Clutch size and egg production inOrthetrum nitidinerveSelys, 1841 (Anisoptera: Libellulidae): effect of body size and age

Abstract

Clutch size is an important fitness component often quantified artificially by inducing oviposition in libellulid females. Female behavior and egg production of the yellow-veined skimmer, Orthetrum nitidinerve, were studied in northeast Algeria during its reproductive season. Data on reproductive behavior and biology of this Mediterranean endemic species has not been published previously. Males guarded territories within the wetland while females came only to lay their eggs and then went back to terrestrial habitat. In this study we induced oviposition, which depletes all the female eggs, to obtain estimations of egg deposition rate and subsequently clutch size. On average an induced clutch was ca. 2200 eggs while a natural one was about 970 eggs. Artificial clutches were positively correlated to body length but negatively related to mature lifespan. The rate of egg deposition was higher in the afternoon than in the morning, probably because of differences in temperature. During their mature lifespan females oviposited between one and three artificial clutches.

Diplacodes lefebvrii in Sardinia, a new species for the Italian fauna (Odonata: Libellulidae)

“…For example Boano & Rolando (2003) found that for Libellula fulva Müller, 1764 the sexratio was strongly biased in favour of males and Kérry & Juillerat (2004) observed that mature males outnumbered mature females by a factor of 1,67 in Orthetrum coerulescens (Fabricius, 1798). Khelifa et al (2012) reported for Orthetrum nitidinerve (Sélys, 1841) a sex ratio at a mating area to be highly male biased, with a daily average of 91% males counted. Female-biased sex-ratios are exceedingly rare in dragonflies and only a few cases are documented (Van Gossum et al 2007).…”

Does water intake after oviposition indicate the end of oviposition and egg depletion in Odonata females?

“…For water intake the females hovered above the water, then rapidly swooped down and struck the water surface with their mouthparts one to four times. While performing this behavior, in 55-91% (73 ± 11%) of Downloaded by [University of Tasmania] at 14:10 29 September 2015 (Cordero & Andrés, 2002); Orthetrum nitidinerve (Khelifa et al, 2012); Crocothemis erythraea, Orthetrum chrysostigma, and Sympetrum fonscolombii (Koch & Suhling, 2005). Clutch sizes before oviposition and after water intake of all species were significantly different (one-sample t-test: p < 0.0001 for species with clutch sizes taken from the literature; Mann-Whitney tests: p < 0.0001 for the remaining species).…”

“…Calopteryx haemorrhoidalis, Orthetrum nitidinerve, Orthetrum chrysostigma, Crocothemis erythraea, and Sympetrum fonscolombii, the estimated clutch size was taken from the literature. Mean clutch size of C. haemorrhoidalis was taken from Cordero and Andrés (2002), that of O. nitidinerve from Khelifa et al (2012), and those of C. erythraea, O. chrysostigma, and S. fonscolombii from Koch and Suhling (2005). In order to estimate the number of mature eggs left after water intake, 10 females of each study species were captured just after performing water intake then they were dissected for egg counting.…”

“…To calculate the proportion of eggs left in each female's abdomen after oviposition, data on both clutch size Downloaded by [University of Tasmania] at 14:10 29 September 2015 before (when a female first visited the oviposition site) and after oviposition (when a female finished oviposition and drank water) were used. In one study species, Orthetrum coerulescens, clutch size was estimated artificially using the method described by Khelifa et al (2012), which consists in immersing the last abdominal segments in a vial containing water. In five species (Coenagrion caerulescens, Erythromma lindenii, Ischnura graellsii, Platycnemis subdilatata, and Sympecma fusca) clutch size was estimated by capturing 10 females during copulation, killing them in 70% ethanol, and dissecting them in the laboratory.…”

“…Moreover, it is even impossible to know whether a female has laid all or only a fraction of her mature eggs during an oviposition episode. Dissection of some females was used as an alternative to confirm egg depletion after oviposition (Bennett & Mill, 1995;Khelifa, Zebsa, Kahalerras, & Mahdjoub, 2012). To obtain appropriate estimates of egg production and lifetime reproductive success it is crucial to know whether a reproductive female lays all her mature eggs or only part of them.…”