Post-copulatory mate guarding by males of the demselfly Hetaerina vulnerata Selys (Odonata: Calopterygidae)

Males of the calopterygid damselfly Hetaerina vulnerata remain with their mates after copulating with them. The species exhibits two unusual features of post-copulatory mate guarding. First, a male will often leave his territory to accompany a female in tandem on a search for oviposition sites elsewhere. Second, a male will perch near his ovipositing female even though she completely submerges when egg-laying and cannot be captured and mated by another male while she is underwater. These activities carry two potential costs: (1) a male may miss other receptive females while guarding one mate and (2) he may lose his territory to an interloper while he is absent. These costs were low, however, because territorial males secured only one mating per 3.6 days on average. Moreover, 23 times out of 26, territorial males reclaimed their plots quickly after being away for 30–60 min. The gain from postcopulatory guarding came from being present to recapture a female should she fly up from the water after rejecting an oviposition site. There was a 40% chance that a female would leave one site to search for another during an oviposition bout. If the male were not present, his mate would be captured and mated by another individual (no female ever selected an oviposition site without being carried to it by a male). Her new partner would fertilize the remaining eggs in the female's clutch (if sperm precedence occurs in this species). The total number of eggs fertilized by a male will be affected by how well he prevents any one mate from copulating again before she lays her entire clutch and the total number of receptive females he captures. The variation in the degree of mate guarding by male odonates seems to be the evolutionary outcome of differences in fitness gains derived from these two competing activities in different ecological settings.     

Mating tactics and male wing dimorphism in the damselfly,Mnais pruinosa costalis selys (Odonata: Calopterygidae)

Males of the damselfly,Mnais pruinosa costalis, exhibit wing color dimorphism: one form has orange wings, and the other hyaline wings which resemble female wings. The former is usually territorial and the latter uses sneaky mate securing tactics. When orange-winged males failed to establish territory, they became floaters that day. Hyaline-winged males perched around their territories and often, formed in tandem without any apparent courtship behavior when they found females. Their copulation frequency was higher and copulation duration longer than those of territorial males. A few females oviposited without remating. Total oviposition duration of females with which a hyaline-winged male mated was more than 32 min per male on average in a day Females that copulated with hyaline-winged males often remated with orange-winged residents before oviposition. Total duration of oviposition bouts of females after mating with floaters was short (15 min), while that with territorial residents was long (66 min). As a result, total oviposition duration of females with which an orange-winged male mated was about 40 min in a day. The reproductive success of the hyaline-winged males may be similar to that of the orange-winged males.     

Differences in adult and reproductive lifespan in the two male forms ofMnais pruinosa costalis selys (Odonata: Calopterygidae)

The damselflyMnais pruinosa costalis (Odonata: Calopterygidae) is unusual in that males are dimorphic, existing as clear-winged non-territorial ‘sneaks’ and orange-winged territorial ‘fighters’. Here we report the results of population census data and behavioural observations in the field and laboratory, and present estimates of emergence period, reproductive period, total lifespan, and reproductive success of each morph. Clear-winged males are smaller and have lower daily reproductive success than orange-winged males, but live for longer in the field and laboratory. We accounted for the difference in the ‘operational reproductive life’ of the two morphs and estimated lifetime reproductive success: there was no difference between clear-winged and orange-winged males. We discuss possible mechanisms for the maintenance of the two forms.     

Female sexual receptivity and male copula guarding during prolonged copulations in the damselflyIschnura senegalensis (Odonata:Coenagrionidae)

Laboratory experiments were conducted to clarify the relationship between female sexual receptivity and male copula guarding inI. senegalensis, a species that copulates for several hours. In insectaries, most copulations were initiated early in the morning, and terminated relatively synchronously between 11 00 and 13 00. Females refused males with wing-flutter display and oviposited alone in the afternoon regardless of copulation events of that morning. Females could sexually receive males only in the morning. Males copulated for several hours until 12 00 after which females could oviposit. To determine whether copulations that last for hours function as male copula guarding or only of sperm displacement, emerged males were kept at various densities and permitted to copulate with virgin and mated females in insectaries. Both with virgin and mated females, “social” (not solitary; 2–4 males / insectary) males initiated copulations early in the morning and always terminated at around 12 00. However, both with virgin and mated females, solitary (one male / insectary) males terminated copulations in the morning. In both cases, duration of copulations did not significantly differ for virgin females and mated females. Therefore, long (several hour) copulation is more likely to function as male copula guarding than as sperm displacement, and duration of copulations is predicted to be shortened when male density is very low.     

Chemical communication in Cavia: Responses of wild (C. aperea), domestic (C. porcellus) and F1 males to urine

Urine preferences of wild (Cavia aperea), domestic (C. porcellus), and F₁ adult male guinea pigs were investigated. Males of all three types preferred female urine to male urine regardless of donor type. When given a choice between female urine of each type, males preferred conspecific urine. In choices between male urine of the three types, a conspecific preference was evident for wild and domestic but not f₁ subjects. These data indicate that a loss of distinctive male and female odours has not occurred as a result of domestication. However, the urine odours of wild and domestic types have diverged. The possible effects of previous individual experience on the preferential response is discussed.     

Chthamalus stellatus (Poli) und C. depressus (Poli) in der adria

A study has been made of the ecology of Chthamalus stellatus (Poli) and C. depressus (Poli) in the region of Rovinj (Yugoslavia). The distribution has been examined at several localities of different habitat conditions particularly with respect to wave action.     

Impact of predation by spiders on a territorial damselfly (Odonata: Calopterygidae)

Summary Predation by orb-weaving spiders and crab spiders on the damselfly Calopteryx haemorrhoidalis was studied at a small stream in Southern France. One species of orb-weaving spider, Larinioides folium, caught 76% of the damselflies which fell prey to spiders. Displacement experiments on spiders on sections of bank and the positioning of webs in male territories show that the density and distribution of damselflies is not influenced by orbweb density or by the position of webs. Predation rates corresponded to orb-web density, but neither for sex nor for stage was there a relationship with damselfly density. Mean daily predation rates ranged between 0.9% for females and 4.1% for adult males. Predation risk to adult damselflies by orb-weaving spiders was male biased, whereas among tenerals there was no bias. Males were captured more frequently at territories near the water. Captures show a maximum at noon when territorial disputes of adult males were most frequent. After orbwebs were placed within territories predation rate of males was strongly increased. Predation risk to adult females in the direct vicinity of the stream was less than in the bank vegetation where they perch close to orbwebs. The risk of predation by crab spiders, which catch damselflies at their perching sites, was not sex-biased.     

Polyunsaturated fatty acids cause apoptosis in C. albicans and C. dubliniensis biofilms

Background

Polyunsaturated fatty acids (PUFAs) have antifungal properties, but the mode by which they induce their action is not always clear. The aim of the study was to investigate apoptosis as a mode of action of antifungal PUFAs (stearidonic acid, eicosapentaenoic acid and docosapentaenoic acid) which are inhibitory towards biofilm formation of C. albicans and C. dubliniensis.

Methods

Candida biofilms were grown in the absence or presence of 1 mM PUFAs (linoleic acid, stearidonic acid, eicosapentaenoic acid, docosapentaenoic acid) for 48 h at 37 °C. The effect of these PUFAs on the membrane fatty acid profile and unsaturation index, oxidative stress, mitochondrial transmembrane potential and apoptosis was evaluated.

Results

When biofilms of C. albicans and C. dubliniensis were exposed to certain PUFAs there was an increase in unsaturation index of the cellular membranes and accumulation of intracellular reactive oxygen species (ROS). This resulted in apoptosis, evidenced by reduced mitochondrial membrane potential and nuclear condensation and fragmentation. The most effective PUFA was stearidonic acid.

Conclusions

The resultant cell death of both C. albicans and C. dubliniensis is due to apoptosis.

General significance

Due to the increase in drug resistance, alternative antifungal drugs are needed. A group of natural antifungal compounds is PUFAs. However, understanding their mechanisms of action is important for further use and development of these compounds as antifungal drugs. This paper provides insight into a possible mode of action of antifungal PUFAs.     

Patterns of adult abundance in Chthamalus stellatus (Poli) and C. montagui Southward (Crustacea: Cirripedia) emerge during late recruitment

The aim of this study was to investigate when adult distribution patterns are established in the barnacles Chthamalus stellatus and C. montagui. Adult ‘zones’ were identified by analysing field counts of both species at mid and upper shore heights. Monthly collections of cyprids, < 1 month old metamorphs and recruits (all metamorphosed individuals older than approximately 1 month) were made for C. stellatus and C. montagui in natural barnacle beds at six shores in SW Ireland. This was carried out over one year in 1996/1997, using a hierarchical sampling design. Abundance of total recruits (0-3 months old) was compared between adult zones after the main settlement season had ended. In addition, scales of variability in 0-3 month recruitment into adult zones were compared between the species at two scales: shores (1000s of metres) and sites within shores (10s of metres). Older recruits of each species, up to 11 months of age, were also compared between adult zones.The majority of settlement (measured as attached cyprids) occurred between August and October 1996. In October, there was no effect of adult zone on the abundance of total (0-3 month) recruitment up to that point in either species. Despite this homogeneity in recruitment between adult zones, significant spatial variation was found in 0-3 month recruits of both species at both of the scales examined. In C. stellatus the amount of variation associated with the larger scale (shore) was more than twice that of sites or of the residual variation (replicates within sites). 0-3 month recruitment in C. montagui was also most variable at the scale of shores but the residual variability (between replicates within site) was of similar magnitude to that of shores. Variability in 0-3 month C. montagui recruitment was relatively low at the scale of sites.There was a small but consistent input of recruits to adult zones over 9 months of the year, complicating the assessment of when adult patterns were set-up in these species. By June 1997, characteristic patterns of adult dominance had been established at all shores. Settlement had completely ceased by this time and individual barnacles were potentially 11 months old. Neither settlement nor early recruitment are significant in determining adult zonation patterns in these species. Instead, differential mortality patterns in individuals up to the age of 11 months are implicated in determining patterns of distribution of both species.     

The C. elegans adult male germline: Stem cells and sexual dimorphism

The hermaphrodite Caenorhabditis elegans germline has become a classic model for stem cell regulation, but the male C. elegans germline has been largely neglected. This work provides a cellular analysis of the adult C. elegans male germline, focusing on its predicted stem cell region in the distal gonad. The goals of this study were two-fold: to establish the C. elegans male germline as a stem cell model and to identify sex-specific traits of potential relevance to the sperm/oocyte decision. Our results support two major conclusions. First, adult males do indeed possess a population of germline stem cells (GSCs) with properties similar to those of hermaphrodite GSCs (lack of cell cycle quiescence and lack of reproducibly oriented divisions). Second, germ cells in the mitotic region, including those most distal within the niche, exhibit sex-specific behaviors (e.g. cell cycle length) and therefore have acquired sexual identity. Previous studies demonstrated that some germ cells are not committed to a sperm or oocyte cell fate, even in adults. We propose that germ cells can acquire sexual identity without being committed to a sperm or oocyte cell fate.     

The Evolution of Wing Shape in Ornamented-Winged Damselflies (Calopterygidae, Odonata)

Flight has conferred an extraordinary advantage to some groups of animals. Wing shape is directly related to flight performance and evolves in response to multiple selective pressures. In some species, wings have ornaments such as pigmented patches that are sexually selected. Since organisms with pigmented wings need to display the ornament while flying in an optimal way, we might expect a correlative evolution between the wing ornament and wing shape. We examined males from 36 taxa of calopterygid damselflies that differ in wing pigmentation, which is used in sexual displays. We used geometric morphometrics and phylogenetic comparative approaches to analyse whether wing shape and wing pigmentation show correlated evolution. We found that wing pigmentation is associated with certain wing shapes that probably increase the quality of the signal: wings being broader where the pigmentation is located. Our results also showed correlated evolution between wing pigmentation and wing shape in hind wings, but not in front wings, probably because hind wings are more involved in signalling than front wings. The results imply that the evolution of diversity in wing pigmentations and behavioural sexual displays might be an important driver of speciation due to important pre-copulatory selective pressures.     

Influence of oviposition date and temperature upon embryonic development in Somatochlora alpestris and S. arctica (Odonata: Corduliidae)

In two bog-dwelling dragonflies, Somatochlora alpestris and S. arctica , the influence of oviposition date and temperature upon duration of embryonic development was studied. Egg diapause was facultative. With advancing season, the proportion of diapause eggs increases from 0 to 37% in S. alpestris and from 0 to 18% in S. arctica. Eggs needed at least 17 to 38 days for development. Hatching curves were temperature-independent in nearly all experiments but developmental rate increased at higher ambient temperature. In S. arctica , responses of developmental rate to temperature differed in eggs laid on different dates. In S. alpestris , duration of egg development decreased as season progressed. The duration of egg development of non-diapause eggs and proportion of diapause eggs in S. alpestris and possibly in S. arctica may also both be a function of female age at the time of oviposition. The ecological significance of the different development patterns is discussed.     

Coupling and oviposition behaviour in two macrodiplacinid libellulids–Aethriamantha rezia (Kirby) and Urothemis assignata Selys (Libellulidae: Odonata)

Coupling and oviposition behaviour were studied in two macrodiplacinid libellulids– Aethriamantha rezia (Kirby) and Urothemis assignata Selys in die Ibadan area of Nigeria. Sperm translocation occurs in both libellulids after the male has secured the female. Pre-mating tandem flight occurs prior to mating. Mating is long in A. rezia (384–716 s, mean 480) and shorter in U. assignata (69–122 s, mean 94). After mating, both libellulids rest in tandem, the duration being longer in A. rezia (25–82 s, mean 42) than in U. assignata (0–24 s, mean 11). This is followed by tandem exploration in A. rezia and later by oviposition, the male guarding the female. In U. assignata , tandem exploration is absent, but oviposition is usually in tandem. The duration of oviposition is similar in both libellulids–6 7–148 s, mean 95, in A. rezia and 63–183 m, mean 133, in U. assignata. Aethriamantha rezia oviposits mainly on Pistia stratiotes while plants utilized by U. assignata are more variable, although P. stratiotes is also preferred. The number of eggs laid per oviposition is high, averaging 435 in A. rezia and 398 in U. assignata. High population of males at water prolongs mating and oviposition in the two species. The ecological habitats of both overlap.     

Novel aspects of the flowers and floral pigmentation of two Cleome species (Cleomaceae), C. hassleriana and C. serrulata

Palely pigmented inflorescences of cultivated Cleome hassleriana Chodat (spider flower) have a unique two-toned appearance shown in the present study to be due to a loss of petal pigmentation within 24 h of anthesis, accompanied by an equally unique loss of petal mass. A similar loss occurs in deeply pigmented petals but is less evident to the eye because of the high initial content due to the presence, in the petal mesophyll, of globular anthocyanic vacuolar inclusions (AVIs). Inflorescences of the wild species, Cleome serrulata Pursh. (Rocky Mountain bee flower) are also two-toned because of the deeper pink colour of the unopened bud. No AVIs were seen. The pink colour of the bee flower petals is due to the same five acylated cyanidin glycosides as those previously isolated from mauve petals of spider flower. The structural pattern of the spider flower anthocyanins is shared with at least three genera of the Brassicaceae.     

Comparative courtship behaviour in two species of the parasitic chalcid wasp Melittobia (Hymenoptera: Eulophidae)

Timing and form of courtship behaviour elements constitute a major isolating mechanism for two morphologically and ecologically similar parasitic wasps. Because males are blind, the complex courtship of Melittobia chalybii and a new as yet undescribed species previously confused with it, designated as M. sp. A, depends upon tactile and chemical cues. In both species, after the female orients to the male's abdomen, the male turns in the direction of contact and mounts. However, chalybii males antennate females continuously, lifting mesothoracic legs at regular intervals, while in sp. A male antennation alternates with metathoracic leg pumping. Courtship and copulation duration are greater in Chalybii than in sp. A.     

Releasing signals of oviposition behaviour in Bombyx mori

The oviposition behaviour of Bombyx mori was studied by eliminating the sensory input received by the tactile setae of the anal papillae.It is shown that the removal of mechanical stimuli of the setae affects oviposition and its time course to some extent. In comparing this experimental result with the theory of Lorenz, summarized in the ‘hydromechanic model’, it is postulated that the sensory information from the mechanoreceptive setae surrounding the ovipositor is a key stimulus which releases the accumulated action-specific energy (‘drive’) and triggers and controls the organs involved in the behaviour.