Life cycle of natural populations of Metriocnemus (Inermipupa) carmencitabertarum Langton &amp; Cobo 1997 (Diptera: Chironomidae) in The Netherlands: indications for a southern origin?

Jan Kuper

doi:10.5324/cjcr.v0i30.2268

Abstract

The life-history and behaviour of the chironomid Metriocnemus (Inermipupa) carmencitabertarum was studied for three years and a comparison was made between two populations in the Netherlands. Key life-history characteristics are reported, including the number of generations (2-5 generations) and duration of larval development (19-55 days). Life-history characteristics differed between the two populations and between generations within a population. These differences were likely related to differences in competitors (mainly Chironomus riparius Meigen) and thermal characteristics of the habitat from variations in water volume and ambient temperature. Results suggested a diapause in summer, when water levels dropped, and not in winter. A clear seasonal pattern in body size was found with pupal length increasing steeply at the beginning of the summer. The increase in body size was positively correlated with mean ambient temperature during larval development. This correlation is in contrast with the Temperature-Size Rule (TSR) in ectotherms, which postulates a negative correlation between temperature and adult body size. The chance of ectotherm predators being present in the habitat is low, which may explain this feature. Life history characteristics supported a recent northward range expansionfor M. (I.) carmencitabertarum due to warmer winters. If correct, it is predicted that the species will be found in Scotland and northern Germany and/or southern Denmark in the near future.

Highlights

On 29 December 2013, 40 to 50 larvae were sampled from the Appingedam glass vase and assigned larval stages
The first observations of emergence of the wintering generation in 2012 in Nijmegen were made on May 22, which was presumably a peak in emergence following the onset of emergences around the middle of May. This was about two to three weeks later compared to first observations of adults in Appingedam in 2012
As the volume of the water butt was large (200 litres) it is possible that temperature in the butt was increasing more slowly than in the unknown habitat of the wintering population(s) in Appingedam in late winter and spring

Summary

Introduction

First described from specimens from the northwest of the Iberian peninsula (Langton and Cobo 1997), M. (I.) carmencitabertarum Langton & Cobo 1997 (Diptera: Chironomidae, subfamily Orthocladiinae) has since been found on two islands from the Azores archipelago (Murray et al 2004, Ramos et al 2010), in England in 2010 (Langton and Wilson 2012), in The Netherlands in 2011 (Kuper & Moller Pillot 2012), in Ireland in 2012 (Murray 2012) and in Northern Ireland in 2013 (Langton, 2014; Murray et al 2014). Since larvae have been reported from similar, yet artificial, water-filled habitats such as animal drinking troughs, rain-filled water butts and buckets in urban surroundings (Murray et al 2004, Ramos et al 2010, Langton and Wilson 2012, Kuper & Moller Pillot 2012, Murray 2012, Murray 2013, Murray 2016). Kuper (2015) reported biometric measurements to distinguish the four larval stages and presented biometric data for pupal exuviae (skins), which revealed a larger average size for females. This sexual size difference was probably already present in fourth instar larvae. For the first time, the species’ life cycle characteristics are presented and indications for a southern origin of the Dutch populations of M. (I.) carmencitabertarum are discussed

Methods

Results

Conclusion