What to do if streams go dry? Behaviour of Balkan Goldenring (Cordulegaster heros, Odonata) larvae in a simulated drought experiment in SW Hungary

Abstract

1. In case of dryings, the hyporheic zone is one of the most important refugia for stream macroinvertebrate communities, including the few Odonata species living in these habitats, such as Cordulegaster species. There is no information on the desiccation resistance strategies and methods of any members of the genus, including Cordulegaster heros. 2. We hypothesised that the larvae use burrowing behaviour to survive droughts. In this study, beyond recording the survival rates of the larvae, we tested the effects of the sediment particle size and the body size of the larvae on burrowing behaviour in a 3-week-long simulated drought experiment in an indoor artificial stream system. 3. Eighty larvae were involved in the experiment, from which 60 were treated with drought, and 20 served as controls. Larvae were put into flowing water, into separate special compartments; 1 day later, the flow was ceased, and then, the water level was gradually decreased for 3 weeks. 4. Approximately 15% of larvae could survive the 3 weeks of drying. The survival probability of drought-treated larvae was significantly increased if animals burrowed into the sediment. In addition, the survival probability was higher in case of fine substrate material. Size of the larvae only affected the depth of the burrowing, not the survival rate. 5. However, two-thirds of the larvae did not dig into the sediment, which implies that surviving via burrowing is not the only mechanism of the species to withstand dry periods.

Aquatic Macrophyte Vegetation Promotes Taxonomic and Functional Diversity of Odonata Assemblages in Intermittent Karst Rivers in the Mediterranean

“…In contrast, macrophyte-poor habitats in our study were characterized mainly by the species with all year-round nymphal development and with no drought resilience strategies [63,64]. However, for some of those species, drought-survival strategies and mechanisms may be insufficiently known (e.g., C. splendens, C. heros) [69,98], or their occurrence in the studied IRES could be the result of the adult search for food resources (e.g., S. meridionalis, O. forcipatus) [69,99]. Thus, their occurrence in IRES should be confirmed with future, nymph-focused studies.…”

Assemblage reorganization of South African dragonflies due to climate change

“…Annual temperatures as well as temperature range are also known to affect dragonfly physiology, such as phenology, seasonal regulation, immune function and pigment production used for thermoregulation (Hassall & Thompson, 2008). Precipitation of the driest quarter was selected as prolonged periods of drought are known to drastically impact larvae survival (Pernecker et al., 2020). Thus, we extracted four present‐day bioclimatic variables, with two describing air temperature and two describing precipitation (http://www.worldclim.org; Hijmans et al., 2005), over the period from 1970 to 2000.…”

The influence of relief morphometric characteristics upon the occurrence of the species Cordulegaster bidentata in the particular conditions of the Western Carpathians

“…An essential and new contribution to knowledge is the impact of the morphometric (not yet examined) relief characteristic -the orientation of the watercourse towards the cardinal points on the occurrence of C. bidentata species. This ecological characteristic has not yet received increased attention in research on other species of the genus Cordulegaster (Lang et al, 2001;Leipelt, 2005;Manenti et al, 2013;Holuša & Holušová, 2014;Boda et al, 2015;Jabiol et al, 2015;Pernecker et al, 2020). According to preliminary results, altitude, orientation of the watercourse towards the cardinal points, forest cover of streams, small soil fraction, covering with organic material and the stream basin slope appear to be important factors for the occurrence of the species.…”