The Gregarine Infection in Different Species of Odonata from the Same Habitat

A qualitative and quantitative study of eugregarine parasites in different dragonfly species was performed around a breeding site at Bergen (Western Norway). Dragonfly larvae were never found to harbour gregarines. As a general rule, the number of dragonflies infected and the number of gregarines present in each individual host increased during the flying season. In the zygopterans Coenagrion hastulatum (Charp.), Enallagma cyathi-gerum (Charp.), and Pyrrhosoma nymphula (Sulz.), the majority became heavily infected. Discoloured, feeble specimens captured in the field exhibited extensive damage to the midgut, probably progressing to bacterial septicaemia. The histopathology of the midgut wall has been recorded from scarcely visible alterations to massive disruption of the epithelium. In these species, gregarine infection apparently reduced the longevity of adults. The population of Lestes sponsa (Hansem.) was moderately infected and injuries of the midgut seldom occurred. In the only infected anisopteran, Sympetrum danae (Sulz.), gregarines seemed unimportant and caused no damage to their hosts. Each gregarine species seemed to thrive in several dragonfly hosts, and a host could harbour at least two different gregarine species at the same time. The pattern of infection is discussed against the background of climatic and edaphic conditions.     

华南部分地区束翅亚目(Odonata:Zygoptera)蜻蜓区系聚类分析

采用类平均法和最近相邻法对位于广东、海南、香港、台湾、澳门等地8个动物地理小区现有分布的蜻蜓目束翅亚目41属进行系统聚类分析。类平均法将澳门、内伶仃、珠江三角洲、黑石顶、尖峰岭、香港、台湾等7个小区依次逐类聚合后在最大距离处与8个小区中地处最北的南岭聚合;南岭类群与其它类群的距离最远;整体呈现基于纬度,即南北向的束翅亚目类群合并。最近相邻法将8个小区先分别聚合成岛屿型（澳门与内伶仃）、山地型（黑石顶和尖峰岭、南岭）、山地与平原混合型（香港和台湾、珠江三角洲）,最终聚合成一大类;岛屿型与其它两型的距离最远,联系性最小;整体呈现基于海拔高度的聚合,即主要体现束翅亚目类群垂直分布的差异。     

First Baltic amber megapodagrionid damselfly (Odonata: Zygoptera)

Electropodagrion szwedoi n. gen., n. sp., first Baltic amber megapodagrionid damselfly, is described. The European and North American fossils document a very high diversity and a much wider distribution of this group of damselflies during the Cenozoic than today. A checklist of described fossil species of damselflies of the family Megapodagrionidae is given.     

Zum Fortpflanzungsmodus fossiler Kleinlibellen (Insecta,Odonata, Zygoptera)

Fossil egg-sets of damselflies (Insecta, Odonata, Zygoptera) are recognized from well known localities such as Randecker Maar, Messel (both in Germany) and in an old record about sediments from the Upper Cretaceous of Bohemia (Czech Republic). Such finds bearing witness to the behaviour of certain fossil insects are extremely rare, especially in stratified sediments. Hitherto they have only been recorded from the Upper Oligocene Fossillagerstätte Rott near Bonn (Germany). Two different types of egg-sets could be distinguished; they were described and figured byHellmund &Hellmund (1991, 1993). It is striking that the gap between finds from the Upper Oligocène and those from modern times is mainly due to insufficient observations. The explained strategy of reproduction obviously evolved at least 95 m.a. ago and has been practiced unchanged today.     

Anti-predator strategies in oviposition site selection of Pyrrhosoma nymphula (Zygoptera: Odonata)

Summary Selection of sites for oviposition when the risk of predation by green frogs was variable studied in tandems of the damselfly Pyrrhosoma nymphula. In the absence of predators the number of tandems landing increased with the size of the oviposition site and with the number of pairs already present. Pairs approaching an oviposition site landed promptly and preferred locations near other ovipositing pairs. Pairs which had landed near others left the landing site and flew to another water plant after a shorter period than those landing alone. They stayed in groups for only 16.5% of the total duration of stay at the oviposition site. With predators present fewer tandems landed. There was no relationship between the landing site of solitary tandems and the locations of the perching frogs. Pairs landing in groups were disturbed by frogs after a shorter period than pairs landing alone. Damselfly aggregation did not affect the predation success of the frogs, but the predation risk to individual tandem pairs was reduced.     

The natural prey of larvae of the damselfly, Ischnura elegans (Odonata: Zygoptera)

SUMMARY. A method for determining the prey of a damselfly larva under natural conditions is described, with its shortcomings.
Within the limits of the method, it would appear that Ischnura elegans consumes different prey items in roughly the same proportions as their occurrence in the field.
Anomalous results are explained in terms of differences in encounter rates between predator and prey and/or ease with which prey can be handled.     

Territoriality and male-biased sexual size dimorphism in Argia reclusa (Odonata: Zygoptera)

In Odonata, many species present sexual size dimorphism (SSD), which can be associated with male territoriality in Zygoptera. We hypothesized that in the territorial damselfly Argia reclusa, male–male competition can favor large males, and consequently, drive selection pressures to generate male-biased SSD. The study was performed at a small stream in southeastern Brazil. Males were marked, and we measured body size and assessed the quality of territories. We tested if larger territorial males (a) defended the best territories (those with more male intrusions and visiting females), (b) won more fights, and (c) mated more. Couples were collected and measured to show the occurrence of sexual size dimorphism. Results indicated that males are larger than females, and that territorial males were larger than non-territorial males. Larger territorial males won more fights and defended the best territories. There was no difference between the mating success of large territorial and small non-territorial males. Although our findings suggest that male territoriality may play a significant role on the evolution of sexual size dimorphism in A. reclusa, we suggest that other factors should also be considered to explain the evolution of SSD in damselflies, since non-territorial males are also capable of acquiring mates.     

Redefining the damselfly families: a comprehensive molecular phylogeny of Zygoptera (Odonata)

An extensive molecular phylogenetic reconstruction of the suborder Zygoptera of the Odonata is presented, based on mitochondrial (16S, COI) and nuclear (28S) data of 59% of the 310 genera recognized and all (suspected) families except the monotypic Hemiphlebiidae. A partial reclassification is proposed, incorporating morphological characters. Many traditional families are recovered as monophyletic, but reorganization of the superfamily Coenagrionoidea into three families is proposed: Isostictidae, Platycnemididae and Coenagrionidae. Archboldargia Lieftinck, Hylaeargia Lieftinck, Palaiargia Förster, Papuargia Lieftinck and Onychargia Selys are transferred from Coenagrionidae to Platycnemididae, and Leptocnemis Selys, Oreocnemis Pinhey and Thaumatagrion Lieftinck from Platycnemididae to Coenagrionidae. Each geographically well‐defined clade of Platycnemididae is recognized as a subfamily, and thus Disparoneurinae (i.e. Old World ‘Protoneuridae’) is incorporated, Calicnemiinae is restricted, and Allocnemidinae (type genus: Allocnemis Selys) subfam.n ., Idiocnemidinae (type genus: Idiocnemis Selys) subfam.n . and Onychargiinae (type genus: Onychargia Selys) subfam.n . and Coperini trib.n . (type genus: Copera Kirby) are described. Half of Coenagrionidae belongs to a well‐supported clade incorporating Coenagrion Kirby and the potential subfamilies Agriocnemidinae, Ischnurinae and Pseudagrioninae. The remainder is less well defined, but includes the Pseudostigmatidae and New World Protoneuridae that, with Argiinae and Teinobasinae, may prove valid subfamilies with further evidence. Ninety‐two per cent of the genera formerly included in the polyphyletic Amphipterygidae and Megapodagrionidae were studied. Pentaphlebiidae, Rimanellidae and Devadattidae fam.n . (type genus: Devadatta Kirby) are separated from Amphipterygidae, and Argiolestidae, Heteragrionidae, Hypolestidae, Philogeniidae, Philosinidae and Thaumatoneuridae from Megapodagrionidae. Eight further groups formerly placed in the latter are identified, but are retained as incertae sedis; the validity of Lestoideidae, Philogangidae and Pseudolestidae is confirmed. For some families (e.g. Calopterygidae, Chlorocyphidae) a further subdivision is possible; Protostictinae subfam.n . (type genus: Protosticta Selys) is introduced in Platystictidae. Numerous new combinations are proposed in the Supporting Information. Many long‐established families lack strong morphological apomorphies. In particular, venation is incongruent with molecular results, stressing the need to review fossil Odonata taxonomy: once defined by the reduction of the anal vein, Protoneuridae dissolves completely into six clades from five families.     

Female internal genital organs of the damselfly Pseudagrion rubriceps selys (Zygoptera: Odonata)

The morphology, anatomy and histology of the female internal genital organs of the adult damselfly Pseudagrion rubriceps Selys were studied in detail. The paired, long, panoistic ovaries each lead posteriorly into an oviduct. The oviducts unite to form a short common median oviduct leading into the "eighth complex" localized in the 8th abdominal segment. The "eighth complex" comprises the bursa copulatrix, spermatheca and vagina. A pair of prominent accessory reproductive glands, localized in the 9th segment, open into the vagina.     

The ecological role of caudal lamellae loss in the larval damselfly,Ischnura posita (Hagen) (Odonata: Zygoptera)

Summary Damselfly larvae may autotomize and regenerate any of their 3 caudal lamellae. At least one missing or regenerating lamella was evident in 50.1% of field collected Ischnura posita larvae. Lamellae loss during molting is very infrequent (1 out of 117 recorded molts). Laboratory trials indicate that conspecifics remove lamellae and that this process is density dependent. The percentage of larvae losing lamellae during 24 h trials ranged from 73.5 at the highest density tested to 17.3 at the lowest density. I. posita larvae are cannibalistic. The presence of lamellae reduces an individual's chance of being cannibalized. More than twice as many final instar lamellae-less larvae were cannibalized during 24 h trials than analogous individuals having 3 lamellae at experimental initiation. Costs are also associated with lamellae autotomy. 1) Although individuals without lamellae can swim they are more reluctant to release from a wooden stalk and swim when threatened (9% release) than are larvae with lamellae (29% release). Since swimming is part of their repertoire of anti-predator behaviors this behavioral shift should be detrimental. 2) Caudal lamellae function in O₂ uptake. Trials were conducted with larvae having and not having lamellae in an experimental horizontal oxygen gradient system. Relative to larvae without lamellae, those with lamellae preferred deeper depths at PO₂ values greater than 70 torr. Many lamellae-less larvae distributed themselves at the water surface throughout the range of PO₂ values tested. Differential depth distribution between larvae with and without lamellae is highly significant (P < 0.01).     

Three new species of Peristicta Hagen in Selys (Odonata: Zygoptera: Protoneuridae) from Brazil

Three new species of Peristicta Hagen in Selys from Brazil are described and illustrated: P. janiceae from Minas Gerais State (Diamantina, Gouvêa, Lagoa Santa, Serra do Cara?a, Serra do Cipó, Urobotanga), P. jalmosi from Goiás State (Chapada dos Veadeiros, Reserva da Universidade de Brasília) and Minas Gerais State (Urobotanga, Lagoa Santa, Ponte Nova, S?o Jo?o del Rey,) and P. muzoni from Mato Grosso State (Serra da Bodoquena). An identification key for males of Peristicta is presented.     

Biogeography and systematics of endemic island damselflies: The Nesobasis and Melanesobasis (Odonata: Zygoptera) of Fiji

The study of island fauna has greatly informed our understanding of the evolution of diversity. We here examine the phylogenetics, biogeography, and diversification of the damselfly genera Nesobasis and Melanesobasis, endemic to the Fiji Islands, to explore mechanisms of speciation in these highly speciose groups. Using mitochondrial (COI, 12S) and nuclear (ITS) replicons, we recovered Garli ‐part maximum likelihood and Mrbayes Bayesian phylogenetic hypotheses for 26 species of Nesobasis and eight species/subspecies of Melanesobasis. Biogeographical patterns were explored using Lagrange and Bayes ‐Lagrange and interpreted through beast relaxed clock dating analyses. We found that Nesobasis and Melanesobasis have radiated throughout Fiji, but are not sister groups. For Nesobasis, while the two largest islands of the archipelago—Viti Levu and Vanua Levu—currently host two distinct species assemblages, they do not represent phylogenetic clades; of the three major groupings each contains some Viti Levu and some Vanua Levu species, suggesting independent colonization events across the archipelago. Our Beast analysis suggests a high level of species diversification around 2–6 Ma. Our ancestral area reconstruction (Rasp ‐Lagrange ) suggests that both dispersal and vicariance events contributed to the evolution of diversity. We thus conclude that the evolutionary history of Nesobasis and Melanesobasis is complex; while inter‐island dispersal followed by speciation (i.e., peripatry) has contributed to diversity, speciation within islands appears to have taken place a number of times as well. This speciation has taken place relatively recently and appears to be driven more by reproductive isolation than by ecological differentiation: while species in Nesobasis are morphologically distinct from one another, they are ecologically very similar, and currently are found to exist sympatrically throughout the islands on which they are distributed. We consider the potential for allopatric speciation within islands, as well as the influence of parasitic endosymbionts, to explain the high rates of speciation in these damselflies.     

Maximum and actual field feeding-rates in larvae of the damselfly Pyrrhosoma nymphula (Sulzer) (Odonata: Zygoptera)

The paper presents information on factors influencing maximum feeding-rates (measured in the laboratory) in larvae of the damselfly Pyrrhosoma nymphula, and compares estimates of feeding rates in the field with maximum feeding-rates for larvae of the same size at the same temperature. Maximum feeding-rates in Pyrrhosoma larvae of different sizes were measured at 4, 5, 10 and 15°C. At low temperatures (4–5°C) maximum feeding-rate was depressed more than predicted either from the effects of temperature on the gut-clearance time of larvae or their respiratory rate. Maximum feeding-rate declined steadily throughout metamorphosis in the final instar and stopped completely prior to emergence of the adult. Feeding-rates in the field were calculated from ‘balanced’ energy equations, i.e. from the sum of larval growth, respiration and the production of faeces and exuviae. Feeding rates in the field were always much less than maximum feeding-rates for the same size of larva at the same temperature, and at the most were never more than 70% of the latter; they were closer to the maximum in summer than in winter, when they fell as low as 20% of the maximum. The relevance of these findings to studies on the efficiency with which carnivores utilize energy in the field, and the importance of Odonata larvae as predators in aquatic ecosystems is discussed.     

Mechanical properties of the endophytic ovipositor in damselflies (Zygoptera, Odonata) and their oviposition substrates

Damselfly females use their ovipositor valves to saw aquatic plants in order to insert their eggs into the plant tissues. Stiffness of the plant substrata is therefore an important parameter for oviposition substrate choice by females. Using a force transducer combined with a motorised micromanipulator, the bending stiffness of the ovipositor at the axial compressional load was studied in seven European damselfly species and compared to the local stiffness of seven preferred plant substrates. The puncture force of tested plant samples ranged from 105 to 1500 mN, and their local stiffness ranged from 208 to 1776 N/m. The bending stiffness of the ovipositor was estimated as 173-409 N/m depending on the damselfly species. Using original and literature data, a significant positive correlation between mechanical properties of the ovipositor and preferred oviposition substrates was demonstrated. Possible behavioural adaptations to overcome high stiffness of plant tissues during oviposition are discussed.     

Responses of rectal pumping to oxygen lack by larval Calopteryx splendens (Zygoptera: Odonata)

Abstract. Larvae of most stadia of Calopteryx splendens (Harris) have been shown to pump water in and out of the rectum for much of the time. In each cycle of pumping there are from three to seven inhalant stokes which progressively fill the ileum with water. A short pause intervenes before a strong compression of segments 5–8 expels the water in a jet. The pattern resembles the gulping ventilation of aeshnid and libellulid dragonfly larvae. Larvae made hypoxic or otherwise stressed show a rise in the frequency and amplitude of pumping. The increase in frequency is brought about by a reduction of the pause duration, while the gain of amplitude results from a rise in both the number of inhalations/cycle and the magnitude of the stroke volume of each inhalation. Some evidence concerning the role of stretch receptors in the execution of the cycle is presented. It is proposed that rectal pumping promotes the exchange of ions and dissolved gases between the rectal water and the hindgut epithelia, supplying mainly the chloride-absorbing cells in the rectal pads. Pumping also stirs the water in the vicinity of the caudal lamellae which are probably the insect's major sites of gaseous exchange.