Possible functions of oxytocin/vasopressin-superfamily peptides in annelids with special reference to reproduction and osmoregulation

J Exp Zool. 1999 Sep 1;284(4):401-6. doi: 10.1002/(sici)1097-010x(19990901)284:4<401::aid-jez6>3.3.co;2-l.


Annetocin is an earthworm oxytocin-related peptide that we previously isolated from the whole body of a lumbricid earthworm Eisenia foetida. We have reported that annetocin induces egg-laying-like behaviors in E. foetida and a gnathobdellid leech, Whitmania pigra, when it is injected into the respective animals. The present study was undertaken to probe physiological functions of invertebrate oxytocin-vasopressin-superfamily peptides with special reference to reproductive and osmoregulatory events in which vertebrate peptides of this superfamily are involved. Annetocin, Lys-conopressin (a leech vasopressin-related peptide) and two analog peptides, [Tyr(3)]-annetocin ((3)Y-annetocin) and [Phe(3)]-annetocin ((3)F-annetocin), were compared for their activities to induce egg-laying-like behavior and to change body weight as a measure of water balance in the leech W. pigra. Injection of annetocin, Lys-conopressin, and (3)F-annetocin caused both egg-laying-like behavior and reduction of body weight in the animals, but (3)Y-annetocin induced neither. Furthermore, leeches in the non-breeding season responded to peptides less conspicuously than those in the breeding season. Such a concomitant induction of egg-laying-like behavior and body-weight reduction suggests that these two phenomena are unitary and might be accounted for by the fact that egg-laying in leeches and earthworms is accompanied by secretion of a large quantity of mucus, which should significantly contribute to body-weight loss. J. Exp. Zool. 284:401-406, 1999.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Body Weight
  • Female
  • Invertebrate Hormones / physiology*
  • Leeches / physiology*
  • Molecular Sequence Data
  • Oxytocin / analogs & derivatives*
  • Oxytocin / physiology
  • Peptide Fragments / physiology*
  • Peptides, Cyclic / physiology*
  • Reproduction / physiology*
  • Seasons
  • Water-Electrolyte Balance / physiology*


  • Invertebrate Hormones
  • Peptide Fragments
  • Peptides, Cyclic
  • conopressin G
  • annetocin
  • Oxytocin