Long-term effects of prey-availability, partnering and temperature on overall egg capsule output of ‘New Zealand flatworms’, Arthurdendyus triangulates

John Baird, Ian Fairweather, Archie Murchie

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Arthurdendyus triangulatus is an invasive terrestrial flatworm that preys on earthworms. To assess A. triangulatus egg capsule production, flatworms were maintained in ventilated polypropylene tubs (7.5 L) kept in controlled environment (CE) chambers or outdoors in the ground. Controlled environment chambers were maintained at 8°C or 14°C, flatworms kept singly or paired within tubs and offered Eisenia fetida according to a weight equalling one-eighth or one-half of the mean flatworm weight, or left unfed. The tubs were a successful method for keeping flatworms, with some surviving for over one year. The greatest number of egg capsules produced by an individual A. triangulatus was nine over a 16 week period for a flatworm kept at 14°C and fed at the one-half regime (0.56 egg capsules flatworm-1 week-1). Although the effects of treatments varied with CE chambers, there was some evidence from flatworms kept outdoors, that feeding affected egg capsule output, with those flatworms fed at the one-half regime tending to produce more egg capsules (P= 0.057). Flatworms at the one-eighth regime or that were unfed produced progressively lighter egg capsules and substantially declined in weight themselves. Nevertheless, even unfed flatworms continued to produce egg capsules for 18 weeks. The lightest egg capsule weighed 8 mg, whilst the heaviest was 180 mg. In the CE chambers at 14°C, there was evidence for two different reproductive/survival strategies. Some flatworms produced cumulatively more egg capsules the longer they survived, whereas others lived longer but produced fewer egg capsules. Flatworms kept without a partner still produced egg capsules up to 35 weeks later. Egg capsules contained a mean of 4.14 (CE chambers) or 4.62 (outdoors) juveniles, with a maximum of 11. Overall, juveniles were 45% of the weight of egg capsules, although larger egg capsules had more juveniles, which comprised a greater proportion of the egg capsule. The conversion of earthworm prey to egg capsule production was estimated at 13%.
Original languageEnglish
Pages (from-to)289-301
Number of pages13
JournalAnnals of Applied Biology
Issue number3
Publication statusPublished - Apr 2005


  • Artioposthia triangulata
  • earthworms
  • egg capsules
  • planarian
  • reproduction
  • terrestrial flatworm


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