title: Not only soldiers have weapons: evolution of the frontal gland in imagoes of the termite families Rhinotermitidae and Serritermitidae.
abstract: BACKGROUND
  The frontal gland is a unique adaptation of advanced termite families. It has been intensively studied in soldiers with respect to its anatomy and chemistry, with numerous novel compounds being discovered within the tremendous richness of identified products. At the same time, the presence of the frontal gland in non-soldier castes received only negligible attention in the past.
  
  
  RESULTS
  Here, we report on the development of the frontal gland in alate imagoes of 10 genera and 13 species of Rhinotermitidae and Serritermitidae, in order to shed light on the evolution and function of this gland in imagoes. All investigated species possess a frontal gland. In most cases, it is well-developed and equipped with a sac-like reservoir, located in the postero-dorsal part of cranium, but reaching as far as the seventh abdominal segment in some Rhinotermitinae. The only exception is the genus Psammotermes, in which the gland is very small and devoid of the reservoir.
  
  
  CONCLUSIONS
  Our direct observations and comparisons with soldiers suggest a defensive role of the gland in imagoes of all studied species. This functional analogy, along with the anatomic homology between the frontal gland in soldiers and imagoes, make it likely that the gland appeared once during the early evolution of rhinotermitid ancestors, and remained as a defensive organ of prime importance in both, soldiers and imagoes.
authors.affiliation: Research Team of Infochemicals, Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Prague, Czech Republic.
authors.forename: Jan
authors.initials: J
authors.lastname: Šobotník
authors.forename: Thomas
authors.initials: T
authors.lastname: Bourguignon
authors.forename: Robert
authors.initials: R
authors.lastname: Hanus
authors.forename: David
authors.initials: D
authors.lastname: Sillam-Dussès
authors.forename: Jitka
authors.initials: J
authors.lastname: Pflegerová
authors.forename: František
authors.initials: F
authors.lastname: Weyda
authors.forename: Kateřina
authors.initials: K
authors.lastname: Kutalová
authors.forename: Blahoslava
authors.initials: B
authors.lastname: Vytisková
authors.forename: Yves
authors.initials: Y
authors.lastname: Roisin
mesh_terms: D000818:Animals; D005075:Biological Evolution; D004702:Endocrine Glands / Q000033:anatomy & histology* / Q000502:physiology; D005260:Female; D006257:Head / Q000033:anatomy & histology* / Q000254:growth & development; D020049:Isoptera / Q000033:anatomy & histology* / Q000254:growth & development; D008297:Male; D008855:Microscopy, Electron, Scanning / Q000379:methods; D012886:Skull / Q000502:physiology; D013045:Species Specificity