non-feeding apterous immatures, also occur. These individuals are unable to proceed to the winged imago stage, but store large amounts of fat and also give rise to large soldiers. Soldiers therefore originate from a wide range of apterous instars, consequently being highly polymorphic.
  
  
  CONCLUSIONS
  The caste system of P. hybostoma is essentially linear, as in other basal Rhinotermitidae, but is distinguished by the late bifurcation leading to large apterous immatures. Because these large worker-like individuals deviate late and do not perform worker tasks, they cannot be considered homologous to the true workers of Termitidae and advanced Rhinotermitidae, but they provide a novel example of the evolution of sterile immatures in termites.
authors.affiliation: Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bourguignon
authors.forename: Jan
authors.initials: J
authors.lastname: Šobotník
authors.forename: David
authors.initials: D
authors.lastname: Sillam-Dussès
authors.forename: Pavel
authors.initials: P
authors.lastname: Jiroš
authors.forename: Robert
authors.initials: R
authors.lastname: Hanus
authors.forename: Yves
authors.initials: Y
authors.lastname: Roisin
authors.forename: Toru
authors.initials: T
authors.lastname: Miura
mesh_terms: D000818:Animals; D005260:Female; D020049:Isoptera / Q000502:physiology*; D008297:Male; D012919:Social Behavior