Mating behaviour and insemination in Diplatys flavicollis, an earwig with double-barrelled penises and a variable number of female sperm-storage organs

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Abstract

Earwigs (Insecta, Dermaptera) show astonishing diversity in penis morphology. In several families, males have a single penis (termed virga), whereas males of other families possess two functional virgae. Taxonomists have assumed that the two-virgae state is ancestral; however, ecological reasons why the ancestor acquired two virgae have not been explored. This study investigated in detail male and female genital structures, mating behaviour and insemination processes in the earwig Diplatys flavicollis (Diplatyidae). Diplatyidae are considered to be the most primitive family of earwigs. SEM and light-microscopy revealed that males of this species have two gonopores on each of two virgae, similar to those reported in other diplatyids (i.e. two double-barrelled penises), while females have four to six independent sperm-storage organs (spermathecae). Rapid fixation of mating pairs and insemination success of males from which one virga had been removed clearly revealed that only one virga was used for mating and was usually sufficient for inseminating multiple spermathecae. This finding rejects the one-to-one correspondence between male gonopores and female spermathecae. Based on allometric analysis of spermathecal variation, the possible significance of multiple spermathecae in relation to sperm-storage strategies of females is discussed. Compared to studies of male genital morphology, few studies have described spermathecal morphology. Based on compiled data of spermathecal and virgal morphology among earwigs, a parallel evolutionary trend between spermathecae and virgae from complicated (multiple) to simple (single) ones is suggested, and further investigation of the phylogeny, female genital morphology and insemination processes among earwigs is encouraged.

Original languageEnglish
Pages (from-to)37-46
Number of pages10
JournalJournal of Zoology
Volume262
Issue number1
DOIs
Publication statusPublished - 2004 Jan
Externally publishedYes

Fingerprint

Dermaptera
storage organs
mating behavior
penis
sperm
insemination
spermatozoa
female genitalia
male genitalia
Insecta
light microscopy
ancestry
organ
earwig
fixation
microscopy
phylogeny
scanning electron microscopy

Keywords

  • Diplatys flavicollis
  • Earwig
  • Genital morphology
  • Paired penises
  • Sperm storage

ASJC Scopus subject areas

  • Animal Science and Zoology

Cite this

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title = "Mating behaviour and insemination in Diplatys flavicollis, an earwig with double-barrelled penises and a variable number of female sperm-storage organs",
abstract = "Earwigs (Insecta, Dermaptera) show astonishing diversity in penis morphology. In several families, males have a single penis (termed virga), whereas males of other families possess two functional virgae. Taxonomists have assumed that the two-virgae state is ancestral; however, ecological reasons why the ancestor acquired two virgae have not been explored. This study investigated in detail male and female genital structures, mating behaviour and insemination processes in the earwig Diplatys flavicollis (Diplatyidae). Diplatyidae are considered to be the most primitive family of earwigs. SEM and light-microscopy revealed that males of this species have two gonopores on each of two virgae, similar to those reported in other diplatyids (i.e. two double-barrelled penises), while females have four to six independent sperm-storage organs (spermathecae). Rapid fixation of mating pairs and insemination success of males from which one virga had been removed clearly revealed that only one virga was used for mating and was usually sufficient for inseminating multiple spermathecae. This finding rejects the one-to-one correspondence between male gonopores and female spermathecae. Based on allometric analysis of spermathecal variation, the possible significance of multiple spermathecae in relation to sperm-storage strategies of females is discussed. Compared to studies of male genital morphology, few studies have described spermathecal morphology. Based on compiled data of spermathecal and virgal morphology among earwigs, a parallel evolutionary trend between spermathecae and virgae from complicated (multiple) to simple (single) ones is suggested, and further investigation of the phylogeny, female genital morphology and insemination processes among earwigs is encouraged.",
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